51
INTERVIEW 3G Atunu Gorai
INTERVIEW
3GAtunu Gorai
WCDMA Frequency and Spectrum
bull Uplink=1920MHz -1980 MHzbull Downlink= 2110MHz -2170MHzbull Bandwidth=60 MHz Actual BW assign to operator is 5MHz And out of that 384 MHZ is utilizeIn WCDMA frequency reuse factor =1 because time and frequency
remains constant
bull Eb NO= Bit energyNoise energybull EcNo = Chip Energy Noise Energy
bull EcNo= EbNo - process gainbull As per EbNo is fixed for each service for Ex voice =2 and
video=4bull EcN0= 2- 10= -8 for voice(for voice -8 is good limit)bull EcN0= 4-18= -14 for video(for video -14 is good limit)
bull Process gain(voice) = chip ratebit rate= 10dBbull Process gain (video) = chip rate bit rate= 18dBbull Chip rate = 384Mchips in WCDMA
Cyclic Redundancy Check (CRC) is used to detect if there are anyuncorrected errors left after error correction
The next part in the transmitter is Forward Error Correction (FEC)The function of this block is to help the receiver correct bit errorscaused by the air interface
The error-protected signal is then multiplied by a particularchannelization code to provide the necessary channel separationThis is necessary since all the channels will be added togetherwhich will produce a composite data stream
Channelization codes
In the downlink the channelization codes are used to separate thedifferent data channels coming from each cell For the dedicatedchannels this represents the different users since only onescrambling code is used for all downlink transmission from thecell
In the uplink the channelization codes are used to separate thedifferent data channels sent from the UE to the each cell Theseparation of the different UEs will here be done with differentscrambling codes
The number of codes used in the downlink is restricted to 8192 intotal This is done to speed up the process for the UE to find thecorrect scrambling code 512 of these are primary codes (the restare secondary codes 15 codes per primary) divided into 64 codegroups each group containing 8 different codes The UE candetermine which scrambling code group a cell is using by thesynchronization procedure (see chapter 5) Note that there are norestrictions for the number of codes generated by the 24 bits startkey in the uplink case
Data Drive
bull There is 3 modulation technique QPSK16QAM64QAMbull For high through put 16QAM and 64QAM should have high Utilizationbull So if There is less Utilization of QPSK in downlink than data throughput is
also highbull CQI is like SQI in speech which ensure good channel quality for data
transferbull Retransmission of HS- DSCH(High-Speed Downlink Shared Channel) packet
is high than also throughput is decreasesbull In case of stationary Data Test- 2Mbits speed can be achieved bull In case of moving Vehicle ndash 800kbits to 12 Kbits speed can be achievedbull Application throughput is always 85 of physical layer data rate
throughput because at application level IP inclusion and overhead information will be there
bull Latency time is round trip time from server and for 3G it should be 150 ms for 32 bit data
bull The modulation scheme and coding is changed on a per-user basis depending on signal quality and cell usage The initial scheme is Quadrature phase-shift keying (QPSK) but in good radio conditions 16QAM and 64QAM can significantly increase data throughput rates With 5 Code allocation QPSK typically offers up to 18 Mbits peak data rates while 16QAM offers up to 36 Mbits Additional codes (eg 10 15) can also be used to improve these data rates or extend the network capacity throughput significantly
bull Data Throughput will be also depend on MS class which support 510 and 15 codes resp
bull CQI- Channel quality indication may include carrier level received signal strength indication (RSSI) and bit error rate (BER) I
bull Channel quality indicators are messages that are sent on a communication system (such as a mobile communication system) that provide the remote connection (eg base station) with channel quality information
Notes on quantities denoting signal power
KEY PERFORMANCE INDICATORS
Accessability (Call set-up success rate)
Retainability (Dropped calls)
Mobility (Handover success rate)
Integrity (BLER and throughput)
Integrity- quality
Integrity-throughput
What is the major difference in link budgets between UMTS and GSMTDMA In UMTS you generally have a link budget for each service (voice data video etc) in GSM you usually only use 1 for voice Each service has a different EbNo target In UMTS you have to consider the target traffic load you will have and add a noise-rise margin in GSM you may have a slight interference margin but not normally related to traffic In UMTS some services (like voice) will show up as uplink limited but other services (like HSDPA 384kbps service) will show as downlink limited In UMTS you usually have to consider that all users use the same power from the BTS therefore the more number of users the lower the maximumpower available per user (maximum power per connection) which is a starting point in the link budget
KPI Requirements Formula
CPICH RSCP ge-95dBm NA(nbr_of_samples_RSCPgt=-95dBm)
(tot_nbr_of_samples_RSCP)
CPICH EcIo ge-12dB NA(nbr_of_samples_EcIogt=-12dB)
(tot_nbr_of_samples_EcIo)
Voice call setup success rate
Min ge98(nbr_of_successful_voice_call_setup)
(nbr_of_voice_call_attemp)
Voice call setup time(Mobile to 1764440)
le10s ge99(nbr_of_voice_call_setup_timele10s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
le9s ge95(nbr_of_voice_call_setup_timele9s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
Voice call drop rate Max le2(nbr_of_voice_call_drop)
[(call_duration_time)90sec]
PDP activation successful rate
Min ge99(nbr_of_PDP_context_activation_accept)(nbr_of_PDP_context_activation_request)
PDP activation delay le2s ge99
(nbr_of_PDP_activation_delayle2s)(nbr_of_PDP_context_activation_accept)
PDP_activation_delay= [T(PDP_context_activation_accept)- T(PDP_context_activation_request)]
PS 384k FTP DL Avg Throughput 280kbps(downloaded_data_kbit)(data_session_duration)
PS 384k FTP UL Avg Throughput 280kbps(uploaded_data_kbit)
(data_session_duration)
HSDPA FTP Avg Throughput 45Mbps(downloaded_data_kbit)(data_session_duration)
HSUPA FTP Avg Throughput 11Mbps(uploaded_data_kbit)
(data_session_duration)
KPI calculation
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
WCDMA Frequency and Spectrum
bull Uplink=1920MHz -1980 MHzbull Downlink= 2110MHz -2170MHzbull Bandwidth=60 MHz Actual BW assign to operator is 5MHz And out of that 384 MHZ is utilizeIn WCDMA frequency reuse factor =1 because time and frequency
remains constant
bull Eb NO= Bit energyNoise energybull EcNo = Chip Energy Noise Energy
bull EcNo= EbNo - process gainbull As per EbNo is fixed for each service for Ex voice =2 and
video=4bull EcN0= 2- 10= -8 for voice(for voice -8 is good limit)bull EcN0= 4-18= -14 for video(for video -14 is good limit)
bull Process gain(voice) = chip ratebit rate= 10dBbull Process gain (video) = chip rate bit rate= 18dBbull Chip rate = 384Mchips in WCDMA
Cyclic Redundancy Check (CRC) is used to detect if there are anyuncorrected errors left after error correction
The next part in the transmitter is Forward Error Correction (FEC)The function of this block is to help the receiver correct bit errorscaused by the air interface
The error-protected signal is then multiplied by a particularchannelization code to provide the necessary channel separationThis is necessary since all the channels will be added togetherwhich will produce a composite data stream
Channelization codes
In the downlink the channelization codes are used to separate thedifferent data channels coming from each cell For the dedicatedchannels this represents the different users since only onescrambling code is used for all downlink transmission from thecell
In the uplink the channelization codes are used to separate thedifferent data channels sent from the UE to the each cell Theseparation of the different UEs will here be done with differentscrambling codes
The number of codes used in the downlink is restricted to 8192 intotal This is done to speed up the process for the UE to find thecorrect scrambling code 512 of these are primary codes (the restare secondary codes 15 codes per primary) divided into 64 codegroups each group containing 8 different codes The UE candetermine which scrambling code group a cell is using by thesynchronization procedure (see chapter 5) Note that there are norestrictions for the number of codes generated by the 24 bits startkey in the uplink case
Data Drive
bull There is 3 modulation technique QPSK16QAM64QAMbull For high through put 16QAM and 64QAM should have high Utilizationbull So if There is less Utilization of QPSK in downlink than data throughput is
also highbull CQI is like SQI in speech which ensure good channel quality for data
transferbull Retransmission of HS- DSCH(High-Speed Downlink Shared Channel) packet
is high than also throughput is decreasesbull In case of stationary Data Test- 2Mbits speed can be achieved bull In case of moving Vehicle ndash 800kbits to 12 Kbits speed can be achievedbull Application throughput is always 85 of physical layer data rate
throughput because at application level IP inclusion and overhead information will be there
bull Latency time is round trip time from server and for 3G it should be 150 ms for 32 bit data
bull The modulation scheme and coding is changed on a per-user basis depending on signal quality and cell usage The initial scheme is Quadrature phase-shift keying (QPSK) but in good radio conditions 16QAM and 64QAM can significantly increase data throughput rates With 5 Code allocation QPSK typically offers up to 18 Mbits peak data rates while 16QAM offers up to 36 Mbits Additional codes (eg 10 15) can also be used to improve these data rates or extend the network capacity throughput significantly
bull Data Throughput will be also depend on MS class which support 510 and 15 codes resp
bull CQI- Channel quality indication may include carrier level received signal strength indication (RSSI) and bit error rate (BER) I
bull Channel quality indicators are messages that are sent on a communication system (such as a mobile communication system) that provide the remote connection (eg base station) with channel quality information
Notes on quantities denoting signal power
KEY PERFORMANCE INDICATORS
Accessability (Call set-up success rate)
Retainability (Dropped calls)
Mobility (Handover success rate)
Integrity (BLER and throughput)
Integrity- quality
Integrity-throughput
What is the major difference in link budgets between UMTS and GSMTDMA In UMTS you generally have a link budget for each service (voice data video etc) in GSM you usually only use 1 for voice Each service has a different EbNo target In UMTS you have to consider the target traffic load you will have and add a noise-rise margin in GSM you may have a slight interference margin but not normally related to traffic In UMTS some services (like voice) will show up as uplink limited but other services (like HSDPA 384kbps service) will show as downlink limited In UMTS you usually have to consider that all users use the same power from the BTS therefore the more number of users the lower the maximumpower available per user (maximum power per connection) which is a starting point in the link budget
KPI Requirements Formula
CPICH RSCP ge-95dBm NA(nbr_of_samples_RSCPgt=-95dBm)
(tot_nbr_of_samples_RSCP)
CPICH EcIo ge-12dB NA(nbr_of_samples_EcIogt=-12dB)
(tot_nbr_of_samples_EcIo)
Voice call setup success rate
Min ge98(nbr_of_successful_voice_call_setup)
(nbr_of_voice_call_attemp)
Voice call setup time(Mobile to 1764440)
le10s ge99(nbr_of_voice_call_setup_timele10s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
le9s ge95(nbr_of_voice_call_setup_timele9s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
Voice call drop rate Max le2(nbr_of_voice_call_drop)
[(call_duration_time)90sec]
PDP activation successful rate
Min ge99(nbr_of_PDP_context_activation_accept)(nbr_of_PDP_context_activation_request)
PDP activation delay le2s ge99
(nbr_of_PDP_activation_delayle2s)(nbr_of_PDP_context_activation_accept)
PDP_activation_delay= [T(PDP_context_activation_accept)- T(PDP_context_activation_request)]
PS 384k FTP DL Avg Throughput 280kbps(downloaded_data_kbit)(data_session_duration)
PS 384k FTP UL Avg Throughput 280kbps(uploaded_data_kbit)
(data_session_duration)
HSDPA FTP Avg Throughput 45Mbps(downloaded_data_kbit)(data_session_duration)
HSUPA FTP Avg Throughput 11Mbps(uploaded_data_kbit)
(data_session_duration)
KPI calculation
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
bull Eb NO= Bit energyNoise energybull EcNo = Chip Energy Noise Energy
bull EcNo= EbNo - process gainbull As per EbNo is fixed for each service for Ex voice =2 and
video=4bull EcN0= 2- 10= -8 for voice(for voice -8 is good limit)bull EcN0= 4-18= -14 for video(for video -14 is good limit)
bull Process gain(voice) = chip ratebit rate= 10dBbull Process gain (video) = chip rate bit rate= 18dBbull Chip rate = 384Mchips in WCDMA
Cyclic Redundancy Check (CRC) is used to detect if there are anyuncorrected errors left after error correction
The next part in the transmitter is Forward Error Correction (FEC)The function of this block is to help the receiver correct bit errorscaused by the air interface
The error-protected signal is then multiplied by a particularchannelization code to provide the necessary channel separationThis is necessary since all the channels will be added togetherwhich will produce a composite data stream
Channelization codes
In the downlink the channelization codes are used to separate thedifferent data channels coming from each cell For the dedicatedchannels this represents the different users since only onescrambling code is used for all downlink transmission from thecell
In the uplink the channelization codes are used to separate thedifferent data channels sent from the UE to the each cell Theseparation of the different UEs will here be done with differentscrambling codes
The number of codes used in the downlink is restricted to 8192 intotal This is done to speed up the process for the UE to find thecorrect scrambling code 512 of these are primary codes (the restare secondary codes 15 codes per primary) divided into 64 codegroups each group containing 8 different codes The UE candetermine which scrambling code group a cell is using by thesynchronization procedure (see chapter 5) Note that there are norestrictions for the number of codes generated by the 24 bits startkey in the uplink case
Data Drive
bull There is 3 modulation technique QPSK16QAM64QAMbull For high through put 16QAM and 64QAM should have high Utilizationbull So if There is less Utilization of QPSK in downlink than data throughput is
also highbull CQI is like SQI in speech which ensure good channel quality for data
transferbull Retransmission of HS- DSCH(High-Speed Downlink Shared Channel) packet
is high than also throughput is decreasesbull In case of stationary Data Test- 2Mbits speed can be achieved bull In case of moving Vehicle ndash 800kbits to 12 Kbits speed can be achievedbull Application throughput is always 85 of physical layer data rate
throughput because at application level IP inclusion and overhead information will be there
bull Latency time is round trip time from server and for 3G it should be 150 ms for 32 bit data
bull The modulation scheme and coding is changed on a per-user basis depending on signal quality and cell usage The initial scheme is Quadrature phase-shift keying (QPSK) but in good radio conditions 16QAM and 64QAM can significantly increase data throughput rates With 5 Code allocation QPSK typically offers up to 18 Mbits peak data rates while 16QAM offers up to 36 Mbits Additional codes (eg 10 15) can also be used to improve these data rates or extend the network capacity throughput significantly
bull Data Throughput will be also depend on MS class which support 510 and 15 codes resp
bull CQI- Channel quality indication may include carrier level received signal strength indication (RSSI) and bit error rate (BER) I
bull Channel quality indicators are messages that are sent on a communication system (such as a mobile communication system) that provide the remote connection (eg base station) with channel quality information
Notes on quantities denoting signal power
KEY PERFORMANCE INDICATORS
Accessability (Call set-up success rate)
Retainability (Dropped calls)
Mobility (Handover success rate)
Integrity (BLER and throughput)
Integrity- quality
Integrity-throughput
What is the major difference in link budgets between UMTS and GSMTDMA In UMTS you generally have a link budget for each service (voice data video etc) in GSM you usually only use 1 for voice Each service has a different EbNo target In UMTS you have to consider the target traffic load you will have and add a noise-rise margin in GSM you may have a slight interference margin but not normally related to traffic In UMTS some services (like voice) will show up as uplink limited but other services (like HSDPA 384kbps service) will show as downlink limited In UMTS you usually have to consider that all users use the same power from the BTS therefore the more number of users the lower the maximumpower available per user (maximum power per connection) which is a starting point in the link budget
KPI Requirements Formula
CPICH RSCP ge-95dBm NA(nbr_of_samples_RSCPgt=-95dBm)
(tot_nbr_of_samples_RSCP)
CPICH EcIo ge-12dB NA(nbr_of_samples_EcIogt=-12dB)
(tot_nbr_of_samples_EcIo)
Voice call setup success rate
Min ge98(nbr_of_successful_voice_call_setup)
(nbr_of_voice_call_attemp)
Voice call setup time(Mobile to 1764440)
le10s ge99(nbr_of_voice_call_setup_timele10s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
le9s ge95(nbr_of_voice_call_setup_timele9s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
Voice call drop rate Max le2(nbr_of_voice_call_drop)
[(call_duration_time)90sec]
PDP activation successful rate
Min ge99(nbr_of_PDP_context_activation_accept)(nbr_of_PDP_context_activation_request)
PDP activation delay le2s ge99
(nbr_of_PDP_activation_delayle2s)(nbr_of_PDP_context_activation_accept)
PDP_activation_delay= [T(PDP_context_activation_accept)- T(PDP_context_activation_request)]
PS 384k FTP DL Avg Throughput 280kbps(downloaded_data_kbit)(data_session_duration)
PS 384k FTP UL Avg Throughput 280kbps(uploaded_data_kbit)
(data_session_duration)
HSDPA FTP Avg Throughput 45Mbps(downloaded_data_kbit)(data_session_duration)
HSUPA FTP Avg Throughput 11Mbps(uploaded_data_kbit)
(data_session_duration)
KPI calculation
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Cyclic Redundancy Check (CRC) is used to detect if there are anyuncorrected errors left after error correction
The next part in the transmitter is Forward Error Correction (FEC)The function of this block is to help the receiver correct bit errorscaused by the air interface
The error-protected signal is then multiplied by a particularchannelization code to provide the necessary channel separationThis is necessary since all the channels will be added togetherwhich will produce a composite data stream
Channelization codes
In the downlink the channelization codes are used to separate thedifferent data channels coming from each cell For the dedicatedchannels this represents the different users since only onescrambling code is used for all downlink transmission from thecell
In the uplink the channelization codes are used to separate thedifferent data channels sent from the UE to the each cell Theseparation of the different UEs will here be done with differentscrambling codes
The number of codes used in the downlink is restricted to 8192 intotal This is done to speed up the process for the UE to find thecorrect scrambling code 512 of these are primary codes (the restare secondary codes 15 codes per primary) divided into 64 codegroups each group containing 8 different codes The UE candetermine which scrambling code group a cell is using by thesynchronization procedure (see chapter 5) Note that there are norestrictions for the number of codes generated by the 24 bits startkey in the uplink case
Data Drive
bull There is 3 modulation technique QPSK16QAM64QAMbull For high through put 16QAM and 64QAM should have high Utilizationbull So if There is less Utilization of QPSK in downlink than data throughput is
also highbull CQI is like SQI in speech which ensure good channel quality for data
transferbull Retransmission of HS- DSCH(High-Speed Downlink Shared Channel) packet
is high than also throughput is decreasesbull In case of stationary Data Test- 2Mbits speed can be achieved bull In case of moving Vehicle ndash 800kbits to 12 Kbits speed can be achievedbull Application throughput is always 85 of physical layer data rate
throughput because at application level IP inclusion and overhead information will be there
bull Latency time is round trip time from server and for 3G it should be 150 ms for 32 bit data
bull The modulation scheme and coding is changed on a per-user basis depending on signal quality and cell usage The initial scheme is Quadrature phase-shift keying (QPSK) but in good radio conditions 16QAM and 64QAM can significantly increase data throughput rates With 5 Code allocation QPSK typically offers up to 18 Mbits peak data rates while 16QAM offers up to 36 Mbits Additional codes (eg 10 15) can also be used to improve these data rates or extend the network capacity throughput significantly
bull Data Throughput will be also depend on MS class which support 510 and 15 codes resp
bull CQI- Channel quality indication may include carrier level received signal strength indication (RSSI) and bit error rate (BER) I
bull Channel quality indicators are messages that are sent on a communication system (such as a mobile communication system) that provide the remote connection (eg base station) with channel quality information
Notes on quantities denoting signal power
KEY PERFORMANCE INDICATORS
Accessability (Call set-up success rate)
Retainability (Dropped calls)
Mobility (Handover success rate)
Integrity (BLER and throughput)
Integrity- quality
Integrity-throughput
What is the major difference in link budgets between UMTS and GSMTDMA In UMTS you generally have a link budget for each service (voice data video etc) in GSM you usually only use 1 for voice Each service has a different EbNo target In UMTS you have to consider the target traffic load you will have and add a noise-rise margin in GSM you may have a slight interference margin but not normally related to traffic In UMTS some services (like voice) will show up as uplink limited but other services (like HSDPA 384kbps service) will show as downlink limited In UMTS you usually have to consider that all users use the same power from the BTS therefore the more number of users the lower the maximumpower available per user (maximum power per connection) which is a starting point in the link budget
KPI Requirements Formula
CPICH RSCP ge-95dBm NA(nbr_of_samples_RSCPgt=-95dBm)
(tot_nbr_of_samples_RSCP)
CPICH EcIo ge-12dB NA(nbr_of_samples_EcIogt=-12dB)
(tot_nbr_of_samples_EcIo)
Voice call setup success rate
Min ge98(nbr_of_successful_voice_call_setup)
(nbr_of_voice_call_attemp)
Voice call setup time(Mobile to 1764440)
le10s ge99(nbr_of_voice_call_setup_timele10s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
le9s ge95(nbr_of_voice_call_setup_timele9s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
Voice call drop rate Max le2(nbr_of_voice_call_drop)
[(call_duration_time)90sec]
PDP activation successful rate
Min ge99(nbr_of_PDP_context_activation_accept)(nbr_of_PDP_context_activation_request)
PDP activation delay le2s ge99
(nbr_of_PDP_activation_delayle2s)(nbr_of_PDP_context_activation_accept)
PDP_activation_delay= [T(PDP_context_activation_accept)- T(PDP_context_activation_request)]
PS 384k FTP DL Avg Throughput 280kbps(downloaded_data_kbit)(data_session_duration)
PS 384k FTP UL Avg Throughput 280kbps(uploaded_data_kbit)
(data_session_duration)
HSDPA FTP Avg Throughput 45Mbps(downloaded_data_kbit)(data_session_duration)
HSUPA FTP Avg Throughput 11Mbps(uploaded_data_kbit)
(data_session_duration)
KPI calculation
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Channelization codes
In the downlink the channelization codes are used to separate thedifferent data channels coming from each cell For the dedicatedchannels this represents the different users since only onescrambling code is used for all downlink transmission from thecell
In the uplink the channelization codes are used to separate thedifferent data channels sent from the UE to the each cell Theseparation of the different UEs will here be done with differentscrambling codes
The number of codes used in the downlink is restricted to 8192 intotal This is done to speed up the process for the UE to find thecorrect scrambling code 512 of these are primary codes (the restare secondary codes 15 codes per primary) divided into 64 codegroups each group containing 8 different codes The UE candetermine which scrambling code group a cell is using by thesynchronization procedure (see chapter 5) Note that there are norestrictions for the number of codes generated by the 24 bits startkey in the uplink case
Data Drive
bull There is 3 modulation technique QPSK16QAM64QAMbull For high through put 16QAM and 64QAM should have high Utilizationbull So if There is less Utilization of QPSK in downlink than data throughput is
also highbull CQI is like SQI in speech which ensure good channel quality for data
transferbull Retransmission of HS- DSCH(High-Speed Downlink Shared Channel) packet
is high than also throughput is decreasesbull In case of stationary Data Test- 2Mbits speed can be achieved bull In case of moving Vehicle ndash 800kbits to 12 Kbits speed can be achievedbull Application throughput is always 85 of physical layer data rate
throughput because at application level IP inclusion and overhead information will be there
bull Latency time is round trip time from server and for 3G it should be 150 ms for 32 bit data
bull The modulation scheme and coding is changed on a per-user basis depending on signal quality and cell usage The initial scheme is Quadrature phase-shift keying (QPSK) but in good radio conditions 16QAM and 64QAM can significantly increase data throughput rates With 5 Code allocation QPSK typically offers up to 18 Mbits peak data rates while 16QAM offers up to 36 Mbits Additional codes (eg 10 15) can also be used to improve these data rates or extend the network capacity throughput significantly
bull Data Throughput will be also depend on MS class which support 510 and 15 codes resp
bull CQI- Channel quality indication may include carrier level received signal strength indication (RSSI) and bit error rate (BER) I
bull Channel quality indicators are messages that are sent on a communication system (such as a mobile communication system) that provide the remote connection (eg base station) with channel quality information
Notes on quantities denoting signal power
KEY PERFORMANCE INDICATORS
Accessability (Call set-up success rate)
Retainability (Dropped calls)
Mobility (Handover success rate)
Integrity (BLER and throughput)
Integrity- quality
Integrity-throughput
What is the major difference in link budgets between UMTS and GSMTDMA In UMTS you generally have a link budget for each service (voice data video etc) in GSM you usually only use 1 for voice Each service has a different EbNo target In UMTS you have to consider the target traffic load you will have and add a noise-rise margin in GSM you may have a slight interference margin but not normally related to traffic In UMTS some services (like voice) will show up as uplink limited but other services (like HSDPA 384kbps service) will show as downlink limited In UMTS you usually have to consider that all users use the same power from the BTS therefore the more number of users the lower the maximumpower available per user (maximum power per connection) which is a starting point in the link budget
KPI Requirements Formula
CPICH RSCP ge-95dBm NA(nbr_of_samples_RSCPgt=-95dBm)
(tot_nbr_of_samples_RSCP)
CPICH EcIo ge-12dB NA(nbr_of_samples_EcIogt=-12dB)
(tot_nbr_of_samples_EcIo)
Voice call setup success rate
Min ge98(nbr_of_successful_voice_call_setup)
(nbr_of_voice_call_attemp)
Voice call setup time(Mobile to 1764440)
le10s ge99(nbr_of_voice_call_setup_timele10s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
le9s ge95(nbr_of_voice_call_setup_timele9s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
Voice call drop rate Max le2(nbr_of_voice_call_drop)
[(call_duration_time)90sec]
PDP activation successful rate
Min ge99(nbr_of_PDP_context_activation_accept)(nbr_of_PDP_context_activation_request)
PDP activation delay le2s ge99
(nbr_of_PDP_activation_delayle2s)(nbr_of_PDP_context_activation_accept)
PDP_activation_delay= [T(PDP_context_activation_accept)- T(PDP_context_activation_request)]
PS 384k FTP DL Avg Throughput 280kbps(downloaded_data_kbit)(data_session_duration)
PS 384k FTP UL Avg Throughput 280kbps(uploaded_data_kbit)
(data_session_duration)
HSDPA FTP Avg Throughput 45Mbps(downloaded_data_kbit)(data_session_duration)
HSUPA FTP Avg Throughput 11Mbps(uploaded_data_kbit)
(data_session_duration)
KPI calculation
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Data Drive
bull There is 3 modulation technique QPSK16QAM64QAMbull For high through put 16QAM and 64QAM should have high Utilizationbull So if There is less Utilization of QPSK in downlink than data throughput is
also highbull CQI is like SQI in speech which ensure good channel quality for data
transferbull Retransmission of HS- DSCH(High-Speed Downlink Shared Channel) packet
is high than also throughput is decreasesbull In case of stationary Data Test- 2Mbits speed can be achieved bull In case of moving Vehicle ndash 800kbits to 12 Kbits speed can be achievedbull Application throughput is always 85 of physical layer data rate
throughput because at application level IP inclusion and overhead information will be there
bull Latency time is round trip time from server and for 3G it should be 150 ms for 32 bit data
bull The modulation scheme and coding is changed on a per-user basis depending on signal quality and cell usage The initial scheme is Quadrature phase-shift keying (QPSK) but in good radio conditions 16QAM and 64QAM can significantly increase data throughput rates With 5 Code allocation QPSK typically offers up to 18 Mbits peak data rates while 16QAM offers up to 36 Mbits Additional codes (eg 10 15) can also be used to improve these data rates or extend the network capacity throughput significantly
bull Data Throughput will be also depend on MS class which support 510 and 15 codes resp
bull CQI- Channel quality indication may include carrier level received signal strength indication (RSSI) and bit error rate (BER) I
bull Channel quality indicators are messages that are sent on a communication system (such as a mobile communication system) that provide the remote connection (eg base station) with channel quality information
Notes on quantities denoting signal power
KEY PERFORMANCE INDICATORS
Accessability (Call set-up success rate)
Retainability (Dropped calls)
Mobility (Handover success rate)
Integrity (BLER and throughput)
Integrity- quality
Integrity-throughput
What is the major difference in link budgets between UMTS and GSMTDMA In UMTS you generally have a link budget for each service (voice data video etc) in GSM you usually only use 1 for voice Each service has a different EbNo target In UMTS you have to consider the target traffic load you will have and add a noise-rise margin in GSM you may have a slight interference margin but not normally related to traffic In UMTS some services (like voice) will show up as uplink limited but other services (like HSDPA 384kbps service) will show as downlink limited In UMTS you usually have to consider that all users use the same power from the BTS therefore the more number of users the lower the maximumpower available per user (maximum power per connection) which is a starting point in the link budget
KPI Requirements Formula
CPICH RSCP ge-95dBm NA(nbr_of_samples_RSCPgt=-95dBm)
(tot_nbr_of_samples_RSCP)
CPICH EcIo ge-12dB NA(nbr_of_samples_EcIogt=-12dB)
(tot_nbr_of_samples_EcIo)
Voice call setup success rate
Min ge98(nbr_of_successful_voice_call_setup)
(nbr_of_voice_call_attemp)
Voice call setup time(Mobile to 1764440)
le10s ge99(nbr_of_voice_call_setup_timele10s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
le9s ge95(nbr_of_voice_call_setup_timele9s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
Voice call drop rate Max le2(nbr_of_voice_call_drop)
[(call_duration_time)90sec]
PDP activation successful rate
Min ge99(nbr_of_PDP_context_activation_accept)(nbr_of_PDP_context_activation_request)
PDP activation delay le2s ge99
(nbr_of_PDP_activation_delayle2s)(nbr_of_PDP_context_activation_accept)
PDP_activation_delay= [T(PDP_context_activation_accept)- T(PDP_context_activation_request)]
PS 384k FTP DL Avg Throughput 280kbps(downloaded_data_kbit)(data_session_duration)
PS 384k FTP UL Avg Throughput 280kbps(uploaded_data_kbit)
(data_session_duration)
HSDPA FTP Avg Throughput 45Mbps(downloaded_data_kbit)(data_session_duration)
HSUPA FTP Avg Throughput 11Mbps(uploaded_data_kbit)
(data_session_duration)
KPI calculation
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
bull The modulation scheme and coding is changed on a per-user basis depending on signal quality and cell usage The initial scheme is Quadrature phase-shift keying (QPSK) but in good radio conditions 16QAM and 64QAM can significantly increase data throughput rates With 5 Code allocation QPSK typically offers up to 18 Mbits peak data rates while 16QAM offers up to 36 Mbits Additional codes (eg 10 15) can also be used to improve these data rates or extend the network capacity throughput significantly
bull Data Throughput will be also depend on MS class which support 510 and 15 codes resp
bull CQI- Channel quality indication may include carrier level received signal strength indication (RSSI) and bit error rate (BER) I
bull Channel quality indicators are messages that are sent on a communication system (such as a mobile communication system) that provide the remote connection (eg base station) with channel quality information
Notes on quantities denoting signal power
KEY PERFORMANCE INDICATORS
Accessability (Call set-up success rate)
Retainability (Dropped calls)
Mobility (Handover success rate)
Integrity (BLER and throughput)
Integrity- quality
Integrity-throughput
What is the major difference in link budgets between UMTS and GSMTDMA In UMTS you generally have a link budget for each service (voice data video etc) in GSM you usually only use 1 for voice Each service has a different EbNo target In UMTS you have to consider the target traffic load you will have and add a noise-rise margin in GSM you may have a slight interference margin but not normally related to traffic In UMTS some services (like voice) will show up as uplink limited but other services (like HSDPA 384kbps service) will show as downlink limited In UMTS you usually have to consider that all users use the same power from the BTS therefore the more number of users the lower the maximumpower available per user (maximum power per connection) which is a starting point in the link budget
KPI Requirements Formula
CPICH RSCP ge-95dBm NA(nbr_of_samples_RSCPgt=-95dBm)
(tot_nbr_of_samples_RSCP)
CPICH EcIo ge-12dB NA(nbr_of_samples_EcIogt=-12dB)
(tot_nbr_of_samples_EcIo)
Voice call setup success rate
Min ge98(nbr_of_successful_voice_call_setup)
(nbr_of_voice_call_attemp)
Voice call setup time(Mobile to 1764440)
le10s ge99(nbr_of_voice_call_setup_timele10s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
le9s ge95(nbr_of_voice_call_setup_timele9s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
Voice call drop rate Max le2(nbr_of_voice_call_drop)
[(call_duration_time)90sec]
PDP activation successful rate
Min ge99(nbr_of_PDP_context_activation_accept)(nbr_of_PDP_context_activation_request)
PDP activation delay le2s ge99
(nbr_of_PDP_activation_delayle2s)(nbr_of_PDP_context_activation_accept)
PDP_activation_delay= [T(PDP_context_activation_accept)- T(PDP_context_activation_request)]
PS 384k FTP DL Avg Throughput 280kbps(downloaded_data_kbit)(data_session_duration)
PS 384k FTP UL Avg Throughput 280kbps(uploaded_data_kbit)
(data_session_duration)
HSDPA FTP Avg Throughput 45Mbps(downloaded_data_kbit)(data_session_duration)
HSUPA FTP Avg Throughput 11Mbps(uploaded_data_kbit)
(data_session_duration)
KPI calculation
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Notes on quantities denoting signal power
KEY PERFORMANCE INDICATORS
Accessability (Call set-up success rate)
Retainability (Dropped calls)
Mobility (Handover success rate)
Integrity (BLER and throughput)
Integrity- quality
Integrity-throughput
What is the major difference in link budgets between UMTS and GSMTDMA In UMTS you generally have a link budget for each service (voice data video etc) in GSM you usually only use 1 for voice Each service has a different EbNo target In UMTS you have to consider the target traffic load you will have and add a noise-rise margin in GSM you may have a slight interference margin but not normally related to traffic In UMTS some services (like voice) will show up as uplink limited but other services (like HSDPA 384kbps service) will show as downlink limited In UMTS you usually have to consider that all users use the same power from the BTS therefore the more number of users the lower the maximumpower available per user (maximum power per connection) which is a starting point in the link budget
KPI Requirements Formula
CPICH RSCP ge-95dBm NA(nbr_of_samples_RSCPgt=-95dBm)
(tot_nbr_of_samples_RSCP)
CPICH EcIo ge-12dB NA(nbr_of_samples_EcIogt=-12dB)
(tot_nbr_of_samples_EcIo)
Voice call setup success rate
Min ge98(nbr_of_successful_voice_call_setup)
(nbr_of_voice_call_attemp)
Voice call setup time(Mobile to 1764440)
le10s ge99(nbr_of_voice_call_setup_timele10s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
le9s ge95(nbr_of_voice_call_setup_timele9s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
Voice call drop rate Max le2(nbr_of_voice_call_drop)
[(call_duration_time)90sec]
PDP activation successful rate
Min ge99(nbr_of_PDP_context_activation_accept)(nbr_of_PDP_context_activation_request)
PDP activation delay le2s ge99
(nbr_of_PDP_activation_delayle2s)(nbr_of_PDP_context_activation_accept)
PDP_activation_delay= [T(PDP_context_activation_accept)- T(PDP_context_activation_request)]
PS 384k FTP DL Avg Throughput 280kbps(downloaded_data_kbit)(data_session_duration)
PS 384k FTP UL Avg Throughput 280kbps(uploaded_data_kbit)
(data_session_duration)
HSDPA FTP Avg Throughput 45Mbps(downloaded_data_kbit)(data_session_duration)
HSUPA FTP Avg Throughput 11Mbps(uploaded_data_kbit)
(data_session_duration)
KPI calculation
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
KEY PERFORMANCE INDICATORS
Accessability (Call set-up success rate)
Retainability (Dropped calls)
Mobility (Handover success rate)
Integrity (BLER and throughput)
Integrity- quality
Integrity-throughput
What is the major difference in link budgets between UMTS and GSMTDMA In UMTS you generally have a link budget for each service (voice data video etc) in GSM you usually only use 1 for voice Each service has a different EbNo target In UMTS you have to consider the target traffic load you will have and add a noise-rise margin in GSM you may have a slight interference margin but not normally related to traffic In UMTS some services (like voice) will show up as uplink limited but other services (like HSDPA 384kbps service) will show as downlink limited In UMTS you usually have to consider that all users use the same power from the BTS therefore the more number of users the lower the maximumpower available per user (maximum power per connection) which is a starting point in the link budget
KPI Requirements Formula
CPICH RSCP ge-95dBm NA(nbr_of_samples_RSCPgt=-95dBm)
(tot_nbr_of_samples_RSCP)
CPICH EcIo ge-12dB NA(nbr_of_samples_EcIogt=-12dB)
(tot_nbr_of_samples_EcIo)
Voice call setup success rate
Min ge98(nbr_of_successful_voice_call_setup)
(nbr_of_voice_call_attemp)
Voice call setup time(Mobile to 1764440)
le10s ge99(nbr_of_voice_call_setup_timele10s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
le9s ge95(nbr_of_voice_call_setup_timele9s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
Voice call drop rate Max le2(nbr_of_voice_call_drop)
[(call_duration_time)90sec]
PDP activation successful rate
Min ge99(nbr_of_PDP_context_activation_accept)(nbr_of_PDP_context_activation_request)
PDP activation delay le2s ge99
(nbr_of_PDP_activation_delayle2s)(nbr_of_PDP_context_activation_accept)
PDP_activation_delay= [T(PDP_context_activation_accept)- T(PDP_context_activation_request)]
PS 384k FTP DL Avg Throughput 280kbps(downloaded_data_kbit)(data_session_duration)
PS 384k FTP UL Avg Throughput 280kbps(uploaded_data_kbit)
(data_session_duration)
HSDPA FTP Avg Throughput 45Mbps(downloaded_data_kbit)(data_session_duration)
HSUPA FTP Avg Throughput 11Mbps(uploaded_data_kbit)
(data_session_duration)
KPI calculation
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
KPI Requirements Formula
CPICH RSCP ge-95dBm NA(nbr_of_samples_RSCPgt=-95dBm)
(tot_nbr_of_samples_RSCP)
CPICH EcIo ge-12dB NA(nbr_of_samples_EcIogt=-12dB)
(tot_nbr_of_samples_EcIo)
Voice call setup success rate
Min ge98(nbr_of_successful_voice_call_setup)
(nbr_of_voice_call_attemp)
Voice call setup time(Mobile to 1764440)
le10s ge99(nbr_of_voice_call_setup_timele10s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
le9s ge95(nbr_of_voice_call_setup_timele9s)
(nbr_of_successful_voice_call_setup)voice_call_setup_time =[T(CC_alerting) - T(first_RRC_connection_request)]
Voice call drop rate Max le2(nbr_of_voice_call_drop)
[(call_duration_time)90sec]
PDP activation successful rate
Min ge99(nbr_of_PDP_context_activation_accept)(nbr_of_PDP_context_activation_request)
PDP activation delay le2s ge99
(nbr_of_PDP_activation_delayle2s)(nbr_of_PDP_context_activation_accept)
PDP_activation_delay= [T(PDP_context_activation_accept)- T(PDP_context_activation_request)]
PS 384k FTP DL Avg Throughput 280kbps(downloaded_data_kbit)(data_session_duration)
PS 384k FTP UL Avg Throughput 280kbps(uploaded_data_kbit)
(data_session_duration)
HSDPA FTP Avg Throughput 45Mbps(downloaded_data_kbit)(data_session_duration)
HSUPA FTP Avg Throughput 11Mbps(uploaded_data_kbit)
(data_session_duration)
KPI calculation
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Case 1 Drop due to missing neighborProblem Detected Nighbor (DN)bull UE sends a Measurement Report that contains an event1a means adding a new RL
(cell) to Active Setbull If the reported cell is not in the current neighbor cell list and the reported EcNo is
better than the best serving cell EcNo in AS by some dBs (set by a RNC parameter)bull If for any reason the new cell can not be added to AS call will be released2 If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop missing neighbor cell is probable Confirm it by measurement control (search the messages back from call drop for the latest intra-frequency measurement control message Check the neighbor cell list of this measurement control message)
3 UEs might report detected set information If corresponding scramblling code information is in the monitor set before call drop the cause must be missing neighbor cell
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Weak Coverage
bull Weak coverage usually refers to weak RSCP
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by the following methods
bull If the uplink transmission power reaches the maximum before call drop the uplink BLER is weak the call drop is probably due to weak uplink coverage
bull Out of Uplink coverage may be caused by not only by low CPICH_RSCP But also by high UL_RSSI
bull If the downlink transmission power reaches the maximum before call drop and the downlink BLER is weak the call drop is probably due to weak downlink coverage High downlink RSSI received by UE is an indication of weak coverage during that time UE tries to increase its target SIR to listen to the network
Multipath propagation yields signal paths of different lengths withdifferent times of arrival at the receiver Typical values of timedelays (μs) are 02 in Open environment 05 Suburban and 3 inUrban
When coded data rates of services are incompatibleldquoRate Matchingrdquo is used to equalize the data ratesndash Rate Matching may be performed by1048707 Padding with extra bits1048707 Puncturing of bits using a pseudo-random algorithm
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Case 2 Drop due to Poor Coverage (low RSCP)Problem Poor DL coverageWhen UE gets to an area with low RSCP ( lt -105 dBm)regardless EcNo values there is high risk for dropUE will likely ramp up the transmitted power and reach its max power The UL BLER will probably increase and SIR target cannot maintain anymore finally the call drops
Explain the concept of Cell Breathing How is the accounted for in the linkBudget Ans Io or No (the interference part of EcIo and EbNo) increase as the traffic on the network increases since everyone is using the same frequency Therefore as Io or No increases the UE or BTS needs to use more power to maintain the same EbNo or EcIo When the power required is more thanthe maximum power allowed the connection cannot be made Users at the cell edge are usually the first to lose service hence the service area of a cell shrinks As traffic decreases the reverse happens and the service area increases They should say that it is accounted for in the Noise Rise Margin found in the Link Budget
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Interference
In downlink when the active set CPICH RSCP is greater than ndash85 dBm and the active set EcIo is gt= ndash12 dB the call drop is probably due to downlink interference Downlink interference usually refers to pilot pollution
Interference in Uplink is detected when the Uplink RTWP exceeds a certain configurable Threshold In general Expected level of RTWP is formed by sum of the the following components 1Thermal noise floor (KTB =-108132dBm) 2Node B noise figure (Typically 18 dB for our equipment) 3Noise raise due to load (50 load in Uplink corresponds to 3 db) 4Compensation for inaccuracies in Radio NW algoriths (2dB)WHAT IS THE PILOT POLLUTION Area where the SIR (Signal interference ratio) is too low and below the expected value (EcIo gt= -12 dB) there is too much interference =gt the mobile cannot understand the pilot channel
HOW TO REDUCE THE PILOT POLLUTION PROBLEM Maximise the signal inside the best server Minimise the energy overshoot from the neighbor cells with some RF consideration (tilt azimuthhellip)
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Pilot Pollution
Excessive strong pilots exist at a point but no one is strong enough to be primary pilot
1 Definition of strong pilot (CPICH_RSCP gt ThRSCP)
2 Definition of Excessive CPICH_Number gt ThN
3 Definition of no best server strong enoughrdquo CPICH_RSCP1st-CPICH_RSCP(ThN+1)th lt ThRSCP_Relative
Following is the case from cluster Mongkok West Probable Solution adjust engineering parameters of an antenna so that a best server forms around the antenna For handover problems caused by pilot pollution adjust engineering parameters of other antennas so that signals from other antennas becomes weaker and the number of pilots drops For this case reduce antenna height of site SGI
Many definitions A cell that has a high signal strength at a location but is not part of the active set A cell that meets thecriteria for addition into the Active Set but can not enter because the active set is full
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
1UE fails to receive active set update command (Delayed Handover)
After UE reports measurement message the EcIo of original cell signals decreases sharply When the RNC sends active set update message the UE powers off the transmitter due to asynchronization The UE cannot receive active set update messageThis may be due to EcIo of original cell decreases sharply and that of the target cell increases greatly (Turnings)
2 The best server changes frequently Two or more cells alternate to be the best server The RSCP of the best server is strong The period for each cell to be the best server is short
Probable solution Lower the triggering time for event 1a adjust antennas to expand the handover area
adjust the antenna to form a best serverreduce Ping-pong handover by setting the handover parameter of 1B event
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
17
Radio Interface Protocol Architecture
RadioInterfaceProtocol
Architecture
Transport Channel (SAP)
Physical Channels
Logical Channel
L3
cont
rol
cont
rol
cont
rol
cont
rol
LogicalChannels
TransportChannels
C-plane signalling U-plane information
PHY
L2MAC
L1
RLC
DCNtGC
L2RLC
MAC
RLCRLC
RLCRLC
RLCRLC
RLC
Duplication avoidance
UuS boundary
BMC L2BMC
RRC
control
PDCPPDCP L2PDCP
DCNtGC
Packet Data Convergence Protocol
Is only for PS domain services
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
18
Radio Interface protocol architecture
L2MAC
L2RLC
L1
RLC
MAC
L3RRC
PHY
TransportChannels
LogicalChannels
C-plane signallingU-plane information
GC Nt DC
RLC RLC
RLC
GCNTDCRRCRLCMAC
General ControlNotificationDedicated ControlRadio Resource ControlRadio Link ControlMedium Access Control
UTRA Protocol Architecture
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
19
Logical Channel StructureS y n c h r o n i s a t i o n C o n t r o l C h a n n e l ( S C C H )
B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )
P a g i n g C o n t r o l C h a n n e l ( P C C H )
D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )C o m m o n C o n t r o l C h a n n e l ( C C C H )
C o n t r o l C h a n n e l ( C C H )
D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )
O D M A D e d i c a t e d C o n t r o l C h a n n e l ( O D C C H )
O D M A C o m m o n C o n t r o l C h a n n e l ( O C C C H )
O D M A D e d i c a t e d T r a f f i c C h a n n e l ( O D T C H )
C o m m o n T r a f f i c C h a n n e l ( C T C H )
S h a r e d C h a n n e l C o n t r o l C h a n n e l ( S H C C H )
(TDD)
(ODMA)
(ODMA)
(TDD)
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
20
Channels
Transport Channels
Dedicated Transport Channel (DCH) ULDL mapped to DCCH and DTCHBroadcast Channel (BCH) DL mapped to BCCHForward Access Channel (FACH) DL mapped to BCCH CCCH CTCH DCCH and DTCHPaging Channel (PCH) DL mapped to PCCHRandom Access Channel (RACH) UL mapped to CCCH DCCH and DTCHUplink Common Packet Channel (CPCH) UL mapped to DCCH and DTCHDownlink Shared Channel (DSCH) DL mapped to DCCH and DTCH
The speech service in UMTS will employ the AdaptiveMulti - rate technique1048707 This is a single integrated codec with eight source rates122 102 795 740 670 590 515 and 475 kbps Tofacilitate interoperability with existing cellular networkssome of the modes are the same as in existing networks
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
21
ChannelsPhysical Channels
Primary Common Control Physical Channel (PCCPCH) mapped to BCHSecondary Common Control Physical Channel (SCCPCH) mapped to FACH PCHPhysical Random Access Channel (PRACH) mapped to RACHDedicated Physical Data Channel (DPDCH) mapped to DCHDedicated Physical Control Channel (DPCCH) mapped to DCHPhysical Downlink Shared Channel (PDSCH) mapped to DSCHPhysical Common Packet Channel (PCPCH) mapped to CPCHSynchronisation Channel (SCH)Common Pilot Channel (CPICH)Acquisition Indicator Channel (AICH)Paging Indication Channel (PICH)CPCH Status Indication Channel (CSICH)Collision DetectionChannel Assignment Indication Channel (CDCA-ICH)
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
AMR
The bit rate of the AMR speech connection is controlled by theradio access network depending on the air interface loading and thequality of the speech connections During high loading such asduring busy hours it is possible to use lower AMR bit rates to offerhigher capacity while providing slightly lower speech quality Alsoif the mobile is running out of the cell coverage area and using itsmaximum transmission power a lower AMR bit rate can be used toextend the cell coverage area
Adaptive multi-rate also contains error concealment The purposeof frame substitution is to conceal the effect of lost speech framesIf several frames are lost muting is used to prevent possiblyannoying sounds as a result of the frame substitutionIn P5 with AMR NB it is possible to use lower speech codec ratesthan 122 kbps The radio network also supports 795 kbps 59kbps and 475 kbps AMR codecs There is no adaptation in thesense that AMR codecs are changed during an ongoing speechconnection rather there is a possibility to adapt the rate at initialselection
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
23
Link Budget
bull Cell range amp cell capacity are limited by the same parameters Interference in uplink Power in downlink
bull Cell breathing phenomenon
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
ldquoPowerrdquo Link Budget
Tx power + All Gains ndash Path Loss ndash Other losses = Rx powerTx power + All Gains ndash Path Loss ndash Other losses = Rx power
Path loss = Tx Signal + All Gains ndash Other losses ndash Rx powerPath loss = Tx Signal + All Gains ndash Other losses ndash Rx power
Max Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivityMax Path loss = Tx Signal + All Gains ndash Other losses ndash Rx sensitivity
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
25
Initial Cell Search
The initial Cell Search is carried out in three steps
Step 1 Slot synchronisation - using the primary synchronisation channel
Step 2 Frame synchronisation and code-group identification- using the secondary synchronisation channel
Step 3 Scrambling-code identification-identified through symbol- by-symbol correlation over the primary CCPCH with all the scrambling codes within the code group
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
26
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
27
Frame Synchronization
helliphellip
2560 chips
acp
Slot
P-SCH acp
Slot
16 11S-SCH
acp
Slot
2 Group 4Slot 121314
slot number Scrambling Code Group 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16
Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10
Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12
Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7
Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2
hellip
Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11
Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16
Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10
256 chips
S-SCH
P-SCH
512 Primary Scrambling Codes divided into 64 groups
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
28
Slot Synchronization
P-SCH1
P-SCH3
P-SCH2
P-SCH1S-SCH1 P-CCPCH P-CCPCH
P-SCH2S-SCH2 P-CCPCH P-CCPCH
P-SCH3S-SCH3 P-CCPCH P-CCPCHP-CCPCH
1 Slot = 667ms
UE synchronizes on the strongest correlation peak
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
29
Cell Information
P-SCH Coverage indication Slot Synchronization
S-SCH Frame Synchronization Group identification
P-CPICH Scrambling Code Identification
P-CCPCH System Information Broadcast
Logical Channel
BCCH
Transport Channel
BCH
Physical Channel
P-CCPCH
OVSF Cch2561
Primary Scrambling CodeTransmitted during 910th slot
Bit Rate 123 kbps RLC Mode transparentMac-B transparent
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
30
Intra-Frequency Cell Reselection sample
Time
Quality
Serving CellServing Cell
Neighboring Cell
Neighboring Cell
Neighboring cell criterion S
is fulfilled and is ranked
Neighboring cell better ranking
than Serving cell
UE perform cell reselection
Treselections
Qmeans + Qhyst2s
Qmeann - Qoffset2sn
Qqualmin
UE perform intra-frequency measurements
Qqualmin + SIntraSearch
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
31
Cell selection and reselection Cell Selection criteria
The cell selection criterion S is fulfilled when
where
Squal = Qqualmeas ndash Qqualmin
Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation
Pcompensation ＝ max(UE_TXPWR_MAX_RACH ndash P_MAX 0)
for FDD cells Srxlev gt 0 AND Squal gt 0
for TDD cells Srxlev gt 0
for GSM cells Srxlev gt 0
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
32
Cell Selection Parameters
Parameter Object Range Default Value Recommended Value Class
qQualMin CellSelectionInfo Int [-240](dB)
-10 -16 C2
qRxLevMin CellSelectionInfo Int [-115-25]Step = 2 (dBm)
-45 -115 C2
maxAllowedUlTxPower UlUsPowerConf Int [-5033](dBm)
33 33 C3
P_Max = maximum UE output power (dBm) according to its class
Power Class Maximum Output Power (dBm)
1 33
2 27
3 24
4 21
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
33
Cell Reselection Procedure
Squal
SintraSearch
SinterSearch
SinterRATMeasurement on same frequency Measurement on
other frequencies Measurement on other RAT
If Squal = CPICH_EcNo ndash qQualMin lt Threshold
Associated measurements are performed
Thresholds are broadcasted in SIB 11In UMTS02 2 types of measurements are done Intra frequency and inter RAT
Thr
eseh
olds
giv
en a
s ex
ampl
e
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
34
Cell Reselection ParametersParameter Object Range Default Value Recommended Value Class
qHyst1 CellSelectionInfo Int [040] (dBm)Step = 2
10 4 C2
qHyst2 CellSelectionInfo Int [040] (dB)Step = 2
4 6 C2
qOffset1sn GSMCell Int [-5050] (dB) 0 TBD C0
qOffset2sn UMTSFDDNeighbouring Int [-5050] (dB) 0 TBD C0
qualMeas CPICH_EcNo or CPICH_RSCP
CPICH_EcNo NA Static
tReselection CellSelectionInfo Int [031] (s) 31 6 C2
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
35
Measurements
The different types of air interface measurements are
bull Intra-frequency measurements measurements on downlink physical channels at the same frequency as the active set A measurement object corresponds to one cell
bull Inter-frequency measurements measurements on downlink physical channels at frequencies that differ from the frequency of the active set A measurement object corresponds to one cell
bull Inter-RAT measurements measurements on downlink physical channels belonging to another radio access technology than UTRAN eg GSM A measurement object corresponds to one cell
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
36
Handover (Handoff)bull There are following categories of handover (also referred to as handoff)
bull Hard handover means that all the old radio links in the UE are removed before the new radio links are established Hard handover can be seamless or non-seamless Seamless hard handover means that the handover is not perceptible to the user In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover
bull Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN Soft handover is performed by means of macro diversity which refers to the condition that several radio links are active at the same time
bull Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (ie the site of co-located base stations from which several sector-cells are served
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
37
Handover (Handoff)
bull The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission less interference) It may however also be performed for other reasons such as system load control
bull Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (ie the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set)
bull The maximum active set size at the RNC is determined by the parameter MaxAciveSetSize
bull 3 to 4 cells the larger the active set size the more likely it is that Iub link efficiency is reduced (more than one resource for a single connection due to SHO)
bull Cells which are not included in the active set but are included in the CELL_INFO_LIST belong to the Monitored Set
bull Cells detected by the UE which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
38
PRIMARY CELL ELECTION ALGORITHM (MONITORED SET UPDATE)
bull The primary cell election algorithm applies to soft HO It is used for monitored set determination and a pointer to mobility parameter
bull The Monitored Set should be updated each time the primary cell of active set changes A measurement control message is sent (with measurement commend set to modify) is sent to the UE in order to update the monitored set The message contains the cell to addremove from the monitored and should follow the ACIVE SET UPDATE message
bull The primary cell algorithm is called from SHO algorithm therefore it is performed each time a MEASUREMENT REPORT is received by the SRNC
Measurement control used for monitored set update
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Compressed modebull Compressed mode is when the mobile goes into a slotted transmit mode whereby
it opens up an idle period (transmission gap) where it can monitor another carrier or technology (GSM) The impact is that to maintain the same bit rate it halves the SF and therefore increases power level causing higher interference to the network If the SF cannot be halved then the bit rate of the bearer decreases If they seem knowledgably ask them if they know what messages and events trigger and configure compressed mode onoff 2D event for on 2F for off Messages would for configuration would be RADIO BEARER RECONFIGURATION TRANSPORT CHANNEL RECONFIGFURATION or PHYSICAL CHANNEL RECONFIGURATION
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
40
Compressed Mode bull During inter-frequency handover the UErsquos must be given time to make the necessary measurements on the different WCDMA
carrier frequency 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover)
bull Why is compressed mode neededndash In UTRAN FDD transmissionreception by the mobile is continuous no idle periods are available for monitoring other frequencies if
the UE has only a single receiver
bull How is it donendash Transmission gaps are created in the radio frame in DL andor UL to allow the UE to switch to another frequency perform
measurements on another carrier (FDD TDD or GSM) and switch backndash Transmission gaps are positioned in one radio frame or at the boundary of 2 radio frames in regular intervals referred to as a
transmission gap pattern sequencebull no more than 7 slots are used in any one radio frame to create the transmission gap
bull How is it donendash Two approaches can be taken in creating the transmission gaps of the transmission gap pattern sequence
bull Modifiy the physical layer parameters (by puncturing or spreading factor reduction) to allow all information bits to be transmitted
bull Restrict the bit rate (by higher layer scheduling) to match the fewer available transmission slots in a compressed radio frame
ndash In both approaches the goal is to not loose transmission framesbull Who controls it
ndash Compressed mode is under the control of the UTRANndash Compressed mode is configured by the RNC per UE in the form of transmission gap pattern sequences
bull given to the UE via RRC signallingbull given to the node B via NBAP signallingbull a transmission gap pattern sequence is associated with a specific measurement purpose
ndash FDD measurements ndash TDD measurements ndash GSM initial BSIC identification GSM BSIC reconfirmation
GSM RSSI measurement
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
41
Physical layer Aspects Compressed Mode Methods
bull Three methods are available to create transmission gapsndash Puncturing additional puncturingfewer repetitions are performed compared to
normal mode bull to be used only in DLbull to be used only in the case of mapping to fixed positionsbull scrambling and channelisation code remain unchanged
ndash Spreading Factor Reduction SF is divided by 2bull can be used in UL and DLbull can be used with mapping to flexible positionsbull to be used only when SFgt4bull only 2nd DTX insertion and physical channel mapping is modifiedbull may lead to channelisation code shortage and the need to use a secondary scrambling code
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
42
Cell Shakedown
bull Purposendash To test Call Setup (Voice and FTP) in each cellndash To test Handoffs (Soft and Softer) between Cellsndash Verify antenna orientationndash Primary Pilot EcIondash Scrambling Code for each cellndash UE transmit powerndash Path Balance
bull Methodndash By driving clockwise and anticlockwise within a designated route
around the the base station (about 30 of the site coverage area)
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
43
Difference between Scanner data amp UE Data Collection
bull Scannerbull Primary Common Pilot Channel (P-CPICH)
scrambling code measurementsbull Continuous Wave (CW) measurementsbull Spectrum analysisbull Synchronization Channel (SCH) code word
measurements
bull UEbull DataVoiceVideo Callsbull Layer 3 messages loggingbull Layer 2 messages logging (Transport channel)bull RRC State loggingbull UE Transmit Powerbull SIRbull Serving Cell Active Set Monitored Setbull Events bull GSM neighbor measurements
bullDifference in data collection Antenna Cable Sampling
bullSolution Perform a calibration drive
An overview of cluster performance based on scanner Best Serving CPICH RSCP and EcIo measured data
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Inner loop amp Scannerbull In pre-launch optimization
how are missing neighbors usually detected
bull Usually you use a scanner and compare the best pilots in EcIo from the scanner against that of the active set and monitored set from an active UE If there is a stronger pilot from a nearby cell that appears on the scanner but not on the UE there is a possible missing neighbor One would thenverify that the neighbor appears in defined neighbor list from the OSS
Explain Inner and Outer loop power control and who controls themIf they start talking about Open and Closed Loop PC tell them you want InnerOuter Closed Loop PC Inner loop power control is performed by the NodeB to set the transmitpower of the UE and BTS to compensate for signal variations due to fading or pathloss to maintain the set SIR (occurs up to 1500 times per sec) Outer loop power control is performed by the RNC to set the target SIR based on the required BERBLER for the requested services (occurs up to 100 times per sec)
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
45
Drop after active set update
Symptombull Normally the observed sequent messages in the UE side are
ndash UTRAN -gt UE Active set update (to request the UE to remove a cell eg SC281)ndash UE -gt UTRAN Active set update completendash UTRAN -gt UE Measurement Control (update neighbour list)ndash UE -gt UTRAN Measurement report (to propose to add7)ndash UTRAN -gt UE Active set update (to request the UE to add SC 137)ndash DROP(since no Active set update completion was sen after 12 secs )
bull The radio performances no matter DL and UL are very good
Possible solution No solution check this problem with UE vendor
bull In Softbull Handover the UE is connected to more than one Radio Base Stationbull (RBS) simultaneously At least one radio link is always active andbull there is no interruption in the dataflow during the actual handoverbull The signals are received in the UE and combined in the RAKEbull receiver to give protection against fading
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
46
SoftSofter Handover Radio Link Addition and
Radio Link Removal
ReferenceUser Description and Engineering Guidelines 751551-HSD 101 021 Uen B2
copy Ericsson AB 2003 - All Rights Reserved
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
47
Drop after active set update Cont
BLER is getting worse
RF conditionis ok
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
48
Drop after active set update Cont
No Active Set Completion was sent after Active Set Update
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
FINAL WORDS
bull For network tuning we need to relay on field measurements which require extensive drive testsbull Finding the best possible configuration for antenna heights tilts azimuths and parameter setting for all the
present cellssectors in the network and also for any new sites that might be needed to improve coveragebull Power adjustment can also be used for network tuning but can become complicated and result in poor
network performancebull Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antennabull Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference
reduction) Keep neighbour list upto 20 bull Automated tools are needed that could suggest the best possible neighbour relations antenna heights and
tilts by using both the field measurements and the propagation models amp simulations bull Skilled people right methods and advanced tools are needed to perform 3G tuning and optimisation
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
If a UE is on a data call (CELL-DCH state) and there is in no activity for awhile what would you expect to see occurUE should go from CELL-DCH to CELL-FACH then if still no activity to either CELL-PCH or URA-PCH (via CELL-FACH) If they talk about inactivity timers and mention that the state goes from CELL-DCH straight to CELL-PCH or URA-PCH that is also possible Bonus they say they would see RADIO BEARER RECONFIGURATION messages when the states are changing
Name the 4 RRC Connected Modes (states) and describe the characteristics of eachCell-DCH UE has been allocated a dedicated physical channel inuplink and downlinkCell-FACH UE listens to RACH channel (DL) and is allocated a FACH channel (UL) Small amounts of ULDL data can be transfers in this state The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE messageCell-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the cell level and cell reselections are possible with the CELL UPDATE message No data can be transferred in the UL in this stateURA-PCH UE monitors (using discontinuous reception) a PCH channel (PCH) indicated by the PICH channel The RNC tracks the UE down to the URA level
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
Power control
In the uplink the base station measures the received Signal-to-Interference Ratio (SIR) and compares this to a target SIR If themeasured SIR is below the target then the base station requests themobile to increase its power (and vice versa) This type of powercontrol is known as the Inner-loop power control and is capable ofadjusting the transmit power in steps of for example 1 dB at a rateof 1500 times per second Inner-loop power control is onlyapplicable for connections on dedicated channels
