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Aalborg University, RATE/TBS, 2006slide 1
SIPCOM9-2, lecture 10MultiUserComm
Multi-User Communication
Lecture 10
WCDMA Overview
Aalborg University, RATE/TBS, 2006slide 2
SIPCOM9-2, lecture 10MultiUserComm
Objective
Introduce WCDMA
from a systems perspective, but with a focuson lower layers (FDD mode)
WCDMA Release 99
giving you, hopefullya technology context to which you can apply
e.g. the theory on multi-user communication
a system context from which you can explorerecent advances on WCDMA (HSxPA) and itsevolution (LTE)
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Aalborg University, RATE/TBS, 2006slide 3
SIPCOM9-2, lecture 10MultiUserComm
Outline
WCDMA introduction
UMTS and 3GPP specifications
UTRAN architecture
Basic radio resource management
Physical layer channels and procedures
Short on TDD mode
MUD in WCDMA uplink (gain potential)
References
Acronyms
Aalborg University, RATE/TBS, 2006slide 4
SIPCOM9-2, lecture 10MultiUserComm
WCDMA
UE 1Time
(Code) Power
UE 2
UE 3
UE 4
Node BUE
Available resources:Spreading Codes (OVSF)
andTransmission Power
Soft/Softer
Handover
non-orth
ogonal
codes
orthogonalcodes
DATA
Bit rate Chip rate
Channelisationcode
Scrampling
code
Chip rate
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Aalborg University, RATE/TBS, 2006slide 5
SIPCOM9-2, lecture 10MultiUserComm
3
5
4
6
7
8
10
9
Cellrange(km)
Maximump
athloss(dB)
100 200 300 400 500 600 700 800 900 1000
145
150
155
160
165
Cell load (kbps)
Downlink 10WDownlink 20W
Uplink(144 kbps / 125 mW terminal)
Typisk maks. tab
3 dB forbedring af dkningsomrde
Downlink 20W
Dkning er
begrnset
af uplink
Kapacitet er
begrnset
af downlink
WCDMA Coverage
and Capacity
Aalborg University, RATE/TBS, 2006slide 6
SIPCOM9-2, lecture 10MultiUserComm
3GPP Specifications
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Aalborg University, RATE/TBS, 2006slide 7
SIPCOM9-2, lecture 10MultiUserComm
UMTS releases
v3.0.0 v3.1.0 v3.2.0 v3.3.0 v3.4.0
v4.0.0 v4.1.0 v4.2.0
v5.0.0 v5.1.0
etc.
Corrections
New Functions
Release 99
Release 403/01
Release 5
12/99
06/02
Release 606/05 v6.0.0
etc.
etc.
etc.
Standardized by 3rd Generation Partnership Project (3GPP), see http://www.3gpp.org [North America: 3GPP2]
UMTS LongTerm Evolution
UMTS used for designating 3rd generation systems (ITU: IMT-2000)
Aalborg University, RATE/TBS, 2006slide 8
SIPCOM9-2, lecture 10MultiUserComm
3GPP specs
Main rule for 3GPP specifications (http://www.3gpp.org): XX.INN
XX: series specification
I: (0) applies to both 3G and GSM (GPRS/EDGE)
(1,2) applies to 3G only
GSM means GERAN 3GPP RAN while 3G means a 3GPP UTRAN RAN
Examples TS25.211 (v. 6.1.0), Physical channels and mapping of transport channels onto physical
channels (FDD), release 6, Technical Specification Group Radio Access Network, July
2004
TS25.213 (v. 6.0.0), Spreading and Modulation (FDD), Technical Specification GroupRadio Access Network, December 2003
TS25.104 (v. 6.8.0), Base Station (BS) radio transmission and reception (FDD),Technical Specification Group Radio Access Network, December 2004
TS25.212 (v. 6.3.0), Multiplexing and channel coding (FDD), Technical SpecificationGroup Radio Access Network, December 2004
TR25.887 (v. 6.0.0), Beamforming enhancements (release 6), Technical SpecificationGroup Radio Access Network, March 2004
TR25.876 (v. 1.7.0), Multiple input multiple output in UTRA, Technical SpecificationGroup Radio Access Network, August 2004
TR25.869 (v. 1.2.1), Tx diversity solutions for multiple antennas, TechnicalSpecification Group Radio Access Network, February 2004
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Aalborg University, RATE/TBS, 2006slide 9
SIPCOM9-2, lecture 10MultiUserComm
3GPP Series
Aalborg University, RATE/TBS, 2006slide 10
SIPCOM9-2, lecture 10MultiUserComm
UTRAN Architecture
UMTS Terrestrial Radio Access Network
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Aalborg University, RATE/TBS, 2006slide 11
SIPCOM9-2, lecture 10MultiUserComm
Radio-specific part
Public Land Mobile Network
UTRAN/GERAN
Uu/Um
CNUE/MS
Iu
From Release 5 GSM and UMTS have the same interface to the radio
specific part of the network
PLMN Architecture
Aalborg University, RATE/TBS, 2006slide 12
SIPCOM9-2, lecture 10MultiUserComm
Uu/Um
Node B/BTS
RNC/BSC
Node B/BTS
Node B/BTS
Node B/BTS
RNC/BSC
USIM
ME
Iub/Abis
Iur
MSC/VLR
GMSC
SGSN GGSN
HLR/AuC
UTRAN/GERAN
UE/MS CN External Network
Iu
PLMN, PSTN,
ISDN, etc.
Internet,X25, etc.
PLMN
CS
PS
Radio-specific part
Public Land Mobile Network
PLMN Architecture
The geographical area covered by a PLMN is
partitioned into MSC serving areas; a location
area is a subset of a single MSC serving area.
Typically, there is one (logically speaking)
HLR in an operators PLMN.
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Aalborg University, RATE/TBS, 2006slide 13
SIPCOM9-2, lecture 10MultiUserComm
BS C
BT S
BT S
BSS (RAN/ G ERAN)
RN C
Node B
Node B
U T R A N
ME
SIM
USIM
MS
SGSN
PS Domain
GGSN
CS MGW
CS Dom ai nHSS/AuC
RN C
MSC-Serv./VLRAbis
SIM-ME
Iu bisCu
Um
Uu
Iu CsGb
A
Iu PS
C
D
IurGn
Gr Gc
Gs
CS MG WMSC-Serv./VLR
CS MG W
G MSC-Serv.
I MS Dom ai n
(Release 5)
M b/ Gi
Cx
Mc
Nb
Nb
G/E/Nc
Nc
Mc
User E qu ipm ent Dom ain
A ccess Ne t work Dom ain Core Ne t work Dom ain
Inf rast ructure Domain
Circuit-switched core
network
MSC
Packet-switched core
network
SGSN
Aalborg University, RATE/TBS, 2006slide 14
SIPCOM9-2, lecture 10MultiUserComm
NRT Packet Switched Data
Protocol stack of a NRT packet switched session in UMTS Release 99
Retransmission, sequence numbering,flow control, multiplexing, etc.
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Aalborg University, RATE/TBS, 2006slide 15
SIPCOM9-2, lecture 10MultiUserComm
Basic RRM
Radio Resource Management
Aalborg University, RATE/TBS, 2006slide 16
SIPCOM9-2, lecture 10MultiUserComm
I
u
b
I
u
b
Uu Iub
UE Node B RNC
PC
AC
LC
PS
RM
HC PC
PC LC
RRM Overview
AC Admission Control; PS Packet Scheduler; LC Load Control;RM Resource Manager; HC Handover control; PC Power Control
RRM in UMTS Release 99
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Aalborg University, RATE/TBS, 2006slide 17
SIPCOM9-2, lecture 10MultiUserComm
Power Control
Fast Closed Loop PowerControl (CLPC)at rate 1500 Hz
RNC adjusts the SIR target in
the Node B for the fast CLPCin response to link quality
UE
Node B RNC
Node B adjusts the power to
keep the SIR at the SIR target
Slow Outer Loop PowerControl (OLPC)at rate 2-100 Hz
In uplink to keep the receivedsignal level the same for all
users (near-far effect)
In downlink to increase thereception quality of stationary
users and users at the cell edge
To increase spectralefficiency
?
Aalborg University, RATE/TBS, 2006slide 18
SIPCOM9-2, lecture 10MultiUserComm
Uplink Fast PC
UE1 and UE2 are transmitting atthe same frequency => equalizingreceived powers at Node B iscritical to avoid near-far problems
Closed loop power control: NodeB commands UE to increase or to
decrease its transmission powerat a rate of 1.5 kHz (1 dB steps)
Closed loop power controlfollows also the fast fadingpattern at low and mediumspeeds (< 50 km/h)
Fast PC algorithm in Node B:If Eb/N0 < Eb/N0,target,
send "power-up" command.Else If Eb/N0 > Eb/N0,target,
send "power-down" command.
PCcomm
ands
UE1
UE2
Node B
L1
L2
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Aalborg University, RATE/TBS, 2006slide 19
SIPCOM9-2, lecture 10MultiUserComm
500 1000 1500 2000 2500 30004
4.5
5
5.5
6
6.5
7
1 minute period
Estimatedquality better than
required?NoYes
IncreaseEb/N0 target
DecreaseEb/N0 target
Outer Loop PC
General outer loop algorithm
Example adjustments of Eb/N0target for AMR speechservice, BLER target 1%
If error in frame, increaseEb/N0 target by 0.5 dB
If no errors, decrease Eb/N0target with such a rate thatBLER = 1% on average.
Aalborg University, RATE/TBS, 2006slide 20
SIPCOM9-2, lecture 10MultiUserComm
Softer Handover
Softer handover
UE is connected totwo sectors of onebase station
Softer handoverprobability 5 - 15 %
UL/DL
Basically sameRake combining asfor multipath andantenna diversity(Node B and UE)
RNC
Sector 1
Sector 2
Uplink combing from two sectorsin Node B Rake receiver (maximalratio combining)
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Aalborg University, RATE/TBS, 2006slide 21
SIPCOM9-2, lecture 10MultiUserComm
Soft Handover
Soft handover UE is connected to two base
stations
Soft handover probability is 20 -50 %
Required to avoid near-fareffects
Extra transmission over Iub
More baseband processingneeded (both base stations)
DL Maximal ratio combining in UE
in the same way as with softerhandover or multipath diversity
UL Frame selection combining in
RNC
RNC
Uplink combing fromtwo base stations in RNC(selection combining)
Aalborg University, RATE/TBS, 2006slide 22
SIPCOM9-2, lecture 10MultiUserComm
Soft HandoverExecution (1/2)
Active Set (AS) cells have the knowledge of service used by UE
RNC informs the new cell (to be added to AS) about the neededconnection, forwarding the following:
Coding schemes, number of parallel code channels, the differenttransport channel configuration parameters in use by UL and DL
UE ID and uplink scrambling code
The relative timing information of the new cell with respect to theexisting connection (as measured by the UE at its location). Basedon this, the new Node B can determine what should be the timing of
the transmission initiated with respect to the timing of the commonchannels (CPICH) of the new cell
MS is informed about the channelisation codes to be used intransmission and relative timing information through existingconnection
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Aalborg University, RATE/TBS, 2006slide 23
SIPCOM9-2, lecture 10MultiUserComm
Soft Handover
Execution (2/2)
PCCCHframe
PDCH/PCCHframe
Measure Toffset
Handovercommandand Toffset
UTRAN
Transmision channeland Toffset
BS Bchannelinformation
BS ABS B
Toffset
The relative timing information, which needs to be madeavailable at the new cell is indicated in the above figure
It makes transmissions capable to be combined in the Rakereceiver from timing point of view
Aalborg University, RATE/TBS, 2006slide 24
SIPCOM9-2, lecture 10MultiUserComm
Fast Power Controlin Soft Handover
BS 1
BS 2
Both Node BsDetect downlink PC command from mobile
Adjust downlink transmission power
RNC:Power drifting
control
UE:Check reliability of uplink PC command
Adjust uplink transmission power
Power
drifting
Reliabilitycheck
Independent power control commandsare sent from Node Bs to UE to controluplink transmission power
Base stations detect independently thepower control command from mobile tocontrol downlink transmission power
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Aalborg University, RATE/TBS, 2006slide 25
SIPCOM9-2, lecture 10MultiUserComm
DATA
Bit rate Chip rate
Channelisationcode
Scramplingcode
Chip rate
Uplink Downlink
Spreading Separate bearer
services
Separate users/
bearer services
Scrambling Separate users Separate cells
Code Allocation and Code Tree Management
All physical channels are spread with individual spreadingcodes, Cm(n) and subsequently by the scrambling code, CFSCR
Resource Manager generates DL spreading codes.
The code layer, m and the code number, n designates each andevery code in the layered orthogonal code sequences.
Resource Management
Aalborg University, RATE/TBS, 2006slide 26
SIPCOM9-2, lecture 10MultiUserComm
Code Types
Downlink OVSF channelisation (or spreading) codes (SF 4 - 512)
Scrambling codes long scrambling code (Gold code with 18 degree polynomial), but
using only one frame (38400 chips) complex valued code is formed by time delayed version of the same
code
limited to 512 possible codes divided into 64 code groups
Uplink OVSF channelisation (or spreading) codes (VSF 4 256)
Scrambling codes short and long codes
long scrambling code (Gold code with 25 degree polynomial), butusing only 38400 chips
complex valued code is formed by time delayed version of the same code
short 256 chips extended S(2) code family complex valued code is formed by combining two codes
millions of scrambling codes
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Aalborg University, RATE/TBS, 2006slide 27
SIPCOM9-2, lecture 10MultiUserComm
Resource Manager
Code Allocation Code Allocation Algorithm chooses the proper spreading code depending on
the transport format combination type.
The codes are layered from 0 to 11 according to the code type (~SF)
Only layers 2 to 8 are available for DL and 2 to 7 for UL
C0(0)=(1)
C1(0)=(1,1)
C1(1)=(1,-1)
C2(0)=(1,1,1,1)
C2(1)=(1,1,-1,-1)
C2(2)=(1,-1,1,-1)
C2(3)=(1,-1,-1,1)
C3(0)=()
C3(1)=()
C3(2)=()
C3(3)=()
C3(4)=()
C3(5)=()
C3(6)=()
C3(7)=()
Layer0
Layer1 Layer2 Layer
3
Aalborg University, RATE/TBS, 2006slide 28
SIPCOM9-2, lecture 10MultiUserComm
RM Examples
Examples: Ordinary DL speech 30 kbps channel (AMR 12.2-4.75
kbps & control part with 1/3 channel coding - code type7 (128 chips/symbol)
C2(1) code layer = 2; code number = 1 code = 11002
120 kbps channel - code type 5 (32 chips/symbol)
C4(5) code layer = 4; code number = 5 code = 11001100001100112
The Resource Manager maintains code treeorthogonality
If a code Cm(n) is in use, all the codes that are below it inthe same branch and the codes that are above it in thesame branch to the root are made unavailable
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Aalborg University, RATE/TBS, 2006slide 29
SIPCOM9-2, lecture 10MultiUserComm
Physical Layer
Channels and Procedures
Aalborg University, RATE/TBS, 2006slide 30
SIPCOM9-2, lecture 10MultiUserComm
Transportchannels
Medium Access Control (MAC), Layer 2
Physical Layer, Layer 1
MAC selects appropriate bit rateaccording to the instantaneous
source bit rate.
Physical layer supports variablebit rates up to 2 Mbps
Logical channels
Physical channels
Channel Types
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Aalborg University, RATE/TBS, 2006slide 31
SIPCOM9-2, lecture 10MultiUserComm
WCDMA ChannelsBCH
Broadcast
PCCPCHPrimary Common
Control
SCCPCHSecondary
Common Control
PRACH
DPDCH
DPCCHPDSCH
PCPCH
SCHSynchronisation CPICH
CommonPilot
AICHAcquisitionIndication
PICHPaging
Indication
CSICHCPCH Status
Indication
CD/CA-ICHCollision
Detect/Avoidance
FACHForward Access
CPCHCommon Packet
PCHPaging
RACHRandom Access
DCHDedicated
DSCHDownlink SharedTransport Channels
Physical Channels
how and withwhat
characteristics
Aalborg University, RATE/TBS, 2006slide 32
SIPCOM9-2, lecture 10MultiUserComm
Transport Channels(1/2)
Random access channel RACH: Data + signaling from one user
Dedicated channel DCH: data + signaling to one user
Broadcast channel BCH: Cell and system info
Forward access channel FACH:Data + signaling for one or more users within one cell
Paging channel PCH: For mobile terminated calls
Downlink shared channel DSCH: Packet data channel.Time multiplexed by several users.
Common packet channel CPCH:Extension of RACH for longer data packets
Mobile
Node B
DSCH optional for network
CPCH optionalfor network
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Aalborg University, RATE/TBS, 2006slide 33
SIPCOM9-2, lecture 10MultiUserComm
Transport Channels
(2/2) Due to direct support of variable bit rate and service multiplexing in
UTRA/FDD there is only one dedicated transport channel(DCH). DCHcontains user data and control information from higher layers.
There exist a total of six common transport channelsin UTRA/FDD:
Broadcast channel (BCH): General information of UTRA network or the currentcell (e.g. random access codes, access slots). BCH is sent at low data rate(single TF) and high power to reach all users in intended coverage area.
Forward access channel (FACH): Downlink transmission of control informationto UE's in current cell. Slow power control and low data rates.
Paging channel (PCH): Downlink paging information (e.g. call initiation).
Random access channel (RACH): Uplink control information (e.g. UE requests to
set up connection/initiate call). Single frame only.Optional uplink common packet channel (CPCH): Extended RACH for sending
data over multiple frames.
Optional downlink shared channel (DSCH): Somewhat similar to RACH but canbe shared by multiple users to increase data throughput.
Aalborg University, RATE/TBS, 2006slide 34
SIPCOM9-2, lecture 10MultiUserComm
Services in UMTS are classified according to their QoS requirements into
one of 4 service classes
The service classes are characterised by certain bearer attributes provided
by the UMTS Radio Access Bearer
Each Radio Access Bearer (RAB) is transmitted on
a specific Transport Channel (TrCh)
In a multi-service environment (with different QoS requirements)
transmission is done on a combination of TrChs which are transmitted on
the same physical channel(s)
RABs and TrChs
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Aalborg University, RATE/TBS, 2006slide 35
SIPCOM9-2, lecture 10MultiUserComm
Transport Format (TF)
group of parameters describing the transmission "mode" on a specific
TrCh during a TTI (TTI size is part of the TF)
TF Set (TFS)
corresponds to a group of TFs applying to one specific TrCh
TF Combination Set (TFCS)
the product of TF Sets of all the TrChs forming the combination
TF Indicator (TFCI)Each TF Combination (TFC) of the TFCS is indexed with the TFC
Index (TFCI) at the physical layer
TrCh Details (1/2)
Aalborg University, RATE/TBS, 2006slide 36
SIPCOM9-2, lecture 10MultiUserComm
8
16
32
64
128
256
320
384
8
16
32
64
Examplebit rates for
NRT
64
Peak bit ratein bearer
parametersis requested
from PS
256
Scheduledbit rate
TFS for NRTRB includes
allintermediate
rates
64
32
TFS subsetfor TFCS
construction
0 0 0
32
64
0
16
0
TFCS (SL & NRTRB)
TFCI 0TFCI 3
TFCI 1TFCI 4
TFCI 2TFCI 5
TrCh1
TrCh2
TFI0
TFI1
TFI2
TFI3
TFI4
TFI0
TFI4
TFI3
TFI0
TFI1
TFI0
TFI3
TFI4
TFCI TFITrC
H1
TFITrC
H20 0 0
1 0 3
2 0 4
3 1 0
4 1 3
5 1 4TFCS Construction by cartesian product
Example with radiobearer for user
data and signalling
TrCh Details (2/2)
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Aalborg University, RATE/TBS, 2006slide 37
SIPCOM9-2, lecture 10MultiUserComm
Dedicated Channel (DCH/DPCH)
Speech and data services
Aalborg University, RATE/TBS, 2006slide 38
SIPCOM9-2, lecture 10MultiUserComm
Target
Characteristics forUL and DL
Dedicated physicalcontrol channel (DPCCH)
Dedicated physicaldata channel (DPDCH)
Keep physical layerconnection running
Carry user data andhigher layer control data
Content
(1) Reference symbol:Channel and SIR estimation(2) Power control signaling(3) TFCI: bit rate information
(1) User data(2) Higher layer signaling
(RRC)
Bit rateConstant bit ratefor reliable detection
Variable bit rate. Bit rateindicated with TFCI on DPCCH.
Dedicated channel (DPCH) consists of two physical channels:
DPCCH keeps physical layer connection running reliably
DPDCH carriers user bits with variable bit rate
Possible to have a power offset between the two channels
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Aalborg University, RATE/TBS, 2006slide 39
SIPCOM9-2, lecture 10MultiUserComm
Solution
Target
Multiplexing of
DPCCH and DPDCH
The code consumption is not an issue in uplink since the number ofcodes is very large
The discontinuous transmission is not an issue in downlink sincecommon channels (10-20% of BTS max power) are transmitted all the
time Blind rate detection (no TFCI bits) is easier for the mobile when the
channel bit rate remains constant in time multiplexed solution
Variable rate transmission for data can be implemented bydiscontinuous transmission (DTX) on a slot interval (DL) and frame(UL) basis, symbol repetition where frame is always full, or variablespreading factor (UL).
Uplink Downlink
I/Q code multiplexing Time multiplexing
Continuous transmission reduce audible interference
(1) Only one code needed saves orthogonal codes(2) Support for blind rate detection
Aalborg University, RATE/TBS, 2006slide 40
SIPCOM9-2, lecture 10MultiUserComm
Variable Rate inUplink
DPCCH
DPDCH
Service in DTX(e.g. silence in speech)Higher bit rate Low bit rate
Continuous mobile transmission regardless of the bitrate (also during service DTX) Reduced audible interference to other equipment (nothing to do
with normal interference, does not affect the spectral efficiency)
Services can still have DTX, like silence period in speech. Duringthat time no DPDCH transmitted but still continuous DPCCH
Fast power control keeps received power of DPCCHconstant
10 ms frame 10 ms frame 10 ms frame
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Aalborg University, RATE/TBS, 2006slide 41
SIPCOM9-2, lecture 10MultiUserComm
DPCH (DPCCH/DPDCH)
SF = (4 - 256)
DPCCH
DPDCH
DPDCH
TTI
TCFI, (DL) TPC, PILOT
Pairedwith
UL
DL
10 ms
SF = 256
Code(Power)
TCFI, (UL) TPC, (PILOT)
SF = 4 - 256
DPCCH
DPDCH
DPDCH
Transmission Time Interval (TTI)
TFCI (DL), TPC, PILOT
TFCI (UL), TPC, (PILOT)
Paired with
Code(Power)
Channel Structure
(DPCH)
Carries the Dedicated(DCH) transport channel
DPCH (DPCCH/DPDCH)
DPDCH Dedicated Physical Data ChannelDPCCH Dedicated Physical Control Channel
TFCI Transport Format Combination IndicatorTPC Transmitter Power Control
Aalborg University, RATE/TBS, 2006slide 42
SIPCOM9-2, lecture 10MultiUserComm
UplinkDPDCH/DPCCH
Pilot
Npilot bits
TPC
NTPC bits
Data
Ndata bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10 bits
1 radio frame: Tf= 10 ms
DPDCH
DPCCHFBI
NFBI bitsTFCI
NTFCI bits
Tslot = 2560 chips, Ndata = 10*2k
bits (k=0..6)
Fixed SF256
Lets the receiverknow what is
coming whichTrChs are activein frame!
Variable SF from 4 to 256 on a frame-by-frame basis aresupported in the uplink
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Aalborg University, RATE/TBS, 2006slide 43
SIPCOM9-2, lecture 10MultiUserComm
Uplink Processing
Frame 1 Frame 2 Frame 72
Super frame 720 ms
10 ms
Frame 1 Frame 2 Frame 72
Slot 1 Slot 2Slot 1 Slot 2 Slot 15
(2) Detect PC commandand adjust DL tx power
Slot 0.667 ms = 2/3 ms
Pilot TFCI
Data
DPCCH
DPDCH
TPC
(1) Channel estimate+ SIR estimate for PC for
adjusting UL tx power
(3) Detect TFCI(10 ms frame)
(4) Interleaving (TTI) :Detect data
Aalborg University, RATE/TBS, 2006slide 44
SIPCOM9-2, lecture 10MultiUserComm
Uplink TX (I)
CRC encoding: Cyclic redundancy check (CRC)attachment is done to enable error detection atthe receiver. The CRC indicator length can beset to 0/8/12/16/24 bits depending on thedesired error detection accuracy.
Encoder block size adjustment: Transport blockconcatenation is used for smaller amounts of
data in order to reduce the overhead of tail bitsand to increase the block size to improve thechannel encoding performance. On the otherhand, code blocks segmentation is done to avoidexcessively large block sizes.
CRC encoding
Encoderblock sizeadjustment
Raw bits
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Aalborg University, RATE/TBS, 2006slide 45
SIPCOM9-2, lecture 10MultiUserComm
Uplink TX (II)
Channel encoding is done in order to improvethe bit or frame error rate (BER/FER)performance of the link. Variable coding issupported (from no coding to high coding). Forthe relatively low data rates (similar to secondgeneration systems), convolutional encoding( and 1/3 rate) is used for simplified detectionand good performance. The highest data ratesuses 1/3-rate Turbo encoding for best codinggain.
Radio frame equalization is done by eitherconcatenating transport blocks together or bysegmenting blocks such that data is dividedinto equal-sized blocks when they do not fit asingle 10 ms frame.
Radio frameequalization
Channelencoding
Aalborg University, RATE/TBS, 2006slide 46
SIPCOM9-2, lecture 10MultiUserComm
Uplink TX (III)
Inter-frame interleaving is done whenever thedelay-budget (for the current QoS) allows formore than 10 ms (1 frame) of delay. Theinterleaving length may be 20/40/80 ms.Interleaving reduces correlation betweenadjacent chips and thus improves detection(basic assumption for efficient channeldecoding).
Radio frame segmentation is padding the input bitsequence in order to ensure that the output canbe segmented in an integer number of datasegments of same size (subclause 4.2.6 inTR25.212). The frame segmentation is onlyperformed in the uplink since in the downlink, therate matching output block length is always aninteger multiple of the desired number of datasegments.
Inter-frameinterleaving
Radio framesegmentation
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Aalborg University, RATE/TBS, 2006slide 47
SIPCOM9-2, lecture 10MultiUserComm
Rate matching
Transport channel
multiplexing
+
intra-frame
interleaving
+
physical layermapping
DPCCH/DPDCH#
Uplink TX (IV)
Rate matching ensures that the frames arefilled up with data. To do this, either bypuncturing or by repetition. Repetition isusually preferred for the uplink. The ratematching is dynamically updated on aframe-to-frame basis. The rate matchingalgorithm is detailed in TR25.212.
Multiplexing: Finally, all the active transportchannels are multiplexed and a 10 ms intra-frame interleaving is conducted. After the
interleaving, the data is mapped onto thephysical channels.
Aalborg University, RATE/TBS, 2006slide 48
SIPCOM9-2, lecture 10MultiUserComm
Uplink TX (V) block diagram
Depending on which data rate is desired, each user can simultaneouslyhave 6 DPDCH channels (data) and one DPCCH channel (controlinformation).
SpreadingDPDCH1
DPDCH3
DPDCH2
DPCCH
Spreading
Spreading
Spreading
Scaling
Scaling
Rotation
Scaling
Scaling
d
d
j
Complex
Scrambling
Re{}
Im{}
cos(t)
sin(t)
RRC
RRC
S(t)
Dual-channel QPSK modulation(BPSK modulation + I/Q code multiplexing)
d
c
Example 3 x DPDCH configuration
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Aalborg University, RATE/TBS, 2006slide 49
SIPCOM9-2, lecture 10MultiUserComm
Slot Format #i Channel Bit Rate(kbps)
Channel SymbolRate (ksps)
SF Bits/Frame
Bits/Slot
Ndata
0 15 15 256 150 10 101 30 30 128 300 20 202 60 60 64 600 40 403 120 120 32 1200 80 804 240 240 16 2400 160 1605 480 480 8 4800 320 3206 960 960 4 9600 640 640
Physical Layer Rates
(Uplink)
A single code at SF 4 allows 960 kbps which turns into a user data rate
of 480 kbps with rate coding; 6 parallel DPDCHs at rate codingleads to a maximum user data rate in excess of 2 Mbps.
Beneficial to stick to a single DPDCH for as long as possible to reducePeak to Average Ratio (PAR).
Aalborg University, RATE/TBS, 2006slide 50
SIPCOM9-2, lecture 10MultiUserComm
DownlinkDPDCH/DPCCH
One radio frame, Tf= 10 ms
TPC
NTPC bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10*2k
bits (k=0..7)
Data2
Ndata2 bits
DPDCH
TFCI
NTFCI bits
Pilot
Npilot bits
Data1
Ndata1 bits
DPDCH DPCCH DPCCH
Lets the receiverknow what is
coming whichTrChs are active
in frame!
Constant SFs from 4 to 512 are supported in the downlink (somerestrictions for SF 512).
The SF for the highest transmission data rate determines thechannelisation code reserved from the code tree.
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Aalborg University, RATE/TBS, 2006slide 51
SIPCOM9-2, lecture 10MultiUserComm
Downlink Processing
Frame 1 Frame 2 Frame 72
Slot 1 Slot 2 Slot 16
PilotData
Super frame 720 ms
10 ms
Slot 0.667 ms = 2/3 ms
TPC
Frame 1 Frame 2 Frame 72
Slot 1 Slot 2 Slot 15
DPDCH DPDCH
Data
DPCCH DPCCH
TFCI
(2) Detect PC commandand adjust UL tx power
(1) Channel estimate+ SIR estimate for PC for
adjusting DL tx powerCan use CPICH
(3) Detect TFCI(10 ms frame
(4) Interleaving (TTI) :Detect data
Aalborg University, RATE/TBS, 2006slide 52
SIPCOM9-2, lecture 10MultiUserComm
Re{}
Im{}
sin(t)
RRC
RRC
S(t)
All channels(except SCH)Odd
bit
Evenbit
Rotation
j
Downlink transmitter
The downlink uses time multiplexing between data and control information.This is possible since there are multiple users and there are always generalcontrol channels being transmitted from the BS (e.g. SCH). On the uplink,multiplexing like this would cause audible interference during discontinuoustransmission.
Spreading
Spreading
ComplexScrambling
Otherchannels(users)
.........
SCH
cos(t)
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Aalborg University, RATE/TBS, 2006slide 53
SIPCOM9-2, lecture 10MultiUserComm
Physical Layer Rates
(Downlink)
Spreadingfactor
Channelsymbol
rate(kbps)
Channelbit rate(kbps)
DPDCHchannel bitrate range
(kbps)
Maximum userdata rate with -
rate coding(approx.)
512 7.5 15 36 13 kbps
256 15 30 1224 612 kbps
128 30 60 4251 2024 kbps
64 60 120 90 45 kbps
32 120 240 210 105 kbps
16 240 480 432 215 kbps
8 480 960 912 456 kbps
4 960 1920 1872 936 kbps
4, with 3parallelcodes
2880 5760 5616 2.8 Mbps
Half rate speech
Full rate speech
144 kbps
384 kbps
2 Mbps
Symbol_rate=Chip_rate/SF
Bit_rate=Symbol_rate*2
User_bit_rate=Channel_bit_rate/2
DPCCHoverhead
Aalborg University, RATE/TBS, 2006slide 54
SIPCOM9-2, lecture 10MultiUserComm
Signaling 3.4 kbps with 40 ms interleaving
Speech 12.2 kbps Speech 12.2 kbps
40 ms
Radio frame Radio frame Radio frame Radio frame
10 ms
81 class A bits 12 CRC 8 tail 103 class B bits 8 tail 60 class C bits 8 tail+ +AMR 12.2 kbps
136 data bitsRLC+
MAC 12 bits 24 CRCDPCH 3.4 kbps
Downlink Speech + Signalling
Example
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Aalborg University, RATE/TBS, 2006slide 55
SIPCOM9-2, lecture 10MultiUserComm
AMR Class A 1/3 rate conv
AMR Class B 1/3 rate conv
AMR Class C 1/2 rate conv
DPCH 1/3 rate conv
Channel coding
SF=256 240 bits
SF=128 510 bits
Downlink L1 bit rates
Spreading factor Bits per frame
960 bits
2040 bits
Bits per 40 ms
Bits per 20 ms Bits per 40 ms
AMR 12.2 kbps 772 bits 1544 bits
DPCH 3.4 kbps - 516 bits
2060 bits
1544 bits
AMR12.2+DPCH
AMR 12.2
Ratematching
1% puncturing
32% repetition
AMR12.2+DPCH
AMR 12.2
SF=128
SF=128
Channelcoding
Transport channelmultiplexing
Most suitable spreadingfactors and required rate
matching
Example
Aalborg University, RATE/TBS, 2006slide 56
SIPCOM9-2, lecture 10MultiUserComm
Speech, full rate 128 channels Number of codes withspreading factor of 128
(AMR 12.2 kbps *(128 4)/128 Common channel overhead
and 10.2 kbps) /1.2 Soft handover overhead
= 103 channels
Speech, half rate 2*103 channels Spreading factor of 256
(AMR 7.95 kbps) = 206 channels
Packet data 3.84e6 Chip rate
*(128 4)/128 Common channel overhead/1.2 Soft handover overh ead
*2 QPSK modulation
*0.9 DPCCH overhead
/3 1/3 rate channel coding
/(1 0.3) 30% puncturing
= 2.65 Mbps
4 channels withSF=128 for commonchannels assumed
20% soft handoveroverhead assumed
Result103 speech channels or
2.65 Mbps data withone scrambling code
Note: usually interference limits the capacitybefore the number of orthogonal codes
Downlink Capacity
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Aalborg University, RATE/TBS, 2006slide 57
SIPCOM9-2, lecture 10MultiUserComm
Basic Procedures
Common channels and
synchronisation
Aalborg University, RATE/TBS, 2006slide 58
SIPCOM9-2, lecture 10MultiUserComm
SCH,CP
ICH,AIC
H,PICH
These channels do notcarry transport channels
but are needed fornetwork operation
Synchronizationchannel SCH
Common pilotchannel CPICH
Acquisition indicatorchannel AICH
Paging indicatorchannel PICH
For the mobile to synchronize to the cell.
For the mobile synchronization, channel estimation, andfor the neighbor cell measurements
Response to RACH preamble
For indicating to the mobile that there is paging on PCH
Additional DownlinkPhysical Channels
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Aalborg University, RATE/TBS, 2006slide 59
SIPCOM9-2, lecture 10MultiUserComm
Common channels (I)
Common pilot channel (CPICH):
Purpose of run-time synchronization betweenthe BS and UE's located in the cell.
CPICH unmodulated, scrambled by cell-specific primary scrambling code (SF=256).
Used for initial synchronization, channelestimation and measurements for handoverand cell selection.
With multiple BS antennas (antenna diversity),CPICH's from each BS antenna are separatedby simple modulation patterns.
Aalborg University, RATE/TBS, 2006slide 60
SIPCOM9-2, lecture 10MultiUserComm
CPICH is transmitted continuously and it takes typically 5-15% of thebase station max power (IS-95 typically 20-25%, narrowband =>relatively higher overhead)
CPICH is used for downlink channel estimation in the mobile forcoherent combining of multipath components
CPICH is unmodulatedsignal under the cellspecific scrambling
code
Channelestimation
Other cellmeasurements
CPICH
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Aalborg University, RATE/TBS, 2006slide 61
SIPCOM9-2, lecture 10MultiUserComm
Common channels (II)
Synchronization channel (SCH):
Purpose of initial synchronization between the BS andUE's located in the cell.
SCH is used for cell search. It consists of primary andsecondary synchronization channels.
The primary channel uses a 256-chip spreadingsequence which is identical for every cell (global).
Secondary channels use sequences individual to eachgroup of cells and which identify one out of 64 possiblescrambling code groups. Once the UE has found the
secondary SCH it has obtained both frame and slotsynchronization.
(determined by the sequence used on the secondary SCHchannel)
Aalborg University, RATE/TBS, 2006slide 62
SIPCOM9-2, lecture 10MultiUserComm
SCH
0 1 14...PrimarySCH
0 1 14...SecondarySCH
256-chip sequencemodulated, identifies the code
group of the cell
2560-256=2304 chips256chips
256-chip sequencethe same in every cell
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Aalborg University, RATE/TBS, 2006slide 63
SIPCOM9-2, lecture 10MultiUserComm
Cell Search
512 scrambling codes in downlink are divided into 64 groups to speedup the cell search, each group contains 8 codes (8 x 64 = 512)
(1) Chip synchronization(2) Symbol synchronization(3) Slot synchronization
Primary SCH
(1) Code group (which of 64)(2) Frame synchronization
Secondary SCH
Exact scrambling code (which of 8)Pilot channel
CPICH
Which part of synchronization is obtainedWhich channel
is used
Step 1
Step 2
Step 3
Note: SCH is not under the cell specific scrambling code because it must bereceived before knowing the scrambling code
As a consequence, SCH is non-orthogonal to other channels
All other downlink channels are under the scrambling code
Aalborg University, RATE/TBS, 2006slide 64
SIPCOM9-2, lecture 10MultiUserComm
ML approach: Correlate with the PN sequence at all delays within theuncertainty region, and then determine the delay Thus, the meansynchronization time equals KLT, where Tis the correlation time andKis the number of correlations per chip interval.
Serial search: Correlate with the PN sequence at one delay anddetermine if the output is above the noise+MAI floor. If the output isbelow the the noise+MAI floor, then move the correlator to the nextdelay. Here the mean synchronization time is less than KLT.
Synchronization
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Aalborg University, RATE/TBS, 2006slide 65
SIPCOM9-2, lecture 10MultiUserComm
Serial Acquisition Scheme
Aalborg University, RATE/TBS, 2006slide 66
SIPCOM9-2, lecture 10MultiUserComm
Probability of Detectionand False Alarm
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Aalborg University, RATE/TBS, 2006slide 67
SIPCOM9-2, lecture 10MultiUserComm
Dual-Dwell Serial
Search
Aalborg University, RATE/TBS, 2006slide 68
SIPCOM9-2, lecture 10MultiUserComm
Tracking of PN-Sequences
After coarse synchronization is obtained within +/- one chip, amore accurate synchronization is initiated (tracking).
Tracking of the received PN-sequence is performed separatelyfor each RAKE finger.
Tracking is performed continuously during the transmission
since there is a time-varying drift between the received andlocally generated PN-sequence.
The time-drift is mainly caused by two factors:
Movement of mobile unit. At a speed of 100km/h, the time drift is onthe order of 100nsec/sec.
Oscillator drift between Tx and Rx.
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Aalborg University, RATE/TBS, 2006slide 69
SIPCOM9-2, lecture 10MultiUserComm
Early-Late Gate
Tracking The early-late gate algorithm aims at maximising the auto-
correlation between the received and the locally generated PN-sequence.
The tracking algorithm is a simple gradient search algorithm
The two power estimates can be obtained from the pilotsignal/symbol.
Aalborg University, RATE/TBS, 2006slide 70
SIPCOM9-2, lecture 10MultiUserComm
Tracking Uncertainty
Deterministic uncertainty due to filtering
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Aalborg University, RATE/TBS, 2006slide 71
SIPCOM9-2, lecture 10MultiUserComm
TDD Mode
In brief!
Aalborg University, RATE/TBS, 2006slide 72
SIPCOM9-2, lecture 10MultiUserComm
GeneralCharacteristics
Combined TDMA/CDMA (TDD) multiple access
Allows operation in unpaired band
Requires synchronization between base stationsto avoid uplink/downlink interference
Allows for assymmetric uplink/downlink capacity Discontinuous transmission leads to power
disadvantage cell range reduction
Has the advantage of a reciprocal channel
used for (open loop) uplink power control
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Aalborg University, RATE/TBS, 2006slide 73
SIPCOM9-2, lecture 10MultiUserComm
WCDMA TDD
UE 1
Time
(Code) Power
UE 2
UE 3
UE 4
Node BUE
non-ort
hogona
lcodes
orthogonalcodes
Available resources:Spreading Codes (OVSF)
and SlotsUp to 16 users codemultiplexed per slot
Single-userdetection
Multi-userdetection
UE 1
UE 2
frame n frame n+1
Aalborg University, RATE/TBS, 2006slide 74
SIPCOM9-2, lecture 10MultiUserComm
Generalized TDD Frame
Data symbols
(976 chips)
Data symbols
(976 chips)
Midamble
(512 chips)
Guard
(96 chips)
2560 chips
Data symbols
(976 chips)
Data symbols
(976 chips)
Guard
(96 chips)
TS 0 TS 14
10 ms
Burst Type I
Number of allocated time slots
# allocatedcodes (SF=16)
2.54 Mbps781 kbps195 kbps16
1.26 Mbps390 kbps97 kbps8
158 kbps48.8 kbps12.2 kbps1
1341
Midamble (training sequence) forjoint channel estimation
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Aalborg University, RATE/TBS, 2006slide 75
SIPCOM9-2, lecture 10MultiUserComm
MultiUser Detection
Interference Cancellation
Aalborg University, RATE/TBS, 2006slide 76
SIPCOM9-2, lecture 10MultiUserComm
MUD analysis
If we define the Interference Cancellation receiver efficiency, , as the
ratio between the equivalent intra-cell interference after and before
interference cancellation [Hmlinen], then the required (matched filter)
SINR (Eb/No) of userj (per antenna) can be expressed as
where Wis the chip rate, Rj
the selected data rate for transmission, Pj
the
total receiver power (per antenna), Pown the total received own-cell power
(per antenna), Pother the total received other-cell power (per antenna), and
Pnoise is the background noise power (per antenna).
A practical IC implementation (with acceptable complexity) can achieve
an efficiency of 30%, whereas about optimum for multi-stage IC achieves
70% efficiency
( )( )1j
jj own j other noise
PW
R P P P P
=
+ +
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Aalborg University, RATE/TBS, 2006slide 77
SIPCOM9-2, lecture 10MultiUserComm
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
50
100
150
200
250
Cellthrough
putgain[%]
i = 0.0i = 0.2i = 0.4i = 0.6i = 0.8i = 1.0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
10
20
30
40
50
Cellthroughputgain[%]
i = 0.0i = 0.2
i = 0.4i = 0.6i = 0.8i = 1.0 The gain from IC can be
approximated as:
35
i
iG
UL +
+
1
1
The cell throughput gain from ICdecreases with isince IC is only
effective towards intra-cellinterference.
Also, the impact of the IC efficiencyon the cell throughput gain is scaled
by the uplink fractional load UL.
18%
54
%
=0.7
iis the other-to-own interferenceratio
is the efficiency of the IC receiver
UL is the uplink fractional load
UL
UL
=0.3
27%
100%
IC Gain
from
[ C. Rosa, Enhanced plink Packet Access in WCDMA, Ph.D. dissertation, AAU, December 2004]
Aalborg University, RATE/TBS, 2006slide 78
SIPCOM9-2, lecture 10MultiUserComm
Wideband received power based RRM
Throughput based RRM
riseNoise
1-riseNoise1 ==
total
NUL
I
P
( ) ( )
( )
= =
+
+=+=N
j
N
j
jjjb
jUL
RNE
WiLi
1 1
0/1
111
Measure total wideband
received power Itotal
Calculate sum ofthe bit rates in a cell
Noise Rise andfractional load
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Aalborg University, RATE/TBS, 2006slide 79
SIPCOM9-2, lecture 10MultiUserComm
References and Acronyms
Aalborg University, RATE/TBS, 2006slide 80
SIPCOM9-2, lecture 10MultiUserComm
References
H. Holma and A. Toskala, WCDMA for UMTS Radio Access for Third
Generation Mobile Communications, John Wiley & Sons, 3rd edition,
2004 (HSDPA chapter!)
T.E. Kolding et al.,High Speed Downlink Packet Access: WCDMA
Evolution, IEEE Vehicular Technology Society (VTS) News, vol. 50, no.
1, pp. 4-10, February 2003
S. Hmlinen, H. Holma, and A. Toskala, Capacity Evaluation of a
Cellular CDMA Uplink with Multiuser Detection, International
Symposium on Spread Spectrum Techniques and Applications, vol. 1, pp.
339-343, September 1996
C. Rosa, T.B. Srensen, J. Wigard, and P.E. Mogensen, Interference
Cancellation and 4-Branch Antenna Diversity for WCDMA Uplink
Packet Access, Proceedings of VTC Spring 2005, Stockholm, Sweden,
May-June 2005
B. Vejlgaard, Data Receiver for the Universal Mobile
Telecommunications System (UMTS), Ph.D dissertation, AAU, 2000
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Aalborg University, RATE/TBS, 2006slide 81
SIPCOM9-2, lecture 10MultiUserComm
Acronyms
3GPP 3rd Generation Partnership Project
AC Admission Control
AuC Authentication Centre
BSS Base Station Subsystem
BTS Base Transceiver Station
CDMA Code Division Multiple Access
CN Core Network
CS Circuit Switched
DL Downlink (broadcast)
EUTRA Evolved UMTS Terrestrial Radio Access
FDD Frequency Division Duplexing
FDMA Frequency Division Multiple Access
GERAN GSM Evolved Radio Access Network
GGSN Gateway GPRS Support Node
GPRS General Packet Radio Service
GSM Global System for Mobile communications
HC Handover Control
HLR Home Location Register
HSS Home Subscriber Services
HSxPA High Speed Downlink/Uplink Packet Access
IMS Internet Multimedia Subsystem IMT International Mobile Telephony (ITU-2000)
ITU International Telecommunications Union
LTE Long Term Evolution
LC Load Control
ME Mobile Equipment
MS Mobile Station
Aalborg University, RATE/TBS, 2006slide 82
SIPCOM9-2, lecture 10MultiUserComm
Acronyms (cont.)
MSC Mobile Switching Centre
PLMN Public Land Mobile Network
PS Packet Switched
QoS Quality of Service
PC Power Control
PS Packet Scheduler
RM Resource Manager
RNC Radio Network Controller
RNS Radio Network Subsystem
RRM Radio Resource Management
RTT Round Trip Time
SF Spreading Factor
SGSN Serving GPRS Support Node
SHO Soft Handover
SIP Session Initiation Protocol
SS7 Signalling System 7
TDD Time Division Duplexing
TDMA Time Division Multiple Access
TMSI Temporary Mobile Subscriber Identity
UE User Equipment
UL Uplink (multiple access)
UMTS Universal Mobile Telecommunications System
USIM UE Subscriber Identification Module
UTRAN UMTS Terrestrial Radio Access Network
VLR Visitor Location Register
VSF Variable Spreading Factor
WCDMA Wideband Code Division Multiple Access