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WCDMA for UMTS
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1 Context
1.1 Historical
Early 70s
CDMA developed for military field for its great qualities of privacy (lowprobability interception, interference rejection)
1996CDMA commercial launch in the US
This system called IS-95 or cdmaOne was developed by Qualcomm and has
reached 50 million subscribers worldwide
2000IMT-2000 has selected three CDMA radio interfaces:
- WCDMA (UTRA FDD)
- TD-CDMA (UTRA TDD)
- CDMA 2000
In the following material we will only refer to WCDMA (UTRA FDD)
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1 Context
1.2 Advantages & Disadvantages
CDMA is very attractive:
Better spectrum efficiency than 2G systems
Suitable for all type of services (circuit, packet) and for multi-services
Enhanced privacy
Evolutionary (linked with progress in signal processing field)
BUT:
Complex system: not easy to configure and to manage
Unstable in case of congestion
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1 Context
1.3 3GPP
The 3GPP is the organization in charge of the standardization of the
UMTS.It is made of standardization organization (ETSI in Europe, T1 in USA,ARIB in Japan or CTWS in China ), member of manufacturers andoperators.
The UMTS frequency allocations are :
TDD FDD MSS TDD
1900 1980 2010 20251920
MSSFDD
2110 2170 2200
FDD: Frequency Division Duplex
TDD: Time Division Duplex
MSS: Mobile Satellite SystemUplink Downlink
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2 Analogy
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Cell
Restaurant room
2 Analogy
2.1 WCDMA and Restaurant
WCDMA Restaurant Room
UE
People at table
Code
Language
Enjoy yourmeal !
Code 1
Code 2
Gutenappetite !
Bon appetit!
Bomapetite !
Ues, like people, sendand receive on thesame time and thesame frequency. Theyare separeted by:
For a table, the conversations of the neighbours
are noise, for a UE it is the same principle:
neighbour conversations are interference
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2 Analogy
2.1 WCDMA and Restaurant [cont.]
WCDMA Restaurant Room
Node B
Steward
Downlink
Who have orderthis cake ?
????
???Impacts:
Power Control in DL
Control Admission
Very important !
Interference level in DL
problem:
If some UE use too muchpower
If there are too manyusers in the cell
Enjoy yourmeal !
COMOESTAS ?
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2 Analogy
2.1 WCDMA and Restaurant [cont.]
WCDMA Restaurant Room
It is for me!
Who have orderthis cake ?
QUIERO LATARTA!!
Es istmeine
Uplink
Cest la
pomme ?
????
At the Node B level:
If a UE, close to the NB,speak too loud
If there are too manyusers
Problem of interferencelevel too high.
The NB cant decode any
users anymore.
Impacts:
Power Control in UL
Admission Control
Very important
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3 Spread Spectrum Modulation
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3 Spread Spectrum Modulation
3.1 A Code as a Shell against Noise
The letter A represents the signal to transmit over the radio interface.
At the transmitter the height (ie the power) ofA is spread, while a color
(i.e a code) is added to A to identify the message .
At the receiver A can be retrieved with knowledge of the code, even if
the power of the received signal is below the power of noise due to theradio channel.
ReceiverTransmitter
Spreading
Noise
DespreadingRadio Channel
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3 Spread Spectrum Modulation
3.2 Spectrum spreading
At the transmitter the signal is multiplied by a code which spreads thesignal over a wide bandwidth while decreasing the power (per unit of
spectrum).
At the receiver it is possible to retrieve the wanted signal by multiplying
the received signal by the same code: you get a peak of correlation,while the noise level due to the radio channel remains the same, because
this is not correlated with the code.
But the interference level is too high, it is not possible to decode any
message.
???
f
P
Spreading
Radio channel
Despreading
Interference Level
f
P
f
P
f
P
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3 Spread Spectrum Modulation
3.3 Transmission Chain
Air Interface
The narrowband data signal is multiplied bit per bit by a code sequence:
it is known as chipping.
The chip rate (fixed) of this code sequence is much higher than the bit
rate of the data signal: it produces a wideband signal, also called spread
signal.
At the receiver the same code sequence in phase should be used toretrieve the original data signal.
Modulator Demodulator
Code Sequence
Data Data
Code sequence
NB-Signal WB-Signal NB-SignalWB-Signal
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3 Spread Spectrum Modulation
3.4 Code & Spreading factor
The code is applied on each bit of the user data.
The Spreading Factor, called SF, is the length of this code.
Example: Data to transmit: 1 0 , SF=8.
1
-1
1
-1
Spread data
Code
Coded data
Tr
ansmission
Reception
Received data,
without error
1
-1
A chip
Chip rate fixed at 3.84 Mchip/s
Code applied
1
-1
1
-1
1
-1
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3 Spread Spectrum Modulation
3.5 Spreading factor & Data Rate
The chip rate is fixed, 3.84 Mchip/s.
If the SF is divided by 2, the data rate is multiplied by 2 !
Example: Data to transmit: 1 0 , SF=4.
Spread data
Code
Coded data
Tr
ansmission
Reception
Received data,
without error
Code applied
Received
data
Small SF = High data rate
High SF = Small data rate
1
-1
1
-1
1
-1
1
-1
1
-1
1
-1
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3 Spread Spectrum Modulation
3.6 Spreading factor & Error at reception
When an error occurs at the reception, the determination of the bit value is less trivial.
Example: Data to transmit: 1 0 , SF=8.
1
-1
1
-1
Signal sent onthe air
Signal receivedwith error
Code
SF=8
Zoom
onthedecoded
signal
Decoded data
1
-1
0
The
determination ofthe bit value is
based on the area
of the received
signal.
Here is 6 areaunits over 8
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3 Spread Spectrum Modulation
3.6 Spreading factor & Error at reception [cont.]
1
-1
1
-1
Signal sent onthe air
Signal receivedwith error
Code
SF=4
Zoomonthe
decodedsignal
Decoded data
1
-1
0
The
determination ofthe bit value is
based on the area
of the received
signal.
Here is 2 areaunits over 4
With a small SF, the signal is more sensitive to errors.So to have the same error ratio you use more power
If you need a high data rate(video downloading), you
will use a small SF. You willhave more errors on your
message. So if you want to
keep the same error ratio,
you will use more power totransmit your message
To keep in mind
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3 Spread Spectrum Modulation
3.7 Exercise: Orthogonal Code
Here, there is a received signal and two orthogonal codes
Could you apply these codes on the received signal and determinate whichcode has been used to spread the signal? What could you conclude about theorthogonality?
Received signal
Code 1
Decoded signal
1
Code1
Code2
Code 2
1
-1
1
-1
1
-1
1
-1
1
-1
1
-1
Received signal
Decoded signal
2
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3 Spread Spectrum Modulation
3.7 WCDMA, Power Density & Processing Gain
RSSI: Received Signal Strength IndicatorTotal received wideband power over 5
MHz including thermal noise
ISCP (No): Interference Signal CodePower
Interference on the received signal
RSCP (Ec): Received Signal Code Power
Unbiaised measurement on the received
signal on one channelization code
Eb : energy per useful bit
PG : Processing Gain = Eb-Ec (in dB)
Power Gain after despreading. PG= 20 log (SF) f
P
RSSI or Io
ISCP or NoSIR
PG
Eb
RSCP or Ec
At Node B reception level
Wss
Ws
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Depending on the service, more or less
errors are allowed. UTRAN computesthe error ratio and then set the SIR
required for the service.
What are the modifications on the
diagram if:
The number of users increases ?The SF decreases ?
SIR: Signal Interference Ratio
No
RSCPSFSIR
.
3 Spread Spectrum Modulation
3.7 WCDMA, Power Density & Processing Gain [cont.]
f
P
RSSI or Io
ISCP or NoSIR
PG
Eb
RSCP or Ec
At Node B reception level
Wss
Ws
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4 Code Division Multiple Access
4 C d Di i i M l i l A
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4 Code Division Multiple Access
4.1 One-cell reuse
The area is divided into cells, but the entirebandwidth is reused in each cell (frequency
reuse of one)
> Inter-cell interference
> Cell orthogonality is achieved by codes
The entire bandwidth is used by each user at the
same time
> Intra-cell interference
> User orthogonality is achieved by codes
4 C d Di i i M lti l A
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4 Code Division Multiple Access
4.2 Multiple access
All the users transmit on the same 5 MHz carrier at the same time and
interfere with each other.
At the receiver the users can be separated by means of (quasi-
)orthogonal codes.
Transmitter 2
Spreading 1
Spreading1
Spreading 2 Receiver
Radio ChannelTransmitter 1
The receiver aims at receiving Transmitter 1 only.
4 C d Di i i M lti l A
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4 Code Division Multiple Access
4.2 Multiple access [cont.]
If a user transmits with a very high power, it will be impossible for the
receiver to decode the wanted signal (despite use of quasi-orthogonalcodes)
CDMA is unstable by nature and requires accurate power control.
Transmitter 2
Receiver
Radio ChannelTransmitter 1
The receiver aims at receiving Transmitter 1 only.
Spreading 1
Spreading1
Spreading 2
4 C d Di i i M lti l A
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4 Code Division Multiple Access
4.3 Spreading: Channelization and Scrambling
2chc
3chc
1chc
scramblingc
The channelization code (or spreading code) is signal-specific: the codelength is chosen according to the bit rate of the signal.
The scrambling code is equipment-specific.
air
interfaceModulator
4 Code Division Multiple Access
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4 Code Division Multiple Access
4.4 Channelization Codes (Spreading Codes)
The channelization codes are OVSF (Orthogonal Variable Spreading Factor)codes:
their length is equal to the spreading factor of the signal: they can
match variable bit rates on a frame-by-frame basis. orthogonality enables to separate physical channels:
UL: separation of physical channels from the same terminal
DL: separation of physical channels to different users within one cell
SF = 1
C ch,1,0 = (1)
C ch,2,0 = (1,1)
C ch,2,1 = (1,-1)
C ch,4,0 =(1,1,1,1)
C ch,4,1 = (1,1,-1,-1)
C ch,4,2 = (1,-1,1,-1)
C ch,4,3 = (1,-1,-1,1)
SF = 4SF = 2 SF = 8
The code tree is shared by severalusers (usually one code tree per
cell)
4 Code Division Multiple Access
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4 Code Division Multiple Access
4.5 Scrambling codes
The scrambling codes provide separation between equipment:
UL: separation of terminalsNo need for code planning (millions of codes!)
There are 224 long and 224 short scrambling codes in uplink
DL: separation of cells
Need for code planning between cells (but trivial task)There are only long scrambling codes in downlink
(512 to limit the code identification during cell search procedure)
The long scrambling codes are truncated to the 10 ms frame length.
Only one DL scrambling code should be used within a cell.
Another scrambling code may be introduced in one cell if necessary
(example : shortage of channelization code), but orthogonality between
users will be degraded.
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5 Soft Handover
5 Soft Handover
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5 Soft Handover
5.1 Introduction
Principle: As the UEs are separated by codes, they send and receive data at the
same time and on the same frequency and one frequency is used in a set of adjacentcells, the soft handover is possible.
A UE is in case ofSoft Handover when it is linked to several cells at the same time.
So , in downlink, the UE receives several time the same data and combine them to
increase the quality. In Uplink, a Node B can receive the same message from several
cells and combines them to increase the quality.
Soft Handover doesnt exist in GSM, it is not possible because there are
different frequencies in a set of adjacent cells.
Interest: Asthe quality of the signal is increased afterthe reception, it is possible to use less power. That
allows to save the interference level.If thisinterference level is too high, it is not possible to
decode the data and the call is drop.
5 Soft Handover
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5 Soft Handover
5.2 Scenarios: Softer Handover
Iu
Core Network
Iubs Iubs
Iur
Iu
Serving RNC
5 Soft Handover
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5 Soft Handover
5.3 Scenarios: Soft Handover
Iu
Core Network
Iubs Iubs
Iur
Iu
Serving RNC
5 Soft Handover
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5 Soft Handover
5.4 Scenarios: Soft Handover inter RNC
Iu
Core Network
Iubs Iubs
Iu
Serving RNC Drift RNCIur
5 Soft Handover
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5 Soft Handover
5.5 Scenarios: SRNC Relocation
Iu
Core Network
Iubs Iubs
Iu
Serving RNC Drift RNCServing RNCIur
5 Soft Handover
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In Downlink,
Scrambling Code
One DL SC per Cell
Channelization Code
One DL CC per radio link to avoid having the
same code sequence on 2 radio links
In Uplink, Scrambling Code
One UL SC per UE
Channelization Code
One UL CC per service (per physical
channel).
The UE sends one signal which can be
received by several cells.
The UE receives several signals
Conclusion:
5 Soft Handover
5.6 Soft Handover & Code Management
Iu
Core Network
Iubs
Serving RNC
CellA Cell B
DL SC cellA
DL CC1 user 1
DL SC cellB
DL CC2 user 1
UL SC eqUL CC user
5 Soft Handover
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Why do we need soft HO?Imagine that a UE penetrates from one cell deeply into an adjacent cell:
it may cause near-far effect
hard HO is not a good solution, due to the hysteresis mechanism
Better spatial repartition of the power, so lower interference level
Additional resources due to soft HO:- Additional rake receiver in Node-B
- Additional Rake Fingers in UE
- Additional transmission links between Node-Bs and RNCs
Soft HO provides Diversity (also called Macro-Diversity), but requiresmore network resource.
5.7 Cost & Benefit
5 Soft Handover
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Soft Handover execution:
Soft Handover is executed by means of the following procedures Radio Link Addition (FDD soft-add);
Radio Link Removal (FDD soft-drop);
Combined Radio Link Addition and Removal.
The cell to be added to the active set needs to have information forwardedby the RNC:
Connection parameters (coding scheme, layer 2 information, )
UE ID and uplink scrambling code,
Timing information from UE
The UE needs to get the following information
Channelization & scrambling codes to be used
Relative timing information (Timing offset based on CPICH synchro)
5.7 Cost & Benefit [cont.]
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6 Rake Receiver
6 Rake Receiver
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6.1 Rake Receiver principle
In a CDMA system there is a single carrier which contains all user signals.
Decoding of all these signals by one receiver is only a question of signal
processing capacity.
A Rake receiver is capable to decode several signals simultaneously in
the so called fingers and to combine them in order to improve thequality of the signal or to get several services at the same time.
A Rake receiver is implemented in mobile phones and in base stations.
A Rake receiver can provide:
- multi-service (via handling of multiple physical channels that arecarrying the services)
- soft handover- path diversity
6 Rake Receiver
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6.1 Rake Receiver principle [cont.]
The components of the multi-code signal are demodulated in parallel each
in one finger of the Rake Receiver.
The outputs of the fingers:
can provide independent data signals
can be combined to provide a better data signal(s)
Delay 1Code Sequence 1
Code Sequence 2 or 3
Code Sequence 2Delay 2
Delay 3
Data 2
1st
Finger
2nd
Finger
3rd
Finger
Data 1
Multi-codesignal
Delay Adjustment
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6.2 Rake Receiver and Multi-Service
As a first approach, we can say:
One service, one code! (*)
Multimedia receiverTransmitter
Spreading 1 Despreading 1
Radio ChannelSpreading 2
Despreading 2
>> Which codes make it possible to
separate the two signals at the
receiver?
6 Rake Receiver
6 3 R k R i d f h d
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6.3 Rake Receiver and soft handover
Soft handover is possible, because the two mobile stations use the same
frequency band. The mobile phone need only one transmission chain to
decode both simultaneously.
Base Station 2
Spreading 1
Despreading 1&2
Spreading 2 Mobile phone
Radio ChannelBase station 1
>> Which codes make it possible to
separate the two signals at the
receiver?
6 Rake Receiver
6 4 R k R i d P h Di i
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6.4 Rake Receiver and Path Diversity
Natural obstacles (buildings, hills) cause reflections, diffractions and
scattering and consequently multipath propagation.
The delay dispersion depends on the environment and is typically:
1 s (300 m) in urban areas 20 s (6000 m) in hilly areas
The delay dispersion should be compared with the chip duration 0,26 s (78 m)
of the CDMA system.
If the delay dispersion is greater than the chip duration, the multipathcomponents of the signal can be separated by a Rake Receiver.
In this case, CDMA can take advantage of multipath propagation.
6 Rake Receiver
6 4 R k R i d P th Di it [ t ]
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6.4 Rake Receiver and Path Diversity [cont.]
Dispersion > Chip duration
The Rake Receiver can provide path diversity to improve the quality of the signal.
ReceiverTransmitter
Spreading
Direct path
Reflected path
ReceiverTransmitter
Spreading Despreading
Direct path
Reflected path
Dispersion > Which codes make it
possible to separate the two
signals at the receiver?
Despreading
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7 Power Control
7 Power Control
7 1 Wh ?
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SIR
7.1 Why ?
Iub
Serving RNC
Main Problem : If the interference level is to high, it is not possible to decode the signal.
f
P
ISCP or No
PG
Eb
RSCP or Ec
At Node B reception level
SIR
7 Power Control
7 2 Diff t ki d f P C t l
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Physical channels:
Not associated with transport channels
(Physical signaling)
Associated with transport channels
Dedicated channels
Common channels
7.2 Different kinds of Power Control
Channel power fixed and set by the
operator
Channel power fixed and set by theoperator
Open Loop Power Control
Closed & Open Loop power control
7 Power Control
7 3 O L P C t l
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7.3 Open Loop Power Control
The Open Loop Power Control is used to set the initial transmit power when: The UE requests a RRC Connection,
The UE sends the first dedicated radio frame,
The Node B sends the first dedicated radio frame.
Based on CPICH measurements
Based on UE measurement reports
CPICH
Initial Access
First dedicated Radio Frame
Measurement reports
First dedicated Radio Frame
7 Power Control
7 4 Closed Loop Power Control: Principle
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Iub
RNC
Outer Closed LoopInner Closed Loop
SIR Estimation
Comparison
between SIRest andSIRtarget
Generation of a TCP
command: increaseor decrease
On each Time slot !
(1500 Hz)...
Power down
Power up
Power down
Power ...
***
***
SIR target
Errormeasurements
The Node-B controls the power of the UE (and vice versa) by performing a SIR estimation (inner loop) andby generating TPC command for each time slot of the radio frame.
The RNC controls parameters of the SIR estimation (outer loop) and set the initial SIR target, defined bythe operator and modify it according to the error measurement reports.
Closed Loop Power Control
7.4 Closed Loop Power Control: Principle
***
***
***
***
7 Power Control
7 4 Closed Loop Power Control: Power Density
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Iub
Assuming a user using a service.
It is initial SIR target is 3dB.
The error ratio required is 0.01 .
Several error ratio reports are between 0.002
and 0.007
How do the SIR target evolve ?
What is the impact on the user or on thesystem if the estimated SIR is too high ? Toosmall ?
7.4 Closed Loop Power Control: Power Density
RNC...
Power up
Power ...
SIR target
Errormeasurement
s
ISCP or No
f
P
SIRest
Eb
RSCP or Ec
At Node B reception level
SIRTarget
7 Power Control
7 5 UL Closed Loop PC in case of Soft Handover
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What is the behavior of the UE in UL in case ofsoft handover ?
The UE takes in to account all the command
according to the 3GPP
P(t)=P(t-1) + F(TPC1(t) + TPC2(t))
The function F(TPC(t)) is implemented by the UE
manufacturer.
F(TPC(t))=min(TCP1(t), , TPCi(t))
With i= number of involved Node B
7.5 UL Closed Loop PC, in case of Soft Handover
Iub
Power up !!!
TPC=1
Power down !!!
TPC=-1
???
1 2
7 Power Control
7 5 DL Closed Loop PC in case of Soft Handover
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Iub
What is the behaviour of the Node B involed
in the call in DL in case of soft handover ?
The UE sends the same command for all
the Node B involved.
Node Bs must transmit data with the same
power for a user
Due to reception errors their power can
shift themselves
A mechanism, the DL Power Balancing,allows to readjust the transmission power of
the Node B.
The SRNC selects the best radio link, andreadjust, step by step, the transmission
power.
P(t) = P(t-1) + Ptpc(t) + Pbal(t)
Power up !!!TPC=1
Power
up
Power
up
7.5 DL Closed Loop PC, in case of Soft Handover
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8 Capacity, Coverage & Quality
8 Coverage, Capacity & Quality
8 1 Links between Coverage Capacity and Quality
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8.1 Links between Coverage, Capacity and Quality
Example: Increase the quality in UL
How to do ?
Decrease the error ratio at the Node B level
So increase the SIR at the Node B level
So the UEs use more power
Impacts !
Increase the UL Interference level
So decrease of the cell size
And decrease the capacity of the cell.
RNC
Node B
Iub
f
P
SIR
SIR
8 Coverage, Capacity & Quality
8 2 Improvement Ways
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8.2 Improvement Ways
AMR speech Codecit enables to switch to a lower bit rate if the mobile is moving out of thecell coverage area: it is a trade-off between quality and coverage.
Multipath diversityit consists of combining the different paths of a signal (due to reflections,
diffractions or scattering) by using a Rake Receiver.
Multipath diversity is very efficient with W-CDMA.
Soft(er) handoverthe transmission from the mobile is received by two or more base stations.
Receive antenna diversitythe base station collects the signal on two uncorrelated branches. It can be
obtained by space or polarization diversity.
Base stations algorithmse.g. accuracy of SIR estimation in power control process
8 Coverage, Capacity & Quality
8 3 Typical Values
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8.3 Typical Values
Quality: The quality is measured with the Block Error Ratio (BLER). Here some example according
different services.
Coverage:
Dense Urban Cell: about 300 meters
SubUrban Cell: about 1 km
Rural Cell: 3 km
Capacity:The main limitation is the interference level due to the WCDMA technology.
But the system is also limited by capacity processing of the Node B and the RNC, by the codes, and by
the transmission capacity.
AMR CS64 PS64 PS128 PS384 DCCH
TargetBLER
0.001 0.01 0.001 0.01 0.1 0.01 0.01 0.01 0.01
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1 Logical Architecture
1 Logical Architecture
1 1 UTRAN Situation & Core Network in 3GPP R4
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1.1 UTRAN Situation & Core Network in 3GPP R4
Core Network
PS-CN
Access Network
Iu-PS
External Networks
HLR
PSTN
IN network
UTRAN
RNC
Node B
PDN
CS Links
PS Links
Gb
Backbone
iGGS
N
SGSNGSM
BSS
BSC
BTSPCU
CS-CN
MSC Server
MGWGMSC
Iu-CS
1 Logical Architecture
1 2 UTRAN Logical Architecture
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1.2 UTRAN Logical Architecture
Core Network
UTRAN
UE
Iub Iub
Iu-CS Iu-PS
Iur
Uu Interface
RNS
CS-CN PS-CN
RNC RNC
Node B Node B
UEs
1 Logical Architecture
1 3 Interfaces
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1.3 Interfaces
Open Interfaces:
The function of the Network Elements have been clearly specified by the
3GPP.
Their internal implementation issues are open for the manufacturer
All the interfaces have been defined in such a detailed level that the
equipment at the endpoints can be from different manufacturers.Open Interfaces aim at motivating competition between manufacturers.
Physical implementation of Iu interfaces
Each Iu Interface may be implemented on any physical connection using
any transport technology, mainly on E1 (cable), STM1 (Optic fiber) andmicro-waves.
ATM will be provided in the 3GPP R4 release and IP is for the 3GPP R6
1 Logical Architecture
1 4 Network Element Function
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1.4 Network Element Function
RNC: Radio Network ControllerIt is the intelligent part of the UTRAN:
- Radio resource management (code allocation, Power Control, congestion
control, admission control)
- Call management for the users
- Connection to CS and PS Core Network- Radio mobility management
Iub IubIur
RNS
Node B Node B
RNC RNC
1 Logical Architecture
1 4 Network Element Function [cont ]
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1.4 Network Element Function [cont.]
Node-B
A Node-B can be considered, as first approximation, like a transcoder
between the data received by antennas and the data in the ATM cell on the
Iub.
- Radio transmission and reception handling
- Involved in the mobility management
- Involved in the power control
Iub
RNC
Node B
ATM Transport
Technology
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2 Network Protocols
2 Network Protocols
2.1 Protocols in UTRAN
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2.1 Protocols in UTRAN
Uu Interface
Core Network
RNC RNC
Node B
Iub
Iu
Iur
Iu Protocols
The Iu protocols Used to exchange data (traffic
and signaling) between RNCs,Node Bs and the Core Network.
Radio Protocols
The Radio protocols Used to process the data sent on
the air and for the signalingbetween UTRAN and the UEs
NAS Signaling Signaling between a UE and
the Core Network. Typically, the Authentification
and the Location
NAS Signaling
2 Network Protocols
2.2 Protocol Stack on the Interfaces based on ATM
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2.2 Protocol Stack on the Interfaces based on ATM
Iub
Iub
Iur
Iu- PS
Iu- CS
Node B
RNC
RNC
RNSAP
RANAP
RANAP
Iu UP
Voice
Iur FP
Iu UP
Data
Control plane User plane
Iub
Node B
CS-CN
PS-CN
RadioSig Voice
NBAPIub FP
Radio
Sig Voice Data
AAL5 AAL2
ATM
AAL5 AAL2
ATM
AAL5 AAL2
ATM
AAL5 AAL5
ATM
Data
Node B
2.2 Protocol Stack on the Interfaces based on ATM
2.2.1 General model
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The same general protocol model is applied for all Iu interfaces:
Application Protocols:
Radio
Network
Layer
Transport
Network
Layer
Physical Layer
Signaling
Bearer(s)
Signaling
Bearer(s)
Data
Bearer(s)
ALCAP
Application
ProtocolData
Stream(s)
Transport Network
Control PlaneTransport Network
User Plane
Transport Network
User Plane
Control
PlaneUser Plane
- NBAP for Iub interface
- RNSAP for Iur interface
- RANAP for Iu-CS and Iu-PS interfaces
1. What is the
purpose of the
separation between
the Radio Network
Layer and the
Transport Network
Layer?
2. Why is ALCAP
protocol
necessary?
2.2.1 General model
2.2 Protocol Stack on the Interfaces based on ATM
2.2.2 Iub protocols
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ATM
Radio
Network
Layer
Transport
Network
Layer
Physical Layer
AAL5 AAL2
ALCAP
NBAPFrame
Protocols
(IubFP)
Control Plane User Plane
AAL5
RRC Connection
Establishment*
Radio Link
Establishment
RABs* NAS signalling*
Transport Network
Control Plane
Transport Network
User Plane
Transport Network User
Plane
2.2.2 Iub protocols
2.2 Protocol Stack on the Interfaces based on ATM
2.2.3 Iur Protocols
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ATM
Radio
Network
Layer
Transport
Network
Layer
Physical Layer
...
AAL5 AAL2
ALCAP
RNSAPFrame
Protocols
(Iur FP)
Control Plane User Plane
AAL5
RRC Connection
Establishment*
Establishment of an
additional radio link
to an UE
(for soft HO)
RABs* NAS signalling*
Transport Network
Control Plane
Transport Network
User Plane
Transport Network User
Plane
2 Network Protocols
2.3 Protocol Stack on the Interfaces based on IP
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Characteristics
Optimized HSPA Offload Hybrid Iub
RNC
Node B
R99 over ATM
E1 Leased
Lines
Ethernet
HSPA over
IPLow CostBackhaul
GigE
STM
E1/T1andEth
SGSN
MSC Server
CS over ATM
PS over Eth
IP Evolution in UA06
2.3 Protocol Stack on the Interfaces based on ATM
UTRAN Interfaces Based on IP (User Plane)
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( )
Voice
AAL2
ATM
Physical
Data
UDP / IP
ETH
Physical
GTP-uVoice
AAL2
ATM
Physical
Data
UDP / IP
ETH
Physical
IP Evolution in UA06
2.3 Protocol Stack on the Interfaces based on ATM
UTRAN Interfaces Based on IP (Control Plane)
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( )
RANAP
IP
ETH
Physical
M3UA
SCTP
SCCP
NBAP
AAL5
ATM
Physical
ALCAP
AAL5
IP Evolution in UA06
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3 Radio Channels
3 Radio Channels
3.1 Global Situation
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UTRAN SGSN GGSN PDNInternet
UMTS Bearer Service External BearerService
UMTS Bearer Service
Radio Access Bearer Service(RAB) CN BearerService
BackboneBearer Service
Iu BearerService
Radio BearerService
Uu Iu
Teleservice
UE
Logical
Channel
TransportChannel
Physical
Channel
3 Radio Channels
3.2 RAB Presentation
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The RAB provides confidential transport of signaling and user data
between UE and CN with the appropriate QoS.
UTRAN
UE UMTS Bearer
UMTS Bearers
RABs (mapped on Radio & Iu Bearers)
CN-CS
CN-PS
Radio Bearers Iu Bearers
UMTS Bearer
UMTS bearer
services
3 Radio Channels
3.3 Radio Channels, Protocols & Network Elements
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RRC
RLC
MAC
BMCPDCP
Physical Layer Physical Layer
NAS
Signaling
RRC
Sig.
VoiceWeb
BrowsingSMS Cell
Broadcast
RadioBearers
Traffic
Logical Ch.
Transport
Channels
Uu Interface
RNC Node B UE
Physical Channels
MAC
Transport
Channels
Control
Logical Ch.
3 Radio Channels
3.4 Radio Bearers
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Signaling Radio Bearers (SRB)
SRBs can carry:
- layer 3 signaling (e.g. RRC connection establishment)
- NAS signaling (e.g location update)
There can be up to 4 SRBs per RRC connection (one UE has one RRC
connection when connected to the UTRAN).
User Plane Radio Bearers
RABs are mapped on user plane RBs.
One RAB can be divided on RAB sub-flows and each sub-flow is mapped on
one user plane RB.
e.g the AMR codec encodes/decodes speech into/from three sub-flows; each
sub-flow can have its own channel coding.
3 Radio Channels
3.5 Logical Channels
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Control Channels (CCH)
Broadcast Control Channel (BCCH)
Traffic Channels (TCH)
Paging Control Channel (PCCH)
Dedicated Control Channel (DCCH)
Common Control Channel (CCCH)
Dedicated Traffic Channel (DTCH)
Common Traffic Channel (CTCH)
UTRAN UELogical Channels
3 Radio Channels
3.5 Logical Channels [cont.]
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UL ( )
/DL ( )
What type of information?
BCCH System control information
e.g cell identity, uplink interference level
PCCH Paging information
e.g CN originated call when the network does not know the
location cell of the UECCCH Control information
e.g initial access (RRC connection request), cell update
DCCH Control information (but the UE must have a RRC connection)
e.g radio bearer setup, measurement reports, HO
DTCH Traffic information dedicated to one UE
e.g speech, fax, web browsing
CTCH Traffic information to all or a group of UEs
e.g SMS-Cell Broadcast
3 Radio Channels
3.6 Why Transport Channels?
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A transport channel offers a flexible pattern to arrange information on any
service-specific rate, delay or coding before mapping it on a physical
channel:
it provides flexibility in traffic variation
it enables multiplexing of transport channels on the same physical channel
Transport channels provide an efficient and fast flexibility in radio
resource management.
Time
Traffic
Time Interval
Transport
Channel
3 Radio Channels
3.7 Structure of a Transport Channel
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168
168
168
168
168
168
168 bits
20 ms
Time Transmission
Interval (TTI): periodicityat which a Transport Block
Set is transferred by the
physical layer on the radio
interface
20 ms
Transport Block: basic
unit exchanged over
transport channels.
Transport Format (TF): it may be changed every TTI. Each
TF must belong to the Transport Format Set (TFS) of the
transport channel
168
168
>> The system delivers one Transport Block Set to thephysical layer every TTI: what is the delivery bit rate of the
transport blocks to the physical layer during the first TTI?
20 ms 20 ms
3 Radio Channels
3.7 Structure of a Transport Channel [cont.]
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Transport Format (TF)
Semi-static part (can be changed, but long process)
Transmission Time Interval (TTI),
Coding scheme...
Dynamic part (may be changed easily)
Size of transport block,
Number of transport blocks per TTI
Transport Format Set (TFS)
It is the set of allowed Transport Formats for a transport channel, which is
assigned by RRC protocol entity to MAC protocol entity.
MAC chooses TF among TFS.MAC may choose another TF every TTI without interchanging with RRC
protocol (fast radio resource control).
3 Radio Channels
3.8 Transport Channels: Example
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576
576
576
576
576
576
576 bits
576
576
40 ms
3. How many Transport Format(s) may be chosen for this transport channel?
4. Can you imagine why the transfer has been interrupted during the third TTI?
Static Part
TTI ?
Coding scheme Turbo coding, coding rate= 1/3
CRC 16 bits
Dynamic Part
Transport Block Size ?
Transport Block Size Set 576*B (B= 0,1,2,3,4)
1. Complete the table
2. What is the delivery
bit rate of the transport
blocks to the physical
layer during the first TTI?
3 Radio Channels
3.9 Transport Channels
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Common Channels
Broadcast Channel (BCH)
Dedicated Channels
Paging Channel (PCH)
Random Access Channel (RACH)
Forward Access Channel (FACH)
Dedicated Channel (DCH)
Common Packet Channel (CPCH)
Downlink Shared Channel (DSCH)
UTRAN Transport Channels UE
3 Radio Channels
3.10 Common Transport Channels
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BCH: Broadcast Channel
A downlink transport channel that is used to carry BCCH. The BCH is
always transmitted with high power over the entire cell with a low fixed bit
rate.
>> The BCH is the only transport channel with a single transport format (no
flexibility). Can you explain why?
PCH: Paging Channel
A downlink transport channel that is used to carry PCCH. It is always
transmitted over the entire cell.
>> Is it possible to carry all types of information on the PCH?
3 Radio Channels
3.10 Common Transport Channels [cont.]
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FACH: Forward Access Channel
A downlink transport channel that is used to carry control information. It may alsocarry short users packets. The FACH is transmitted over the entire cell or over only a
part of the cell using beam-forming antennas. The FACH uses open loop power
control (slow power control).
>> In which case is it interesting to use beam-forming antennas? would it also be
relevant to implement this feature for PCH?
RACH: Random Access Channel
An uplink transport channel that is used to carry control information from the mobile
especially at the initial access. It may also carry short user packets. The RACH is
always received from the entire cell and is characterized by a limited size data field,
a collision risk and by the use of open loop power control (slow power control).
>> Why is it interesting to carry short user packets on RACH in spite of limited data
field and collision risk (instead of using a dedicated channel)?
3 Radio Channels
3.10 Common Transport Channels [cont.]
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DSCH: Downlink Shared Channel
A downlink transport channel shared by several UEs to carry dedicated
control or user information. When a UE is using the DSCH, it always has
an associated DCH, which provides power control.
CPCH: Common Packet Channel
An uplink transport channel that is used to carry long user data packetsand control packets. It is a contention based random access channel. It is
always associated with a dedicated channel on the downlink, which
provides power control.
Transfer of signalling and traffic on a shared basis
3 Radio Channels
3.11 Dedicated Transport Channels
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DCH: Dedicated Channel
A downlink or uplink transport channel that is used to carry user or control
information. It is characterized by features such as fast rate change (on a
frame-by-frame basis), fast power control, use of beam-forming and
support of soft HO.
3 Radio Channels
3.12 Mapping Logical / Transport Channels
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Control Logical Channels
BCCH PCCH CCCH DCCH
Traffic Logical Channels
DTCH CTCH
BCH PCH RACH FACH DSCH CPCH DCH
Common Transport Channels Dedicated
Transport
Channels
3 Radio Channels
3.12 Mapping Logical / Transport Channels [cont.]
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Control Logical Channels
BCCH PCCH CCCH DCCH
Traffic Logical Channels
DTCH CTCH
BCH PCH RACH FACH DSCH CPCH DCH
Common Transport Channels Dedicated
Transport
Channels
3 Radio Channels
3.13 Physical Channels
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RNC
Node B
IubTransport
Channels
For the UE point of view, the network is just the physical channels.
There are several kinds of physical channels. Channel associated with transport channel
UTRAN Signaling (mobility management)
Core Network Signaling (authentication)
User Traffic (voice)
There are common and dedicated channels
Channels not associated with transport channel, the physical
signaling.
Cell Search Selection
System Information Collection
Connection Request and Paging Surveillance
These channels and resources allowing the UE to share these
channels with other users are the radio resources
We will see later how data from transport channel are processed to be
mapped on the physical channels and how a UE uses these channels.
3 Radio Channels
3.14 Physical Channel List
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Not associated with transport channels
CPICH: Common Pilot Channel
PICH: Page Indicator Channel
P-SCH & S-SCH: Primary & Secondary Synchronization Channel
AICH:Acquisition Indicator Channel
Common Physical Channels, associated with transport channels
P-CCPCH & S-CCPCH: Primary & Secondary Common Control Channel
PRACH: Physical Random Access Channel
PDSCH: Physical Downlink Shared Channel
PCPCH: Physical Common Packet Channel
Dedicated Physical Channels, associated with transport channels
DPDCH: Dedicated Physical Data Channel
DPCCH: Dedicated Physical Control Channel
3 Radio Channels
3.15 Downlink
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Logical Ch
Transport Ch
Physical Ch
AICHNot associated with
transport channels PICH CPICH P-SCHS-SCH
PDSCH S-CCPCH P-CCPCHDPDCH
+
DPCCH
DTCH, DCCH CCCH, CTCH
DCH BCHPCHFACHDSCH
Not implemented
yet in Alactel-Lucent
Solution
PCCH BCCH
DPDCH and DPCCH
multiplexed by time
Common Physical ChDedicated
Physical Ch
3 Radio Channels
3.16 Uplink
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Logical Ch
Transport Ch
Physical Ch
PRACH PCPCHDPDCH
+DPCCH
DTCH, DCCH CCCH
DCH1 RACHDCH2
CCTrCH
CPCH
DPDCH and DPCCH
multiplexed bymodulation
Dedicated Physical Ch Common Physical Ch
3 Radio Channels
3.17 Physical Channels: Structure
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A physical channel is defined by:
A carrier Some codes (see 4.3 and 4.4 part)
A start and stop instant
Physical channels are sent continuously on the air interface between start and stop instants.
15 Time
Slots
RadioFrame =10 ms
N bits
(according to the bit rate)
.
1 Time slot =
0.666 ms
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4 UTRAN Radio Protocols
4 UTRAN Radio Protocols
4.1 Radio protocol stack
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Layer 3
Control plane User plane
Layer 2/MAC
Layer 1
Transport Channels
Bearers (called
RAB in user plane)Access Stratum
SAP
Non Access Stratum
control
cont
rol
control
PHY
MAC
RRC
Logical Channels
Layer 2/RLC
Radio Bearers
RLC RLCRLC
RLCRLC
RLCRLCRLC
PDCPPDC
P
BMCcontrol
control
Layer 2/PDCP
Layer 2/BMC
Physical Channels
4 UTRAN Radio Protocols
4.2 Radio Resource Control (RRC)
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control
control
control
PHY
MAC
RRC
RLC
BearersCall management
Radio mobility management
Measurement control and reporting
Outer loop power controlRadio Bearers(control plane)
RRC is the brain of the radio interface protocol stack.
Layer 3
control
control
PDCP
BMC
4 UTRAN Radio Protocols
4.3 PDCP and BMC Protocols
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PDCP (Packet Data Convergence Protocol)
- in the user plane, only for services from the PS domain
- it contains compression methods
In R99 only a header compression method is mentioned (RFC2507).
Why is header compression valuable?
e.g a combined RTP/UDP/IP headers is at least 60 bytes for IPv6, when IPvoice service header can be about 20 bytes or less.
BMC (Broadcast/Multicast Services)
- in the user plane
- to adapt broadcast and multicast services from NAS on the radio interface
In R99 the only service using this protocol is SMS Cell Broadcast Service
(directly taken from GSM).
4 UTRAN Radio Protocols
4.4 Radio Link Control (RLC)
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Traffic
Logical
Channels
Radio Bearers
(user plane)Radio Bearers
(control plane)
RLC RLC
RLCRLCRLC
RLCRLCRLC
Control
Logical
Channels
Segmentation
Buffering
Data transfer with 3
configuration modes:- Transparent (TM)
- Unacknowledged (UM)
- Acknowledged (AM)
Ciphering
RLC provides segmentation and (in AM mode) reliable data transfer.
Layer 2/
upper part
4 UTRAN Radio Protocols
4.5 Medium Access Control (MAC)
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TransportChannels
(common and
dedicated)
Basic data transfer
Multiplexing of logical channels
Priority handling/Scheduling
(TFC selection)
Reporting of measurements
Ciphering
MAC can switch a common channel into a dedicated channel if higher bit rate
is required (on request of L3-level).
MAC can change dynamically Transport Format (bit rate) of each transport
channel on a frame basis (each 10 ms) without interchanging with L3-level.
MAC provides flexible data transfer.
TrafficLogical
Channels
ControlLogical
Channels
MACLayer 2/
lower part
4 UTRAN Radio Protocols
4.6 The Physical Layer
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Dedicated
Physical
Channels
Multiplexing of transport ch.
Spreading/modulation
RF processing
Power control
Measurements
Physical layer
Dedicated
Transport
Channels
The physical layer provides multiplexing and radio frequency
processing with a CDMA method.
Air Interface
Common
Transport
Channels
Common
Physical
Channels
Layer 1
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1 Introduction to UTRAN Scenarios
1 Introduction to UTRAN Scenarios
1.1 Introduction
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Iub
Serving RNC
CN
Collection of System Information
System
InformationRRC
Connection
RRC Connection
IMSI Attachment
IMSI
Attachment
Paging
Paging
The UE is switched on !
How can it retrieve network
parameters to request a service?
1 Introduction to UTRAN Scenarios
1.1 Introduction [cont.]
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Iub
Serving RNC
CN
The UE requests a service.
How and in which conditions are the
resources required setup ?
Admission Control
? RAB Establishment
RAB
1 Introduction to UTRAN Scenarios
1.1 Introduction [cont.]
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Iub
Serving RNC
CN
The UE uses a service and moves !How UTRAN can provide the service despite
the mobility ?
A new radio link is added
Hard Handover on another FDD carrier
Inter RAT Handover
BSCBTS
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2 Radio Channels Mapping
2 Radio Channels Mapping
2.1 Downlink
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Logical Ch.
Transport Ch.
Physical Ch.
AICHNot associated withtransport channels PICH CPICH P-SCH
S-SCH
PDSCH S-CCPCH P-CCPCHDPDCH +
DPCCH
DTCH, DCCH CCCH, CTCH
DCH BCHPCHFACHDSCH
Not implemented
yet in EvoliumTM
Solution
PCCH BCCH
DPDCH and DPCCH
multiplexed bytime
Common Physical Ch.DedicatedPhysical Ch.
2 Radio Channels Mapping
2.2 Uplink
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Logical Ch.
Transport Ch.
Physical Ch.
PRACH PCPCHDPDCH +
DPCCH
DTCH, DCCH CCCH
DCH1 RACHDCH2
CCTrCH
CPCH
DPDCH and DPCCH
multiplexed bymodulation
DedicatedPhysical Ch.
CommonPhysical Ch.
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3 Service Request
3 Service Request
3.1 System Information Collection
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Principles
The UE synchronize itself at the
slot on the P-SCH
UE synchronize itself at the
frame level on the S-SCH andretrieve a group of 8 Scrambling
codes.
The UE test the 8 SC on the
CPICH to find the SC of the cell
The UE decode theBCH
channel
to read the system information
The UE select the best cell
Iub
Serving RNC
CN
???
3.1 System Information Collection
3.1.1 P-SCH & S-SCH
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P-CCPCH Radio Frame 10 ms
Slot #0 Slot #1 Slot #14
acpP-SCH
S-SCH acs0
acp acp
acs2 acs14
The SCH is time-multiplexed with the P-CCPCH (which carries the BCH) and consists of 2 sub-channels.
The Primary SCH (P-SCH) made of always the slot on all the FDD Cells. The UE uses it to acquire the
slot synchronization to a cell.
The Secondary SCH (S-SCH) contains a sequence of 15 codes which identifies the Code Group of the
Downlink Scrambling Code (DL SC) of the cell. The UE uses it to acquire the frame synchronization to acell and to identify the Code Group of the DL SC.
256 chips
3.1 System Information Collection
3.1.2 CPICH
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CPICH (Common Pilot CHannel)
The pilot carries a pre-defined symbol sequence at a fixed rate.
It is a reference:
To aid the channel estimation at the terminal (time or phase reference)
To perform handover measurements and cell selection/reselection (power reference)
The UE tests the 8 DL SC of the Group Code. The DL SC which allows to retrieve the pre-define
sequence is the DL SC of the cell.
Slot #0 Slot #1 Slot #14
Pre-defined symbol sequenceSF=256 Tslot=2560
chips 20 bits
3.1 System Information Collection
3.1.3 System Information Broadcast
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The broadcast system information:
May come from CN, RNC or Node-B.
Contains static parameters (Cell identity, supported PLMN types...) and dynamic
parameters (UL interference level...).
Is arranged in System Information Blocks (SIB), which group together elements of
the same nature.
Some exemple:
SIB1: Core Network Information
SIB3: Cell Selection, Access Restriction
SIB7: UL Interference
SIB11: Measurement
CN
LA, RA
DL SC, Power Control info
UL interference level
3.1 System Information Collection
3.1.3 System Information Broadcast [cont.]
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The broadcast system information can be carried on BCH which is transmitted permanently over
the entire cell.
Transport Ch.
Logical Ch.
Physical Ch.
BCCH
BCH
P-CCPCH
The broadcast system information is made of 128 periodic radio frame. So its period is 1280 ms.
There are a Master SIB or MIB and several SIB (System Information Block) organised by domain.
Frame #0 Frame #1 Frame #2
Frame #i-1 Frame #i Frame #i+1
Frame #125 Frame #126 Frame #127
MIB SIB3 SIB11
SIB5 SIB7 MIB
SIB5SIB11 SIB7
Thanks to this channel, the UE is able to retrieve information allowing the request of aRRC connection like the Channelization code used on the uplink common channel
3.1 System Information Collection
3.1.4 Procedure
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System InformationUpdate Request
Master/Segment InfoBlock(s), BCCH
modification time
Master/Segment Info Block(s)
System Information (BCCH:BCH)
UE Node-B RNC
RRC RRC
NBAP
CN
Master/Segment Info Block(s)
System Information (BCCH:BCH)RRC RRC
Master/Segment Info Block(s)
System Information (BCCH:BCH)RRC RRC
System Information
Update ResponseNBAP NBAP
>> Why does RRC protocolterminate at Node-B for
BCH (not at RNC)?
NBAP
3.1 System Information Collection
3.1.5 Radio Channel Mapping: P-CCPCH
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The Primary CCPCH carries the BCH, which provides system- and cell-specific information (e.g set of uplink scrambling codes)
The P-CCPCH is a fixed rate 30 kbps DL physical channel, which provide atiming reference for all physical channels (directly for DL, indirectly for
UL).
CCPCH is scrambled under the Primary Scrambling code.
Slot #0 Slot #1 Slot #13 Slot #14Slot #i
SCH
Tslot=2560 chips
20 bits
256 chips
Payload of 18 bits
3.1 System Information Collection
3.1.6 Cell Selection Principle
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Now, the UE can read the BCH of one cell.
But this cell is not necessary the best becausethe SCH has been chosen randomly.
The UE compares the cells to be camped on thebest one.
There are 2 criterion:
QRxLev, from the CPICH RSCP, to estimate the
reception level.
Qqual, from the CPICH Ec/No, to estimate thequality of reception. It takes in account the
interference level.
When a UE is not connected, like here, and is
moving, it has to reselect regularly the best cellfor itself. To protect some cells, it is possible to
facilitate or not the selection of one cell.
Iub
RNC
CN
???
3 Service Request
3.2 RRC Connection
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Why?The UE is switched on and has selected a cell.
The UE is in idle mode.
UTRAN doesnt know anything about this UE.
The UE has neither UTRAN identifier nor
Scrambling and Channelization code.
The UE cant exchange any data with UTRAN.
To be known by UTRAN and to use dedicated radio
resources, the UE has to be RRC connected.
After, the UE can attach its IMSI or update its
location to the Core Network and can request a
service
Iub
RNC
CN
RRC Connected
3.2 RRC Connection
3.2.1 UE Status
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UE
detached
UE
in idle mode
UE
in connected
mode
RRC Connection Release
RRC Connection Establishment
out of coverage
just after switch on process
Including Cell search procedure
Just after the switch on, the UE has to attach its IMSI. Thanks to his procedure the Core Network
knows, the UE is on the network and where it is located at the Location or routing area level.
Several sub-status in theconnected
mode
To attach its IMSI and update its location the UE has to be in connected mode, so it
has to request a RRC Connection
3.2 RRC Connection
3.2.1 UE Status [cont.]
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Cell DCH
Cell FACH
URA PCH
Cell PCH
UE
in idle
mode
UE in connectedmode
Cell_DCH state
Signalling and traffic data
dedicated to the UE (mapped
on DCCH and DTCH
respectively) are carried on
DCH transport channel
Cell_FACH state
Signalling and traffic data
dedicated to the UE (mapped
on DCCH and DTCH
respectively) are carried onRACH (uplink) and FACH
(downlink) transport channels
Cell_DCH Cell_FACHNo traffic UL/DL at expiry of timer
Cell_FACH Cell_DCHTraffic volume UL/DL too large
3.2 RRC Connection
3.2.1 UE Status [cont.]
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Cell_PCH state
No transmission of signalling andtraffic data dedicated to the UE
(no DCCH and no DTCH)
But the RRC connection is still
active (UTRAN keeps RNTI for UE)
and UE location at a cell level.
- a DCCH (and possibly a DTCH) canbe reestablished very quickly (this
procedure is initiated by sending a
paging signal PCH)
URA_PCH state
Very similar to cell_PCH state
UTRAN keeps the location of the UE at
the URA level (set of UMTS cells)
Cell_PCH
Cell_FACH
URA_PCHToo many cell reselections
Cell_FACHCell_PCHNo traffic UL/DL at expiry of timer 2
Cell/URA_PCH Cell_FACHIncoming DL or UL traffic
Cell DCH
Cell FACH
URA PCH
Cell PCH
UE
in idle
mode
UE in connectedmode
3.2 RRC Connection
3.2.2 Procedure: RRC Connection Establishment
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Initial UE identity, Establishment cause, Initial UE capability
1. RRC Connection Request (CCCH:RACH)
UE
RRC RRC
3. Radio Link Establishment
Initial UE identity, RNTI, capability update requirement, TFS, TFCS, frequency, UL
scrambling code, power control info
4. RRC Connection Setup (CCCH:FACH)RRC RRC
Integrity information, ciphering information
5. RRC Connection Setup Complete (DCCH:RACH or DCH)RRC RRC
2. Allocate RNTI, Select Level
1 and Level 2 parameters
(e.g. TFCS, scrambling code)
>> Can the UE send user information (e.g voice call) after completing this stage?
Node-B RNC
3.2 RRC Connection
3.2.3 Procedure: RRC Connection: RRC Connection Release
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Node-B(DRNC)
SRNCDRNCNode-B(SRNC)
RRC RRC4. RRC Connection Release (DCCH:DCH )
Cause
RANAP RANAP
1. Iu Release
Command
Cause
RANAP RANAP
2. Iu Release
Complete
-
3. ALCAP Iu Bearer Release
RRC RRC5. RRC Connection Release Complete (DCCH:DCH )
-
6. Radio Link Deletion
7. Radio Link Deletion
8. Radio Link Deletion
UE CN
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3 Service Request
3.3 IMSI Attachment & Location Update
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HLRSGSNMSC/VLR
MSC/VLR SGSN
Iub
RNCThe UE has selected a cell.
It had to declared its identity and its
location (LA & RA) to the Core Network.
So, it requests a RRC connection to send to
the Core Network information about its
situation.
The parameters are mainly the LA, the RAand its IMSI
Initial Attachment
3.3 IMSI Attachment & Location Update3.3.1 Principles
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When camping on a cell, the terminal must register its LA and/or its RA.
When the terminal moves across the network, it must update its LA (RA) which is stored in VLR
(SGSN) in the Core Network.
LA (RA) Update is performed periodically or when entering a new LA (RA).
HLRSGSNMSC/VLR
Location Area
(LA)Routing Area (RA)MSC/VLR SGSN
3.3 IMSI Attachment & Location Update3.3.2 Procedure: Direct Transfer
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RANAP RANAP1. Direct Transfer
CN Domain Indicator,NAS PDU
RRC RRC
2. Downlink Direct Transfer
(DCCH:FACH or DCH)
NAS message
UE Node-B SRNC CN
Use mainly for the IMSI attachment, location update and the authentification between the UE and
the Core Network
RANAP RANAP2. Direct Transfer
CN Domain Indicator,NAS PDU
RRC RRC
1. Uplink Direct Transfer
(DCCH:RACH or DCH)
CN node indicator, NAS message
3 Service Request3.4 Paging
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Core Network
Called number
HLRMSC/VLR MSC/VLR
Location Area
Some one is calling
me, I request a RRC
connection
Principle
Paging messagewith the IMSI of the
called UE
Iub
RNC
Iub
RNC
Iub
RNC
3.4 Paging3.4.1 Procedure 1: UE in Connected Mode
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RANAP RANAP1. Paging
CN Domain Indicator, UEidentity, Paging cause
RRC RRC2. Paging Type 2 (DCCH:FACH or DCH)
In this case the UE is already connected and is using a service (voice call, web-browsing ).
The Core Network knows the situation of the UE and mainly its Serving RNC. The CN
contacts directly the Serving RNC.
The RNC doesnt use the PCCH and the PCH but the channel used for the UE, dedicated or
common, according to the status of the UE.
UE Node-B SRNC CN
3.4 Paging3.4.2 Procedure 2: UE in Idle Mode
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RRC RRC2. Paging Type 1 (PCCH:PCH)
RRC RRC2. Paging Type1 (PCCH:PCH)
RANAP RANAP1. Paging
CN Domain Indicator, UEidentity, Paging cause
RANAP RANAP1. Paging
Idem
When the is in idle mode, UTRAN doesnt know where it is located and the Core Network
knows its location at the LA or RA level. UTRAN uses the PCCH and the PCH radio channels.
UE 1 Node-B1UE 2 Node-B2 RNC1 RNC2 CN
3.4 Paging3.4.3 Paging: PICH & PCH Radio Channels
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The UE doesnt watch the S-CCPCH.
It watches the PICH (Page Indicator
Channel) at regular and defined
interval and look for its PI, for
Paging Indicator.
The PI is based on the IMSI. Several
UEs can have the same PI.
When the UE find its PI on the
PICH, it watches the S-CCPCH to
check if it is for it and what is the
cause.
Then it requests on RRC connection
to have a RAB.
Transport Ch
Iub
RNC
PICHS-CCPCH
PCH
PCCH Logical Ch
Physical Ch
MAC
Physical
layer
In RNC
In Node B
PICHS-CCPCH
Paging
message
PI
PI
PI
...
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4 RAB Establishment
4 RAB Establishment4.1 Admission Control
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According to the previous part WCDMA in UMTS, if the interference level at the Node B level is
too high, the Node B cant decode all the signal. The size of the cell decreases. The interferences
are due to several causes:
The radio environment and the load of the adjacent cells,
Some users use too much power, the power control manages this problem,
There are too many users on the the cells
UTRAN has to check if there is enough UL radio resource
Iub
RNC
f
P
ISCP = NoSIR
PG
Eb
RSCP = Ec
At Node B reception level
SIR too small to
retrieve the message
2 others questions before adding a new user : Is there sufficient DL radio resource and
sufficient processing resources ?
4 RAB Establishment4.1 Admission Control [cont.]
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Is there sufficient UL Radio Resource -> Rx RAC