Download - 2- WCDMA Power Control.ppt
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OWJ200107 WCDMA Power Control
ISSUE 1.0
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Chapter 1 Power Control OverviewChapter 1 Power Control Overview
Chapter 2 open loop Power Control Chapter 2 open loop Power Control
Chapter 3 closed loop Power Control Chapter 3 closed loop Power Control
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Uplink transmission character
Self-interference
Capacity is limited by interference
Near-far effect
Fading
Uplink power control
Ensure uplink quality with minimum transmission power
Decrease interference to other UE, and increase capacity
Solve the near-far effect
Save UE transmission power
Purpose of uplink power control
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Downlink transmission character
Interference among different subscribers since the orthogonality is
influenced by transmission environment
Interference from other adjacent cells
Downlink capacity is limited by NodeB transmission power
Fading
Downlink power control
Ensure Downlink quality with minimum transmission power
Decrease interference to other cells, and increase capacity
Save NodeB transmission power
Purpose of downlink power control
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The Relationship between Transmitted Power and Received Power after Power Control Methods Introduced
0 200 400 600 800-20
-15
-10
-5
0
5
10
15
20
Time (ms)
Rel
ati
ve
po
wer
(d
B)
Channel
Transmitted power
Received power
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Power Control Classification
Power control classification:
open loop power control
closed loop power control
− Uplink inner-loop power control
− Downlink inner-loop power control
− Uplink outer-loop power control
− Downlink outer-loop power control
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Power control methods adopted for various physical channels
Power control methods adopted for various physical channels
“Y" can be applied,
– not applied
Physi calchannel
Open l ooppowercontrol
I nner l ooppowercontrol
Outer l ooppowerControl
No power control process,power i s speci fi ed byupper l ayers.
DPDCH - Y Y -DPCCH Y Y Y -PCCPCH - - - YSCCPCH - - - YPRACH Y - - -AI CH - - - YPI CH - - - Y
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Chapter 1 Power Control OverviewChapter 1 Power Control Overview
Chapter 2 open loop Power ControlChapter 2 open loop Power Control
Chapter 3 closed loop Power Control Chapter 3 closed loop Power Control
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Chapter 2 open loop Power Control Chapter 2 open loop Power Control
2.1 open loop power control overview2.1 open loop power control overview
2.2 PRACH open loop power control2.2 PRACH open loop power control
2.3 DPCCH open loop power control2.3 DPCCH open loop power control
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open loop Power Control Overview
Purpose
UE estimates the power loss of signals on the propagation path
by measuring the downlink channel signals, then calculates the
transmission power of the uplink channel
principle
Path loss of the uplink channel is related to path loss of the
downlink channel
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open loop Power Control Overview
Disadvantage
This power control method is rather rough
Application scenarios
In a cell, signal fading caused by fast fading is usually more serious
than that caused by propagation loss.
open loop power control is applied only at the beginning of connection
setup, generally in setting the initial power value.
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Chapter 2 Open Power Control Chapter 2 Open Power Control
2.1 open loop power control overview2.1 open loop power control overview
2.2 PRACH open loop power control2.2 PRACH open loop power control
2.3 DPCCH open loop power control2.3 DPCCH open loop power control
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open loop Power Control of PRACH
AICH accessslots RX at UE
PRACH accessslots TX at UE
One access slot
p-a
p-mp-p
Pre-amble
Pre-amble
Message part
Acq.Ind.
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open loop Power Control of PRACH
The initial value of PRACH power is set through open loop power
control:
Preamble_Initial_Power
= PCPICH DL TX power - CPICH_RSCP + UL
interference + Constant Value
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open loop power control of PRACH
NO. Parameter Parameter meaning
1 Power Offset Pp-m The power offset of the last access preamble and message control part. This
value plus the access preamble power is the power of the control part
2 Constant Value This parameter is the correction constant used for the UE to estimate the
initial transmission power of PRACH according to the open loop power
3 PRACH Power Ramp Step This parameter is the ramp step of the preamble power when the UE has not
received the capture indication from NodeB
4 Preamble Retrans Max This parameter is the permitted maximum preamble repeat times of the UE
within a preamble ramp cycle
Power Ramp Step
Pp-m
10ms/20ms
Preable_Initial_power
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open loop power control of PRACH open loop power control of PRACHApplication scenariosApplication scenarios
1. CCCH : RRC Connection Request
open loop power control of PRACH
5. Downlink Synchronization
UE Node BServing RNS
Serving RNC
DCH - FP
Allocate RNTISelect L1 and L2parameters
RRC RRC
NBAP NBAP
3. Radio Link Setup Response
NBAP NBAP
2. Radio Link Setup Request
RRC RRC
7. CCCH : RRC Connection Set up
Start RX description
Start TX description
4. ALCAP Iub Data Transport Bearer Setup
RRC RRC
9. DCCH : RRC Connection Setup Complete
6. Uplink Synchronization
NBAP NBAP
8. Radio Link Restore Indication
DCH - FP
DCH - FP
DCH - FP
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Chapter 2 open loop Power Control Chapter 2 open loop Power Control
2.1 open loop power control overview2.1 open loop power control overview
2.2 PRACH open loop power control2.2 PRACH open loop power control
2.3 DPCCH open loop power control2.3 DPCCH open loop power control
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open loop power control of DL DPCCH
The DL DPDCH open loop power control can be calculated by the following formula:
P=(Ec/Io)Req-CPICH_Ec/Io + CPICH_Power
Parameters explanation
(Ec/Io)req is the required Ec/Io, which should ensure that UE can receive the message from the dedicated channel correctly
CPICH_Ec/Io is measured by UE, then it is sent to UTRAN by RACH
CPICH_Power is the transmission power of CPICH
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open loop power control of DL DPCCH open loop power control of DL DPCCH
Application scenariosApplication scenarios
1. CCCH : RRC Connection Request
open loop power control of DPCCH
5. Downlink Synchronization
UE Node BServing RNS
Serving RNC
DCH - FP
Allocate RNTISelect L1 and L2 parameters
RRC RRC
NBAP NBAP
3. Radio Link Setup Response
NBAP NBAP
2. Radio Link Setup Request
RRC RRC
7. CCCH : RRC Connection Set up
Start RX description
Start TX description
4. ALCAP Iub Data Transport Bearer Setup
RRC RRC
9. DCCH : RRC Connection Setup Complete
6. Uplink Synchronization
NBAP NBAP
8. Radio Link Restore Indication
DCH - FP
DCH - FP
DCH - FP
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open loop power control of UL DPCCH
The UL DPCCH open loop power control can be calculated by
the following formula:
DPCCH_Initial_Power
= DPCCH_Power_Offset - CPICH_RSCP
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open loop power control of UL DPCCH open loop power control of UL DPCCH
Application scenariosApplication scenarios
1. CCCH : RRC Connection Request
open loop power control of DPCCH
5. Downlink Synchronization
UE Node BServing RNS
Serving RNC
DCH - FP
Allocate RNTISelect L1 and L2parameters
RRC RRC
NBAP NBAP
3. Radio Link Setup Response
NBAP NBAP
2. Radio Link Setup Request
RRC RRC
7. CCCH : RRC Connection Set up
Start RX description
Start TX description
4. ALCAP Iub Data Transport Bearer Setup
RRC RRC
9. DCCH : RRC Connection Setup Complete
6. Uplink Synchronization
NBAP NBAP
8. Radio Link Restore Indication
DCH - FP
DCH - FP
DCH - FP
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Chapter 1 Power Control OverviewChapter 1 Power Control Overview
Chapter 2 open loop Power Control Chapter 2 open loop Power Control
Chapter 3 closed loop Power Control Chapter 3 closed loop Power Control
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Chapter 3 closed loop Power Control Chapter 3 closed loop Power Control
3.1 closed loop power control overview3.1 closed loop power control overview
3.2 Uplink inner loop power control3.2 Uplink inner loop power control
3.3 Downlink inner loop power control3.3 Downlink inner loop power control
3.4 Outer loop power control3.4 Outer loop power control
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closed loop power control overview
The characteristics of open loop power control
The results from open loop power control are not accurate enough
open loop power control can only decide the initial power
The advantages of closed loop power control
Guarantee the QoS
Decrease the interference
Increase the system capacity
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closed loop power control overview
Inner loopOuter loop
BLERmea>BLERtar→SIRtar
BLERmea<BLERtar→SIRtar
Until BLERmea=BLERtar
SIRtar
SIRmea>SIRtar→TPC=0
SIRmea<SIRtar→ TPC=1
UntilSIRmea=SIRtar
TPC
TPC=0 Power
TPC=1 Power
BLERtar
Ensure the QoS with minimum
power
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Chapter 3 closed loop Power Control Chapter 3 closed loop Power Control
3.1 closed loop power control overview3.1 closed loop power control overview
3.2 Uplink inner loop power control3.2 Uplink inner loop power control
3.3 Downlink inner loop power control3.3 Downlink inner loop power control
3.4 Outer loop power control3.4 Outer loop power control
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Uplink-inner loop power control
NodeB compares the measured SIR to the preset target SIR
NodeB
UE
Transmit TPC
Inner-loop
set SIRtar
1500Hz1500Hz
Each UE has its own loop
Each UE has its own loop
TPC Decision(0 , 1)
TPC_CMD( -1, 0, 1)
Adjust DPCCH Tx△ DPCCH= tpc×TPC_cmd△
PCA1 PCA2
Adjust DPDCH Tx(βc,βd)
Compare SIRmeas with SIRtar
SIRmea>SIRtar→TPC=0SIRmea<SIRtar→ TPC=1
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UE gets one TPC in each time slot
If TPC=0, TPC_cmd= -1
If TPC=1, TPC_cmd= 1
This control is done in each time slot
Power control frequency is 1500HZ
0 1 1 0 1 1 0 1 1 0…… ……
…… ……TPC_CMD
TPC
-1 1 1 -1 1 1 -1 1 1 -1
Uplink inner-loop PCA1 without soft handover
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0 1 1 0 1 1 0 1 1 0…… ……
RLS1-TPC (W1)
…… ……RLS2-TPC (W2) 1 0 1 1 0 1 0 1 0 1
…… ……
…… ……TPC_CMD
0 0 1 0 0 1 1 0 1 1
0 0 1 0 0 1 0 0 0 0
Each time slot, combine TPC from different RLS , then get Wi
CELL1 CELL2
CELL4CELL3
RL11 RL12
RLS1
RLS2 RLS3
RLS3-TPC (W3)
Get TPC_cmd based on
TPC_cmd = γ (W1, W2, … WN)
Uplink inner-loop PCA1 with soft handover
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0 1 1 0 1 1 0 1 1 0…… ……
RLS1-TPC (W1)
…… ……RLS2-TPC (W2) 1 0 1 1 0 1 0 1 0 1
…… ……
…… ……TPC_CMD
0 0 1 0 0 1 1 0 1 1
0 0 1 0 0 1 0 0 0 0
Each time slot, combine TPC from different RLS , then get Wi
CELL1 CELL2
CELL4CELL3
RL11 RL12
RLS1
RLS2 RLS3
RLS3-TPC (W3)
Get TPC_cmd based on
TPC_cmd = γ (W1, W2, … WN)
Uplink inner-loop PCA1 with soft handover
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TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS8 TS9 TS10 TS11 TS12 TS13 TS14
0 0 0 0 0 1 1 1 1 1 1 1 0 1 1
10ms/frame
Group 2Group 1 Group 3
…… ……
0 0 0 0 -1 0 0 0 0 1 0 0 0 0 0
TPC
TPC_CMD
Transmission power will be controlled in each 5 time slots
The frequency is 300HZ
…… ……
Uplink inner-loop PCA2 Without soft handover
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Combine TPC from same RLS in each time slot
Calculate TPC_cmd
TPC_CMD=1
TPC_CMD=-1
Otherwise TPC_CMD=0
Calculate TPC_tempi for each RLSIf 5 TPC are all 1, TPC_tempi=1
If 5 TPC are all 0, TPC_tempi=-1Otherwise, TPC_tempi =0
5.0_1
1
N
iitempTPC
N
5.0_1
1
N
iitempTPC
N
CELL1 CELL2
CELL4CELL3
RL11 RL12
RLS1
RLS2 RLS3
Uplink inner-loop PCA2 With soft handover
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TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS8 TS9 TS10 TS11 TS12 TS13 TS14
RLS1 0 0 1 0 0 0 0 0 0 0 0 1 0 0 1
RLS2 1 1 1 1 1 0 0 0 0 0 1 1 0 0 1
RLS3 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1
…… ……
10ms/frameGroup 1 Group 2 Group 3
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS8 TS9 TS10 TS11 TS12 TS13 TS14
RLS1 0 0 0 0 0 0 0 0 0 -1 0 0 0 0 0
RLS2 0 0 0 0 1 0 0 0 0 -1 0 0 0 0 0
RLS3 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1
…… ……
TPC
TPC_tempi
TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS8 TS9 TS10 TS11 TS12 TS13 TS14
0 0 0 0 1 0 0 0 0 -1 0 0 0 0 0…… ……
TPC_CMD
Power is controlled in each 5 time slots
The power control frequency is 300HZ
Uplink inner-loop PCA2 with soft handover
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Comparison between PCA1 and PCA2
The control frequency
TPC1, the power control frequency is 1500Hz
TPC2, the power control frequency is 300Hz
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Chapter 3 closed loop Power Control Chapter 3 closed loop Power Control
3.1 closed loop power control overview3.1 closed loop power control overview
3.2 Uplink inner loop power control3.2 Uplink inner loop power control
3.3 Downlink inner loop power control3.3 Downlink inner loop power control
3.4 Outer loop power control3.4 Outer loop power control
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NodeB
set SIRtar
Transmit TPC
Measure and compare SIR
Measure and compare BLER
Outer loop
Inner loop L1
L3
10-100Hz1500Hz
Downlink closed loop power control
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Downlink Inner loop power control
NodeB
Set SIRtar
Transmit TPC in each TS
Measure SIR and compare
it with SIRtar
Adjust Tx power
with 0.5, 1, 1 or 2dB
1500HzL3
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Downlink inner loop power control
When UE is not in soft handover
The TPC which is generated by UE is transmitted in TPC domain
of UL channel
When UE is in soft handover, two power control modes can be used,
which is decided by DPC_mode:
DPC_MODE = 0 , UE will transmit TPC in every slot
DPC_MODE = 1 , UE will transmit the same TPC in every three
time slot
When the downlink channel is in out of synchronization, UE will
transmit TPC 1 because UE can not measure the downlink SIR
How to generate TPCHow to generate TPC
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The transmission power can not higher than Maximum_DL_Power, and not
less than Minimum_DL_Power neither.
Downlink power adjustment:
Pk Pk 1PTPCkPbalk
Where
P(k-1) is power of previous
PTPC(k) is the adjustment
Pbal(k) is correction value
Downlink inner-loop power controlHow to adjust powerHow to adjust power
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Where
PTPC(k) is the adjustment value
TPCest(k) is uplink TPC value
△TPC is downlink power adjustment step(0.5, 1, 1.5 or
2dB)
PTPC(k)
Without “Limited Power Raise Used”
Downlink inner-loop power controlHow to adjust powerHow to adjust power
0)(TPCifΔ
1)(TPCifΔ)(P
estTPC
estTPCTPC k
kk
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Where
PTPC(k)
With “Limited Power Raise Used”
Downlink inner-loop power control
0)(TPC if
e_LimitPower_Rais)( and 1)(TPC if
e_LimitPower_Rais)( and 1)(TPC if
0)(
est
est
est
k
kk
kk
kP TPCsum
TPCsum
TPC
TPC
TPC
PTPC(k) is the adjustment value
TPCest(k) is uplink TPC value
△TPC is downlink power adjustment step(0.5, 1, 1.5 or 2dB)
Power_Raise_Limit: the limited value for Power ramping in a timer
DL_power_averaging_window_size : timer for power ramping (TS)
1
1____
)()(k
SizeWindowAveragingPowerDLkiTPCsum iPk
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Downlink inner-loop power control
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Downlink Power Balance
Downlink power balance process
SRNC can monitor every single
NodeB’s transmission. If SRNC found
the power offset in soft handover is
excessive, it will initiate the DPB
process
The initiation and stop of DPB
The power offset of two RLs is greater
than the DPB initial threshold, the
DPB process is initiated
The power offset of two RLs is less
than the DPB stop threshold, the DPB
process is stopped
NodeB
NodeB
Initiate the DPB process
DPB process
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Chapter 3 closed loop Power Control Chapter 3 closed loop Power Control
3.1 closed loop power control overview3.1 closed loop power control overview
3.2 Uplink inner loop power control3.2 Uplink inner loop power control
3.3 Downlink inner loop power control3.3 Downlink inner loop power control
3.4 Outer loop power control3.4 Outer loop power control
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Outer loop power control
The character of outer loop power control
The QoS which NAS provides to CN is BLER, not SIR
The relationship between inner loop power control and outer loop
power control
SIRtar should be satisfied with the requirement of decoding
correctly. But different multi-path radio environments request
different SIR
Therefore, the outer loop power control can adjust the SIR to get a
stable BLER in the changeable radio environment
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Uplink outer loop power control
NodeB UE
Transmit TPC
Measure and compare SIR
Inner-loop
Set SIRtar
Out loop
RNC
Measure received data and compare BLER in the TrCH
Set BLERtar
10-100Hz
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NodeB
set SIRtar
Transmit TPC
Measure and compare SIR
Measure and compare BLER
Outer loop
Inner loop L1
L3
10-100Hz1500Hz
Downlink outer loop power control
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Outer loop power control
SIR target adjustment SIR target adjustment stepstep
etBLERt
etBLERtBLERmeastepSIRAdjustSoefficientSIRAdjustcSIRtar
arg
arg**
Where
SirAdjustStep: Outer loop power control adjustment step
SirAdjustcoefficient : Coefficient for outer loop power control
BLERest: Estimated BLER
BLERtar: Target BLER
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Outer loop power control
Uplink outer loop power control command transmit to NodeB
through DCH-FP of Iub interface
Node B SRNC
……
Outer loop power control
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