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HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
www.huawei.com
Internal
OWJ200107 WCDMA Power Control
ISSUE 1.1
HUAWEI TECHNOLOGIES CO., LTD. Page 2All rights reserved
Chapter 1 Power Control OverviewChapter 1 Power Control Overview
Chapter 2 Open Loop Power Control Chapter 2 Open Loop Power Control
Chapter 3 Close Loop Power Control Chapter 3 Close Loop Power Control
HUAWEI TECHNOLOGIES CO., LTD. Page 3All rights reserved
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
HUAWEI TECHNOLOGIES CO., LTD. Page 4All rights reserved
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
HUAWEI TECHNOLOGIES CO., LTD. Page 5All rights reserved
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
HUAWEI TECHNOLOGIES CO., LTD. Page 6All rights reserved
Power control classification
Power control classification :
Open loop Power control
Closed loop Power control
− Uplink inner power control
− Downlink inner-power control
− Uplink outer power control
− Downlink outer power control
HUAWEI TECHNOLOGIES CO., LTD. Page 7All rights reserved
Power control methods adopted for various physical channels
Power control methods adopted for various physical channels
"X" – can be applied, "–" – not applied
Physical
channel
Open loop
power
control
Inner loop
power
control
Outer loop
power
Control
No power control process,
power is specified by upper
layers.
DPDCH - X X -
DPCCH X X X -
PCCPCH - - - X
SCCPCH - - - X
PRACH X - - -
AICH - - - X
PICH - - - X
HUAWEI TECHNOLOGIES CO., LTD. Page 8All rights reserved
Chapter 1 Power Control OverviewChapter 1 Power Control Overview
Chapter 2 Open Loop Power ControlChapter 2 Open Loop Power Control
Chapter 3 Close Loop Power Control Chapter 3 Close Loop Power Control
HUAWEI TECHNOLOGIES CO., LTD. Page 9All rights reserved
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
HUAWEI TECHNOLOGIES CO., LTD. Page 10All rights reserved
Open Loop Power Control Overview
Purpose
UE estimates the power loss of signals on the propagation path
by measuring the downlink channel signals, then calculate the
transmission power of the uplink channel
The open loop power control principle
Fast fading of the uplink channel is unrelated to fast fading of the
downlink channel
HUAWEI TECHNOLOGIES CO., LTD. Page 11All rights reserved
Open Loop Power Control Overview
the disadvantage of open loop power control
This power control method is rather vague
Application scenarios of open loop power control
In the range of 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.
HUAWEI TECHNOLOGIES CO., LTD. Page 12All rights reserved
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
HUAWEI TECHNOLOGIES CO., LTD. Page 13All rights reserved
Open Loop Power Control of PRACH
The random access procedure of PRACH is shown in above figure: UE transmit a preamble using the selected uplink
access slot, signature, and preamble transmission power. After that ,UTARN will response AI if the preamble is
received. Then the UE will transmit the message part if the AI is received. But, if UE does not receive the AI from
UTRAN in τp-p period, a next preamble will be transmitted. The process won’t stop until the AI received by UE.
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.
HUAWEI TECHNOLOGIES CO., LTD. Page 14All rights reserved
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
Parameters explanation
The values of PCPICH DL TX power 、 UL interference and Constant
Value are given in system information.
The value of CPICH_RSCP is measured by UE
PCPICH DL TX power is very closed to the downlink coverage ability,
which is already given in cell setup.
UL interference can be measured by NodeB, then it will be reported to RNC.
Constant Value is the threshold of preamble message. This value has to be
analysed very carefully.
HUAWEI TECHNOLOGIES CO., LTD. Page 15All rights reserved
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
HUAWEI TECHNOLOGIES CO., LTD. Page 16All rights reserved
Open loop power control of PRACH
Different Constant Values for different stage of WCDMA network
lifecycle. Take the beginning stage for example:
Constant Value could be greater (-16dB or -15dB) so that the
preamble message can be received easier by UTRAN
The power ramp step could be greater so that the possibility which
the preamble message can be received correctly will be higher
With the increasing of subscribers, the Constant value could be
less 1dB.
HUAWEI TECHNOLOGIES CO., LTD. Page 17All rights reserved
Open loop power control of PRACH Open loop power control of PRACH
Application scenariosApplication scenarios
1. CCCH : RRC Connection Request
Open loop power control of PRACH
5. Downlink Synchronisation
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 Synchronisation
NBAP NBAP
8. Radio Link Restore Indication
DCH - FP
DCH - FP
DCH - FP
HUAWEI TECHNOLOGIES CO., LTD. Page 18All rights reserved
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
HUAWEI TECHNOLOGIES CO., LTD. Page 19All rights reserved
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+PCPICH
Parameters explanation
(Ec/Io)req is the required Ec/Io, which should satisfied UE can receive the message from the dedicated channel correctly
CPICH_Ec/Io is measured by UE, then it is given to UTRAN by RACH
PCPICH is the transmission power of CPICH
Comments
Similar to UL, the (Ec/Io)Req value should be considered very carefully
Because there is not power ramp in the initial DL DPCCH, the initial power should be satisfied with the requirements. Therefore, this value can begreater than the one from simulation to ensure the success ratio
With PO1, PO2 and PO3, initial transmission power for DPCCH can be calculated
HUAWEI TECHNOLOGIES CO., LTD. Page 20All rights reserved
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 Synchronisation
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 Synchronisation
NBAP NBAP
8. Radio Link Restore Indication
DCH - FP
DCH - FP
DCH - FP
HUAWEI TECHNOLOGIES CO., LTD. Page 21All rights reserved
Open loop power control of UL DPCCH The UL DPCCH open loop power control can be calculated by the
following formula:
DPCCH_Initial_power = PCPICH DL TX power-CPICH_RSCP
+UL interference+ Default Constant Value
References explanation
PCPICH DL TX power is the transmission power of CPICH
CPICH_RSCP can be measured by UE
UL interference can be measured by NodeB
Comments
Default Constant Value will decide initial transmission power of Uplink DPCCH
This value is different from the previous “Constant value” for PRACH
HUAWEI TECHNOLOGIES CO., LTD. Page 22All rights reserved
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 Synchronisation
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 Synchronisation
NBAP NBAP
8. Radio Link Restore Indication
DCH - FP
DCH - FP
DCH - FP
HUAWEI TECHNOLOGIES CO., LTD. Page 23All rights reserved
Chapter 1 Power Control OverviewChapter 1 Power Control Overview
Chapter 2 Open Loop Power Control Chapter 2 Open Loop Power Control
Chapter 3 Close Loop Power Control Chapter 3 Close Loop Power Control
HUAWEI TECHNOLOGIES CO., LTD. Page 24All rights reserved
Chapter 3 Close Loop Power Control Chapter 3 Close Loop Power Control
3.1 Close Loop power control overview3.1 Close 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
HUAWEI TECHNOLOGIES CO., LTD. Page 25All rights reserved
Close loop power control overview
The deficiencies of open loop power control
the open loop power control can decided the initial power, but it’s still inaccurate
For WCDMA-FDD system, the uplink fading is not related to the downlink one because of the big frequency interval of them
Therefore, the path loss and interference estimated by downlink can not reflect the one in uplink completely. But, the close loop power control can solve this problem
The advantages of close loop power control
Can convergence the transmission power of uplink and downlink very fast, and decrease interference in system.
Maintains a higher quality of service
Why the close loop power control is neededWhy the close loop power control is needed
HUAWEI TECHNOLOGIES CO., LTD. Page 26All rights reserved
Close loop power control overview
Inner loopOuter loop
Control process:BLERmea>BLERtar→SIRtar
BLERmea<BLERtar→SIRtar
Until to BLERmea=BLERtar
SIRtar
Control process :SIRmea>SIRtar→TPC=0
SIRmea<SIRtar→ TPC=1
Until toSIRmea=SIRtar
TPC
Control process :TPC=0 Power
TPC=1 Power
Inner loop power control With TPC in DPCCH, the SIR can be ensured to the level of target SIR. Inner loop power control can be done 1500 times in 1 second
Outer loop power control Through adjusting the SIR target value, BLER can be ensured to the QoS requirement
BLERtar
Ensure the QoS with minimum
power
HUAWEI TECHNOLOGIES CO., LTD. Page 27All rights reserved
Chapter 3 Close Loop Power Control Chapter 3 Close Loop Power Control
3.1 Close Loop power control overview3.1 Close 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
HUAWEI TECHNOLOGIES CO., LTD. Page 28All rights reserved
Uplink-inner loop power control
NodeB compares the measured signal-to-interference ratio
to the preset target signal-to-interference ratio (SIRtarget).
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
HUAWEI TECHNOLOGIES CO., LTD. Page 29All rights reserved
Uplink inner-loop power control
The receivers calculate the SIR by estimating the power strengthen
and the current interference. Then, compare this one with SIRtarget,
If less than SIRtarget, the TPC is 1 to tell receivers increase
transmission power
If greater than SIRtarget, the TPC is 0 to tell receivers decrease
transmission power
The receiver which get the TPC will adjust the transmission power by
algorithms. The inner loop power control can convergence the
estimated SIR to SIR target
How to produce TPCHow to produce TPC
HUAWEI TECHNOLOGIES CO., LTD. Page 30All rights reserved
Uplink inner-loop power control
In 3GPP protocol, UE can get different TPC_cmd (1, 0, -1) based
on different PCA (power control algorithm)
Adjustment on DPCCH
△DPCCH= tpc×TPC_cmd△
− If TPC_cmd=1 , Uplink DPCCH Tx should increase △ tpc
− If TPC_cmd=-1 , Uplink DPCCH Tx should decrease △ tpc
− If TPC_cmd=0 , uplink DPCCH Tx does not change
△tpc
PCA1 , uplink power control step is tpc=△ 1dB or 2dB
PCA2 , uplink power control step is tpc=△ 1dB
TPC_cmdTPC_cmd
HUAWEI TECHNOLOGIES CO., LTD. Page 31All rights reserved
Uplink DPDCH power is decided by the offset between DPCCH and DPDCH
This offset is decided by upper layer
Uplink inner-loop power control
Pilot N pilot bits
TPC NTPC bits
DataNdata bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10 bits
1 radio frame: T f = 10 ms
DPDCH
DPCCHFBI
N FBI bitsTFCI
N TFCI bits
Tslot = 2560 chips, N data = 10*2 k bits (k=0..6)
HUAWEI TECHNOLOGIES CO., LTD. Page 32All rights reserved
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 TS
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 power controlWithout soft handover in PCA1Without soft handover in PCA1
HUAWEI TECHNOLOGIES CO., LTD. Page 33All rights reserved
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
…… ……
…… …… Final TPC
0 0 1 0 0 1 1 0 1 1
0 0 1 0 0 1 0 0 0 0
Each TS, 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)
With soft handover in PCA1With soft handover in PCA1
Uplink inner-loop power control
HUAWEI TECHNOLOGIES CO., LTD. Page 34All rights reserved
Each time slot, UE will receive TPC from different RL. UE can get the final
TPC_cmd based on the following steps:
Combine TPC from same RLS. Actually, the TPCs for same RLS are same;
Combine TPC from different RLS. Suppose the TPC for RLSi is W i, and for
each RLS, if
− TPC=0, Wi =0
− TPC=1, Wi =1
About TPC_cmd = γ (W1, W2, … Wn)
If any Wi is 0, TPC_cmd=-1
If all Wi are 1, TPC_cmd=1
With soft handover in PCA1With soft handover in PCA1
Uplink inner-loop power control
HUAWEI TECHNOLOGIES CO., LTD. Page 35All rights reserved
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 power controlWithout soft handover in PCA2Without soft handover in PCA2
HUAWEI TECHNOLOGIES CO., LTD. Page 36All rights reserved
Only one TPC is received in one time slot. The power control can be done once by
each 5 time slots. Each frame is divided 3 groups with 5 time slots. In the first 4 time
slots, the TPC_cmds are 0, which means the power does not change. In the 5th time
slot, the TPC_cmd can be achieved by the following rules:
If all the TPC are 0, the TPC_cmd is -1 and the transmission will decrease 1dB;
If all the TPC are 1, the TPC_cmd is 1 and the transmission will increase 1dB;
Otherwise, TPC_cmd= 0.
TPC ( RX) TPC_cmd
0000 0 0000 -1
1111 1 0000 1
else 0000 0
Without soft handover in PCA2Without soft handover in PCA2
Uplink inner-loop power control
HUAWEI TECHNOLOGIES CO., LTD. Page 37All rights reserved
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=1If 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 power controlWith soft handover in PCA2With soft handover in PCA2
HUAWEI TECHNOLOGIES CO., LTD. Page 38All rights reserved
Uplink-inner loop power control
When UE is in soft handover, the TPC_cmd can be achieved by the following two steps
First, combine the TPC from a same RLS
− N TPCi (i = 1,2......N) can be achieved from N RLSes in each time slot
− The N TPC_cmds from different RLS can be achieved by the above mentioned rules. So the first 4 time slot, the TPC_cmd is 0. And the each final TPC_cmd is decided in the 5th time slot
− Assume the each final TPC_cmd from N RLS are TPC_tempi ( i = 1,2......N )
− The first 4 time slots, all TPC_tempi = 0
− the TPC_cmd in fifth time slot can get by the following ruls :
▪ Mathematic average for N TPC_temps. If it is greater than 0.5, TPC_cmd=1. If it is less than -0.5, TPC_cmd=-1, otherwise TPC_cmd=0
With soft handover in PCA2With soft handover in PCA2
HUAWEI TECHNOLOGIES CO., LTD. Page 39All rights reserved
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 power controlWith soft handover in PCA2With soft handover in PCA2
HUAWEI TECHNOLOGIES CO., LTD. Page 40All rights reserved
Uplink-inner loop power control
The control frequency
TPC1, the power control frequency is 1500Hz
TPC2, the power control frequency is 300Hz
Application scenarios
When UE is moving with high speed (80Km/h), the fast
inner-loop power control can not catch up with the fast
fading, which produce negative gain. In this situation,
PCA2 is prefered.
Comparison between PCA1 and PCA2Comparison between PCA1 and PCA2
HUAWEI TECHNOLOGIES CO., LTD. Page 41All rights reserved
Chapter 3 Close Loop Power Control Chapter 3 Close Loop Power Control
3.1 Close Loop power control overview3.1 Close 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
HUAWEI TECHNOLOGIES CO., LTD. Page 42All rights reserved
NodeB
set SIRtar
Transmit TPC
Measure and compare SIR
Measure and compare BLER
Outer loop
Inner loop L1
L3
10-100Hz1500Hz
Downlink close loop power control
HUAWEI TECHNOLOGIES CO., LTD. Page 43All rights reserved
Downlink Inner-loop power control
NodeB
Set SIRtar
Transmit TPC in each TS
Measure SIR and compareAdjust Tx power
with 0.5, 1, 1.5 or 2dB
1500Hz
HUAWEI TECHNOLOGIES CO., LTD. Page 44All rights reserved
Downlink inner-loop power control
Firstly, UE should estimate the downlink DPDCH/DPCCH
power and the current SIR
Then, UE can generate TPC by comparing the estimated
SIR to target SIR
If the estimated SIR is greater than the target one, TPC is 0
(decrease power)
If the estimated SIR is less than the target one, TPC is 1
(increase power)
The step of DL inner-loop power control could be
0.5 、 1 、 1.5 or 2dB
HUAWEI TECHNOLOGIES CO., LTD. Page 45All rights reserved
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 produce TPCHow to produce TPC
HUAWEI TECHNOLOGIES CO., LTD. Page 46All rights reserved
The transmission power can not higher than Maximum_DL_Power, and not less than
Minimum_DL_Power neither.
Downlink power adjustment:
Pk Pk 1PTPCkPbalkWhere
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
HUAWEI TECHNOLOGIES CO., LTD. Page 47All rights reserved
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
HUAWEI TECHNOLOGIES CO., LTD. Page 48All rights reserved
Where
PTPC(k)
With “Limited Power Raise Used”
Downlink inner-loop power controlHow to adjust powerHow to adjust power
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
HUAWEI TECHNOLOGIES CO., LTD. Page 49All rights reserved
Downlink inner-loop power control
The inner-loop power control of downlink DPCCH include two typies: one is the inner-loop power control in compressed mode, the other is the inner-loop power control in non-compressed mode.
Timeslot structure of Downlink DPCH :
- PO1 defines the power offset of the TFCI bit in the downlink DPCCH to DPDCH.
- PO2 defines the power offset of the TPC bit in the downlink DPCCH to DPDCH.
- PO3 defines the power offset of the Pilot bit in the downlink DPCCH to DPDCH.
- The values of PO1 、 PO2 and PO3 are defined by RNC.12 3
HUAWEI TECHNOLOGIES CO., LTD. Page 50All rights reserved
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
too much, it will command the DPB
process
The initiation and stop of DPB
The power offset of two RL is greater
than the DPB initial threshold, the
DPB process is initiated
The power offset of two RL is less
than the DPB stop threshold, the DPB
process is stopped
NodeB
NodeB
Initiate the DPB process
DPB process
HUAWEI TECHNOLOGIES CO., LTD. Page 51All rights reserved
Chapter 3 Close Loop Power Control Chapter 3 Close Loop Power Control
3.1 Close Loop power control overview3.1 Close 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
HUAWEI TECHNOLOGIES CO., LTD. Page 52All rights reserved
Outer-loop power control
The limitation of inner loop power control
The purpose of inner loop power control of the WCDMA system is to
maintain a certain signal-to-interference ratio of transmission signal
power when the signals reach the receiving end.
The character of outer-loop power control
The Qos which NAS provide to CN is BLER, not SIR
The relationship between inner-loop power control and outer-loop power control
SIR target should be satisfied with the requirement of decoding correctly.
But different multiple path radio environment 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
get the good quality service data get the good quality service data
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
SirAdjustFactor: 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
Node B SRNC
……
OUTER LOOP PC
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