08 wcdma power control

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Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.

WCDMA Power Control and

Relevant Parameters


Objectives

� Upon completion of this course, you will be able to:

� Describe the purpose and function of power control

� Explain open loop power control and parameters

� Explain inner loop power control and relevant parameters

� Explain outer loop power control and relevant parameters


Contents

1. Power Control Overview

2. Open Loop Power Control

3. Closed Loop Power Control


Purpose of Uplink Power Control

� Uplink Transmission Character

� Self-interference system

� Uplink capacity is limited by interference level

� Near-far effect

� Fading

� Uplink Power Control Function

� 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 Downlink Power Control

� Downlink Transmission Character

� Interference among different subscribers

� Interference from other adjacent cells

� Downlink capacity is limited by NodeB transmission power

� Fading

� Downlink Power Control Function

� Ensure downlink quality with minimum transmission power

� Decrease interference to other cells, and increase capacity

� Save NodeB transmission power


Effect of Power Control

Time (ms)0 200 400 600 800

-20

-15

-10

-5

0

5

10

15

20

Rel

ativ

e po

wer

(dB

)Channel Fading

Transmitting power

Receiving power


Power Control Classification

� Open Loop Power Control

� Uplink / Downlink Open Loop Power Control

� Closed Loop Power Control

� Uplink / Downlink Inner Loop Power Control

� Uplink / Downlink Outer Loop Power Control


Power Control For Physical Channels

� Power control methods are adopted for these physical channels:

� “√" – can be applied, “×" – not applied

√√√√×××SCH

√√√√×××PICH

√√√√×××AICH

×××√√√√PRACH

√√√√×××SCCPCH

√√√√×××PCCPCH

×√√√√√√√√√√√√DPCCH

×√√√√√√√√√√√√DPDCH

Outer Loop

Power Control

Inner Loop

Power Control

No Power

Control

Closed Loop Power ControlOpen Loop

Power

Control

Physical

Channel


Common Physical Channel Power Parameters

� MAXTXPOWER

� Parameter name: Max transmit power of cell

� The recommended value is 430, namely 43dBm

� PCPICHPOWER

� Parameter name: PCPICH transmit power

� The recommended value is 330, namely 33dBm



� PSCHPOWER or SSCHPOWER

� Parameter name: PSCH / SCCH transmit power

� The recommended value is -50, namely -5dB

� BCHPOWER

� Parameter name: BCH transmit power




� MAXFACHPOWER

� Parameter name: Max transmit power of FACH

� The recommended value is 10, namely 1dB

� PCHPOWER

� Parameter name: PCH transmit power




� AICHPOWEROFFSET

� Parameter name: AICH power offset

� The default value of this parameter is -6, namely -6dB

� PICHPOWEROFFSET

� Parameter name: PICH power offset

� The default value of this parameter is -7, namely -7dB


Contents





Contents


2.1 Open Loop Power Control Overview

2.2 PRACH Open Loop Power Control

2.3 Downlink Dedicated Channel Open Loop Power Control

2.4 Uplink Dedicated Channel Open Loop Power Control


Open Loop Power Control Overview

� Purpose

� Calculate the initial transmission power of uplink / downlink channels

� Principle

� Estimates the downlink signal power loss on propagation path

� Path loss of the uplink channel is related to the downlink channel

� Application

� Open loop power control is applied only at the beginning of connection

setup to set the initial power value.


Contents







PRACH Open Loop Power Control

5. Downlink Synchronization

UE Node BServing

RNC

DCH - FP

Allocate RNTISelect L1 and L2parameters

RRCRRC

NBAPNBAP3. Radio Link Setup Response

NBAPNBAP2. Radio Link Setup Request

RRCRRC7. CCCH: RRC Connection Set up

Start RX description

Start TX description

4. ALCAP Iub Data Transport Bearer Setup

RRCRRC9. DCCH: RRC Connection Setup Complete

6. Uplink Synchronization

NBAPNBAP8. Radio Link Restore Indication

DCH - FP

DCH - FP

DCH - FP

Open loop powercontrol of PRACH

1. CCCH: RRC Connection Request



� Initial Power Calculation for the First Preamble

� When UE needs to set up a RRC connection, the initial power of

uplink PRACH can be calculated according to the following

formula:

Power Tx Initial gCalculatin For Value Constant+ceInterferen UL+

CPICH_RSCP-Power Transmit PCPICH=ernitial_PowPreamble_I


PRACH Open Loop Power Control Parameters

� CONSTANTVALUE

� Parameter name: Constant value for calculating initial TX power




� Timing relationship of PRACH and AICH

AICH

PRACH

1 access slot

ττττ p-a

ττττ p-mττττ p-p

Pre-amble

Pre-amble

Message part

Acq. Ind.



� AICHTXTIMING

� Parameter name: AICH transmission timing

� Content:

� When AICHTXTIMING = 0,

ττττpppp----p,minp,minp,minp,min = 15360 chips, ττττpppp----aaaa = 7680 chips, ττττpppp----mmmm = 15360 chips

� When AICHTXTIMING = 1,

ττττpppp----p,minp,minp,minp,min = 20480 chips, ττττpppp----aaaa = 12800 chips, ττττpppp----mmmm = 20480 chips

� The recommended value is 1



� Power Ramping for Preamble Retransmission

Power Ramp Step

Power Offset P p-m

Preamble_Initial_Power

Message part

Pre-amblePre-

amble……

Pre-amblePre-

amble

＃＃＃＃1 ＃＃＃＃3 ＃＃＃＃N＃＃＃＃2



� POWERRAMPSTEP

� Parameter name: Power increase step


� PREAMBLERETRANSMAX

� Parameter name: Max preamble retransmission

� The Recommended value is 20



� MMAX

� Parameter name: Max preamble loop

� The recommended value is 8

� NB01MIN / NB01MAX

� Parameter name: Random back-off lower / upper limit

� The recommended value: 0 for both NB01MIN / NB01MAX



� POWEROFFSETPPM

� Parameter name: Power offset

� The default value:

-3dB for signalling transmission;

-2dB for service transmission.


Contents







DL DPDCH Open Loop Power Control


UE Node BServing

RNC

DCH - FP


RRCRRC










DCH - FP

DCH - FP

DCH - FP





� When a dedicated channel is set up, the initial power of

downlink DPDCH can be calculated according to the following

formula:

−××= Total

CPICH

CPICHDLInitial P

)No/Ec(

P)

No

Eb(

W

RP α



Data1 TPC TFCI Data2 Pilot

DownlinkTransmit

Power

DPCCHDPDCH DPDCH DPCCH

PO2PO1

PO3

1 timeslot


DL DPDCH Open Loop Power Control Parameter

� TFCIPO

� Parameter name: TFCI power offset


� TPCPO

� Parameter name: TPC power offset



DL DPDCH Open Loop Power Control Parameter

� PILOTPO

� Parameter name: Pilot power offset



Downlink Power Control Restriction

� The power of downlink dedicated channel is limited by an

upper and lower limit for each radio link.

� The DL DPDCH power could not exceed Maximum_DL_Power, nor

could it be below Minimum_DL_Power.

� RLMAXDLPWR / RLMINDLPWR

� Parameter name: RL Max / Min DL TX power

� The recommended value is shown in the following table.


Downlink Power Restriction Parameters

� Referential configurations for typical services:

8-114384 kbps

8-132256 kbps

16-150144 kbps

32-17-264 kbps

64-19-432 kbps

128-23-88 kbps

PS Domain

32-15064 kbps

32-15056 kbps

64-17-232 kbps

64-17-228 kbps

128-18-312.2 kbps AMR

CS Domain

Downlink SFRL Min Downlink

Transmit Power

RL Max Downlink

Transmit PowerService


Contents







UL DPCCH Open Loop Power Control


UE Node BServing

RNC

DCH - FP


RRCRRC










DCH - FP

DCH - FP

DCH - FP


Open Loop PowerControl of UL DPCCH


UL DPCCH Open Loop Power Control

� The initial power of the uplink DPCCH can be calculated according to the

following formula:

� Where

� CPICH_RSCP means the received signal code power, the received power

measured on the CPICH.

� DPCCH_Power_Offset is provided by RNC to the UE via RRC signaling.

RSCP_CPICHOffset_Power_DPCCHPower_Initial_DPCCH −=

Value Constant DefaultceInterferen ULPower Transmit PCPICHOffsetPowerDPCCH ++=__


UL DPCCH Open Loop Power Control Parameter

� DEFAULTCONSTANTVALUE

� Parameter name: Constant value configured by default

� The recommended value is -27, namely -27dB.


Uplink Power Control Restriction

� During the operation of uplink power control, the UE transmit

power shall not exceed the Maximum Allowed Uplink Transmit

Power.

� MAXALLOWEDULTXPOWER

� Parameter name: Max allowed UE UL TX power

� The recommended value is 21, namely 21 dBm.


Uplink Power Control Restriction

� In addition, there are four parameters which correspond to the maximum

allowed transmit power of four classes of services respectively:

� MAXULTXPOWERFORCONV

� Parameter name: Max UL TX power of Conversational service

� MAXULTXPOWERFORSTR

� Parameter name: Max UL TX power of Streaming service

� MAXULTXPOWERFORINT

� Parameter name: Max UL TX power of Interactive service

� MAXULTXPOWERFORBAC

� Parameter name: Max UL TX power of Background service

� The recommended value is 24, namely 24 dBm.


Contents





Contents


3.1 Closed Loop Power Control Overview

3.2 Uplink Inner Loop Power Control

3.3 Downlink Inner Loop Power Control

3.4 Outer Loop Power Control


Closed Loop Power Control Overview

� Why closed loop power control is needed?

� Open loop power control is not accurate enough, it can only

estimate the initial transmission power.

� Closed loop power control can guarantee the QoS with minimum

power. By decreasing the interference, the system capacity will be

increased.

Inner LoopOuter Loop

SIRtar

SIRmea>SIRtar→→→→ TPC=0

SIRmea<SIRtar→→→→ TPC=1

UntilSIRmea=SIRtar

TPCBLER tar

BLERmea>BLER tar→→→→SIRtar

BLERmea<BLER tar→→→→SIRtar

Until BLERmea=BLER tar

TPC=1 PowerTPC=0 Power


Contents







Uplink Inner Loop Power Control

� NodeB compares the measured SIR to the preset target SIR, then derives TPC

and sends the TPC Decision to UE.

TPC Decision( 0, 1 )

Generate TPC_cmd( -1, 0, 1 )

Adjust DPCCH Tx△△△△DPCCH =△△△△TPC××××TPC_cmd

Single RL / Soft HOPCA1 / PCA2

Adjust DPDCH Tx( ββββc , ββββd )

NodeB UETransmit TPC

Inner Loop

Set SIRtar

Compare SIRmea with SIRtarSIRmea >>>> SIRtar →→→→ TPC = 0SIRmea ≤≤≤≤ SIRtar →→→→ TPC = 1


Uplink Inner Loop PCA1 with Single Radio Link

� For single radio link and PCA1, UE derives one TPC_cmd in each time

slot as follows:

0110110110…… ……

…… ……TPC_cmd

TPC

-111-111-111-1

This control is performed in each time slot, so the power control frequency is 1500Hz


Uplink Inner Loop PCA2 with Single Radio Link

� For single radio link and PCA2, UE derives one TPC_cmd in each 5-slot

group as follows:

This control is performed in each 5-slot group, so the power control frequency is 300Hz

110111111100000

TS14TS13TS12TS11TS10TS9TS8TS7TS6TS5TS4TS3TS2TS1TS0

10ms radio frame

Group 2Group 1 Group 3

…… ……

0000010000-10000

TPC

TPC_cmd

…… ……


Uplink Inner Loop with Soft Handover

� When UE enters soft handover state, on the NodeB side, there

are two phases :

� Uplink synchronization phase

� Multi-radio link phase

� On UE side, UE will receive different TPCs from different RLS in

one time slot. Therefore, the UE should combine all the TPCs to

get a unique TPC_CMD.


Uplink Inner Loop PCA1 with Soft Handover

For each slot, combine TPC from the same RLS, then get Wi

CELL1 CELL2

CELL4CELL3

RL1-1 RL1-2

RLS1

RLS2 RLS3Get TPC_cmd based onTPC_cmd = γγγγ (W1, W2, … WN)

0110110110…… ……RLS1-TPC (W1)

…… ……RLS2-TPC (W2) 1010101101

…… ……

…… ……TPC_cmd

1101100100

-1-1-1-11-1-11-1-1

RLS3-TPC (W3)



Combine TPC from same RLSin each time slot

Calculate TPC_cmd� If any TPC_tempi = -1 , TPC_cmd = -1

� If , TPC_cmd = 1

� Otherwise, TPC_cmd = 0

Calculate TPC_temp i for each RLS i

5.0_1

1

>∑=

N

iitempTPC

N

CELL1 CELL2

CELL4CELL3

RL1-1 RL1-2RLS1

RLS2 RLS3



RLS3

RLS2

RLS1 100100000000100

100110000011111

111110000011111


…… ……

10ms/frame

Group 1 Group 2 Group 3

RLS3

RLS2

RLS1 00000-1000000000

00000-1000010000

10000-1000010000


…… ……

TPC

TPC_temp i

00000-1000010000

TS14TS13TS12TS11TS10TS9TS8TS7TS6TS5TS4TS3TS2TS1TS0…… ……

TPC_cmd


Uplink Inner Loop Power Control Parameters

� PWRCTRLALG

� Parameter name: Power control algorithm selection

� The recommended value is ALGORITHM1

� ULTPCSTEPSIZE

� Parameter name: UL closed loop power control step size



Contents







Downlink Inner Loop Power Control

� UE L1 compares the measured SIR to the preset target SIR, then derives TPC

and sends the TPC Decision to NodeB.

Derive TPCest(k)( 0, 1 )

Generate PTPC(k)

Calculate P(k)

Adjust DPCH Tx Power

DPC_MODE

NodeB

L3 Set SIRtar

Derive and transmit TPC based on DPC_MODE

Inner Loop

UE

L1 compare SIRmea with

SIRtar


Downlink Inner Loop Power Control Mode

� Two DPC_MODE (Downlink Power Control Mode) could be used:

� If DPC_MODE = 0, UE sends a unique TPC in each slot, UTRAN shall

derive TPCest to be 0 or 1, and update the power every slot;

� If DPC_MODE = 1, UE repeats the same TPC over 3 slots, UTRAN

shall derive TPCest over three slots to be 0 or 1, and update the

power every three slots.


Downlink Inner Loop Power Control Parameters

� DPCMODE

� Parameter name: Downlink power control mode

� The recommended value is SINGLE_TPC, namely DPC_MODE = 0



� After estimating the TPC, the UTRAN shall set the downlink power to

P(k) for k:th slot according to the following formula:

Where

� P(k-1) is downlink transmission power in (k-1):th slot

� PTPC(k) is the adjustment of downlink power in k:th slot

� Pbal (k) is correction value according to the downlink power balance

procedure. For a single radio link, Pbal (k) equals 0.

)k(P)k(P)1k(P)k(P balTPC ++−=



� PTPC(k) is calculated according to the following:

� If the value of “Limited Power Increase Used” parameter is “Not

Used” , then:

Where

� TPCTPCTPCTPCest est est est (k)(k)(k)(k) is uplink received TPC of the k:th slot

� ∆ ∆ ∆ ∆TPCTPCTPCTPC is downlink power adjustment step size

=−=+

=0)k(TPC if

1)k(TPC if )k(P

estTPC

estTPCTPC ∆

∆



� If the value of “Limited Power Increase Used” parameter is

“Used” , then:

Where ∑−

−=

=1k

Size_Window_Average_Power_DLkiTPCsum )i(P)k(∆

=−≥+=<+=+

=0)k(TPC if

Limit_Raise_Power)k( and 1)k(TPC if 0

Limit_Raise_Power)k( and 1)k(TPC if

)k(P

estTPC

TPCsumest

TPCsumestTPC

TPC

∆∆∆∆∆∆



� INNER_LOOP_DL_LMTED_PWR_INC_SWITCH

� This is one switch in PCSWITCH (Power control algorithm switch)

parameter.

� The default value is 0, namely OFF.

� POWERRAISELIMIT

� Parameter name: Power increase limit

� The recommended value is 10dB



� DLPOWERAVERAGEWINDOWSIZE

� Parameter name: DL power average window size

� The recommended value is 20 time slots

� FDDTPCDLSTEPSIZE

� Parameter name: FDD DL power control step size

� The recommended value is STEPSIZE_1DB, namely 1dB


Downlink Power Balance

� Purpose

� The purpose of this procedure is to

balance the DL transmission powers of

more than one Radio Links.

� The start and stop of DPB

� The power offset of two RLs is greater

than the DPB start threshold, the DPB

process is started

� The power offset of two RLs is less than

the DPB stop threshold, the DPB process

is stopped

NodeB NodeB

Monitor the Tx power of NodeBs and start the DPB

process

DPB process


Downlink Power Balance Parameters

� DOWNLINK_POWER_BALANCE_SWITCH


parameter.

� The default value is 0, namely OFF.

� DPBSTARTTHD / DPBSTOPTHD

� Parameter name: DPB start threshold / DPB stop threshold

� The recommended value:

DPB start threshold 8, namely 4dB;

DPB stop threshold 4, namely 2dB.


Contents







Outer Loop Power Control

� Why we need outer loop power control?

SIR

BLER

Different curves correspond to different multi-path environment


Uplink Outer Loop Power Control

NodeB UETransmit TPC

Measure SIR and compare with SIRtar

Inner loop

Set SIRtar

Out loop

RNC

Measure BLER of received data and compare with the BLERtar

Set BLERtar



� SIRtar Adjustment

Where

� i is the i:th transmission channel.

� n is the n:th adjustment period.

××

−−+−= FactorStep

BLER

BLER)1n(BLER)1n(SIRMAX)n(SIR i

i,tar

i,tari,meastartar


Uplink Outer Loop Power Control Parameters

� OPLC_SWITCH


parameter.

� The default value is 1, namely ON

� INITSIRTARGET

� Parameter name: Initial SIR target value

� The recommended value is shown in following table.



� SIRADJUSTPERIOD

� Parameter name: OLPC adjustment period


� SIRADJUSTFACTOR

� Parameter name: SIR adjustment coefficient

� The recommended value is 10, namely 1



� BLERQUALITY

� Parameter name: Service DCH_BLER target value


� SIRADJUSTSTEP

� Parameter name: SIR adjustment step

� The recommended value is shown in the following table.




-20-20-20-20-20-20-20-20-27-20-20-20Service

DCH_BLER

target value

142122107102102102102102122102122102SIR init

target value

4444444425104SIR

adjustment

step

222222242224OLPC

adjustment

period

PS I/B

384k

PS I/B

256k

PS I/B

144k

PS I/B

128k

PS I/B

64k

PS I/B

32k

PS I/B

16k

PS I/B

8k

CSD

64k

AMR

12.2k

SRB

13.6

k

SRB

3.4kService



� The parameters MaxSirStepUp and MaxSirStepDown limit the

adjustment range of the SIRtar , and the algorithm is:

� If ∆SIRtar > 0 and ∆SIRtar > “MaxSirStepUp” ,

then SIRtar (n+1) = SIRtar (n) + MaxSirStepUp

� If ∆SIRtar < 0 and ABS( ∆SIRtar ) > “MaxSirStepDown” ,

then SIRtar (n+1) = SIRtar (n) – MaxSirStepDown

� The parameters MaxSirtarget and MinSirtarget limit the range of the

SIRtar at any time.



� MAXSIRSTEPUP / MAXSIRSTEPDN

� Parameter name: Maximum SIR increase / decrease step


� MAXSIRTARGET / MINSIRTARGET

� Parameter name: Maximum / Minimum SIR target





4004004004004004004004001000500500400Maximum SIR

increase step

200200200200200200200200100200200200Maximum

SIR decrease step

626262626262626262626262Minimum SIR

target

172152137132132132132132152132132132Maximum SIR

target

PS I/B

384k

PS I/B

256k

PS I/B

144k

PS I/B

128k

PS I/B

64k

PS I/B

32k

PS I/B

16k

PS I/B

8k

CSD

64k

AMR

12.2

k

SRB

13.6

k

SRB

3.4kService


Downlink Outer Loop Power Control

NodeB

set SIRtar

Transmit TPC

Measure SIR and compare with SIRtar

Measure BLER of received data and compare with the

BLERtar

Outer loop

Inner loop

L1

L3

UE


Summary

� In this course, we have discussed function, principle and

common parameters of the following power control algorithm:

� Open loop power control

� Inner loop power control

� Outer loop power control

Thank youwww.huawei.com

08 wcdma power control

Documents

power of cell

function of power control

power control overview2

wcdma power control

uplink power control

open loop power control3

huawei technologies

uplink quality