wcdma ran11 power control algorithm and parameters

8/11/2019 WCDMA RAN11 Power Control Algorithm and Parameters

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Confidential Information of Huawei. No Spreading Without Permission

WCDMA Power Control and Relevant Parameters N-1

www.huawei.com

Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved.

WCDMA Power

Control Algorithm and

Parameters


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Page2Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved.

Foreword

Power control categories:

Uplink power control

Downlink power control

Power control types:

Open loop power control

Closed loop power control

Inner loop power control Outer loop power control

The WCDMA system is an interference-limited system, and the most important way to

restrain system interference is power control. The core purpose of power control is to

minimized the power of transmitting signals while ensuring Quality of Service (QoS).

In the uplink, a UE emitting too high power will cause unacceptable competing interference

on the NodeB in comparison to signals coming from UEs at the cell edge. This is called

near-far effect. To avoid near-far effect, uplink power control is required.

In the downlink, the system capacity is determined by the total code power. Therefore, it is

necessary to keep the transmit power at the lowest possible level while still ensuring signal

quality at the UE.

At open loop power control, the initial transmit power is calculated. This method is rather

inaccurate and it is only applied at the beginning of a connection setup.

At closed loop power control, the transmitter dynamically adjusts its transmit power

according to the feedback from the receiver of the other side. Closed loop power control is

further classified into the following types:

Inner loop power control directly adjusts the transmit power of the transmitter by

using power control commands.

Outer loop power control indirectly controls the transmit power of the transmitter.


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References

3GPP TS 25.211: Physical Channels and Mapping of Transport

Channels onto Physical Channels (FDD)

3GPP TS 25.214: Physical Layer Procedures (FDD)

3GPP TS 25.331: RRC Protocol Specification

3GPP TS 25.433: UTRAN Iub Interface NodeB Application Part

(NBAP) Signaling


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Objectives

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

Describe the purpose and function of power control

Perform parameters modification of open loop power control

Perform parameters modification of inner loop power control

Perform parameters modification of outer loop power control


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Contents

1. Power Control Overview

2. Open Loop Power Control

3. Closed Loop Power Control


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Contents





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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

CDMA system have the embedded characteristics of self-interference, for uplink one users

transmission power become interference to others.

The more connected users, the higher interference. Generally the capacity is limited by

interference level.

WCDMA suffer from Near-far effect, which means if all UE use the same transmission

power, the one close to the NodeB may block the entire cell.

Uplink power control can guarantee the service quality and minimize the required

transmission power. It will resolve the near-far effect and resist fading of signal propagation.

By lowering the uplink interference level, the system capacity will be increased.


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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

The downlink has different characteristics from the uplink, for downlink interference is

caused by multi-path, part of one users power also become interference to others.

Downlink power from adjacent cells also is one part of interference to the own cell.

Transmission power of NodeB is shared by all users channels, so downlink capacity usually

is considered to be limited by transmission power.

Downlink power control also can guarantee the service quality and minimize the required

transmission power, so the capacity is maximized in case that interference is lowered.


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Effect of Power Control

Time (ms)

0 200 400 600 800-20

-15

-10

-5

0

5

10

15

20

Relativepower(dB)

Channel Fading

Transmitting power

Receiving power

Because of channel fading in mobile communication system, the radio signal is deteriorated

and fluctuated, the fast power control become one key technology to resist this

phenomenon.

In this figure, the channel fading is compensated by the transmitting power, which is

adjusted by the fast power control, so the receiving power is almost constant and the radio

propagation condition is improved.


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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

In WCDMA system, power control includes open loop and closed loop power control.

Open loop power control is used to determine the initial transmission power, and the

closed loop power control adjusts the transmission power dynamically and continuously

during the connection.

For uplink, the UEs transmission power is adjusted; and for downlink, the NodeBs

transmission power is adjusted.


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Power Control for Physical Channels

Power control methods are adopted for these physical channels:

" : can be applied; : can not be applied

SCH

PICH

AICH

PRACH

SCCPCH

PCCPCH

DPCCH

DPDCH

Outer LoopPower Control

Inner Loop PowerControl

No Power

Control

Closed Loop Power ControlOpen Loop

Power

Control

Physical

Channel

Open loop power control is used in two cases:

1. to decide the initial transmission power of PRACH;

2. to decide the initial transmission power of DPCCH / DPDCH.

Closed loop power control is only applied on DPCCH and DPDCH.

For other common channels, power control is not applied, they will use fixed transmission

power:

The PCPICH power is defined by the PCPICHPowerparameter as an absolute value in

dBm.

All other common channels power is defined in relation with the PCPICHPower

parameter, and measured in dB.


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Common Physical Channel Power Parameters

MaxTxPower

Parameter name: Max transmit power of cell [0.1dBm]

Recommended value: 430, namely 43dBm

PCPICHPower

Parameter name: PCPICH transmit power [0.1dBm]


MaxTxPower

Content: The sum of the maximum transmit power of all DL channels in a cell.

Value range: 0 to 500

Physical value range: 0 to 50; step: 0.1

Physical unit: dBm

Set this parameter through ADD CELLSETUP, query it through LST CELL and modify

it through MOD CELL.

PCPICHPower

Content: This parameter should be set based on the actual environment and the

downlink coverage should be guaranteed firstly. If PCPICH transmit power isconfigured too great, the cell capacity will be decreased, for power resources is

occupied by common channel and the interference to traffic channels is also

increased.

Value range: -100 to 500

Physical value range: -10 to 50; step: 0.1

Physical unit: dBm

Set this parameter through ADD PCPICH, query it through LST PCPICH and modify it

through MOD CELL.


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Common Physical Channel Power Parameters(Cont.)

PSCHPowerandSSCHPower

Parameter name: PSCH / SSCH transmit power [0.1dB]

Recommended value: -50, namely -5dB

BCHPower

Parameter name: BCH transmit power [0.1dB]


PSCHPowerandSSCHPower

Content: The offset of the PSCH/SSCH transmit power from the PCPICH transmit

power in a cell .



Physical unit: dB

For PSCH Power, set it through ADD PSCH, and query it through LST PSCH; for SSCH

Power, set it through ADD SSCH, and query it through LST SSCH. And modify them

through MOD CELL.

BCHPower

Content: The offset of the BCH transmit power from the PCPICH transmit power in a

cell.



Physical unit: dB

Set this parameter through ADD BCH, query it through LST BCH, and modify it

through MOD CELL.


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MaxFachPower

Parameter name: Max transmit power of FACH [0.1dB]

Recommended value: 10, namely 1dB

PCHPower

Parameter name: PCH transmit power [0.1dB]


MaxFachPower

Content: The offset between the FACH transmit power and PCPICH transmit power

in a cell.



Physical unit: dB

Set this parameter through ADD FACH, query it through LST FACH.

PCHPower

Content: The Offset of the PCH transmit power from the PCPICH transmit power in a

cell.



Physical unit: dB

Set this parameter through ADD PCH, query it through LST PCH, and modify it

through MOD SCCPCH.


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AICHPowerOffset

Parameter name: AICH power offset


PICHPowerOffset

Parameter name: PICH power offset


AICHPowerOffset

Content: The difference between the transmit power of AICH and that of PCPICH.


Physical value range: -22 to 5; step: 1

Physical unit: dB

Set this parameter through ADD CHPWROFFSET, query it through LST

CHPWROFFSET, and modify it through MOD AICHPWROFFSET.

PICHPowerOffset

Content: The difference between the transmit power of PICH and that of PCPICH.



Physical unit: dB

Set this parameter through ADD CHPWROFFSET, query it through LST

CHPWROFFSET, and modify it through MOD PICHPWROFFSET.


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Contents





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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


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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

In downlink open loop power control, the initial transmission power is calculated according

to the downlink path loss between NodeB and UE.

In uplink, since the uplink and downlink frequencies of WCDMA are in the same frequency

band, a significant correlation exists between the average path loss of the two links. This

make it possible for each UE to calculate the initial transmission power required in the

uplink based on the downlink path loss.

However, there is 90MHz frequency interval between uplink and downlink frequencies, the

fading between the uplink and downlink is uncorrelated, so the open loop power control is

not absolutely accurate.


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Contents







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PRACH Open Loop Power Control

5. Downlink Synchronization

UE NodeB SRNC

DCH - FP

Allo cate RNTISelect L1 and L2parameters

RRCRRC

NBAPNBAP

3. Radio Link Setup Response

NBAPNBAP2. Radio Link Setup Request

RRCRRC7. CCCH: RRC Connection Setup

Start RXdescription

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 power

control of PRACH

1. CCCH: RRC Connection Request

In access procedure, the first signaling RRC CONNECTION REQUESTis transmitted in

message part on PRACH.

Before PRACH message part transmission, UE will transmit PRACH preamble, and the

transmission power of first preamble is calculated by this PRACH open loop power control.


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PRACH Open Loop Power Control

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

of uplink PRACH preamble can be calculated according to the

following formula:

lueConstantvaceinterferenUL

CPICH_RSCP-rPCPICHPowe=ernitial_PowPreamble_I

++

In this formula, where

PCPICHPower defines the PCPICH transmit power in a cell. It is broadcast in SIB5.

CPICH_RSCP means received signal code power, the received power measured on

the PCPICH. The measurement is performed by the UE.

UL interference is the UL RTWP measured by the NodeB. It is broadcast in SIB7.

Constantvalue compensates for the RACH processing gain. It is broadcast in SIB5.

The initial value of PRACH power is set through open loop power control. UE operation

steps are as follows:

1. Read Primary CPICH DL TX power, UL interference and Constant value from

system information;

2. Measure the value of CPICH_RSCP;

3. Calculate the Preamble_Initial_Power of PRACH.


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PRACH Open Loop Power ControlParameters

Constantvalue

Parameter name: Constant value for calculating initial TX power


Constantvalue

Content: It is used to calculate the transmit power of the first preamble in the

random access process.

Value range: -35 to -10

Physical value range: -35 to -10; step: 1

Physical unit: dB

Set this parameter through ADD PRACHBASIC, query it through LST PRACH, and

modify it through MOD PRACHUUPARAS.


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PRACH Open Loop Power Control (Cont.)

Timing relationship of PRACH and AICH:

AICH

PRACH

1 access slot

p-a

p-mp-p

Pre-

amble

Pre-

ambleMessage

part

Acq .

Ind.

After UE transmit the first Preamble on PRACH, it will wait for the corresponding AI

(Acquisition Indicator) on the AICH. The timing relationship of PRACH and AICH is shown in

above figure.

There will be 3 parameters used to define the timing relationship:

p-p: time interval between two PRACH preambles. p-p is not a fixed value, it is

decided by selecting access slot of PRACH preambles.

Here p-p has one restriction, it must be longer than a minimum value p-p min,

namely p-p p-p min.

p-a: time interval between PRACH preamble and AICH Acquisition Indicator. If UE

sends the PRACH preamble, it will detect the responding AI after p-a time.

p-m: time interval between PRACH preamble and PRACH message part. If UE sendsthe PRACH preamble and receives positive AI from the AICH, it will send the message

part after p-m time.


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PRACH Open Loop Power ControlParameters (Cont.)

AICHTxTiming

Parameter name: AICH transmission timing

Content:

When AICHTXTIMING = 0,

p p min

= 15360 chips, p a

= 7680 chips, p m

= 15360 chips

When AICHTXTIMING = 1,

p p min

= 20480 chips, p a

= 12800 chips, p m

= 20480 chips

Recommended value: 1

AICHTxTiming

Content: Transmission timing information of an AICH. "0" indicates that there are

7680 chips offset between the access preamble of the PRACH and AICH. "1"

indicates that there are 12800 chips offset between them.

Value range: 0 to 1

Physical value range: 0 to 1; step: 1

Set this parameter through ADD AICH, query it through LST AICH, and modify it

needs de-activated the cell through DEA CELL. After the old configuration of AICH is

deleted through RMV AICH , a new AICH can be established through ADD AICH.


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PowerRampStep

Parameter name: Power increase step

Recommended value: 2, namely 2dB

PreambleRetransMax

Parameter name: Max preamble retransmission


PowerRampStep

Content: The power increase step of the random access preambles transmitted

before the UE receives the acquisition indicator in the random access process.

Value range: 1 to 8


Physical unit: dB



PreambleRetransMax

Content: The maximum number of preambles transmitted in a preamble rampingcycle.






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Mmax

Parameter name: Max preamble loop


NB01min / NB01max

Parameter name: Random back-off lower / upper limit

Recommended value: 0 for both NB01min / NB01max

Mmax

Content: Maximum number of random access preamble loops.



Set this parameter through ADD RACH, query it through LST RACH, and modify it

first de-activated the cell through DEA CELL, then MOD RACH, finally ACT CELL.

NB01min / NB01max

Content: Lower/Upper limit of random access back-off delay.



Physical unit: frame

Set this parameter through ADD RACH, query it through LST RACH, and modify it

first de-activated the cell through DEA CELL, then MOD RACH, finally ACT CELL.


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1510-2Service

1513-3Signaling

GainFactorBetaDGainFactorBetaCPowerOffwetPpmPRACH


PowerOffsetPpm

Parameter name: Power offset

Recommended value:

PowerOffsetPpm

Content: The power offset between the last access preamble and the message

control part. The power of the message control part can be obtained by adding the

offset to the access preamble power.



Physical unit: dB

Set this parameter through ADD PRACHTFC, query it through LST PRACH, and

modify it de-activated the cell through DEA CELL . After the old configuration of

PRACH is deleted through RMV PRACHTFC , a new parameters can be established

through ADD PRACHTFC.

The power of the data part is calculated with the following formula:

, where

Pcontrol is the power for the control part.

d is the power gain factor for the data part. The value is defined by the

GainFactorBetaD parameter.

c is the power gain factor for the control part. The value is defined by the

GainFactorBetaCparameter.


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The transmit power on the PRACH cannot be greater than the

maximum allowed uplink transmit power:

MaxAllowedUlTxPower

Parameter name: Max allowed UE UL TX power


MaxAllowedUlTxPower

Content: The maximum allowed uplink transmit power of a UE in the cell, which is

related to the network planning.



Physical unit: dBm

Set this parameter through ADD CELLSELRESEL, query it through LST CELLSELRESEL,

and modify it through MOD CELLSELRESEL.


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Contents







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DL DPCH Open Loop Power Control

DL DPCH open loop

power control


UE NodeB SRNC

DCH - FP


RRCRRC

NBAPNBAP




Start RXdescription

Start TX

description





DCH - FP

DCH - FP

DCH - FP


According to the RRC connection establishment procedure, after RNC received the RRC

CONNECTION REQUEST message, and NodeB set up the radio link for UE, then Iub

interface resources is established between NodeB and RNC.

When DCH-FP of Iub interface finished downlink and uplink synchronization, the downlink

DPCH starts to transmit, and DPCH initial transmission power is calculated through open

loop power control.


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DL DPDCH Open Loop Power Control

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

downlink DPDCH can be calculated according to the following

formula:

= Total

CPICH

CPICHDLinit P

NoEc

P

No

Eb

W

RP

)/()(

In this formula, where:

Pinit is the initial power of the DPDCH.

PCPICH is the PCPICH power in a cell. The value is configured by the PCPICHPower

parameter on the RNC.

R is the traffic rate requested by the UE and W is the chip rate (3.84 Mcps).

(Eb/No)DL is the Eb/No target of the downlink DPDCH used to ensure the service

quality. Eb is the energy of a signal information bit and No is the noise spectral

density. The RNC estimates a value of Eb/No target dynamically based on cell

environment type and BLER target.

(Ec/No)CPICH is the ratio of received energy per chip to noise spectral density of the

CPICH received by the UE.

is the orthogonal factor in the downlink. The value is fixed to 0.

Ptotal is the downlink transmitted carrier power measured on the NodeB and

reported to the RNC.


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DL DPCCH Open Loop Power Control

Data1 TPC TFCI Data2 Pilot

Downlink

Transmit

Power

DPCCHDPDCH DPDCH DPCCH

PO2PO1

PO3

1 timeslot

The downlink DPCCH consists of three fields: TFCI, TPC, and pilot. Their power is set as the

offset reference to the power of the downlink DPDCHs.

The downlink power on the DPCCH and its associated DPDCHs is simultaneously regulated.

Thus, power control adjusts the power of the DPCCH and DPDCHs with the same step, and

the power offset between the DPCCH and the DPDCH keeps constant.

Power offsets between the DPCCH and the DPDCH in the downlink are identical for all TFCs

in the TFCS, whereas in the uplink the power offsets are TFC-dependent.

The power offsets of TFCI, TPC and pilot fields of the DPCCH reference to the power of

DPDCHs are fixed to 0dB, 3dB, and 3dB respectively.


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Downlink Power Control Restriction

The power of downlink dedicated channel is limited by an

upper and lower limit for each radio link

RlMaxDlPwr/RlMinDlPwr

Parameter name: RL Max/Min DL TX power

Recommended value is shown in the next page

RlMaxDlPwr

Content: This parameter should fulfill the coverage requirement of the network

planning, and the value is relative to PCPICH transmit power.



Physical unit: dB

Set this parameter through ADD CELLRLPWR , query it through LST CELLRLPWR, and

modify it through MOD CELLRLPWR.

RlMinDlPwr

Content: This parameter should consider the maximum downlink transmit power andthe dynamic range of power control, and the value is relative to PCPICH transmit

power.



Physical unit: dB

Set this parameter through ADD CELLRLPWR, query it through LST CELLRLPWR, and

modify it through MOD CELLRLPWR.


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Contents







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UL DPCH Open Loop Power Control

UL DPCH open loop

power control


UE NodeB SRNC

DCH - FP


RRCRRC

NBAPNBAP




Start RXdescription

Start TX

description





DCH - FP

DCH - FP

DCH - FP


According to the RRC connection establishment procedure, after RNC sent the RRC

CONNECTION SETUP message, UE will try to synchronize with NodeB, and the uplink

DPCCH starts to transmit, here DPCCH initial transmission power is calculated through openloop power control.

The power of the uplink DPDCH is set as a power offset (d/c) reference to the uplink

DPCCH. The uplink DPCCH and DPDCHs are transmitted through different channel codes.

To meet a given QoS requirement on the transport channels, different TFCs use different

power offsets.

The RNC has a set of reference values (c,ref and d,ref) that are stored for each

predefined Radio Access Bearer (RAB) or Signaling Radio Bearer (SRB). c,ref and d,ref can

be configured by BETAC and BETAD on the RNC.

The RNC calculates a new power offset for each TFC based on the reference values

dynamically and sends the power offset to the UE.


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UL DPCCH Open Loop Power Control

The initial power of the uplink DPCCH can be calculated

according to the following formula:

Where:

DPCCH_Power_Offset is provided by the RNC to the UE via RRC

signaling

CPICH_RSCP is the received signal code power of the PCPICH

RSCP_CPICHOffset_Power_DPCCHPower_Initial_DPCCH =

For Huawei, DPCCH_Power_Offset is calculated with the following formula:

Where:

The PCPICHPower parameter defines the PCPICH transmit power in a cell. This value

is broadcast in SIB5.

Uplink interference is the uplink RTWP measured by the NodeB and sent to the UE

through the SIB7.

The DefaultConstantValue parameter reflects the target Ec/No of the uplink DPCCH.

tValuesDefaultCon

ceInterferenULrPCPICHPoweOffsetPowerDPCCH

tan

__

+

+=


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UL DPCCH Open Loop Power ControlParameter

DefaultConstantValue

Parameter name: Constant value configured by default


DefaultConstantValue

Content: This parameter specifies the constant that is used by the RNC to compute

the DPCCH_Power_Offset which is further used by the UE to calculate the UL

DPCCH_Initial_Power during the open-loop power control.

Value range: -35 to -10

Physical value range: -35 to -10; step: 1

Physical unit: dB

Set this parameter through SET FRC, query it through LST FRC, and modify it through

SET FRC.


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Uplink Power Control Restriction

There are four parameters which correspond to the maximum

allowed transmit power of four classes of services:

MaxUlTxPowerforConv

MaxUlTxPowerforStr

MaxUlTxPowerforInt

MaxUlTxPowerforBac

Parameter name: Max UL TX power of

conversational/streaming/interactive/background service


MaxUlTxPowerforConv

MaxUlTxPowerforStr

MaxUlTxPowerforInt

MaxUlTxPowerforBac

Content: The maximum UL transmit power for specific services in a cell. It is based on

the UL coverage requirement of the specific services designed by the network

planning.



Physical unit: dBm

Set this parameter through ADD CELLCAC, query it through LST CELLCAC, and

modify it through MOD CELLCAC.


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Contents





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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


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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

Until

SIRmea=SIRtar

TPCBLERtar

BLERmea>BLERtarSIRtar

BLERmea


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Contents







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Uplink Inner Loop Power Control

NodeB compares the measured SIR to the 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 =TPCTPC_cmd

Single RL / Soft HO

PCA1 / PCA2

Adjust DPDCH Tx

( c , d )

NodeB UETransmit TPC

Inner Loop

Set SIRtar

Compare SIRmea with SIRtar

SIRmea SIRtar TPC = 0

SIRmea SIRtar TPC = 1

RNC sends SIRtar (target SIR) to NodeB and then NodeB compares SIRmea (measured SIR)

with SIRtar:

If the estimated SIR is greater than the target SIR, NodeB sends TPC 0 to UE on

downlink DPCCH TPC field;

Otherwise, NodeB sends TPC 1 to UE.

After reception of one or more TPC, UE shall derive a single TPC_cmd (TPC command, with

value among -1, 0, 1):

Two algorithms could be used by the UE for deriving the TPC_cmd, those are PCA1

and PCA2 (PCA means Power Control Algorithm).

For UE is in soft handover state, more than one TPC is received, so firstly multiple

TPC_cmd is combined.

When deriving the combined TPC_cmd, UE shall adjust the transmit power of uplink DPCCH

with a step UL Closed Loop Power Control Step Size, as following:

DPCCH =TPCTPC_cmd

This adjustment is executed on the DPCCH, then associated DPDCH transmit power is

calculated according to DPDCH / DPCCH power ratio d/ c.


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Uplink Inner Loop PCA1 with Single RadioLink

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

When UE has single radio link, only one TPC will be received in each slot. In this case, the

value of TPC_cmd shall be derived by PCA1 as follows:

If the received TPC is equal to 0, then TPC_cmd for that slot is -1;

If the received TPC is equal to 1, then TPC_cmd for that slot is 1.

According to DPCCH channel structure, there are 15 time slots in a 10ms radio frame, and

the control is performed once in each time slot, so the frequency of uplink inner loop PCA1

is 1500Hz.


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Uplink Inner Loop PCA2 with Single RadioLink

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

When UE has single radio link, only one TPC will be received in each slot. In this case, the

value of TPC_cmd shall be derived by PCA2 as follows:

For the first 4 slots of a set, TPC_cmd = 0.

For the fifth slot of a set, UE make the decisions on as follows:

If all 5 TPCs within a group are 1, then TPC_cmd = 1 in the 5th slot;

If all 5 TPCs within a group are 0, then TPC_cmd = -1 in the 5th slot;

Otherwise, TPC_cmd = 0 in the 5th slot.

According to DPCCH channel structure, there are 15 time slots in a 10ms radio frame, and

the control is performed once in each 5-slot group, so the frequency of uplink inner loop

PCA2 is 300Hz.


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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

On the NodeB side, there are two phases during the soft handover state:

Uplink synchronization phase

The NodeB should send durative TPC = 1 to the newly-added RL before successful

synchronization.

Multi-radio link phase

Each NodeB and each cell will estimate the SIR individually and the general TPC

individually. Therefore, the UE may receive different TPC from different RLS.

Especially, when UE is in softer handover state, it means UE has radio links to the same

NodeB, in this case, these RLs (Radio Link) belong to the same RLS (Radio Link Set), and the

all TPCs are the same from each RL.


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Uplink Inner Loop PCA1 with SoftHandover

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 on

TPC_cmd = (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)

When UE is in soft handover state, multiple TPC will be received in each slot from different

cells in the active set. UE will generate the TPC_cmd by PCA1 as follows:

1. Combine the TPC from the same RLS and derive the Wi

When the RLs (Radio Link) are in the same RLS (Radio Link Set), they will transmit the

same TPC in a slot. In this case, the TPCs from the same RLS shall be combined into

one.

After combination, UE will obtain a soft symbol decision Wi for each RLSi.

2. Combine the TPC from different RLSs and derive the TPC_cmd

UE derives TPC_cmd, it is based on a function and all the N soft symbol decisions

Wi:

TPC_cmd = (W1, W2, WN),

Where TPC_cmd can only take the values 1 or -1.

In Huawei implementation, the function shall fulfil the following criteria:

If the TPCs from all RLSs are 1, the output of shall be equal to 1;

If one TPC from any RLS is 0, the output of shall be equal to -1.


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Uplink Inner Loop PCA2 with SoftHandover (Cont.)

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_tempi

00000-1000010000


TPC_cmd

The example of the uplink inner loop PCA2 in soft handover state.


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Contents







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Downlink Inner Loop Power Control

UE L1 compares the measured SIR to the 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 transmi tTPC based on

DPC_MODE

Inner Loop

UE

L1 compare

SIRmea with

SIRtar

Basically the downlink inner loop power control process is similar with uplink, UE L3 sends

SIRtar to UE L1 and then UE L1 compares SIRmea with SIRtar:

If the SIRmea is greater than the SIRtar, UE sends TPC 0 to NodeB on uplink DPCCH

TPC field;

Otherwise, UE sends TPC 1 to NodeB.

The UE shall check the downlink power control mode before generating the TPC, two

algorithm DPC_MODE1 and DPC_MODE2 could be used by UE to derive the TPC. Upon

receiving the TPC, NodeB shall estimate the transmitted TPC and adjust its downlink

DPCCH/DPDCH power accordingly.

After reception of one or more TPC in a slot, NodeB shall derive the estimated TPC TPCest(k)

and calculate a PTPC(k), the power adjustment of k:th slot.

Then NodeB shall adjust the current downlink power P(k-1) to a new power P(k), and adjust

the power of the DPCCH and DPDCH with the same amount, since power difference

between them is fixed.


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Downlink Inner Loop Power Control ModeParameters

DpcMode

Parameter name: Downlink power control mode

Recommended value: SINGLE_TPC, namely DPC_MODE = 0

DpcMode

Content: This parameter specifies the DL power control mode.

- SINGLE_TPC, a fast power control mode, indicates that a unique TPC command is

sent in each timeslot on the DPCCH.

- TPC_TRIPLET_IN_SOFT, a slow power control mode, indicates that the same TPC

command is sent over three timeslots. It is applicable to soft handover, and it can

decrease the power deviation.

- TPC_AUTO_ADJUST, an automatic adjustment mode, indicates that the value of

DPC_MODE can be modified by sending the ACTIVE SET UPDATE message to the UE.

Value range: SINGLE_TPC (DPC_MODE=0), TPC_TRIPLET_IN_SOFT (DPC_MODE=1),

TPC_AUTO_ADJUST

Physical recommended value: SINGLE_TPC


SET FRC.


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Downlink Inner Loop Power Control (Cont.)

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 ++=

If PC_DOWNLINK_POWER_BALANCE_SWITCH is OFF, then Pbal(k) equals 0.


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PTPC(k) is calculated according to the following:

If the value of Limited Power Increase Used parameter is Not

Used, then:

Where:

TPCest (k) is uplink received TPC of the k:th slot

TPC is downlink power adjustment step size

=

=+=

0)k(TPCif

1)k(TPCif)k(P

estTPC

estTPC

TPC


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If the value of Limited Power Increase Used parameter is Used,

then:

Where:

==

1k

Size_Window_Average_Power_DLkiTPCsum )i(P)k(

=

+=


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Downlink Inner Loop Power ControlParameters

PC_INNER_LOOP_LMTED_PWR_INC_SWITCH

This is one switch in PcSwitch (Power control switch) parameter

Recommended value: 0, namely OFF

FddTpcDlStepSize

Parameter name: FDD DL power control step size

Recommended value: STEPSIZE_1DB, namely 1dB

PC_INNER_LOOP_LMTED_PWR_INC_SWITCH

This is one switch in PcSwitch (Power control switch) parameter.

Content: When the switch is on, the limited power increase function is used for DL

inner loop power control.

Value range: 1, 0

Physical value range: ON, OFF

Set this parameter through SET CORRMALGOSWITCH, query it through LST

CORRMALGOSWITCH, and modify it through SET CORRMALGOSWITCH.

FddTpcDlStepSize

Content: This parameter specifies the step size of the closed-loop power controlperformed on DL DPCH in Frequency Division Duplex (FDD) mode.

Value range: STEPSIZE_0.5DB, STEPSIZE_1DB, STEPSIZE_1.5DB, STEPSIZE_2DB

Physical value range: 0.5, 1, 1.5, 2; step: 1

Physical unit: dB


SET FRC.


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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

During soft handover, the UL TPC is demodulated in each RLS, then due to demodulation

errors, the DL transmit power of the each branch in soft handover will drift separately,

which causes loss to the macro-diversity gain.

The DL Power Balance (DPB) algorithm is introduced to reduce the power drift between

links during the soft handover.


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Downlink Power Balance Parameters

PC_DOWNLINK_POWER_BALANCE_SWITCH


Recommended value: 1, namely ON

PC_DOWNLINK_POWER_BALANCE_SWITCH


Content: When the switch is on, the RNC supports DL power balancing. During soft

handover, TPC bit errors may cause DL power drift. DL power balancing is enabled to

balance the DL power between links, thus achieving the optimal gain of soft

handover.

Value range: 1, 0





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Contents







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Outer Loop Power Control

Why we need outer loop power control?

SIR

BLER

Different curves

correspond to

different multi-path

environment

The main reason 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 SIRtar. Therefore, the outer loop

power control can adjust the SIRtar to get a stable BLER in the changeable radio

environment.


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Uplink Outer Loop Power Control

NodeB UE

Transmit TPC

Measure SIR and

compare with SIRtar

Inner loop

Set SIRtar

Out loop

RNC

Measure BLER of receiveddata and compare with theBLERtar

Set BLERtar

Uplink outer-loop power control is performed in the SRNC. The SRNC measures the

received BLER and compares it with the BLERtar. If the BLERmea is greater than the BLERtar,

the SRNC increases the SIRtar; otherwise, the SRNC decreases the SIRtar.


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Initial SIR Setting

The initial SIR target value (Init_SIR_target) is service-dependent

and is provided by the RNC to the NodeB

For the SRB and TRB, the values of SIR target, Max_SIR_target,

and Min_SIR_target must fulfill the following requirement:

Min_SIR_target SIR target Max_SIR_target

The initial SIR target value is transmitted to the NodeB by using NBAP signaling of each

RADIO LINK SETUP or RADIO LINK RECONFIGURATION PREPARE messages.


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Adjusting the SIR Target

SIRtar adjustment formula:

Where:

i is the i:th transport channel

n is the n:th adjustment period

+= FactorStep

BLER

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

i,tar

i,tari,meastartar

According to the formula above,

SIRtar(n) is the target SIR used for the n:th adjustment period.

MAX means the maximum value among the total i transmission channels.

BLERmeas,i (n) is measured for the i:th transmission channel in the n:th adjustment

period.

BLERtar,i is the target BLER of the i:th transmission channel.

Stepi is the adjustment step of the i:th transmission channel.

Factor is the adjustment factor.

In case of multi-service:

The maximum value of the SIR target among multiple services is used for the SIR

target adjustment.

If one of the services requires increase in the SIR target, the reconfigured SIR target

cannot exceed that maximum value.

The maximum value can be decreased only when all the services require decrease in

the SIR target.


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SIR Target Adjustment Limitation

The parameters Max_SIR_increase_step and

Max_SIR_decrease_step limit the adjustment range of the SIRtar,

and the algorithm is:

If SIRtar> 0 and SIRtar> Max_SIR_increase_step,

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

IfSIRtar< 0 and ABS (SIRtar) > Max_SIR_decrease_step,

then SIRtar (n+1) = SIRtar (n) -Max_SIR_decrease_step

Where,

SIRtar is the adjustment of SIRtar, and SIRtar = SIRtar (n+1) - SIRtar (n).

ABS (SIRtar) means absolute value of SIRtar.


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Parameters of BLER-based Outer LoopPower Control on the RAB Basis

0.2 dB0.4 dB0.004 dB20 ms2 dB9 dB6 dB0.01PS I/B 384K


0.2 dB0.4 dB0.004 dB20 ms2 dB5.5 dB2.5 dB0.01PS I/B 144K






0.1 dB1 dB0.002 dB20 ms2 dB7 dB4 dB0.002CSD 64K

0.2 dB0.5 dB0.005 dB20 ms2 dB5 dB2 dB0.01AMR 12.2K

0.2 dB0.5 dB0.01 dB20 ms2 dB5 dB4 dB0.01SRB 13.6K

0.2 dB0.4 dB0.004 dB40 ms2 dB5 dB2 dB0.01SRB 3.4K

Max_SIR_decrease_step

Max_SIR_increase_step

SIR_adjustment_step

OLPCperiod

Min_SIR_target

Max_SIR_target

Init_SIR_target

BLERtarget

Service

Where,

CSD: CS domain Data service.

I/B: Interactive and Background.


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Uplink Outer Loop Power ControlParameters

PC_OLPC_SWITCH


Recommended value: 1, namely ON

PC_OLPC_SWITCH


Comments: When the switch is on, the RNC updates the UL SIR TARGET of radio

links on the NodeB side through IUB DCH FP in-band signaling.

Value range: 1, 0





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Downlink Outer Loop Power Control

NodeB

Set SIRtar

Transmit TPC

Measure SIR and

compare with SIRtar

Measure BLER ofreceived data andcompare with the

BLERtar

Outer loop

Inner loop

L1

L3

UE

The downlink outer loop power control is implemented inside the UE. Therefore, this

algorithm is specified by UE manufacturer.

Generally, the UE L3 measures the received BLER and compares it with the BLERtar. If the

BLERmea is greater than the BLERtar, the L3 increases the SIRtar and send it to UE L1;

otherwise, the L3 decreases the SIRtar.


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wcdma ran11 power control algorithm and parameters

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