Cdma2000 1X Power Control Algorithm

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cdma2000 1X Power Control Algorithm


Objectives

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

State the significance of power control in CDMA

Analyze reverse power control algorithm

Analyze forward power control algorithm

Optimize power control parameter


Contents

1. Purpose and Principle

2. Classification and Application

3. Reverse Power Control Algorithm

4. Forward Power Control Algorithm


Contents



3. Reverse Power Control

4. Forward Power Control


Purpose & Principle

Purpose

Overcome far and near effect

Reduce the interference, increase the system capacity

Basic principle

Control the transmitting power of BTS and MS. Ensure the

power at receiver through complicated wireless

propagation environment can meet the required

demodulation threshold.

Based on the previous point, decrease the power of MS

and BTS as much as possible, to decrease the interference

among the user, make the network performance best.


Contents






Classification

According to the direction, power control is divided:

Reverse power control

Forward power control

According to the function, power control is divided:

Reverse power control

Reverse open loop power control

Reverse closed loop power control (Inner loop + Outer loop)

Forward power control

Measurement report power control

EIB power control

Fast power control (Inner loop + Outer loop)


Application

Forward power control base on the protocol revision:

The revision of MS is 2-5 and RC1 channel is allocated,

measurement report power control has high priority.

The revision of MS is 3-5 and RC2 channel is allocated,

EIB power control is preferred.

The revision of MS is above 6 (including 6), forward

fast power control is preferred.

Reverse power control:

All the version of MS adopts the reverse power control

algorithm, including open loop and closed loop.


Contents






Contents


3.1 Introduction

3.2 Open Loop Power Control

3.3 Closed Loop Power Control


The object of reverse power control is MS The purpose of reverse power control:

Overcome the far and near effect Ensure the power at BTS receiver meet the minimum requi

red Eb/Nt , decrease the interference and increase the syste

m capacity

Reverse Power Control


Power Control in Access Process

Reverse open loop power control starts

Reverse closed loop power control starts

BTS

Channel Assnmt . Msg .

Origination Msg

Base Sta . Acknlgmt . Order

TFC frames of 000s

TFC preamble of 000s


Mobile Sta . Ackngmt . Order

Service Connect Msg .

Svc . Connect Complete Msg


The first access probe

PAGING

FW TFC

PAGING

RV TFC

FW FC

RV TFC

FW TFC

RV TFC

FW TFC

A successful access attempt


Contents

3. Reverse Power Control

3.1 Introduction




Received Powertransmitting

power

Supposing that the property on both link are the same Estimate the transmitting power according to the total r

eceived power The factor to influence on transmitting power of MS:

Circumstance of the channel Path loss Cell Load

Principle


Code Parameter Unit Remark

AMean _receive

_powerdBm Total received power

B Offset _ power dBRelated to RC, band class, and channel

type

C NOM _ PWR dB Getting from APM

D NOM _ PWR _ EXT dB Getting from APM

E INIT_PWR dB Getting from APM

n ntime

sAccess probe sequence

G PWR_STEP dB Getting from APM

Transmitting power (dBm)= -A + B + C - 16×D + E + F F is access _ probe _ correction, the value shall be calcul

ated by Access _ probe _ correction = (n-1)×G

Access Channel (IS95A)



AMean _receive

_powerdBm Total received power

B Offset _ power dB Related to RC, band class, and channel type

C NOM _ PWR dB Getting from APM

D NOM _ PWR _ EXT dB Getting from APM

E INIT_PWR dB Getting from APM

n ntime

sAccess probe sequence

G PWR_STEP dB Getting from APM

HInterference _

correctiondB

Interference _ correction =min { max (

-7-Ec/Io ,0 ) ,7 }

Transmitting power (dBm) = -A + B + C -16×D+ E + F + H

F is access _ probe _ correction, the value shall been calc

ulated by Access _ probe _ correction = (n-1) × G

Access Channel (IS95B, IS2000)


Traffic Channel (RC1, RC2)

Transmitting power (dBm) = -A+ B+ C- 16×D+ E+ F+ H+ J

F is access _ probe _ correction, the value shall been calc

ulated by Access _ probe _ correction = (n-1)×G


A Mean_receive _power dBm Total received power

B, C, D,

E, G, HMixed Parameter dB

The meaning of each

parameter

is the same as previous slide

n n times Access probe sequence

J RLGAIN_ADJ dB Getting from ECAM


Traffic Channel (RC3, RC4) Transmitting power of R-PICH= -A+ B+ C- 16×D+ E+ F+ H+ J

F is access _ probe _ correction, the value shall been calculated

by Access _ probe _ correction = (n-1)×G

Transmitting power of R-FCH= Transmitting power of R-PICH+

KCode Parameter Unit Remark

A Mean_receive _power dBm Total received power

B, C, D,

E, G, HMixed Parameter dB

The meaning of each

parameter

is the same as previous slide

n n times Access probe sequence

J RLGAIN_ADJ dB Getting from ECAM

KRLGAIN_TRAFFIC_PIL

OT dB Getting from ESPM


Open Loop Parameters

Parameter RangeDefault

SettingUnit

NOM_PWR -8~7 4 dB

NOM _ PWR _ EXT Y/ N NY: Sent

N: Not sent

NUMSTEP 0~15 5 Times

INIT_PWR -16~15 0 dB

PWR_STEP 0~7 4 dB

Command: MOD APM


Review Reverse open loop power control is simple and direct,

and it doesn't need to exchange the control information

between the BTS and MS, saving the overload message.

Reverse open loop power control estimate the power

base on forward link measurement, but precision is too

low.

Forward link and reverse link are not correlative

The total received power is subject to the influence on

neighbor cell, and the error is remarkable when the user is

on the border of cell

Response frequency is around 50 Hz.


Contents


3.1 Introduction




Principle

Reverse close loop power control adjust the power of MS base on the R-FER and Eb/Nt, it consists of inner and outer loop

Out loop PC change the setting Eb/Nt on the reverse link periodically

Inner loop PC adjust the power of MS base on the setting Eb/Nt

Inner Loop Power ControlOuter Loop Power Control

Insert power control bit Set Eb/Nt value

Detect reverse Eb/Nt Calculate FER

Power control bit

20ms forward traffic frame

1.25ms

… …


Demodulate R-TCH to get measurement Eb/Nt

Power Control Bit = 1

Forward PC sub-channel

Setting Eb/Nt of BTS (variable)

Adjust the R-TCH power

of MS

-+

Result ≤ 0 ?YES NO


Inner Loop Power Control Flow


Demodulate R-TCH to get the measurement FER

Target FER in BSC

Setting Eb/Nt of BTS (varia

ble)

- +

Increase Eb/Nt

Send it on Abis link

Result ≤ 0 ?YES NO

Decrease Eb/Nt

Outer Loop Power Control Flow


Target FER Configuration

Parameter Range Default Value Unit

F-FCH Voice Service

Expected FER10.2%~30% 1% 1%

R-FCH Voice Service


F-FCH Data Service


R-FCH Data Service


F- nXSCH Data Service Exp

ected FER10.2%~30% Log2

n × 1% 1%

R- nXSCH Data Service Exp

ected FER10.2%~30% Log2

n × 1% 1%

Command: MOD FER


Parameters Parameters

Parameters RangeDefault

ValueUnit

Outer _ Loop _ Power _ Algorithm _

Factor0~100 0 %

Eb/Nt _ Down _ Step 0~255 1 0.125dB

Eb/Nt _ Max. _ Adjustment _ Step 0~255 10 0.125dB

Reverse _ Initial _ Set _ Value 0~255 48 0.125dB

Max. _ Value _ of _ FCH _ Outer _ Loop 0~255 96 0.125dB

Min. _ Value _ of _ FCH _ Outer _ Loop 0~255 16 0.125dB

Reverse _ Power _ Step 0.25~1 0.50.25 /0.5

/1dB

Reverse_Gain_Adjust -8~7 3 dB

Min. _ Value _ of _ SCH 0~255 32 0.125dB

Max. _ Value _ of _ SCH 0~255 96 0.125dB

Command: MOD RCLPC


Adjustment Process

Reverse _ Outer _ Loop _ Power _ Control _ Period

Eb/Nt _ Down _ Step

Eb/Nt _ Up _ Step

Eb/Nt

frame0 33 66 99 132 165 198

Max. _ Value _ of _ FCH _ Outer _ Loop

Min. _ Value _ of _ FCH _ Outer _ Loop


Reverse PC in Soft Handoff

Base on the understanding of purpose and principle

of power control, how to analyze the following power

control?

11

0

Finally, it would increase or decrease ？？


In the current system, reverse power control is realized

by open loop and closed loop power control together. MS starts the reverse open loop power control with the first

access probe

MS starts the reverse closed loop power control after

successfully demodulate the first reverse traffic channel

preamble, to correct the precision of reverse open loop power

control

Compared with forward power control, reverse power

control is more complicated. With large variance range

and high sensitivity, reverse power control compensate

fast fading.

Summary


Contents






Contents


4.1 Introduction

4.2 Measurement Report Power Control

4.3 EIB Power Control

4.4 Fast Power Control


Purpose

The object of forward power control is BTS The purpose of forward power control:

To maximize forward system capacity, it decreases the power of forward traffic channel as much as possible, on the condition that ensure the power at the receiver with the minimum required Eb/Nt

To improve the quality of service on the border of cell, and decrease the interference to the neighbor cell as much as possible


Contents


4.1 Introduction

4.2 Measurement Report Power Control




Classification

MS measure forward traffic frame, and report the

PMRM to BSC, then the BSC adjust forward channel

gain depending on that PMRM, the frame processing

board sends it in forward traffic frame to the BTS

The measurement report power control includes:

Threshold mode: report PMRM to the BTS, only when

the number of bad frame meet the threshold defined in

a period

Period mode: report PMRM to BTS every other a period


Current FERReport PMRM

Target FER in BSC

MS measures the forward traffic frame

-+

Increase

Forward Channel Gain

Result ≤ 0 ?

Decrease

YES NO

Adjust the F-TCH power of

BTS

Period Mode


Report PMRM

BSC measures PMRM periodically

MS measures the forward traffic frame periodically

Forward Channel Gain

Bad frame NO.≤T?

Decrease

YES

NO

Adjust the F-TCH

power of BTS

Increase

PMRM No PMRM

Threshold Mode


Parameters

Parameter RangeDefault

settingUnit

Max. TCH power relative to

pilot

-

200~5

5

0 0.25dB

Min. TCH power relative to

pilot

-

200~5

5

-36 0.25dB

Initial TCH power relative to

pilot

-

200~5

5

0 0.25dB

Power Decrease Step 0~255 2 0.25dB

Reporting Threshold 0~31 2 frame

Reporting Frame Count 5~905 113 frame

Power Report Delay 0~31 1 4 frames

Command: MOD FSLOWPC


Contents

4. Forward Power Control

4.1 Introduction

4.2 Measurement report Power Control




Principle

In IS95B system, specially for rate set 2, BSC adjusts the

forward channel gain according to EIB which is carried in

reverse traffic frame

EIB = 0, it means good frame in forward channel

EIB = 1, it means bad frame in forward channel

Rate set 2 in IS95 system adopts 13K QCELP, the system

control the power of BTS according to the EIB in each

frame, no need PMRM message, so it can do the power

control faster, the power control frequency is 50 Hz


Principle (Cont.)

EIB is fixed in the first bit of each reverse traffic frame.

It takes two frames delay to process the EIB.

i-2 i-1 i i+1

i+2 i+1 i i-1

Frame format of Rate Set 2 :1 frame = 288 bits (20ms)

287 bits0/1


ParametersParameters

Parameters Range Default setting Unit

Max. TCH power relative to pilot

-

200~5

5

-40 0.25dB

Min. TCH power relative to pilot

-

200~5

5

-64 0.25dB

Bad Frame Number 0~255 3 frame

Power Up Step 0~255 8 0.25dB

Power Down Small Step 0~255 1 0.25dB

Power Down Big Step 0~255 2 0.25dB

Command: MOD FEIBPC


Adjustment ProcessGain ( dB )

Frame0 1 2 3 4 5 6 7 8 9 10 11

Power Down Small Step

Max Transmitting Power

Power Down Big Step

Power Up Step

Min Transmitting Power


Contents


4.1 Introduction

4.2 Measurement report Power Control




Principle

Pilot Power Control

1 Power Control Group=1536 PN Chips

384 Chips

1.25 ms

Forward power control contains inner loop and outer loop power control, and the inner loop and outer power control work together

Insert power control bit Set target Eb/Nt value

Detect forward Eb/Nt Calculate FER

Inner LoopOuter Loop

Target FER get from ECAM


Fast Power Control Mode

When the protocol revision of MS is 6, it supports some ty

pes of forward fast power control mode (FPC_MODE):

FPC_MODE= 000: one power control sub-channel ， 800 Hz FPC_MODE= 001: two power control sub-channels, 400-400 Hz FPC_MODE= 010: two power control sub-channels, 200-600 Hz


Inner Loop Power Control

Demodulate F-TCH to get measurement Eb/Nt


Reverse PC sub-channel

Setting Eb/Nt of MS (variable)

Adjust the F-TCH power

of BTS

-+

Result ≤ 0 ?


YES NO


Outer Loop Power Control

Demodulate R-TCH to get measurement FER

Target FER carried by F-PCH

Setting Eb/Nt

(variable) Last Eb/Nt

MS inside

Chip will complete automatically depending on some algorithm


Important Parameter

Channel Parameter Range Default

SettingUnit

Voice/Data FCH

Initial Eb/Nt 0~255 40 0.125dB

Min Eb/Nt 0~255 16 0.125dB

Max Eb/Nt 0~255 80 0.125dB

1X SCH ～ (32X SCH)

Initial Eb/Nt (Relative to FCH) 0~255 -16 (1X) 0.25dB

Min Eb/Nt 0~255 -52 (1X) 0.25dB

Max Eb/Nt 0~255 -16 (1X) 0.25dB

FCH /SCH Forward Power Control Step 1-4 2 0.25dB

Voice/Data FCH Initial Power Correction

Value0~255 46 0.25dB

Command: MOD FFASTPC


Important Parameters (Cont.)

Channel Parameter Range Default Setting Unit

IS95/ IS2000

Forward Power

Control Sub-

channel

Gain 1 0~127

/

0~31

0/ 12 0.25dB

Gain 2 12/ 24 0.25dB

Gain 3 19/ 31 0.25dB

Voice/Data FCH

Channel Min. Gain 1 -255~0 -96 0.25dB



Channel Max. Gain 1 -255~0 0 0.25dB




Forward Fast PC in Soft Handoff In soft handoff, forward branches are combined in MS, and th

e quality of service is guaranteed as long as one branch is good. So the power of the other forward branch shall be waste to the whole system

In soft handoff, MS combines branches based on the maximum ratio algorithm. If the At/Ap of different branches is not balanced, the At won't be combined fully, and the combination gain in forward will be decreased, so it may occur error coding, and need BTS to increase forward power to meet the target FER, it will result in system capacity loss

Maximum ratio (At/Ap)

= power of traffic channel/ power of pilot channel


Power Synchronization

In order to balance the At/Ap among forward soft handoff

branches, save the forward power effectively, and increase the usage of forward resource, Huawei company designes the power synchronization algorithm.

Receive set

Correlator 1

Correlator 2

Correlator 3

Searcher correlator

0°

90°

Combine the branches which have close At/Ap

At/ Ap


Power Synchronization

Principle Make the power of the branch with worse quality close to th

at of the branch with good quality as much as possible, because the power of the branch with good quality must be lower, and in order to get a high combination gain, the At/ Ap of soft handoff branches should be close.

SynchronizationAlgorithm

Reverse traffic frame

Forward traffic frame

BTSBSC


RC1 and RC2 in CDMA 1X system adopt forward power control as same as IS-95 system, RC3~RC5 adopt forward fast power control ；

Forward fast power control contains inner loop and outer loop power control, and in the current system, inner loop and outer loop cooperate to control the power of forward traffic channel of the BTS.

Summary

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Documents

Cdma2000 1X Power Control Algorithm