2- wcdma power control.ppt

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OWJ200107 WCDMA Power Control

ISSUE 1.0


Chapter 1 Power Control OverviewChapter 1 Power Control Overview

Chapter 2 open loop Power Control Chapter 2 open loop Power Control

Chapter 3 closed loop Power Control Chapter 3 closed loop Power Control


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


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


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


Power Control Classification

Power control classification：

open loop power control

closed loop power control

− Uplink inner-loop power control

− Downlink inner-loop power control

− Uplink outer-loop power control

− Downlink outer-loop power control


Power control methods adopted for various physical channels

Power control methods adopted for various physical channels

“Y" can be applied,

– not applied

Physi calchannel

Open l ooppowercontrol

I nner l ooppowercontrol

Outer l ooppowerControl

No power control process,power i s speci fi ed byupper l ayers.

DPDCH － Y Y －DPCCH Y Y Y －PCCPCH －－－ YSCCPCH －－－ YPRACH Y －－－AI CH －－－ YPI CH －－－ Y



Chapter 2 open loop Power ControlChapter 2 open loop Power Control




2.1 open loop power control overview2.1 open loop power control overview

2.2 PRACH open loop power control2.2 PRACH open loop power control

2.3 DPCCH open loop power control2.3 DPCCH open loop power control


open loop Power Control Overview

Purpose

UE estimates the power loss of signals on the propagation path

by measuring the downlink channel signals, then calculates the

transmission power of the uplink channel

principle

Path loss of the uplink channel is related to path loss of the

downlink channel


open loop Power Control Overview

Disadvantage

This power control method is rather rough

Application scenarios

In a cell, signal fading caused by fast fading is usually more serious

than that caused by propagation loss.

open loop power control is applied only at the beginning of connection

setup, generally in setting the initial power value.


Chapter 2 Open Power Control Chapter 2 Open Power Control





open loop Power Control of PRACH

AICH accessslots RX at UE

PRACH accessslots TX at UE

One access slot

p-a

p-mp-p

Pre-amble

Pre-amble

Message part

Acq.Ind.


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


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


open loop power control of PRACH open loop power control of PRACHApplication scenariosApplication scenarios

1. CCCH : RRC Connection Request

open loop power control of PRACH

5. Downlink Synchronization

UE Node BServing RNS

Serving RNC

DCH - FP

Allocate RNTISelect L1 and L2parameters

RRC RRC

NBAP NBAP

3. Radio Link Setup Response

NBAP NBAP

2. Radio Link Setup Request

RRC RRC

7. CCCH : RRC Connection Set up

Start RX description

Start TX description

4. ALCAP Iub Data Transport Bearer Setup

RRC RRC

9. DCCH : RRC Connection Setup Complete

6. Uplink Synchronization

NBAP NBAP

8. Radio Link Restore Indication

DCH - FP

DCH - FP

DCH - FP


open loop power control of DL DPCCH

The DL DPDCH open loop power control can be calculated by the following formula:

P=(Ec/Io)Req-CPICH_Ec/Io + CPICH_Power

Parameters explanation

(Ec/Io)req is the required Ec/Io, which should ensure that UE can receive the message from the dedicated channel correctly

CPICH_Ec/Io is measured by UE, then it is sent to UTRAN by RACH

CPICH_Power is the transmission power of CPICH


open loop power control of DL DPCCH open loop power control of DL DPCCH

Application scenariosApplication scenarios


open loop power control of DPCCH



Serving RNC

DCH - FP

Allocate RNTISelect L1 and L2 parameters

RRC RRC

NBAP NBAP


NBAP NBAP


RRC RRC





RRC RRC



NBAP NBAP


DCH - FP

DCH - FP

DCH - FP


open loop power control of UL DPCCH

The UL DPCCH open loop power control can be calculated by

the following formula:

DPCCH_Initial_Power

= DPCCH_Power_Offset - CPICH_RSCP


open loop power control of UL DPCCH open loop power control of UL DPCCH

Application scenariosApplication scenarios


open loop power control of DPCCH



Serving RNC

DCH - FP

Allocate RNTISelect L1 and L2parameters

RRC RRC

NBAP NBAP


NBAP NBAP


RRC RRC





RRC RRC



NBAP NBAP


DCH - FP

DCH - FP

DCH - FP



3.1 closed loop power control overview3.1 closed loop power control overview

3.2 Uplink inner loop power control3.2 Uplink inner loop power control

3.3 Downlink inner loop power control3.3 Downlink inner loop power control

3.4 Outer loop power control3.4 Outer loop power control


closed loop power control overview

The characteristics of open loop power control

The results from open loop power control are not accurate enough

open loop power control can only decide the initial power

The advantages of closed loop power control

Guarantee the QoS

Decrease the interference

Increase the system capacity


closed loop power control overview

Inner loopOuter loop

BLERmea>BLERtar→SIRtar

BLERmea<BLERtar→SIRtar

Until BLERmea=BLERtar

SIRtar

SIRmea>SIRtar→TPC=0

SIRmea<SIRtar→ TPC=1

UntilSIRmea=SIRtar

TPC

TPC=0 Power

TPC=1 Power

BLERtar

Ensure the QoS with minimum

power


Uplink-inner loop power control

NodeB compares the measured SIR to the preset target SIR

NodeB

UE

Transmit TPC

Inner-loop

set SIRtar

1500Hz1500Hz

Each UE has its own loop

Each UE has its own loop

TPC Decision(0 ， 1)

TPC_CMD（ -1, 0, 1）

Adjust DPCCH Tx△ DPCCH= tpc×TPC_cmd△

PCA1 PCA2

Adjust DPDCH Tx(βc,βd)

Compare SIRmeas with SIRtar

SIRmea>SIRtar→TPC=0SIRmea<SIRtar→ TPC=1


UE gets one TPC in each time slot

If TPC=0, TPC_cmd= -1

If TPC=1, TPC_cmd= 1

This control is done in each time slot

Power control frequency is 1500HZ

0 1 1 0 1 1 0 1 1 0…… ……

…… ……TPC_CMD

TPC

-1 1 1 -1 1 1 -1 1 1 -1

Uplink inner-loop PCA1 without soft handover


0 1 1 0 1 1 0 1 1 0…… ……

RLS1-TPC (W1)

…… ……RLS2-TPC (W2) 1 0 1 1 0 1 0 1 0 1

…… ……

…… ……TPC_CMD

0 0 1 0 0 1 1 0 1 1

0 0 1 0 0 1 0 0 0 0

Each time slot, combine TPC from different RLS ， then get Wi

CELL1 CELL2

CELL4CELL3

RL11 RL12

RLS1

RLS2 RLS3

RLS3-TPC (W3)

Get TPC_cmd based on

TPC_cmd = γ (W1, W2, … WN)

Uplink inner-loop PCA1 with soft handover


TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS8 TS9 TS10 TS11 TS12 TS13 TS14

0 0 0 0 0 1 1 1 1 1 1 1 0 1 1

10ms/frame

Group 2Group 1 Group 3

…… ……

0 0 0 0 -1 0 0 0 0 1 0 0 0 0 0

TPC

TPC_CMD

Transmission power will be controlled in each 5 time slots

The frequency is 300HZ

…… ……

Uplink inner-loop PCA2 Without soft handover


Combine TPC from same RLS in each time slot

Calculate TPC_cmd

TPC_CMD=1

TPC_CMD=-1

Otherwise TPC_CMD=0

Calculate TPC_tempi for each RLSIf 5 TPC are all 1, TPC_tempi=1

If 5 TPC are all 0, TPC_tempi=-1Otherwise, TPC_tempi =0

5.0_1

1

N

iitempTPC

N

5.0_1

1

N

iitempTPC

N

CELL1 CELL2

CELL4CELL3

RL11 RL12

RLS1

RLS2 RLS3

Uplink inner-loop PCA2 With soft handover



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


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


0 0 0 0 1 0 0 0 0 -1 0 0 0 0 0…… ……

TPC_CMD

Power is controlled in each 5 time slots

The power control frequency is 300HZ

Uplink inner-loop PCA2 with soft handover


Comparison between PCA1 and PCA2

The control frequency

TPC1, the power control frequency is 1500Hz

TPC2, the power control frequency is 300Hz


NodeB

set SIRtar

Transmit TPC

Measure and compare SIR

Measure and compare BLER

Outer loop

Inner loop L1

L3

10-100Hz1500Hz

Downlink closed loop power control


Downlink Inner loop power control

NodeB

Set SIRtar

Transmit TPC in each TS

Measure SIR and compare

it with SIRtar

Adjust Tx power

with 0.5, 1, 1 or 2dB

1500HzL3


Downlink inner loop power control

When UE is not in soft handover

The TPC which is generated by UE is transmitted in TPC domain

of UL channel

When UE is in soft handover, two power control modes can be used,

which is decided by DPC_mode:

DPC_MODE ＝ 0 ， UE will transmit TPC in every slot

DPC_MODE ＝ 1 ， UE will transmit the same TPC in every three

time slot

When the downlink channel is in out of synchronization, UE will

transmit TPC 1 because UE can not measure the downlink SIR

How to generate TPCHow to generate TPC


The transmission power can not higher than Maximum_DL_Power, and not

less than Minimum_DL_Power neither.

Downlink power adjustment:

Pk Pk 1PTPCkPbalk

Where

P(k-1) is power of previous

PTPC(k) is the adjustment

Pbal(k) is correction value

Downlink inner-loop power controlHow to adjust powerHow to adjust power


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


Where

PTPC(k)

With “Limited Power Raise Used”

Downlink inner-loop power control

0)(TPC if

e_LimitPower_Rais)( and 1)(TPC if

e_LimitPower_Rais)( and 1)(TPC if

0)(

est

est

est

k

kk

kk

kP TPCsum

TPCsum

TPC

TPC

TPC

PTPC(k) is the adjustment value

TPCest(k) is uplink TPC value

△TPC is downlink power adjustment step(0.5, 1, 1.5 or 2dB)

Power_Raise_Limit: the limited value for Power ramping in a timer

DL_power_averaging_window_size ： timer for power ramping (TS)

1

1____

)()(k

SizeWindowAveragingPowerDLkiTPCsum iPk


Downlink inner-loop power control


Downlink Power Balance

Downlink power balance process

SRNC can monitor every single

NodeB’s transmission. If SRNC found

the power offset in soft handover is

excessive, it will initiate the DPB

process

The initiation and stop of DPB

The power offset of two RLs is greater

than the DPB initial threshold, the

DPB process is initiated

The power offset of two RLs is less

than the DPB stop threshold, the DPB

process is stopped

NodeB

NodeB

Initiate the DPB process

DPB process


Outer loop power control

The character of outer loop power control

The QoS which NAS provides to CN is BLER, not SIR

The relationship between inner loop power control and outer loop

power control

SIRtar should be satisfied with the requirement of decoding

correctly. But different multi-path radio environments request

different SIR

Therefore, the outer loop power control can adjust the SIR to get a

stable BLER in the changeable radio environment


Uplink outer loop power control

NodeB UE

Transmit TPC


Inner-loop

Set SIRtar

Out loop

RNC

Measure received data and compare BLER in the TrCH

Set BLERtar

10-100Hz


NodeB

set SIRtar

Transmit TPC


Measure and compare BLER

Outer loop

Inner loop L1

L3

10-100Hz1500Hz

Downlink outer loop power control



SIR target adjustment SIR target adjustment stepstep

etBLERt

etBLERtBLERmeastepSIRAdjustSoefficientSIRAdjustcSIRtar

arg

arg**

Where

SirAdjustStep: Outer loop power control adjustment step

SirAdjustcoefficient : Coefficient for outer loop power control

BLERest: Estimated BLER

BLERtar: Target BLER



Uplink outer loop power control command transmit to NodeB

through DCH-FP of Iub interface

Node B SRNC

……


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2- wcdma power control.ppt

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