3- Power control - D(1-12-2011)

8/3/2019 3- Power control - D(1-12-2011)

1/18

1

Confidential Information of Brilliance Tech.

No Spreading without Permission.Security Level: Internal www.brilliancetech.net

Contents1. Power Control Overview

2. open loop Power Control

3. closed loop Power Control

8/3/2019 3- Power control - D(1-12-2011)

2/18

2



Purpose of uplink 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

8/3/2019 3- Power control - D(1-12-2011)

3/18

3



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(DL

power congestion)

Fading

Downlink power control

Ensure Downlink quality with minimum transmission power

Decrease interference to other cells, and increase capacity

Save NodeB transmission power

8/3/2019 3- Power control - D(1-12-2011)

4/18

4



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

8/3/2019 3- Power control - D(1-12-2011)

5/18

5



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 thetransmission power of the uplink channel

principle

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

downlink channel

8/3/2019 3- Power control - D(1-12-2011)

6/18

6



Disadvantage

This power control method is not accurate as their 190MHZ

between uplink and downlink

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

Open loop Power Control Overview

8/3/2019 3- Power control - D(1-12-2011)

7/18

7



Open loop Power Control Overview

PRACH open loop power control

DPCCH open loop power control

8/3/2019 3- Power control - D(1-12-2011)

8/18

8



Open loop Power Control of PRACH

AICH access

slots RX at UE

PRACH access

slots TX at UE

One access slot

Xp-a

Xp-m

Xp-p

Pre-amble

Pre-amble

Message part

Acq.Ind.

8/3/2019 3- Power control - D(1-12-2011)

9/18

9



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

8/3/2019 3- Power control - D(1-12-2011)

10/18

10



Power Ramp Step

Pp-m

10ms/20ms

Preable_Initial_

power

NO. Parameter Parametermeaning

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 initialtransmission 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

8/3/2019 3- Power control - D(1-12-2011)

11/18

11



open 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 open loop power control

Guarantee the QoS

Decrease the interference

Increase the system capacity

8/3/2019 3- Power control - D(1-12-2011)

12/18

12



Closed loop power control overview

Inner loopOuter loop

BLERmea>BLERtarSIRtar

BLERmeaSIRtarTPC=0

SIRmea

8/3/2019 3- Power control - D(1-12-2011)

13/18

13



Downlink closed loop power control

Page13

NodeB

set SIRtar

Transmit TPC

Measure and compare SIR

Measure and compare BLER

Outer loop

Inner loop L1

L3

10-100Hz1500Hz

8/3/2019 3- Power control - D(1-12-2011)

14/18

14



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

8/3/2019 3- Power control - D(1-12-2011)

15/18

15



Uplink outer loop power control

NodeB UE

Transmit TPC


Inner-loop

Set SIRtar

Out loop

RNC

Measure received data andcompare BLER in the TrCH

Set BLERtar

10-100Hz

8/3/2019 3- Power control - D(1-12-2011)

16/18

16



Uplink-inner loop power control

NodeB

UE

Transmit TPC

Inner-loop

set SIRtar

1500Hz

Each UE has

its own loop

TPC Decision

(01)

TPC_CMD

-1, 0, 1

Adjust DPCCH Tx

DPCCH=tpcTPC_cmd

PCA1PCA2

Adjust DPDCH Tx

(c,d)

Compare SIRmeas with SIRtar

SIRmea>SIRtarTPC=0

SIRmea

8/3/2019 3- Power control - D(1-12-2011)

17/18

17



Downlink outer loop power control

NodeB

set SIRtar

Transmit TPC


Measure and compare BLER

Outer

loop

Inner loop L1

L3

10-100Hz1500Hz

8/3/2019 3- Power control - D(1-12-2011)

18/18

Thank Youwww.brillaincetech.net

Documents

3- Power control - D(1-12-2011)