05...Power Control

All Rights Reserved © Alcatel-Lucent 2009

Power Control Issues

All Rights Reserved © Alcatel-Lucent 2009Page2

ContentsContents

1. Power Control Overview

2. HWⅡPower Control


Power Control OverviewPower Control Overview

Power control Adjust the transmitting power of BTS and MS when needed. Based on measurement reports of BTS and MS

Purpose Save the power of BTS and MS Reduce the interference of the network Increase the quality of the network



Power control includes uplink power control and downlink power control, Which are performed independently Uplink power control: Adjust TX power of MS to let BTS

receive stable signal, reduce the uplink co-channel and adjacent channel interference, reduce power consumption of MS

Downlink power control: Adjust BTS TX power to let MS receive stable signal, reduce the downlink co-channel and adjacent channel interference, reduce power consumption of BTS


Process of power control commands It takes 3 measurement report periods(480ms/period) from

command sending to execution.

SA0 SA1SA0 SA0SA1SA1 SA2SA2SA2 SA3SA3SA3

BTS sends the command for power control and TA in SACCH header.

MS obtains SACCH block

MS begins to send the measurement report of the last multi-frame.

In the 26 multi-frames, frame 12 sends SACCH.

BTS receives the measurement report

SACCCH report period: 26X4=104 frames (480ms)

MS adopts the new power level and TA

MS begins to set up a new SACCH header to report the new TA and power control message.



Power control judgment Power control judgment is controlled by BTS measurement

report pre-processing item which can be selected in handover control data table

MR. Pre-process (measurement report pre-processing): This switch decide where power control be processed. If measurement report pre-processing is “yes”, power control is processed in BTS, and when setting it “no”, power control is processed in BSC



Up link and Down link power control can be enabled independently



ContentsContents

1. Power Control Overview

2. HWⅡ Power Control


Original data of power control -- measurement report

Network

Downlink Downlink measurement measurement reportreport

Uplink MRUplink MR

BTS

HW II Power ControlHW II Power ControlHW II Power ControlHW II Power Control


Uplink Uplink measuremmeasurement reportent report

Downlink Downlink measuremmeasurement reportent report

Measurement report



Measurement report pre-processing -- interpolation

Each measurement report has a serial number. When the serial

numbers are discontinuous, this indicates that some measurement

reports must be missed. In this case, the network will fill up the

measurement report according to interpolation algorithm.

MR MR MR MR MR

Measurement report serial number n

Measurement report serial number n+4

Consecutive measurement report flow

3 missing measurement reports3 missing measurement reports



Measurement report pre-processing -- filtering Calculate average results of several consecutive

measurement reports to obtain the current information, reduce the influence of some abnormal measurement reports for the judgment of power control.

MR MR

MR

MR

MR MR

Consecutive measurement report flow

FilterFilter



Power control judgment process

Measurement report pre-processing

The power control demand according to the receiving level

Send the power control command

The power control demand according to receiving quality

General power control judgement



Measurement report compensation

Purpose: Ensure the accuracy of selection of the history measurement report before filtering.

Implementation steps:

1. Put the current receiving measurement report into the measurement report compensation queue.

2. Record the changed information of the transmitting power according to the MS and BTS power levels in the measurement report.

3. After finish the measurement report interpolation, system will compensate the receiving level of the history measurement report according to the power change information. The compensated measurement reports will be the original data in the filter process.

4. Filter the compensated measurement reports.



Measurement report compensation

The expected receiving signal level: 30

The power control will be more effective with measurement report compensation.


The power control will be more effective with measurement report compensation.

X axis

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Power control diagram when there is measurement report compensation

Diagram when there is no power control

Power control diagram when there is no measurement report compensation

Power control effect diagram of measurement report compensation



Measurement report prediction

Purpose: Avoid power control later than needed, the delay is

dangerous in case of poor level or bad quality

Implementation procedure

1. Analyze the tendency of MR by the historical measurement reports after

interpolation.

2. Guide by the tendency, to predict the values of measurement report to

be received. There are 0~3 measurement reports prediction, which are

configured on OMC.

3. Filter the interpolated, compensated and predicted measurement

reports, and implement power control judgment.



Measurement report prediction

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No power control

Mean filter power control

Prediction filter power control

Diagram of power control effect comparison between prediction filter and mean filter


The power control with prediction filter will be more effective than that with mean filter


The power control with prediction filter will be more effective than that with mean filter



Power control demand based on receiving level.

After measurement report pre-processing, the power control

module makes a comparison between the expected signal

level and the current receiving signal level.

Calculate the transmitting power level step size to be

adjusted, making the receiving level value closer to the

expected value.

Adopt variable step size when adjusting the transmitting

power according to the receiving level, so as to achieve the

expected level as soon as possible.

HW II Power Control ImplementationHW II Power Control ImplementationHW II Power Control ImplementationHW II Power Control Implementation


Power control demand based on receiving quality After measurement report pre-processing, the power control

module makes comparison between the expected quality level and the current receiving quality level.

Calculate the step size of the transmitting power level to be adjusted.

Increase the transmitting power in case of poor receiving quality. Decrease the transmitting power in case of good receiving quality. Adopt fixed step size when adjust the transmitting power according

to the receiving quality.



General power control judgment General power control judgment


Rxlev power control adjustment

Received quality power control adjustment

Comprehensive power control adjustment

Reduce TP Reduce TP Reduce transmit power

Reduce TP Improve TP No action

Reduce TP No action Reduce TP

Improve TP Reduce TP Improve TP

Improve TP Improve TP Improve TP

Improve TP No action Improve TP

No action Reduce TP Reduce TP

No action Improve TP Improve TP

No action No action No action

Note:

TP = transmit power


Adaptive power control:

Adaptive power control refers to changeable power control

strategy according to the communication environment, it makes

power control more effective and stable.

Automatically change the adjustable maximum step size of power control

according to different communication environment (different receiving

quality).

Adopt different power control strategies according to different

communication environments (different receiving quality and level).

Max. step is different between increase and decrease.

HW II Power Control FeatureHW II Power Control FeatureHW II Power Control FeatureHW II Power Control Feature


Power control within the upper/lower thresholds As for HW II power control in case of calculating power

control step size according to signal level and quality, the signal level and quality have upper/lower thresholds. Power control will not execute if the signal level and quality is within the threshold bands.

Avoid the signal level up-and-down caused by power control. The upper threshold can be increased dynamically in case of

bad quality.

HW II Power Control FeatureHW II Power Control FeatureHW II Power Control FeatureHW II Power Control Feature


Measurement report compensation -- makes power control judgment more accurate

Measurement report prediction --to avoid power control later than needed, the delay is dangerous in case of poor level or bad quality

Power control expected signal level and quality threshold falls within a band, this avoids receiving signal level fluctuate up and down frequently

HW II Power Control AdvantagesHW II Power Control AdvantagesHW II Power Control AdvantagesHW II Power Control Advantages


[HW II power control table] main parameters – 1 [HW II power control table] main parameters – 1

Parameter name

Meaning Value range

Recommended value

filter length for UL

RX_LEV

How many uplink measurement reports obtained for the average uplink signal level to be used for uplink power control adjustment.

1~20 6

filter length for DL

RX_LEV

How many downlink measurement reports obtained for the average downlink signal level to be used for downlink power control adjustment.

1~20 6

filter length for UL Qual.

How many uplink measurement reports obtained for the average uplink quality level to be used for uplink power control adjustment.

1~20 6

filter length for DL Qual.

How many downlink measurement reports obtained for the average downlink quality level to be used for downlink power control adjustment.

1~20 6

MR compensation

allowed

If “yes”, System put the currently received measurement report into the measurement report compensation queue, and record the transmitting power information according to MS and BTS power values. And then interpolation, compensate the receiving level value of the record measurement report according to the power change information.

Yes, no Yes

UL MR number

predicted

The number of uplink pred. MR in the filter using for power control judgment.

0~3 reports

2

DL MR number

predicted

The number of downlink pred. MR in the filter using for power control judgment.

0~3 reports

2

HW II Power Control ConfigurationHW II Power Control ConfigurationHW II Power Control ConfigurationHW II Power Control Configuration


[HW II power control table] main parameters – 2[HW II power control table] main parameters – 2

Parameter name

Meaning Value range

Recommended value

PC interval Time between two power control command implementation 1~30

(SACCH period)

5

UL RX_LEV upper

threshold

This parameter specifies the uplink signal level upper threshold. When the signal level higher than this value, calculate a power

decrement [=receiving level - (upper threshold + lower threshold)/2]. This decrement value should consider together with

the maximum step size allowed for different quality zone which the receiving signal quality located.

0~63 (-110 dBm – -47 dBm)

35

UL RX_LEV lower

threshold

This parameter specifies the uplink signal level lower threshold. When the signal level lower than this value, calculate a power

increase [= (upper threshold + lower threshold)/2- receiving level]. This increase also consider together with the maximum step size

allowed for different quality zone which the receiving signal quality located.

0~63 (-110 dBm – -47 dBm)

25

UL Qual. upper

threshold This parameter specifies the uplink quality upper threshold.

Level 0~7

0

UL Qual. lower

threshold

This parameter specifies the uplink quality lower threshold for power control

Level 0~7

2



[HW II power control table] main parameters [HW II power control table] main parameters – – 33

Parameter name

Meaning Value range

Recommended value

DL RX_LEV upper threshold

This parameter specifies the downlink signal level upper threshold. When the signal level higher than this value, calculate a power decrement [=receiving level – (upper threshold + lower threshold)/2]. This decrement should consider together with the maximum step size allowed for different quality zone which the receiving signal quality located.

0~63 (-110 dBm –

-47 dBm) 40

DL EX_LEV lower threshold

This parameter specifies the downlink signal level lower threshold. When the signal level lower than this value, calculate a power increase [= (upper threshold + lower threshold)/2- receiving level]. This increase also consider together with the maximum step size allowed for different quality zone which the receiving signal quality located.

0~63 (-110 dBm –

-47 dBm) 30

DL Qual. upper threshold

This parameter specifies the downlink quality upper threshold for power control

Level 0~7 0

DL Qual. lower threshold

This parameter specifies the downlink quality lower threshold for power control

Level 0~7 2




Parameter name

Meaning Value range Recommended

value

MAX Down Adj. value Qual.

zone 0

This parameter specifies the maximum downward power adjustment value when the Rx quality is 0.

0~30dB 16


zone 1

This parameter specifies the maximum downward power adjustment value when the Rx quality is 1 or

2 0~30dB 8


zone 2

This parameter specifies the maximum downward power adjustment value when the Rx quality is

equal to or more than 3. 0~30dB 4

MAX Down Adj. PC Value by

Qual.

The adjustment step allowed for the downward power control due to receiving signal quality.

0~4dB 4




Parameter name


value

MAX Up Adj. PC Value by

RX_LEV

It is used to set the maximum adjustment step for upward power control by receive level.

0~32dB 16

MAX Up Adj. PC Value by

Qual.

It is used to set the maximum adjustment step for upward power control by receive quality.

0~32dB 8

UL Qual. Bad TrigThrsh

In uplink power control, when the receiving quality of uplink is not less than this start threshold, the

actual "upper threshold of signal strength of uplink" will be added with "upper threshold offset of level when the receiving quality of uplink is poor" in the

data configuration. Thus, the expected level in uplink power control can be increased furthermore.

0~7 5

UL Qual. Bad UpLEVDiff

In uplink power control, when the receiving quality is not less than "start threshold when the receiving

quality of uplink is poor", the actual "upper threshold of signal strength of uplink" will be added with this

offset value.

0~63dB 0




Parameter name


value

DL Qual. Bad TrigThrsh

In downlink power control, when the receiving quality of downlink is not less than this start

threshold, the actual "upper threshold of signal strength of downlink" will be added with "upper

threshold offset of level when the receiving quality of downlink is poor" in the data configuration. Thus, the expected level in downlink power control can be

increased furthermore.

0~7 5

DL Qual. Bad UpLEVDiff

In downlink power control, when the receiving quality is not less than "start threshold when the receiving quality of downlink is poor", the actual

"upper threshold of signal strength of downlink" will be added with this offset value.

0~63dB 0



Exercises for HW II power control

Given conditions:

The uplink receiving level is -55dBm, the quality is level 0. Power control algorithm is HW II.

Data configuration is as follows: Uplink signal level upper threshold: -60dBm, uplink signal level lower threshold: - 80dBm. Uplink signal upper quality threshold: level 1. Uplink signal lower quality threshold: level 2. The downward adjustable step size of quality band 0 is 16dB, of quality band 1 is 8dB, and of quality 2 is 4 dB. The upward adjustable step size of receiving level is 16dB. The upward or downward adjustable step size for power control by quality are both 4dB.

Question: What will be the uplink stable receiving level after power control?

ExerciseExerciseExerciseExercise


Exercises for HW II power control

Answer.

First, transmitting power to be reduced according to receiving level =

actual receiving level -(uplink signal level upper threshold + uplink signal

level lower threshold)/2 ＝ -55- (-60 + (-80))/2 ＝ (-55)-(-70) ＝ 15dB. As

the receiving quality is level 0, downward adjustable step size of quality

band 0 can be used -- decrease 16dB.

Second, the transmitting power to be decreased according to receiving

quality = as “power control adjustment step size by quality” is 4dB, thus

decrease 4dB.

Therefore, according to the general judgement on power control, 15dB

should be decreased.



Exercises for HW II power control Answer .

After the implementation of step 1 power control, the receiving level becomes: -55dBm-15dB= -70dBm, Suppose the quality reach already in level 1 here.

First: the receiving level value is between -80dBm~-60dBm, needn’t adjust.

Second: the receiving quality value is between 0 and 2, needn’t adjust. Therefore, the uplink stable receiving level =-70dBm.


All Rights Reserved © Alcatel-Lucent 2009

05...Power Control

Documents

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measurement

history measurement

maximum adjustment

measurement

power change

compensated

avoid power