6.Power Control

8/13/2019 6.Power Control

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OMF010003 Power Control

ISSUE1.4

Wireless Training Department


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Power control overview

HWpower control

HWpower control

Course Contents


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Power 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.


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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.


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Process of power control commands

It takes 3 measurement report periods(480ms/period) from

command sending to execution.

SA SA1A SAA1A1 SA2A2A2 SA3A3A3

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 newpower level and TA

MS begins to set up a new SACCH header

to report the new TA and power control

message.


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Huawei power control algorithm: HW I and HW II power control

Measurement reportpre-processing

Power control algorithm

selection

Yes

HW I power control

algorithm

HW II power control

algorithm

GSM0508 power control

algorithm


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Power control judgment and the selection of HWI algorithm or

HWII algorithm

Power control algorithm selected in power control data table

Power control judgment is controlled by BTS measurementreport 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. Ifmeasurement report pre-processing is yes, power control is

processed in BTS, and when setting it no, power control is

processed in BSC.


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HWpower control

HWpower control

Course Contents


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HW I Power Control

HW I power control

Process of HW I power control

MR pre-processing

Data configuration for HW I power control comparison of uplink power control with downlink power control


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Process of HW I power control

Measurement report

pre-processing

Aim achieved ?

Power control calculation and

adjustment

N

Y

HW I Power Control


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Original data of power control -- measurement report

Network

Downlinkmeasurement

report

Uplink MR

BTS

HW I Power Control


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Uplink

measurementreport

Downlink

measurement

report

HW I Power Control

Measurement report


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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 MRMRMR MR

Measurement report

serial number n

Measurement report

serial number n+4

Consecutive measurement report flow

3 missing measurement reports

HW I Power Control


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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.

MRMR MRMR

MR MR

Consecutive measurement report flow

Filter

HW I Power Control


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[BTS power control table]

HW I power control data configuration and parameter

introduction

Parametername

Meaning Valuerange

Recommended value

DL RX_LEVExpected

The expected signal level of MS in stable status, Expected

stable downlink signal level > downlink edge HO threshold

Otherwise, ping-pang HO will be caused.

063 35

DL RX_LEVCompensation

The power adjustment value varies with this parameter. Theadjustment value caused by power level equal to the differencebetween the expected signal level and the actual receivingsignal level multiply this factor.

0100 80(signal ex-signalrx)*80%=adjust

ment value

DL Qual.Expected

Expected signal quality of MS in stable status. 0 7

Levels

1

DLQual.Compensation

The power adjustment value varies with this parameter. Theadjustment value caused by signal quality equal to10*difference between the expected signal quality level and theactual receiving signal quality level multiply this factor.

0100 20[10*(qualityRX-qualityEX)*20%]

MAX PCStep

maximum adjustment range in one BTS power controlcommand

Levels0~16,2dB eachstep

8

HW I Power Control


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HW I Power Control

[BTS power control table]

Parametername

Meaning Valuerange

Recommended value

BTS PCPeriod

Time interval for implementing two power control commands(unit count of SACCH period)

110 5

Filter lengthfor DL

RX_LEV

Content: indicating the number of measurement reports inwhich the average of uplink signal strength is taken before MS

power adjustment at stable stage. The purpose is to removethe influence of some abnormal reports. When the filter lengthis too long, the influence due to abnormal reports will beweakened, but the MS power adjustment is not timely.

132 5

BTS Minpower

Indicating the minimum transmitting power value supported bythe BTS

0~36 4

BTS Maxpower

Indicating the maximum transmitting power value supportedby the BTS.

0~56 According toBTS type


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[MS power control data table]Parameter

nameMeaning Value range Recom-

mendedvalue

initialRX_LEVexpected

The expected BTS receiving signal level in the initial stagewhen MS access the network.

0~63dBm 30

Stable

EX_LEVExpected

The expected BTS receiving signal level in stable status.

Expected stable signal level > uplink margin HO threshold(HO parameter). Otherwise, ping-pang HO will be caused.

0~63dBm 30

UL RX_LEVcompensati

on

Give an adjustment for the power control level value, theactual power level value MS should change is the result ofthis parameter multiply the difference between the expecteduplink signal level and the actual BTS receiving signal level.

0~100 80

UL Qual.Expected

The expected BTS receiving signal quality in stable status.

UL Qual.

compensation

The power adjustment value varies with this parameter. The

adjustment value caused by signal quality equal to10*difference between the expected signal quality level andthe actual receiving signal quality level times this factor.

0100 20

Max PCstep

The maximum level of MS power that can be dynamicallyadjusted.

Level 1~16,2dB/level.

8

HW I Power Control


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Parameter name Meaning Value

rangeValuerecommended

PC interval Time interval between the implementations of twopower control algorithms; unit: SACCH period

0~30 5

Filter length forInitial RX_LEV

This is the number of measurement reportsrequired for predicting the signal strength at theinitial stage. Unit: Measurement reports

1~32 2

Filter length forstable RX_LEV

This is the number of measurement reportsrequired for predicting the signal strength at thestable power control stage. Unit: Measurementreports

1-31 5

Filter length forQual.

This is the number of the measurement reportsrequired for assessing signal quality at the stablestage. Unit: Number of measurement reports

1~30 6

[MS power control table]

HW I Power Control


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HW I power control judgment

The adjustment on the current output power=(Expected signal

strength in stable status - strength of signal currently received) *

up (down) link compensating factor +[quality of uplink(downlink)

currently received - expected uplink(downlink) quality]*10*

uplink(downlink) quality compensating factor

The final adjustment power level should be no more than the

maximum power control step size, the formula for stable level is:

stable level = currently level + the adjustment value on current

out put power

HW I Power Control


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HW I Power Control

Power control will not occur in case of these three conditions

Both level and quality equal to the setting values (HW I power

control), or level and quality are within threshold band(HW II

power control)

Adjusting range less than error tolerance

Adjusting range less than minimum power control step


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HW I power control judgment

Before judging the signal level to be adjusted, query the error

tolerance table according to the current transmitting power level.

Adjustment will not be done if the power adjustment value is less

than the error tolerance value.

Error tolerance table for 900M and 1800M is as follows:

HW I Power Control

1800M:

Level

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Error tolerance 2 2 2 2 2 2 2 2 2 3 3 3 3 3 4 4 4 2 2 2

900M

Level

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Error tolerance 2 2 2 4 4 4 4 4 4 4 4 4 4 4 4 4 6 6 6 6


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Comparison uplink and downlink of HW I power control .

Similarity:

1. To avoid frequently changes of signal level, the PC interval time

between the two consecutive uplink and downlink power control are

limited.

2. To reduce the influence caused by abnormal reports, all

measurement reports should be filtered.

3. Both uplink and downlink power controls include level-specific

and quality-specific power controls.

4. Both uplink and downlink power controls have maximum power

control step size limit and compensating factor.

HW I Power Control


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Comparison uplink and downlink of HW I power control .

Differentia:

1. Including power control for the stable status, MS also has power

control when MS access the network, thus to reduce transmitting

power of MS as soon as possible.

2. For uplink, precautions are ready for increase MS transmitting

power in case HO fails.

3. For downlink, there are maximum and minimum transmitting

power limits in power control data configuration.

HW I Power Control


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HW I power control exercise

Given conditions:

900M MS transmitting at the maximum power, uplink receiving level

of the 900M BTS is 60dBm, uplink quality level is always 0.

Parameter configuration in [BTS power/MS power control table] is

as follows stable RX_LEV Expected is 35, UL RX_LEV

Compensation is 80, UL Qual. expected is 1, and UL Qual.

compensationis 20, and the max. PC step is 16dB.

HW I Power Control


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HW I power control exercise

Question:

1. Suppose that power control will no longer be done once the

power value to be adjusted is less than 2dB, what is the

approximate stable power value after power control with the above

data configuration?

2. According to the error tolerance list, suppose the initial MS

transmitting power is level 3, what is the maximum uplink receiving

level in stable status after power control?

Exercise


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HW I power control exercise Answers for question 1:

Stable level = current actual level + [(expected signal intensity in

stable status current actual level) * uplink path loss compensating

factor] + [actual current quality expected uplink signal quality) * 10 *

uplink quality compensating factor] = -60+[(-75-(-60))*80 ]+[(0-

1)*10*20] = -60-12-2-74dBm. Now itsnecessary to adjust -14dB

(no larger than the maximum power control step size), but it needs

further adjustment because it fails to reach -75dBm, the expected

signal level in stable status. Use -74 in the above formula again forcalculation, and the power to be adjusted is -2.8dB. Because no

power control adjustment will be done when the power value to be

adjusted is smaller than -2, it still needs to be changed 2dB lower, so

the uplink receiving level is -76dBm at last.

Exercise


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HWpower control

HWpower control

Course Contents


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Power control judgment process

HW I I Power Control

Measurement report pre-processing

The power control demand

according to the receiving

level

General power controljudgement

Send the power controlcommand

The power control

demand according to

receiving quality


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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.



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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.



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General power control judgment

Power control by receiving

level

Power control by receiving

quality

Power control by signal level

and quality

AdjStep_Lev AdjStep_Qul

max(AdjStep_Lev,AdjStep_Qul) AdjStep_Lev AdjStep_Qul No action

AdjStep_Lev No action AdjStep_Lev

AdjStep_Lev AdjStep_Qul AdjStep_Lev

AdjStep_Lev AdjStep_Qul

max(AdjStep_Lev,AdjStep_Qul)

AdjStep_Lev No action AdjStep_Lev

No action AdjStep_Qul AdjStep_Qul

No action AdjStep_Qul AdjStep_Qul

No action No action No action



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HW I I power control

Power control algorithm implementation

Main feature of HW I I Power control



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HW II power control has the following advantages:

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


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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 measurementreport 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 compensation, 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.

HW II Power Control


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Measurement report compensation

The expected receiving signal level: 30

The power control will be more effective with measurement report

compensation.

X axis

2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2 222 23 24 25 26 27 28 29 3 3 32 33 34 35 36 37 38 39 44 42 43 44 45 46 47 48 49 51234

567

Yaxi

s

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

HW II Power Control


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Measurement report prediction

Purpose

to 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.

HW II Power Control


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Measurement report prediction

2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2222 23 24 25 26 27 28 29 33 32 33 34 35 36 37 38 39 4 442 43 44 45 46 47 48 49 5X axis

152253354455

Y

ax

is

No power controlMean filter power

control

Prediction filter power

control

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

The expected receiving signal level: 30

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

mean filter

HW II Power Control


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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).

HW II Power Control


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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.

HW II Power Control


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Simple parameter configuration

All needed to do is to configure simple parameters as follows:

Signal level and quality upper/lower thresholds of up/down link

Three kinds of step sizes for adjustment by level

Step size for adjustment by quality

HW II Power Control


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[HW II power control table] main parameters 1:

Parameter

nameMeaning

Value

range

Recommen

ded value

filter lengthfor UL

RX_LEV

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

1~20 6

filter lengthfor DL

RX_LEV

How many downlink measurement reports obtained for the averagedownlink signal level to be used for downlink power controladjustment.

1~20 6

filter lengthfor UL Qual.

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

1~20 6

filter lengthfor DL Qual.

How many downlink measurement reports obtained for the averagedownlink quality level to be used for downlink power controladjustment.

1~20 6

MRcompensation allowed

If yes, System put the currently received measurement report intothe measurement report compensation queue, and record thetransmitting power information according to MS and BTS powervalues. And then interpolation, compensate the receiving level

value of the record measurement report according to the powerchange information.

Yes, no Yes

UL MRnumber

predicted

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

0~3 reports 2

DL MRnumber

predicted

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

0~3 reports 2

HW II Power Control


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[HW II power control table] main parameters

2:Parameter

nameMeaning Value

rangeRecommended

value

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

5

UL RX_LEVupper

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 + lowerthreshold)/2]. This decrement value should consider together withthe maximum step size allowed for different quality zone whichthe receiving signal quality located.

0~63 35

UL RX_LEVlowerthreshold

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

0~63 25

UL Qual.upperthreshold

This parameter specifies the uplink quality upper threshold. Level0~7

0

UL Qual.lowerthreshold

This parameter specifies the uplink quality lower threshold forpower control

Level0~7

2

HW II Power Control


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[HW II power control table] main parameters--3Parameter

nameMeaning Value range

Recommen

ded value

DL RX_LEVupper threshold

This parameter specifies the downlink signal level upperthreshold. When the signal level higher than this value,calculate a power decrement [=receiving level (upperthreshold + lower threshold)/2]. This decrement shouldconsider together with the maximum step size allowed fordifferent quality zone which the receiving signal qualitylocated.

0~63 40

DL EX_LEVlower threshold

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

0~63 30

DL Qual. upperthreshold This parameter specifies the downlink quality upperthreshold for power control Level 0~7 0

DL Qual. lowerthreshold This parameter specifies the downlink quality lowerthreshold for power control Level 0~7 2

HW II Power Control


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[HW II power control table] main parameters--4Parameter

nameMeaning Value range Recommende

d value

max. adj. valuefor Qual. Zone

0

This parameter specifies the maximum power adj.step size allowed when adj. the power according tothe signal level when the Rx quality is 0.

0~30dB 16

max. adj. value

for Qual. Zone1

This parameter specifies the maximum power adj.

step size allowed when adj. the power according tothe signal level when the Rx quality is 1 or 2.

0~30dB 8

max. adj. valuefor Qual. Zone

2

This parameter specifies the maximum power adj.step size allowed when adj. the power according tothe signal level when the R x quality is equal to ormore than 3.

0~30dB 4

adj. PC valueby Rx Qual.

Specifying the adj. step size allow ed when thepower control is adjusted according the receivingsignal quality. That is to say, the step size isconstant for power control by quality, but the stepsize varies with quality in case of power control bysignal level.

0~4dB 4

HW II Power Control


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Exercises for HW II power control

Given conditions:

The uplink receiving level is -85dBm, the quality is level 4. 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 0. Uplink signal lower quality threshold:

level 2. The adjustable step size of quality band 0 is 16dB, of quality

band 1 is 8dB, and of quality 2 is 4 dB. The adjustable step size for

power control by quality is 4dB.

Question: What will be the uplink stable receiving level after

power control?

Exercise


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Answer.

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

(uplink signal level upper threshold + uplink signal level lower

threshold)/2-actual receiving level (-60 + (-80))/2-(-85)(-70)-(-

85)15dB. As the receiving quality is level 4, only adjustable step

size of quality band 2 can be used -- increase 4dB.

Second, the transmitting power to be increased according to

receiving quality = as powercontrol adjustment step size by quality

is 4dB, thus increase 4dB, the same as adjustment by signal level.

Therefore, according to the general judgement on power control,

4dB should be increased for adjustment either by level or by quality.

Exercise


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Answer .

After the implementation of step 1 power control, the receiving level

becomes: -85dBm + 4dB=-81dBm, Suppose the quality reach

already in level 2 here, it still fails within the expected band -

80dBm~-60dBm. Therefore, it needs to be adjusted.

First: adjust by level -- repeat the previous step: adjustment by level

= (-70) (-81) = 11db, i.e. to increase 11dB. If the receiving quality

has been improved to level 2, and the adjustable step size with

quality band 1 is 8dB. Then, the result of adjustment by level is to

increase 8dB.

Second: adjustment by quality--as the receiving quality value is

between 0 and 2, Needntadjust.

Therefore, the uplink stable receiving level = (-81) + 8 = -73dBm.

Exercise


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Documents

6.Power Control