16 Power Control Issue1.4

8/3/2019 16 Power Control Issue1.4

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HUAWEI TECHNOLOGIES CO., LTD. All rights reserved

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Power Control

ISSUE 1.4


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HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 2

Chapter 1 Power control overview

Chapter 2 HWpower control



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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 consumptionof BTS.


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Process of power control commands

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

command sending to execution.

SA0 SA1A0 SA0A1A1 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 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. 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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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 reportpre-processing

Aim achieved ?

Power control calculation andadjustment

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

Downlinkmeasurement

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 tointerpolation algorithm.

MR

MRMR MR

MR

Measurement reportserial number n

Measurement reportserial 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

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, Expectedstable 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


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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]

HW I Power Control

Parametername

Meaning Value range Recom-mended

value

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


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Parameter name Meaning Valuerange

Valuerecommended

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 - expecteduplink(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 is60dBm, uplink

quality level is always 0.

Parameter configuration in [BTS power/MS power

control table] is as followsstable RX_LEV Expected

is 35, UL RX_LEV Compensation is 80, UL Qual.

expected is 1, and UL Qual. compensation is 20, andthe max. PC step is 16dB.

HW I Power Control


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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 afterpower control?

Exercise


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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 its necessary 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 for calculation, 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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Answers for question 2:

Query the error tolerance table, the tolerance of level 3

is 4dB, the power to be adjusted for the second time is

2.8, which is less than 4 and up to the requirement, so

the final uplink receiving level is -74dBm in stablestatus.

Exercise


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HW I I power control

Power control algorithm implementation

Main feature of HW I I Power control

HW I I Power Control


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Power control judgment process

Measurement report pre-processing

The power control demandaccording to the receiving

level

General power controljudgement

Send the power controlcommand

The power controldemand 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 theexpected 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

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 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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HW II Power Control Measurement report compensation

The expected receiving signal level: 30

The power control will be more effective with measurement reportcompensation.

X axis

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 5010203040

506070

Yaxi

s

Power control diagram when there ismeasurement report compensation

Diagram when there is no power control

Power control diagram when there is nomeasurement report compensation

Power control effect diagram of measurement report compensation


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Measurement report predictionPurpose

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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HW II Power Control

Measurement report prediction

1 2 3 4 5 6 7 8 91011121314151617181920212223242526272829303132333435363738394041424344454647484950

X axis

152025303540

4550

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 withmean filter


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HW II Power Control

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 (differentreceiving quality and level).

Max. step is deferent between increase and decrease


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HW II Power Control

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 qualityis within the threshold bands.

Avoid the signal level up-and-down caused by power

control.

The upper threshold can be increased dynamically in caseof bad quality


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[HW II power control table] main parameters

1:Parameter

nameMeaning

Valuerange

Recommended 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

MRcompensati

on 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

valuePC 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 signal

quality 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

Recommended 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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nameMeaning Value range Recommende

d valueMAX Down Adj.

value Qual.zone 0

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

0~30dB 16

MAX Down Adj.value Qual.

zone 1

This parameter specifies the maximum downwardpower adjustment value when the Rx quality is 1 or2

0~30dB 8

MAX Down Adj.value Qual.

zone 2

This parameter specifies the maximum downwardpower adjustment value when the Rx quality isequal to or more than 3.

0~30dB 4

MAX Down Adj.PC Value by

Qual.

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

0~4dB 4

HW II Power Control


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d valueMAX Up Adj.PC Value by

RX_LEV

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

0~32dB 16

MAX Up Adj.PC Value by

Qual.

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

0~32dB 8

UL Qual. BadTrigThrsh

In uplink power control, when the receiving qualityof uplink is not less than this start threshold, theactual "upper threshold of signal strength of uplink"will be added with "upper threshold offset of levelwhen the receiving quality of uplink is poor" in thedata configuration. Thus, the expected level in

uplink power control can be increased furthermore.

0~7 5

UL Qual. BadUpLEVDiff

In uplink power control, when the receiving quality isnot less than "start threshold when the receivingquality of uplink is poor", the actual "upper thresholdof signal strength of uplink" will be added with thisoffset value.

0~63dB 0

HW II Power Control


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d valueDL Qual. Bad

TrigThrshIn downlink power control, when the receivingquality of downlink is not less than this startthreshold, the actual "upper threshold of signalstrength of downlink" will be added with "upperthreshold offset of level when the receiving quality

of downlink is poor" in the data configuration. Thus,the expected level in downlink power control can beincreased furthermore.

0~7 5

DL Qual. BadUpLEVDiff

In downlink power control, when the receivingquality is not less than "start threshold when thereceiving quality of downlink is poor", the actual"upper threshold of signal strength of downlink" willbe added with this offset value.

0~63dB 0

HW II Power Control


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Exercises for HW II power controlGiven 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 upperthreshold: -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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Exercise

Exercises for HW II power control

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 power control adjustment step size by

quality is 4dB, thus increase 4dB, the same as adjustment bysignal level.

Therefore, according to the general judgement on power control,

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


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Exercise

Exercises for HW II power controlAnswer .

After the implementation of step 1 power control, the receivinglevel becomes: -85dBm + 4dB=-81dBm, Suppose the quality reachalready 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 qualityhas been improved to level 2, and the adjustable step size withquality band 1 is 8dB. Then, the result of adjustment by level is toincrease 8dB.

Second: adjustment by quality--as the receiving quality value isbetween 0 and 2, Neednt adjust.

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


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16 Power Control Issue1.4