OG 202 Power Control Issue1.4

HUAWEI TECHNOLOGIES CO., LTD.

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Power Control

ISSUE 1.4

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

Chapter 1 Power control overviewChapter 1 Power control overview

Chapter 2 HW power controlⅠChapter 2 HW power controlⅠ

Chapter 3 HW power controlⅡChapter 3 HW power controlⅡ


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.



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.



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

Measurement report pre-processing

Power control algorithm

selection

Yes

HW I power control

algorithm

HW II power control

algorithm

GSM0508 power control

algorithm



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. If measurement report pre-processing is “yes”, power control is processed in BTS, and when setting it “no”, power control is processed in BSC.






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


Process of HW I power control


Aim achieved ?

Power control calculation and adjustment

N

Y

HW I Power Control


Original data of power control -- measurement report

Network

Downlink Downlink measurement measurement

reportreport

Uplink MRUplink MR

BTS

HW I Power Control


Uplink Uplink measurement measurement

reportreport

Downlink Downlink measurement measurement

reportreport

HW I Power Control

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

HW I Power Control


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

HW I Power Control


[BTS power control table][BTS power control table]

HW I Power Control

HW I power control data configuration and parameter introduction

Parameter name

Meaning Value range

Recommended value

DL RX_LEV Expected

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.

0～63 35

DL RX_LEV Compensation

The power adjustment value varies with this parameter. The adjustment value caused by power level equal to the difference between the expected signal level and the actual receiving signal level multiply this factor.

0～100％ 80％ (signal ex-signal rx)*80%=adjust

ment value

DL Qual. Expected

Expected signal quality of MS in stable status. 0 ～ 7 Levels

1

DL Qual.Compensation

The power adjustment value varies with this parameter. The adjustment value caused by signal quality equal to 10*difference between the expected signal quality level and the actual receiving signal quality level multiply this factor.

0～100％ 20％ [10*(quality RX-quality EX)*20%]

MAX PC Step

maximum adjustment range in one BTS power control command

Levels 0~16, 2dB each step

8


HW I Power Control

[BTS power control table][BTS power control table]Parameter

name Meaning Value

range Recommende

d value BTS PC Period

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

1～10 5

Filter length for DL

RX_LEV

Content: indicating the number of measurement reports in which the average of uplink signal strength is taken before MS power adjustment at stable stage. The purpose is to remove the influence of some abnormal reports. When the filter length is too long, the influence due to abnormal reports will be weakened, but the MS power adjustment is not timely.

1～32 5

BTS Min power

Indicating the minimum transmitting power value supported by the BTS

0~36 4

BTS Max power

Indicating the maximum transmitting power value supported by the BTS.

0~56 According to BTS type


[MS power control data table][MS power control data table]

HW I Power Control

Parameter name

Meaning Value range Recom-mended

value initial

RX_LEV expected

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

0~63dBm 30

Stable EX_LEV Expected

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_LEV compensati

on

Give an adjustment for the power control level value, the actual power level value MS should change is the result of this parameter multiply the difference between the expected uplink 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. compensat

ion

The power adjustment value varies with this parameter. The adjustment value caused by signal quality equal to 10*difference between the expected signal quality level and the actual receiving signal quality level times this factor.

0～100％ 20％

Max PC step

The maximum level of MS power that can be dynamically adjusted.

Level 1~16, 2dB/level.

8


Parameter name Meaning Value

range Value recommended

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

0~30 5

Filter length for Initial RX_LEV

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

1~32 2

Filter length for stable RX_LEV

This is the number of measurement reports required for predicting the signal strength at the stable power control stage. Unit: Measurement reports

1-31 5

Filter length for Qual.

This is the number of the measurement reports required for assessing signal quality at the stable stage. Unit: Number of measurement reports

1~30 6

[MS power control table][MS power control table]

HW I Power Control


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


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


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:

Level0 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


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


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


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. compensation” is 20, and the max. PC step is 16dB.

HW I Power Control



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



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 it’s 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


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 stable status.

Exercise






HW I I power control

Power control algorithm implementation

Main feature of HW I I Power control

HW I I Power Control



Power control judgment process


The power control demand according to the receiving

level

General power control judgement

Send the power control command

The power control demand according to

receiving quality



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.



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

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



HW I I power control

Power control algorithm implementation

Main feature of HW I I Power control



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


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


HW II Power Control Measurement report compensation

The expected receiving signal level: 30

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

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 50

0

10

20

30

40

50

60

70

Y ax

is

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

− 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


HW II Power Control

Measurement report prediction1 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 50

X axis

1520253035404550

Y ax

is

No power control

Mean 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

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 deferent between increase and decrease


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 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 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


[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 35

UL RX_LEV lower threshold

This parameter specifies the uplink signal level lower threshold. When the signal level higher 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 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


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

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 40

DL EX_LEV lower threshold

This parameter specifies the downlink signal level lower threshold. When the signal level higher 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 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

HW II Power Control



name Meaning Value range Recommende

d 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

MAX Down Adj. value Qual.

zone 1

This parameter specifies the maximum downward power adjustment value when the Rx quality is 1 or 2

0~30dB 8

MAX Down Adj. value Qual.

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

HW II Power Control




d 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

HW II Power Control




d 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

HW II Power Control


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


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 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 Exercises for HW II power control

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, Needn’t adjust.

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

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OG 202 Power Control Issue1.4