pciii-gsm power control issue2.01

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Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.

GSM Power Control

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Page2Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.

Contents

1. Power Control Overview

2. HWⅡPower Control

3. HWⅢPower 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 consumption of BTS

1. During handover, MS will access the target cell with the maximum transmitting power (associated with handover command) allowed by the target cell. But if “MS power prediction after HO” is enabled, then MS will use the optimized power to access the target cell.

2. During intra-cell handover, the current power will be retained.

3. Power control can be implemented on TCH carriers only, BCCH carrier is not allowed power control. Because MS needs to measure the receiving level of BCCH from the adjacent cell. It will be inaccurate when power control is performed on BCCH.

4. Power control is performed independently for each channel.

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Power Control OverviewUp link and Down link power

control can be enabled

independently

[UL PC Allowed]

•Value Range: Yes, No Default Value: Yes

•Description: This parameter indicates whether the adjustment of MS power is allowed.

•Remarks: In GSM900 cells, the power control level of an MS is from 0 to 19 (totally 20 levels). Generally, the maximum power control level supported by the MS is 5 (mapping to 33 dBm), and the minimum power control level supported by the MS is 19(mapping to 5 dBm). The other power control levels are reserved for high-power MSs. In GSM900 cells or DCS1800 cells, the power control level of an MS is from 0 to 31 (totally 32 levels). Generally, the maximum power control level supported by the MS is 0 (mapping to 30 dBm), and the minimum power control level supported by the MS is 15 (mapping to 2 dBm). The other power control levels are reserved for high-power MSs.

[DL PC Allowed]

•Value Range: Yes, No Default Value: Yes

•Description: This parameter indicates whether the adjustment of BTS power is allowed.

•Remarks: The downlink power control (at the BTS side) supports a maximum of 15 levels. Each level supports dynamic power control of 2 dB.

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Process of power control commands

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

command sending to getting the feedback.

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.

When MS accesses the network via RACH channel, its transmitting power is the “MS max. TX power level”, which is gotten from the system information on BCCH. MS sends the first message on dedicated channel also uses the “MS max TX power level” ,this is not under the control of the system before the power control command which is carried on SACCH of SDCCH or TCH. The implementation procedure is as following:

1. According to the uplink receiving level and receiving quality reported by BTS, and considering the maximum transmitting power of MS, BSC calculates the proper transmitting power for the MS.

2. Power control command and the TA value will be transmitted to MS at layer 1 header carried by each downlink SACCH block.

3. MS receives the power control command carried by SACCH header at the end of each SACCH report period, Then MS will carry out the command in the beginning of next report period. MS can change power 2dB per 13 frames (60ms) maximum.

4. After MS executed the power control command, it will set the current power class at the layer 1 message header of the next uplink SACCH, and transmit it to BTS in the measurement report. Therefore, it will take 3 measurement report periods for the new power class (in each power control command) to be available.

Note: Each integral SACCH message block (measurement report) is composed of 4 burst. A power control implementation process in whole takes the time of 3 measurement reports.

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Data Configuration of Power Control Period

[PC Interval]

•Value Range: 1~15

•Unit: Measurement report period (480 milliseconds on the TCH; 470 milliseconds on the SDCCH)

•Default Value: 3

•Description: Minimum time interval between two continuous power control commands

•Remarks: If the value of this parameter is too small, the power control may be performed frequently, thus wasting the resources.

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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

Set pre-processing “yes” is to reduce the signaling load in Abis interface.

i.e.:

1.If Abis E1 is in 4:1 mode, it should be set “yes”, otherwise the Abis capacity for speed is not enough;

2.Satellite transmission BTS should be set “yes”;

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Data Configuration of MR Preprocessing(1)

[MR Preprocessing]

•Value Range: Yes, No

•Default Value: No

•Description: This parameter indicates whether the BTS pre-processes the MR.

This parameter determines the location where power control is performed. If this parameter is set to Yes, power control is performed by the BTS. Otherwise, the power control is performed by the BSC.

When this parameter is set to No, the MR is processed by the BSC, in which case, both Transfer original MR, Transfer BS/MS power class and Sent Freq of preprocessed MR are invalid.

When this parameter is set to Yes, the load over Abis interface and that over the BSC are reduced, thus shortening the response time and improving the network performance.

[Transfer Original MR]


•Default Value: No

•Description: This parameter indicates whether the original MR is transferred to the BSC after the BTS pre-processes the MR.

When the parameter is set to Yes, the BTS transfers to the BSC both the processed MR and the original MR.

•Remarks:In case of 4:1 configuration, this parameter must be set to No if SDCCH/8 is greater than 2.

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Data Configuration of MR Preprocessing(1)

[Transfer BS/MS Power Class]


•Default Value: Yes

•Description: This parameter indicates whether the original BS/MS power class is transferred to the BSC.

•Remarks:When MR pre-processing is enabled, uplink and downlink balance measurement is affected if this parameter is set to No. In addition, power compensation handovers, such as PBGT handovers, load handovers, and Concentric Cell handovers, may become abnormal.

[Sent Freq of Preprocessed MR]

•Value Range: Do not Report, Twice every second, Once every second, Once every two seconds, Once every four seconds

•Default Value: Twice every second

•Description: This parameter indicates the frequency that the BTS transfers the preprocessed MR to the BSC. After the MR is preprocessed by BTS, the BTS transfers the preprocessed MR to the BSC. For example, if this parameter is set to Twice every second, the BTS transfers the preprocessed MR to the BSC twice per 0.5 second.

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Contents


2. HWⅡ Power Control


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HW II Power Control

Power control judgment process

The power control demand according to

receiving level

General power control judgment

Send the power control command

The power control demand according to

receiving quality

MR. preprocessing

HWII power control is performed in four steps.

1. Pre-processing of the measurement reports (interpolation, compensation, prediction and filter),

2. Calculate power control demand according to the receiving level,

3. Calculate power control demand according to the receiving quality,

4. Make comprehensive judgment on the receiving level and receiving quality.

The same as HWI power control, measurement report pre-processing includes interpolation and filter. But in HWII it has compensation and forecast functions before filter.

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HW II Power Control

Original data of power control -- Measurement Report(MR)

Network

Downlink MRDownlink MR

Uplink MRUplink MR

BTS

The original data of power control is from measurement report. MS submits a measurement report to the network on SACCH channel every 480ms, the content reported by MS is the downlink measurement values which received by MS.

Uplink measurement report are about the uplink signal received by BTS.

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HW II Power Control

Measurement report

Uplink Uplink measurement measurement

reportreport

Downlink Downlink measurement measurement

reportreport

There are two kind of measurement report for system: FULL (full measurement) and SUB (sub measurement).

FULL--Averaging over 100 TCH bursts(except four idle frames of four 26-multiframes).

SUB--Averaging over 12 bursts(four SACCH bursts, eight TCH bursts).

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MR. preprocessing in HW II PC algorithm consists of four steps

Interpolation

Compensation (optional)

Prediction (optional)

Filter

HW II Power Control

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.

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HW II Power Control

MR Interpolation – recover the lost measurement report

BTS may fail to receive the MR from MS, and it needs to recover

the lost measurement reports. If the lost MR amount is within the

allowed range (Allowed MR Number Lost), then recovers the lost

MR according to the specific algorithm.

Service cell: linear algorithm

Neighboring cell: the lowest value defined in GSM specification (-

110dBm)

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HW II Power Control

MR

MR

No. n

No. n+4

Continuous MR Flow

MRMR

MR

Missing by some reasons

…

…

MR Interpolation – recover the lost measurement report

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Data Configuration of MR Preprocessing

[Allowed MR Number Lost]


•Default Value: 4

•Description: This parameter indicates the number of MRs allowed to be lost in succession. When this threshold is not reached, the lost MR is estimated via the linear interpolation basing on the first and the last MRs received. When this threshold is reached, all previous MRs are discarded, and calculations are made again when new MRs are received.

•Remarks: MRs fail to be decoded correctly when the signal strength in the serving cell is poor. When this threshold is reached, all previous MRs are discarded and handover may fail. Thus, it is advised to assign this parameter with a greater value to enable emergency handover.

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HW II Power Control

MR. compensation

Purpose: Ensure the accuracy of selection of the history measurement

report before filter.

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.

When system makes a power control judgment, the power control module will extract the values of receiving level and receiving quality from several history measurement reports for filter. In these measurement reports,MS or BTS maybe use different transmitting power. Therefore, to ensure the accuracy of receiving level values used for filter, compensation should be made for receiving level values in history measurement report whose history transmitting power is different from the current transmitting power.

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HW II Power ControlMR. 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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Y axis

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

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Data Configuration of MR. Compensation

[MR Compensation Allowed]


•Default Value: Yes

•Description: If this parameter is set to Yes, the BSC or BTS puts the received measurement reports in the measurement report compensation queue. Then record the change of transmit power based on the MS power and the BTS power in the measurement report.After values are added in the measurement report, compensate the received level value in the historical measurement report based on the change of power.

•Remarks: If measurement reports are preprocessed on the BTS side, the BTS performs the compensation of the measurement reports. If measurement reports are preprocessed on the BSC side, the BSC performs the compensation of the measurement reports.

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HW II Power Control

MR. 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 LMT.

3. Filter the interpolated, compensated and predicted measurement

reports, and implement power control judgment.

After the power control module send the power control command, due to the propagation delay and power control process delay, the transmitting power will usually be executed after several measurement report periods. This delay will affect the validity of power control. In order to make up some influence of power control delay, the prediction for measurement reports should be adopted so that the power control command will perform a little earlier.

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HW II Power ControlMR. prediction

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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 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

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Data Configuration of MR. Prediction

[UL MR Number Predicted]

•Value Range: 0~3 Default Value: 0

•Description: After the BSC delivers the power control command, it will be a period before the BSC receives an acknowledgement message. Therefore, the measurement reports that provide basis for power control decision cannot mirror the radio environment that the BTS is in during power adjustment. The measurement reports lag behind the changes in the MS received level and in the MS received signal quality. Thus the power adjustment is delayed.To compensate the hysteresis of power adjustment, the prediction and filtering function is added to the power control algorithm. In other words, in a short period of time, the BSC samples several uplink measurement reports and performs weighted filtering, predicting N measurement reports after the current time. This parameter indicates the number of uplink measurement reports predicted by the BSC. The value of the parameter equals the previous number N.

DL MR. Number Predicted


•Description: After the BSC delivers the power control command, it will be a period before the BSC receives an acknowledgement message. Therefore, the measurement reports that provide basis for power control decision cannot mirror the radio environment that the BTS is in during power adjustment. The measurement reports lag behind the changes in the MS received level and in the MS received signal quality. Thus the power adjustment is delayed. To compensate the hysteresis of power adjustment, the prediction and filtering function is added to the power control algorithm. In other words, in a short period of time, the BSC samples several downlink measurement reports and performs weighted filtering, predicting N measurement reports after the current time. This parameter indicates the number of downlink measurement reports predicted by the BSC. The value of the parameter equals the previous number N.

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HW II Power Control

MR. filter – Smooth the instantaneous fading point

Calculate the average value within the filter window

MR

MRContinuous MR Flow MR

MR

MR

…

…Filter----Average several consecutive MRs

MR

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Data Configuration of MR. filter

[Filter length for UL RX_LEV]

• Value Range: 1~20 Default Value: 5

• Description: When the BSS receives measurement reports, an average value of uplink signal strength in the consecutive measurement reports should be obtained to reflect the current radio environment where the MS locates. This parameter indicates the number of measurement reports in which the average of the uplink signal strength is taken before MS power adjustment.

[Filter Length for DL RX_LEV]


• Description: When the BSS receives measurement reports, an average value of uplink signal strength in the consecutive measurement reports should be obtained to reflect the current radio environment where the MS locates. This parameter indicates the number of measurement reports in which the average of the downlink signal strength is taken before BTS power adjustment.

[Filter Length for UL Qual..]


• Description: When the BSS receives measurement reports, an average value of uplink signal quality in the consecutive measurement reports should be obtained to reflect the current radio environment where the MS locates. This parameter indicates the number of measurement reports in which the average of the uplink signal quality is taken before MS power adjustment.

[Filter Length for DL Qual..]


• Description: When the BSS receives measurement reports, an average value of uplink signal quality in the consecutive measurement reports should be obtained to reflect the current radio environment where the MS locates. This parameter indicates the number of measurement reports in which the average of the downlink signal quality is taken before BTS power adjustment.

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HW II Power Control Judgment

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 decreasing the transmitting power

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

as soon as possible.

When power control is performed based on the receiving level, it adopts three step sizes respectively for different receiving qualities band:

“MAX. Down Adj. Value for Qual. Zone 0 (receiving quality level 0)

“MAX. Down Adj. Value for Qual. Zone 1 (receiving quality level 1~2)

“MAX. Down Adj. Value for Qual. Zone 2 (receiving quality level 3~7)

The worse the quality, the shorter the allowable step size.

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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, and decrease the transmitting power in case of good

receiving quality.

Adopt fixed step size when adjust the transmitting power

according to the receiving quality.

To change the transmitting power according to receiving quality, fixed step size should be adopted --”Adj. PC Value by RXqual” for each receiving quality zone.

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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_A

No action ↑ AdjStep_Qul ↑ AdjStep_B

No action No action No action

Note:

1. Control as required when either level or quality needs to be controlled.

AdjStep_A

If uplink or downlink RXLEV - AdjStep_Qul < lower threshold of uplink or downlink RXLEV, AdjStep_A = 0. No adjustment is required.

If uplink or downlink RXLEV - AdjStep_Qul ≥ lower threshold of uplink or downlink RXLEV, AdjStep_A = AdjStep_Qul.

The purpose is to avoid the power control request when the RXQUAL is good and the RXLEV requires no power control. If power control is made, the RXLEV may become worse and request for power control again, thus leading to frequent power control.

AdjStep_B

If AdjStep_Qul + uplink or downlink RXLEV > upper threshold of uplink or downlink RXLEV, AdjStep_B = upper threshold of uplink or downlink RXLEV –uplink or downlink RXLEV.

If AdjStep_Qul + uplink or downlink RXLEV <= upper threshold of uplink or downlink RXLEV, AdjStep_B = AdjStep_Qul.

The purpose is to avoid the power control request due to bad RXQUAL when the RXLEV requires no power control. If power control is made, the RXLEV may become too good and request for power control again, thus leading to frequent power control.

2. When the controls based on signal level and quality are in an opposite direction, and the level requires decreasing power, so no action should be performed for power control; when the level requires increasing power, then just perform as level required.

3. When they work in the same direction, perform according to the larger value.

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HW II Power Control Feature

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.

Automatic adjustable step size:

When the power control caused by receiving level in HWII power control algorithm, the power control will be performed also considering the receiving quality which are set into three quality zones (0, 1~2, ≥3). Each quality zone allow different maximum adjustment step size. The worse the quality is, the less the adjustable step size will be.

If the maximum step size allowed for power control is set too small, the algorithm can not achieve the purpose of power control as soon as possible; when set it too big, it will decrease the validity of power control.

The step size is fixed when the power should be changed according to receiving quality.

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HW II Power Control Feature

Power control within the upper/lower thresholds

Power control will not execute if the signal level and quality is

within the threshold bands.

Avoid the signal level fluctuation caused by power control.

The upper threshold can be increased dynamically in case of bad

quality.

Configuration parameters include ([HWII power control data table]):

UL RX_LEV upper thrsh/ UL RX_LEV lower thrsh

DL RX_LEV upper thrsh/lower thrsh

UL Qual upper thrsh/lower thrsh

DL Qual upper threh/lower threh

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Data Configuration for UL Rx_LevUpper/Lower Threshold

[UL RX_LEV Upper Threshold]

•Value Range: 0~63 (-110 dBm to -47 dBm) Default Value: 30

•Description: The step of power control is determined by UL RX_LEV Upper Threshold and UL RX_LEV Lower Thrsh. If the uplink signal strength is within the range from UL RX_LEV Upper Threshold to UL RX_LEV Lower Thrsh, power control on the MS is not performed. If the uplink signal strength is beyond the range, power control on the MS is performed.If the signal level exceeds this threshold, the BSC calculates a decreased value:(Received Level of the MSC UL RX_LEV Upper Threshold + UL RX_LEV Lower Thrsh)/2)Compare the decreased value and the maximum adjustment step permitted by the quality zone where the receive signal quality resides( MAX Down Adj. Value Qual. Zone 0,MAX Down Adj. Value Qual. Zone 1,MAX Down Adj. Value Qual. Zone 2) and MAX Down Adj. PC Value by Qual. Set the minimum value to the power adjustment step of the MS.

•Remarks: If the value of this parameter is too great, the uplink level becomes high without power control. Thus, the battery life is reduced, more network interference is caused. If the value of this parameter is too small, the uplink level becomes low, and call drop may easily occur. The value of this parameter is equal to that of UL Expected Level at HO Access.

[UL RX_LEV Lower Thrsh]


•Description: The step of power control is determined by UL RX_LEV Upper Threshold and UL RX_LEV Lower Thrsh. If the uplink signal strength is within the range from UL RX_LEV Upper Threshold to UL RX_LEV Lower Thrsh, power control on the MS is not performed. If the uplink signal strength is beyond the range, power control on the MS is performed.If the signal level is smaller than the value of this parameter, calculate an increased value ((UL RX_LEV Upper Threshold + UL RX_LEV Lower Thrsh)/2 C Received Level). Compare the increased value , MAX Up Adj. PC Value by RX_LEV and MAX Up Adj.C Value by Qual . Set the minimum value to the power adjustment step of the MS.

•Remarks: For details, see UL RX_LEV

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Data Configuration for UL Upper/Lower Quality Threshold

[Upper Threshold.UL Qual.Upper Threshold]

•Value Range: 0~7 (The smaller quality level indicates the better quality.) Unit: Quality level Default Value: 1

•Description: When the BSC controls the power of a MS according to the signal quality, the quality of the signal has UL Qual Lower Threshold and UL Qual. Upper Threshold. When the value of the signal quality is smaller than the value of the UL Qual. Upper Threshold, the power of the MS is decreased. This parameter determines the uplink quality upper threshold of the stable state quality zone. The upper threshold is larger than or equal to the lower threshold. The power of the MS and the BTS is adjusted according to the quality and the level. For details, refer to the Power Control 2nd Generation Control table. The lower the quality level, the better the quality is.

•Remarks: If the value of this parameter is too small, the quality is good without power control. Thus, the battery life is reduced, more network interference is caused.

[UL Qual Lower Threshold]

•Value Range: 0~7 Unit: Quality level Default Value: 3

•Description: When the BSC controls the power of a MS according to the signal quality, the quality of the signal has UL Qual Lower Threshold and UL Qual. Upper Threshold. When the value of the signal quality is greater than or equal to the value of the UL Qual Lower Threshold, the power of the MS is increased. This parameter determines the uplink quality lower threshold for the power control.

•Remarks: If the value of this parameter is too great, the quality is poor without power control, thus affecting the conversation quality.

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Data Configuration for DL Rx_LevUpper/Lower Threshold

[DL RX_LEV Upper Threshold]


•Description: The power control step is calculated based on the signal level. The signal level has an upper threshold and a lower threshold. The signal is not adjusted between the upper threshold and the lower threshold. Power control is performed only when the signal level exceeds the upper threshold or is below the lower threshold.This parameter determines the upper threshold of the downlink signal for power control. If the signal level exceeds this threshold, calculate a decreased value (= Received Level - (DL RX_LEV Upper Threshold+DL RX_LEV Lower Threshold)/2). Compare the decreased value and the maximum adjustment step permitted by the quality zone where the receive signal quality resides( MAX Down Adj. Value Qual. Zone 0,MAX Down Adj. Value Qual. Zone 1,MAX Down Adj. Value Qual. Zone 2) and MAX Down Adj. PC Value by Qual. Set the minimum value to the power adjustment step of the MS.

•Remarks: If the value of this parameter is too great, the downlink level becomes high without power control. If the value of this parameter is too small, the downlink level becomes low, and call drop may easily occur.

[DL RX_LEV Lower Threshold]


•Description: The power control step is calculated based on the signal level. The signal level has an upper threshold and a lower threshold. The signal is not adjusted between the upper threshold and the lower threshold. Power control is performed only when the signal level exceeds the upper threshold or is below the lower threshold.This parameter determines the lower threshold of the downlink signal for power control. If the signal level is below this threshold, calculate an increased value (= (DL RX_LEV Upper Threshold+DL RX_LEV Lower Threshold)/2 - Received Level). Compare the increased value , MAX Up Adj. PC Value by RX_LEV and MAX Up Adj.C Value by Qual . Set the minimum value to the power adjustment step of the MS.

•Remarks: For details, see DL RX_LEV Upper Threshold.

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Data Configuration for DL Upper/Lower Quality Threshold

[DL Qual Upper Threshold]


•Description: When the BSC controls the power of a BTS according to the signal quality, the quality of the signal has DL Qual Lower Threshold and DL Qual Upper Threshold. When the value of the signal quality is smaller than the value of the DL Qual Upper Threshold, the power of the BTS is decreased.This parameter determines the downlink quality upper threshold for the power control.

•Remarks: If the value of this parameter is too small, the quality is good without power control. Thus, the battery life is reduced, more network interference is caused.

[DL Qual Lower Threshold]


•Description: When the BSC controls the power of a BTS according to the signal quality, the quality of the signal has DL Qual Lower Threshold and DL Qual Upper Threshold. When the value of the signal quality is greater than or equal to the value of the DL QualLower Threshold, the power of the BTS is increased. This parameter determines the downlink quality lower threshold for the power control.

•Remarks: If the value of this parameter is too great, the quality is poor without power control, thus affecting the conversation quality.

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Data Configuration of Power Control (Rx_Lev)

[MAX Down Adj. Value Qual. Zone 0]

•Value Range: 0~30 Unit: dB Default Value: 4

•Description: In the Huawei II power control algorithm, three quality zones (0, 1-2,>=3) are defined according to the quality of received signals. A maximum permissible downward power adjustment step is set for each quality zone.When you adjust the down power based on the level, note that the maximum permissible down power adjustment step varies according to the level of received signals.This parameter indicates the maximum power control step permitted when the received signals are within quality zone 2 (RQ value3) and when the power is lowered based on the level.

•Remarks: If this parameter is set to an oversmall value, power control cannot be performed rapidly in the algorithm. If this parameter is set to an overgreat value, the validity of power control is reduced.

[Max Down Adj. Value Qual. Zone 1]


•Description: In the Huawei II power control algorithm, three quality zones (0, 1-2,>=3) are defined according to the quality of received signals. A maximum permissible down power adjustment step is set for each quality zone.When you adjust the down power based on the level, note that the maximum permissible down power adjustment step varies according to the quality of received signals. This parameter indicates the maximum power control step permitted when the received signals are within quality zone 1 (0 < RQ value < 3) and when the power is lowered based on the level.

•Remarks: If the value of this parameter is too small, power control cannot be performed rapidly in the algorithm. If the value of this parameter is too great, the validity of power control is reduced.

[Max Down Adj. Value Qual. Zone 2]


•Description: In the Huawei II power control algorithm, three quality zones (0, 1-2,>=3) are defined according to the quality of received signals. A maximum permissible down power adjustment step is set for each quality zone.When you adjust the down power based on the level, note that the maximum permissible down power adjustment step varies according to the quality of received signals. This parameter indicates the maximum power control step permitted when the received signals are within quality zone 2 (RQ value >= 3) and when the power is lowered based on the level.


37



[MAX Up Adj. PC Value by RX_LEV]


•Description: This parameter determines the maximum permissible adjustment step during up power adjustment based on the level.


38



[MAX Down Adj. PC Value by Qual.]

•Value Range: 0~4

•Unit: dB

•Default Value: 4

•Description: This parameter determines the maximum permissible adjustment step during power adjustment based on the quality.


[MAX Up Adj.C Value by Qual]


•Unit: dB

•Default Value: 8

•Description: This parameter determines the maximum permissible adjustment step during down power adjustment based on the quality of received signals.


39


Data Configuration for UL/DL Bad Quality

[UL Qual Bad Trig Threshold]


•Description: During uplink power control, when the quality of received uplink signals is larger than or equal to this trigger threshold, the actual value of UL RX_LEV Upper Threshold is the one plus the value of UL Qual Bad Up LEVDiff in the data configuration. This parameter further improves the expected level value of uplink power control.

[UL Qual Bad Up LEVDiff]


•Description: During uplink power control, when the quality of received uplink signals is larger than or equal to UL Qual Bad TrigThreshold, the actual value of UL RX_LEV Upper Threshold is the one plus the value of UL Qual Bad Up LEVDiff.

[DL Qual Bad TrigThreshold]


•Description: During downlink power control, when the quality of received downlink signals is larger than or equal to this trigger threshold, the actual value of DL RX_LEV Upper Threshold is the one plus the value of DL Qual Bad Up LEVDiff.

[DL Qual. Bad Up LEVDiff]


•Description: During downlink power control, when the quality of received downlink signals is larger than or equal to DL Qual Bad TrigThreshold, the actual value of DL RX_LEV Upper Threshold is the one plus the value of DL Qual Bad Up LEVDiff.

40


HW II Power Control Advantages

Measurement report compensation – to 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

41


Exercise

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?

42


Exercise


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.

43


Exercise


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.

44


Content


2. HWⅡPower Control


45


HW III Power Control Flow

Number of lost MR. > N?Number of lost MR. > N?Yes

Stop PC, waiting the next MR.

Rx_lev&(Qual.+FH gain) are within expected window?

Rx_lev&(Qual.+FH gain) are within expected window?

No

Calculate the power control step for BTS

and MS

Calculate the power control step for BTS

and MS

No

Exponent FilterExponent Filter

Slide Window FilterSlide Window Filter

MR. InterpolationMR. Interpolation

Initial MR. processInitial MR. process

Power control implement

Power control implement

Yes

No Power Control

MR. Preprocessing

46


For the measurement report preprocessing, there are three

differences between HW II and HW III power control：

Initial discarded MR. number

Interpolation method

Filter calculation

Measurement Report Preprocessing

47



Initial discarded MR. number

Avoiding the access period measurement report influence power

control accuracy, system discards some initial measurement report.

HW II: discard 4 initial MR. fixedly.

HW III: set it via Signal/Traffic Channel Discard MR. Number.

MR. interpolation method

Rx_lev: If Rx_lev(k) is lost, recover it as Rx_lev(k-1).

Rx_qual: If Rx_qual is lost, recover it as quality lever 7.

48


Data Configuration of Initial Discarded MR. Number

[HWIII Number of lost MRs allowed]


•Default Value: 5

•Description: When the number of discarded measurement reports within the power control period is greater than the value of this parameter, the BSC stops power control.

[HWIII Signal Channel Discard MR Number]

•Value Range: 0~5

•Default Value: 1

•Description: This parameter indicates the maximum number of allowed discarded SDCCH measurement reports in a power control period.

[HWIII Traffic Channel Discard MR Number]


•Default Value: 3

•Description: This parameter indicates the maximum number of allowed discarded TCH measurement reports in a power control period.

49



MR. filter calculation

Quality filter

Quality class value will be converted to BER and set up the

correspondence relationship with CIR as below table.

Calculate the average CIR according to the selected filter method.

4691214161822CIR (dB)

76543210Quality Class

50



MR. filter calculation

filter algorithm: exponent filter and slide window filter

Exponent filter

– ca_filtered1 (1)=ca(1) k=1

– ca_filtered1 (k)=a*ca(k)+(1-a)*ca_filtered1 (k-1) k>1

~ ca: original receiving level or quality

~ ca_filtered1: receiving level or quality after exponent filter calculation

~ k: serial number of measurement report

~ a: exponent filter coefficient, a=1 / (2^(w/2)), and w is exponent filter length

In HW III, power control quality will be convert as C/I during filter processing, then calculate the channel gain. The final power control step will be depend on those.

51



Filter algorithm

Slide window filter

ca_filtered (1) = ca_filtered1 (1) k=1

ca_filtered (k) = [ca_filtered 1(1)+…+ca_filtered1 (k)] / k 1<k<w

ca_filtered (k) = [ca_filtered1 (k-w+1)+...+ca_filtered1 (k)] / w k>=w

– ca_filtered1: receiving level or quality after exponent filter

– ca_filtered: receiving level or quality after window filter

– k: serial number of measurement report

– w: slide filter window

52


Data Configuration of Filter(DL)

[HWIII DL RexLev Exponent Filter Length]

•Value Range: 0~19 Unit: Measurement report period (480 milliseconds on the TCH; 470 milliseconds on the SDCCH) Default Value: 3

•Description: This parameter indicates the exponent filter length of signal level through downlink power control.

[HWIII DL Rex Qual.Exponent Filter Length]


•Description: This parameter indicates the exponent filter length of quality level through downlink power control.

[HWIII DL RexLev Slide Window]


•Description: This parameter indicates the smooth window filter length of signal level through downlink power control

[HWIII DL Rex Qual. Slide Window]


•Description: This parameter indicates the smooth window filter length of quality level through downlink power control.

53


Data Configuration of Filter(UL)

[HWIII UL RexLev Exponent Filter Length]


•Description: This parameter indicates the period of the filtering of signal level index through uplink power control.

[HWIII UL Rex Qual.Exponent Filter Length]

•Value Range: 0~19 UnitMeasurement report period (480 milliseconds on the TCH; 470 milliseconds on the SDCCH) Default Value: 3

•Description: This parameter indicates the period of the filtering quality level index through uplink power control.

[HWIII UL RexLev Slide Window]


•Description: This parameter indicates the period of the filtering of signal level smooth window through uplink power control.

[HWIII UL Rex Qual. Slide Window]


•Description: This parameter indicates the period of the filtering of quality level smooth window through uplink power control.

54


Power Control Judgment

During HW III power control judgment, system will calculate

radio channel gain.

Suppose: In SACCH period k, useful signal is c(k), interference is

I(k), radio channel gain is g(k) and transmit power for BTS or MS is

p(k). The below formulas are calculated by logarithm:

=10)(_

10kfilteredca

+10)(

10kc

10)(

10kI

Rx_levRx_lev Useful Useful signelsignel InterferenceInterference

C/IC/I qa_filtered(k) = c(k) – I(k) (2)

c(k) = p(k) – g(k) (3)

(1)

55



Radio channel gain calculation:

According to (1) and (2), we can get c(k)

Input c(k) to (3), get g(k) = p(k) – c(k). So calculate the g(k) for

BTS and MS

)101lg(10)(_)(_)( 10)(_ kfilteredqa

kfilterqakfiltercakc +×−+=

56



BTS power control step calculation:

step(k) = - ( sfactor*( BsTxMaxPower - g(k) - SThr)

+ qfactor*( qa_filtered(k) + QOffFh - QThr) );

SThr = (SThrUp + SThrDown) / 2; Physical meaning is received useful signal.

QThr = (QThrUp + QThrDown) / 2; Physical meaning is received CIR without hopping.

If step(k) >0, so step(k) =0;

Notes:

sfactor：【HWIII DL RexLev Adjust Factor】

qfactor：【HWIII DL Rex Qual. Adjust Factor】

BsTxMaxPower：the maximum power level of occupied carrier

SThr：the mean level of expected receiving level window

QThr：the mean level of expected receiving quality window

QOffFh：frequency hopping gain

57



MS power control step calculation:

step(k) = - ( sfactor*( MsTxMaxPower - g(k) - SThr)

+ qfactor*( qa_filtered(k) + QOffFh - QThr) );

SThr = (SThrUp + SThrDown) / 2;

QThr = (QThrUp + QThrDown) / 2;

If step(k) >0，then step(k) =0;

58


Data Configuration of Power Control Judgment

[HWIII DL RexLev Upper Threshold]

• Value Range: 0~63 Unit: dB Default Value: 35

• Description: This parameter indicates the upper threshold of downlink power control signal level. When the receive level is higher than the value of this parameter, the BSC performs the downlink power control.

[HWIII DL RexLev Lower Threshold]


• Description: This parameter indicates the lower threshold of downlink power control signal level. When the receive level is lower than the value of this parameter, the BSC performs the downlink power control.

[HWIII DL FS Rex Qual. Upper Threshold(dB)]


• Description: This parameter indicates the upper threshold of downlink power control quality level of full-rate traffic channel. When the receive quality is higher than the value of this parameter, the BSC performs HW III power control.

[HWIII DL FS Rex Qual. Lower Threshold(dB)]


• Description: This parameter indicates the lower threshold of downlink power control quality level of full-rate traffic channel. When the receive quality is lower than the value of this parameter, the BSC performs HW III power control.

[HWIII DL HS Rex Qual. Upper Threshold(dB)]


• Description: This parameter indicates the upper threshold of downlink power control quality level of half-rate traffic channel. When the receive quality is higher than the value of this parameter, the BSC performs HW III power control.

59



[HWIII DL HS Rex Qual. Lower Threshold(dB)]


•Description: This parameter indicates the lower threshold of downlink power control quality level of half-rate traffic channel. When the receive quality is lower than the value of this parameter, the BSC performs HW III power control.

[HWIII DL AFS Rex Qual.Upper Threshold(dB)]

•Value Range: 1-30 Unit: dB Default Value: 16

•Description: This parameter indicates the upper threshold of downlink power control quality level of AMR full-rate traffic channel. When the receive quality is higher than the value of this parameter, the BSC performs HW III power control.

[HWIII DL AFS Rex Qual.Lower Threshold(dB)]


•Description: This parameter indicates the lower threshold of downlink power control quality level of AMR full-rate traffic channel. When the receive quality is lower than the value of this parameter, the BSC performs HW III power control.

[HWIII DL AHS Rex Qual.Upper Threshold(dB)]


•Description: This parameter indicates the upper threshold of downlink power control quality level of AMR half-rate traffic channel. When the receive quality is higher than the value of this parameter, the BSC performs HW III power control.

[HWIII DL AHS Rex Qual. Lower Threshold(dB)]

Value Range: 1~30 Unit: dB Default Value: 12

Description: This parameter indicates the lower threshold of downlink power control quality level of AMR half-rate traffic channel. When the receive quality is lower than the value of this parameter, the BSC performs HW III power control.

60



[HWIII UL RexLev Upper Threshold]


•Description: This parameter indicates the upper threshold of uplink power control signal level. When the receive level is higher than the value of this parameter, the BSC performs the HW III power control.

[HWIII UL RexLev Lower Threshold]


•Description: This parameter indicates the lower threshold of uplink power control signal level. When the receive level is smaller than the value of this parameter, the BSC performs the HW III power control.

[HWIII UL FS Rex Qual. Upper Threshold(dB)]


•Description: This parameter indicates the upper threshold of uplink power control quality level of full-rate traffic channel. When the receive quality is higher than the value of this parameter, the BSC performs HW III power control.

[HWIII UL FS Rex Qual. Lower Threshold(dB)]


•Description: This parameter indicates the lower threshold of downlink power control quality level of full-rate traffic channel. When the receive quality is lower than the value of this parameter, the BSC performs HW III power control.

[HWIII UL HS Rex Qual.Upper Threshold(dB)]


•Description: This parameter indicates the upper threshold of uplink power control quality level of half-rate traffic channel. When the receive quality is higher than the value of this parameter, the BSC performs HW III power control.

61



[HWIII UL HS Rex Qual.Lower Threshold(dB)]


•Description: This parameter indicates the lower threshold of downlink power control quality level of half-rate traffic channel. When the receive quality is lower than the value of this parameter, the BSC performs HW III power control.

[HWIII UL AFS Rex Qual.Upper Threshold(dB)]


•Description: This parameter indicates the upper threshold of uplink power control quality level of AMR full-rate traffic channel. When the receive quality is higher than the value of this parameter, the BSC performs HW III power control.

[HWIII UL AFS Rex Qual.Lower Threshold(dB)]


•Description: This parameter indicates the lower threshold of downlink power control quality level of AMR full-rate traffic channel. When the receive quality is lower than the value of this parameter, the BSC performs HW III power control.

[HWIII UL AHS Rex Qual.Upper Threshold(dB)]


•Description: This parameter indicates the upper threshold of uplink power control quality level of AMR half-rate traffic channel. When the receive quality is higher than the value of this parameter, the BSC performs HW III power control.

[HWIII UL AHS Rex Qual.Lower Threshold(dB)]


•DescriptionThis parameter indicates the lower threshold of downlink power control quality level of AMR half-rate traffic channel. When the receive quality is lower than the value of this parameter, the BSC performs HW III power control.

62



[HWIII MA FreqHop Gain 1(2~8)(0.1dB)]


•Unit: 0.1dB

•Default Value: 0

•Description: This parameter indicates the receive quality gain when the number of frequency hopping of a cell is 1(2~8). When the cell is configured with frequency hopping, the receive quality gain is brought out. The BSC performs power control based on the gain.

•Remarks: After the frequency hopping is activated, the call can bear a lower CIR. Therefore, targeting the receive quality, the HW III power control algorithm introduces different FH gains based on different FH frequencies. After the FH gains are introduced, the power control amplitude becomes more accurate and the average transmit power is reduced. Thus the intra-network interference can be greatly reduced.

63


Data Configuration of Power Control Adjust Factor

[HWIII UL RexLev Adjust Factor]


•Default Value: 4

•Description: This parameter indicates the step ratio of the signal strength adjusted by uplink power control.

[HWIII UL Rex Qual.Adjust Factor]


•Default Value: 6

•Description: This parameter indicates the step ratio of the quality level adjusted by uplink power control.

[HWIII DL RexLev Adjust Factor]


•Default Value: 6

•Description: This parameter indicates the step ratio of the signal strength adjusted by downlink power control.

[HWIII DL Rex Qual. Adjust Factor]


•Default Value: 6

•Description: This parameter indicates the step ratio of the quality level adjusted by downlink power control.

64



Adjustment protection

For avoiding too rapid adjustment, parameter [HWIII DL/UL MAX

DownStep/UpStep] is used to control the maximum power control

step.

If the difference between power control step(k) and previous one

step(k-1) is bigger than maximum power control step configured

above, just take the maximum power control step as the

difference between them, so as to limit the current power control

command step(k).

65


Data Configuration of Power Control Step

[HWIII UL MAX DownStep(dB)]


•Unit: dB

•Default Value: 8

•Description: This parameter indicates the maximum permissible adjustment step when the BSC reduces uplink transmit power according to signal quality.

[HWIII UL MAX UpStep(dB)]


•Unit: dB

•Default Value:8

•Description: This parameter indicates the maximum permissible adjustment step when the BSC increases uplink transmit power according to signal quality.

[HWIII DL MAX DownStep(dB)]


•Unit: dB

•Default Value: 8

•Description: This parameter indicates the maximum permissible adjustment step during down power adjustment based on signal quality.

[HWIII DL MAX UpStep (dB)]


•Unit: dB

•Default Value: 8

•Description: This parameter indicates the maximum permissible adjustment step during up power control adjustment based on signal quality.

66



If Rx_lev upper threshold >= Rx_Lev >= Rx_lev lower threshold

and Rx_qual upper threshold >= [RxQual + QOffFh] >= Rx_qual lower

threshold, step(k)=step(k-1)

QOffFh is depended on hopping gain table

5.35.04.74.34320QOffFh (dB)

>=87654321Number of MA

67


HW III Power Control Features

Exponent filter enhance the measurement report process speed.

In HW II PC, receive level and quality be considered independently

and then general power control judgment will be done. While in

HW III PC, the final result will be got from the general formula.

Difference quality threshold be set for the difference service, such

as AMR, FS and HS.

Hopping gain also be considered.

68


Given condition：The current UL_Re_Level: -75dBm， UL_Re_Quality: 4(qa_filtered (k) =12)， Radio

channel gain(g(k)): 110dB, there are 7 hopping frequency, Max power output of MS is

2W(33dBm)

HWIII is available，data configuration is as following:

【[HWIII UL RexLev Upper Threshold]】：30

【 HWIII UL RexLev Lower Threshold 】：20

【 HWIII DL FS Rex Qual. Upper Threshold(dB)] 】：22

【 HWIII UL FS Rex Qual. Lower Threshold(dB)] 】：16

【 HWIII UL RexLev Adjust Factor 】：4 【 HWIII UL Rex Qual.Adjust Factor 】：6

【 HWIII UL MAX DownStep(dB)】：8 【 HWIII UL MAX UpStep(dB)】：8

Question： What will be the power output of MS after power control？

4691214161822CIR (dB)

76543210Quality Class

5.35.04.74.34320QOffFh (dB)

87654321Number of MA

Question

69


Answer:

step(k) = - ( sfactor×( BsTxMaxPower - g(k) - SThr)

＋ qfactor×( qa_filtered(k) + QOffFh - QThr) )

After power control：

Power output of MS: 33-2=31dBm

Suppose the current g(k)=115dB, current quality:3(CIR=14dB)，then

For level：-90dBm<31-115<-80dBm

For quality：16<14+5<22

So power control stops， the power output of MS 33-2=31dBm

dB2

)}2

1622512(6.0)]}1102

2030(11033[4.0{{

−=

+−+×+−

+−−×−=

Question

70


Summary

In this course, we have learned:

Power control procedure

HW II power control algorithm

HW III power control algorithm

Data Configuration of HWII and HWIII

71

Thank youwww.huawei.com

pciii-gsm power control issue2.01

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