OMF010003 Power control ISSUE1.4

Power Control Overview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

OMF010003 Power Control

Power control overview

HW power control Ⅰpower control

HW power control Ⅱpower control

Course Contents

Power Control Overview

Power control

 Adjust the transmitting power of BTS and MS when needed.

 Based on measurement reports of BTS and MS

 Save the power of BTS and MS;

 Reduce the interference of the network;

 Increase the quality of the network.

Power Control Overview

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

Power Control Overview

Process of power control commands

 It takes 3 measurement report periods(480ms/period) from command sending to execution.

BTS sends the command for power

control and TA in SACCH header.

MS obtains SACCH block

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

In the 26 multi-frames,

frame 12 sends

SACCH

BTS receives the measurement report

SACCCH report period:

26X4=104 frames (480ms)

MS adopts the new power level and TA

MS begins to set up a new SACCH header

to report the new TA and power control message

Power Control Overview

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 Overview

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.

Power control overview

HW power control Ⅰpower control

HW power control Ⅱpower control

Course Contents

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

Measurement report pre-processing

Original data of power control measurement report

Network

Downlink measurement report

Uplink MR

BTS

HW I Power Control

Uplink measurement report

Downlink measurement report

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

Measurement report

serial number n

Measurement report serial number n+4

Consecutive measurement report flow

3 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.

[BTS power control table]

0 ～100％ 80 ％

(signal ex-signal rx)*80%=adjust ment value

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

is too long, the influence due to abnormal reports will be weakened, but the MS power adjustment is not timely

[MS power control data table]

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

8

HW I Power Control

Parameter name Meaning Value

ded

power control algorithms; unit: SACCH period

Filter length for

initial stage Unit: Measurement reports

Filter length for

stage Unit: Number of measurement reports

[MS power control table]

HW I Power Control

HW I power control judgment

 The adjustment on the current output power=(Expected signal st rength in stable status - strength of signal currently received) * u

p (down) link compensating factor +[quality of uplink(downlink) c urrently received - expected uplink(downlink) quality]*10* uplink (downlink) quality compensating factor

 The final adjustment power level should be no more than the ma ximum power control step size, the formula for stable level is: sta ble level = currently level + the adjustment value on current out p

ut 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:

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

s 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

HW I power control exercise

 Question:

 1 Suppose that power control will no longer be done once the power value to be adjusted is less than 2dB, what is the approximate stable power value after power control with the above data configuration?

 2 According to the error tolerance list, suppose the initial MS transmitting power is level 3, what is the maximum uplink receiving level in stable status after power control?

Exercise

HW I power control exercise

 Answers for question 1:

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

e 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 i

s -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

Power control overview

HW power control Ⅰpower control

HW power control Ⅱpower control

Course Contents

HW I I power control

 Main feature of HW I I Power control

HW I I Power Control

Power control judgment process

 Power control demand based on receiving level.

 After measurement report pre-processing, the power control module makes a comparison between the expected signal level and the current receiving signal level

 Calculate the transmitting power level step size to be adjusted, making the receiving level value closer to the expected value

 Adopt variable step size when adjusting the transmitting power according to the receiving level, so as to achieve the expected level as soon as possible

HW I I Power Control

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.

HW I I Power Control

General power control judgment

Power control by receiving

↓ 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

HW I I power control

 Power control algorithm implementation

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

Measurement report compensation

The expected receiving signal level: 30

The power control will be more effective with measurement report

compensation

The expected receiving signal level: 30

The power control will be more effective with measurement report

Power control diagram when there is no measurement report compensation

Power control effect diagram of measurement report compensation

HW II Power Control

Measurement report prediction

 3 Filter the interpolated, compensated and predicted measurement reports, and implement power control judgment

HW II Power Control

Measurement report prediction

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

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)

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

HW II Power Control

Simple parameter configuration

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

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

 Three kinds of step sizes for adjustment by level

 Step size for adjustment by quality

HW II Power Control

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

Parameter

Value range

Recommen ded value

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

Parameter

name Meaning range Value 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