Omf810003 gsm power control issue2 01 by Emerson Eduardo Rodrigues

GS M P owe r Control

www.huawei.com

Conte nts 1.

Power Control Overview

HWⅡPower Control

HWⅢPower Control

Page3

P owe r Control Ove rvie w 



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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P owe r Control Ove rvie w 

Power control includes uplink power control and downlink power control, Which are performed independently 

Uplink power control: Adjust TX power of MS to let BTS receive stable signal, reduce the uplink co-channel and adjacent channel interference, reduce power consumption of MS



Downlink power control: Adjust BTS TX power to let MS receive stable signal, reduce the downlink co-channel and adjacent channel interference, reduce power consumption of BTS

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P owe r Control Ove rvie w ď Ź

Up link and Down link power control can be enabled independently

Page6

P owe r Control Ove rvie w 

Process of power control commands 

It takes 3 measurement report periods(480ms/period) from command sending to getting the feedback.

BTS sends the command for power control and TA in SACCH header.

SACCCH report period: 26X4=104 frames (480ms)

BTS receives the measurement report

SA0 SA1SA2 SA3 SA0 SA1 SA2SA3 SA0 SA1SA2 SA3 MS adopts the new power level and TA

In the 26 multi-frames, frame 12 sends SACCH. MS obtains SACCH block

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

MS begins to set up a new SACCH header to report the new TA and power control message.

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Da ta Configura tion of P owe r Control P e riod

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P owe r Control Ove rvie w 

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

Page9

Da ta Configura tion of MR P re proce s s ing(1)

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Da ta Configura tion of MR P re proce s s ing(1)

Page11

Conte nts 1.

Power Control Overview

HWⅡ Power Control

HWⅢPower Control

Page12

HW II P owe r Control ď Ź

Power control judgment process MR. preprocessing

The power control demand according to receiving level

The power control demand according to receiving quality

General power control judgment Send the power control command

Page13

HW II P owe r Control 

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

Uplink MR

BTS

Network

Downlink MR

Page14

HW II P owe r Control ď Ź

Measurement report

Uplink measurement report

Downlink measurement report

Page15

HW II P owe r Control 

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

Interpolation



Compensation (optional)



Prediction (optional)



Filter

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HW II P owe r 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 (Allo w e d MR Num b e r Lo s t), then recovers the lost MR according to the specific algorithm. 

S e r v ic e c e ll: lin e a r a lg o rit h m



Ne ig h b o rin g c e ll: t h e lo w e s t v a lu e d e fin e d in GS M s p e c ific a t io n (-1 1 0 d Bm )

Page17

HW II P owe r Control 

MR Interpolation – recover the lost measurement report Flow R us M o u tin Con

…

No. n+4

…

No. n

Missing by some reasons

Page18

Da ta Configura tion of MR P re proce s s ing

Page19

HW II P owe r Control 

MR. compensation 



Purpose: Ensure the accuracy of selection of the history measurement report before filter. Implementation steps: 

1 . Pu t t h e c u rre n t re c e iv in g m e a s u re m e n t re p o rt in t o t h e m e a s u re m e n t re p o rt c o m p e n s a t io n q u e u e .



2 . Re c o rd t h e c h a n g e d in fo rm a t io n o f t h e t ra n s m it t in g p o w e r a c c o r d in g t o t h e MS a n d BTS p o w e r le v e ls in t h e m e a s u re m e n t re p o rt .



3 . Aft e r fin is h t h e m e a s u re m e n t re p o rt in t e rp o la t io n , s y s t e m w ill c o m p e n s a t e t h e re c e iv in g le v e l o f t h e h is t o ry m e a s u re m e n t re p o rt a c c o r d in g t o t h e p o w e r c h a n g e in fo rm a t io n . Th e c o m p e n s a t e d m e a s u re m e n t re p o rt s w ill b e t h e o rig in a l d a t a in t h e filt e r p ro c e s s .



4 . Filt e r t h e c o m p e n s a t e d m e a s u re m e n t re p o rt s .

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HW II P owe r Control MR. compensation Power control effect diagram of measurement report compensation 70

Y axis

Diagram when there is no power control

Power control diagram when there is measurement report compensation

Power control diagram when there is no measurement report compensation

30 20 10 0

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

ď Ź

X axis

The Theexpected expectedreceiving receivingsignal signallevel: level:30 30 The Thepower powercontrol controlwill willbe bemore moreeffective effectivewith withmeasurement measurementreport reportcompensation. compensation. Copyright ÂŠ 2009 Huawei Technologies Co., Ltd. All rights reserved.

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Da ta Configura tion of MR. Compe ns a tion

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HW II P owe r 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.

An a ly ze t h e t e n d e n c y o f MR b y t h e h is t o ric a l m e a s u r e m e n t re p o r t s a ft e r in t e rp o la t io n .

Gu id e b y t h e t e n d e n c y , t o p r e d ic t t h e v a lu e s o f m e a s u r e m e n t re p o r t t o b e r e c e iv e d . Th e r e a re 0 ~ 3 m e a s u r e m e n t re p o r t s p r e d ic t io n , w h ic h a re c o n fig u re d o n LMT.

Filt e r t h e in t e rp o la t e d , c o m p e n s a t e d a n d p r e d ic t e d m e a s u r e m e n t re p o r t s , a n d im p le m e n t p o w e r c o n t ro l

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HW II P owe r Control MR. prediction Diagram of power control effect comparison between prediction filter and mean filter

50 45 Y axis

No power control

Mean filter power control

Prediction filter power control

25 20 15

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

ď Ź

X axis

The Theexpected expectedreceiving receivingsignal signallevel: level:30 30 The Thepower powercontrol controlwith withprediction predictionfilter filterwill willbe bemore moreeffective effective than thanthat thatwith with mean meanfilter filter Copyright ÂŠ 2009 Huawei Technologies Co., Ltd. All rights reserved.

Page24

Da ta Configura tion of MR. P re diction

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HW II P owe r Control 

MR. filter – Smooth the instantaneous fading point 

Calculate the average value within the filter window

us M o u n ti Con

ow R Fl MR

…

Filter----Average several consecutive MRs

Page26

Da ta Configura tion of MR. filte r

Page27

HW II P owe r Control J udgme nt 

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.

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HW II P owe r Control J udgme nt 

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.

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HW II P owe r Control J udgme nt 

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_Qul

↑AdjStep_Lev

No action

↑AdjStep_Lev

No action

↓ AdjStep_Qul

↓ AdjStep_A

No action

↑ AdjStep_Qul

↑ AdjStep_B

No action

↑ max(AdjStep_Lev,AdjStep_Qul)

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HW II P owe r Control Fe a ture 

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. 

Au t o m a t ic a lly c h a n g e t h e a d ju s t a b le m a x im u m s t e p s ize o f p o w e r c o n t ro l a c c o rd in g t o d iffe r e n t c o m m u n ic a t io n e n v iro n m e n t (d iffe r e n t r e c e iv in g q u a lit y ).



Ad o p t d iffe re n t p o w e r c o n t r o l s t r a t e g ie s a c c o rd in g t o d iffe r e n t c o m m u n ic a t io n e n v ir o n m e n t s (d iffe r e n t r e c e iv in g q u a lit y a n d le v e l).



Ma x . s t e p is d iffe r e n t b e t w e e n in c re a s e a n d d e c re a s e .

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HW II P owe r Control Fe a ture 

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.

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Da ta Configura tion for UL Rx_Le v Uppe r/Lowe r Thre s hold

Page33

Da ta Configura tion for UL Uppe r/Lowe r Qua lity Thre s hold

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Da ta Configura tion for DL Rx_Le v Uppe r/Lowe r Thre s hold

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Da ta Configura tion for DL Uppe r/Lowe r Qua lity Thre s hold

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Da ta Configura tion of P owe r Control (Rx_Le v)

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Da ta Configura tion of P owe r Control (Rx_Le v)

Page38

Da ta Configura tion of P owe r Control (Rx_Le v)

Page39

Da ta Configura tion for UL/DL Ba d Qua lity

Page40

HW II P owe r Control Adva nta ge s 

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

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Exe rcis e 

Exercises for HW II power control 

Given conditions: 

Th e u p lin k re c e iv in g le v e l is -5 5 d Bm , t h e q u a lit y is le v e l 0 . Po w e r c o n t ro l a lg o r it h m is HW II.



Da t a c o n fig u ra t io n is a s fo llo w s : Up lin k s ig n a l le v e l u p p e r t h re s h o ld : -6 0 d Bm , u p lin k s ig n a l le v e l lo w e r t h re s h o ld : - 8 0 d Bm . Up lin k s ig n a l u p p e r q u a lit y t h re s h o ld : le v e l 1 . Up lin k s ig n a l lo w e r q u a lit y t h re s h o ld : le v e l 2 . Th e d o w n w a r d a d ju s t a b le s t e p s iz e o f q u a lit y b a n d 0 is 1 6 d B, o f q u a lit y b a n d 1 is 8 d B, a n d o f q u a lit y 2 is 4 d B. Th e u p w a rd a d ju s t a b le s t e p s iz e o f r e c e iv in g le v e l is 1 6 d B. Th e u p w a rd o r d o w n w a rd a d ju s t a b le s t e p s iz e fo r p o w e r c o n t r o l b y q u a lit y a re b o t h 4 d B.



Question: What will be the uplink stable receiving level after power control?

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Exe rcis e 

Exercises for HW II power control 

Answer. 

Firs t , t ra n s m it t in g p o w e r t o b e re d u c e d a c c o rd in g t o re c e iv in g le v e l = a c t u a l re c e iv in g le v e l -(u p lin k s ig n a l le v e l u p p e r t h re s h o ld + u p lin k s ig n a l le v e l lo w e r t h re s h o ld )/2 ＝ -5 5 - (-6 0 + (-8 0 ))/2 ＝ (5 5 )-(-7 0 ) ＝ 1 5 d B. As t h e re c e iv in g q u a lit y is le v e l 0 , d o w n w a rd a d ju s t a b le s t e p s iz e o f q u a lit y b a n d 0 c a n b e u s e d -- d e c re a s e 1 6 d B.



S e c o n d , t h e t ra n s m it t in g p o w e r t o b e d e c re a s e d a c c o rd in g t o re c e iv in g q u a lit y = a s “p o w e r c o n t ro l a d ju s t m e n t s t e p s iz e b y q u a lit y ”is 4 d B, t h u s d e c re a s e 4 d B.



Th e re fo re , a c c o rd in g t o t h e g e n e ra l ju d g e m e n t o n p o w e r c o n t ro l, 1 5 d B s h o u ld b e d e c re a s e d .

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Exe rcis e 

Exercises for HW II power control 

Answer . 

Aft e r t h e im p le m e n t a t io n o f s t e p 1 p o w e r c o n t r o l, t h e r e c e iv in g le v e l b e c o m e s : -5 5 d Bm -1 5 d B= -7 0 d Bm , S u p p o s e t h e q u a lit y r e a c h a lr e a d y in le v e l 1 h e re .



Firs t : t h e re c e iv in g le v e l v a lu e is b e t w e e n -8 0 d Bm ~ 6 0 d Bm , n e e d n ’ t a d ju s t .



S e c o n d : t h e re c e iv in g q u a lit y v a lu e is b e t w e e n 0 a n d 2 , needn’ t a d ju s t .



Th e re fo re , t h e u p lin k s t a b le re c e iv in g le v e l = -7 0 d Bm .

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Conte nt 1.

Power Control Overview

HWⅡPower Control

HWⅢ Power Control

Page45

HW III P owe r Control Flow MR. Preprocessing

Stop PC, waiting the next MR.

Initial MR. process

Yes

Number of lost MR. > N? No MR. Interpolation

No Power Control

Exponent Filter Slide Window Filter Calculate the power control step for BTS and MS

Yes

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

No Power control implement

Page46

Me a s ure me nt Re port P re proce s s ing 

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

Page47

Me a s ure me nt Re port P re proce s s ing 

Initial discarded MR. number 

Avoiding the access period measurement report influence power control accuracy, system discards some initial measurement report.





HW II: d is c a rd 4 in it ia l MR. fix e d ly .



HW III: s e t it v ia Sig n a l/Tra ffic C h a n n e l Disc a rd MR. Nu m b e r.

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.

Page48

Da ta Configura tion of Initia l Dis ca rde d MR. Numbe r

Page49

Me a s ure me nt Re port P re proce s s ing 

MR. filter calculation 

Quality filter 

Quality class value will be converted to BER and set up the correspondence relationship with CIR as below table.



Ca lc u la t e t h e a v e ra g e CIR a c c o r d in g t o t h e s e le c t e d filt e r m e th od . Quality Class CIR (dB)

Page50

Me a s ure me nt Re port P re proce s s ing 

MR. filter calculation 

filter algorithm: exponent filter and slide window filter 

Ex p o n e n t filt e r – ca _filte re d1 (1)=ca (1)

k=1

– ca _filte re d1 (k)=a *ca (k)+(1-a )*ca _filte re d1 (k-1)

k>1

~ ca : origina l re ce iving le ve l or qua lity ~ ca _filte re d1: re ce iving le ve l or qua lity a fte r e xpone nt filte r ca lcula tion ~ k: s e ria l numbe r of me a s ure me nt re port ~ a : e xpone nt filte r coe fficie nt, a =1 / (2^(w/2)), a nd w is e xpone nt filte r le ngth

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Me a s ure me nt Re port P re proce s s ing 

Filter algorithm 

Slide window filter 

c a _filt e re d (1 ) = c a _filt e re d 1 (1 ) k= 1



c a _filt e re d (k ) = [c a _filt e r e d 1 (1 )+ …+ c a _filt e re d 1 (k )] / k 1 < k< w



c a _filt e re d (k ) = [ c a _filt e re d 1 (k -w + 1 )+ ...+ c a _filt e re d 1 (k )] / w k> = w – ca _filte re d1: re ce iving le ve l or qua lity a fte r e xpone nt filte r – ca _filte re d: re ce iving le ve l or qua lity a fte r window filte r – k: s e ria l numbe r of me a s ure me nt re port – w: s lide filte r window

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Da ta Configura tion of Filte r(DL)

Page53

Da ta Configura tion of Filte r(UL)

Page54

P owe r Control J udgme nt 

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:

ca _ filtered ( k ) 10

Rx_lev

= 10

c(k ) 10

+ 10

Useful signel

I (k ) 10

(1)

Interference

C/I qa_filtered(k) = c(k) – I(k)

(2)

c(k) = p(k) – g(k)

(3)

Page55

P owe r Control J udgme nt 

Radio channel gain calculation: 

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

c(k ) = ca _ filter (k ) + qa _ filter (k ) − 10 × lg(1 + 10 

qa _ filtered ( k ) 10

)

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

fo r BTS and MS

Page56

P owe r Control J udgme nt 

BTS power control step calculation: step(k) = - ( sfactor*( BsTxMaxPower - g(k) - SThr) + q fa c t o r*( q a _filt e re d (k ) + Q O ffFh - Q Th r) ); S Th r = (S Th r Up + S Th rDo w n ) / 2 ; Ph y s ic a l m e a n in g is re c e iv e d u s e fu l s ig n a l. Q Th r = (Q Th rUp + Q Th rDo w n ) / 2 ; Ph y s ic a l m e a n in g is re c e iv e d CIR w it h o u t h o p p in g . If s t e p (k ) > 0 , s o s t e p (k ) = 0 ; No t e s : s fa c t o r ：【 HW III DL Re x Le v Ad ju s t Fa c t o r 】 q fa c t o r ：【 HW III DL Re x Q u a l. Ad ju s t Fa c t o r 】 Bs Tx Ma x Po w e r ： t h e m a x im u m p o w e r le v e l o f o c c u p ie d c a rrie r S Th r ： t h e m e a n le v e l o f e x p e c t e d re c e iv in g le v e l w in d o w Q Th r ： t h e m e a n le v e l o f e x p e c t e d re c e iv in g q u a lit y w in d o w Q O ffFh ： fre q u e n c y h o p p in g g a in Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.

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P owe r Control J udgme nt 

MS power control step calculation: s t e p (k ) = - ( s fa c t o r*( Ms Tx Ma x Po w e r - g (k ) - S Th r) + q fa c t o r*( q a _filt e r e d (k ) + Q O ffFh - Q Th r ) ); STh r = (S Th rUp + S Th rDo w n ) / 2 ; Q Th r = (Q Th rUp + Q Th r Do w n ) / 2 ; If s t e p (k ) > 0 ， t h e n s t e p (k ) = 0 ;

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