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RF Power Control

August 2001

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RF Power Control

What is RF Power Control?

Why we need RF Power Control?

Execution of RF Power Control

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Power Control - Definition

Increasing or Decrease the RF power based

on the Rxlev , quality .

 –  Uplink ( mandatory ).

 –  Downlink (optional).

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RF Power Control - Affect

Uplink 

 –  Battery Saving.

 –  Co-Channel Interference.

Downlink 

 –  Co-Channel Interference.

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RF Power Control - Execution

Power Control Procedure.

Optimized Power Control.

Rapid Power Down.

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RF Power Control - Process

Process for PC for either the Rxlev,

quality

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RF Power Control – MR

MS send SACCH message every 480 ms. It contains

measuring about

 –  Downlink Received Signal Strength.

 –  Downlink Received Qual.

 –  Neighbors BCCH/BSIC with Rx Lev.

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RF Power Control – MR (cont)

The Radio Interface forward measurements about the

uplink to the HDPC .

 –  Uplink Signal Strength.

 –  Uplink Received BER.

 –  Uplink Interference on Idle.

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RF Power Control - Averaging

We can’t depend on just one SACCH message MR, so we

make an algorithm for averaging .

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RF Power Control - Averaging

The Averaging/Voting algorithms are based on four

parameters

 –  HREQAVE

 –  HREQT

 –  N

 –  P

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RF Power Control - Triggering

If P out of N exceed the threshold a decision will take

place

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RF Power Control – Process summery

Decision was taken due to level .

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RF Power Control – Process summery

Decision was taken due to quality.

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RF Power Control - Decision

Decision_alg_number = 1INCREASE 

Check Oscillation before 

There is no such a thing 

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Optimization RF Power Control

GSR3  GSR4 

SINGLE  power increase /  

decrease step size for UL & 

 DL 

Separate for UL & DL 

Power increase step size : 

range of 2 - 6 db Power increase step size : range 

of 2 - 14 db 

Step sizes FIXED in 

database Step sizes DYNAMICALLY 

SET  depd on current power 

level NO DL power level 

oscillation prevention 

control 

DL oscillation prevention 

included 

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Optimization RF PC  – Step Size

SEPARATE increment/decrement step sizes for

uplink and down link 

pow_inc_step_size_ulpow_inc_step_size_dl 

pow_inc_step_size

pow_red_step_size_ul

pow_red_step_size_dl pow_red_step_size

2,4,6,8,10

,12,14 dB

2, 4dB

* The increment step size must be >= the decrement step size

GSR3

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Optimization RF Power Control

GSR3  GSR4 

SINGLE  power increase /  

decrease step size for UL & 

 DL 

Separate for UL & DL 

Power increase step size : 

range of 2 - 6 db Power increase step size : range 

of 2 - 14 db 

Step sizes FIXED in 

database Step sizes DYNAMICALLY 

SET  depd on current power 

level NO DL power level 

oscillation prevention 

control 

DL oscillation prevention 

included 

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Optimization RF Power Control

GSR3  GSR4 

SINGLE  power increase /  

decrease step size for UL & 

 DL 

Separate for UL & DL 

Power increase step size : 

range of 2 - 6 db Power increase step size : range 

of 2 - 14 db 

Step sizes FIXED in 

database Step sizes DYNAMICALLY 

SET  depd on current power 

level NO DL power level 

oscillation prevention 

control 

DL oscillation prevention 

included 

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Optimization RF PC  – Dynamic step size

To ENABLE, set dyn_step_adj = 1 3 types of dynamic step size adjustments

  Dynamic power stepsize increase due to poorRXQUAL

Dynamic power stepsize increase due to poorRXLEV 

Dynamic power stepsize reduction due to goodRXQUAL

* NO Dynamic power stepsize reduction due to good RXLEV

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Optimization RF PC  – Dynamic step size(increase due poor Rxqual)

occurs when rxqual falls below the lower rxqualthreshold

 l_rxqual_ul/dl_pstepsize = DYN_POW_INC_XX_Q =

MAX [ pow_inc_step_size_xx , fhigh ( Y ) ]

where Y = l_rxlev_xx_p + pow_inc_step_size_xx -

current_rxlev_xx 

where fhigh( ) denotes the rounding up of a value to thenearest multiple of 2 dB 

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Optimization RF PC  – Dynamic step size(Increase due to Rxqual)

l_rxlev_ul_p

u_rxlev_ul_p

Power level

pow_inc_step_size_ul 

Dynamic

step size 

current_rxlev_ul 

Current power level

Standard stepsize

• Y = l_rxlev_xx_p + pow_inc_step_size_xx - current_rxlev_xx 

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Optimization RF PC  – Dynamic step size

(Increase due to Rxlev)

occurs when Rxlev falls below the lower rxlevthreshold

 l_rxlev_ul/dl_pstepsize = DYN_POW_INC_XX_L = fhigh ( Y )

where Y = l_rxlev_xx_p + pow_inc_step_size_xx - current_rxlev_xx 

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Optimization RF PC  – Dynamic step size(Reduction due good Rxqual)

occurs when rxqual is above the upper Rxqualthreshold

 u_rxqual_ul/dl_pstepsize = DYN_POW_RED_XX =

MAX [ pow_red_step_size_xx , f low ( Y ) ]

where Y = (dyn_step_adj_fmpr  /10 ) * (current_rxlev_xx -

u_rxlev_xx_p) 

• dyn_step_adj_fmpr = 0 to 10 ( used to control therapidity )

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Optimized RF Power Control

GSR3  GSR4 

SINGLE  power increase /  

decrease step size for UL & 

 DL 

Separate for UL & DL 

Power increase step size : 

range of 2 - 6 db Power increase step size : range 

of 2 - 14 db 

Step sizes FIXED in 

database Step sizes DYNAMICALLY 

SET  depd on current power 

level NO DL power level 

oscillation prevention 

control 

DL oscillation prevention 

included 

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Optimized RF PC  –  Uplink Oscillation prevention

Problem definition

 –  Decrease due to good Rxqual , Increase due to

poor Rxlev

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Optimized RF PC  –  Uplink Oscillation prevention

Solution

 –  Adjust increment step size ( via HDPC)

 –  Ignore decrease due to Rxqual after increasedue to Rxlev ( mspwr_alg =1 )

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Optimized RF PC  –  Downlink Oscillation

prevention

 Decrease due to good Rxqual followed by

 Increase due poor Rxlev immediately

current_rxlev_dl < l_rxlev_dl_p + pow_red_step_size_dl+ 2dB  If the following condition is true, an

RXQUAL based power reduction will NOT

be performed: 

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Optimized RF PC  –  Downlink Oscillation

prevention

current_rxlev_dl < l_rxlev_dl_p +pow_red_step_size_dl + 2dB 

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RF Rapid Power Down

Where ?

 –  In urban area .

Problem

 –  Low step size

 –  Slow change

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RF Rapid Power control - Rapid down

Definition –  MS power is reduced faster

than the standard ramp down

time

 –  Takes precedence over

conventional PC

Benefits –  Reduced UL interference

 –  Reduced MS TX power Fast Power Down OFF 

Fast Power Down ON 

MS Tx Power 

Uplink RxLev  rpd_trigger

 rpd_offset

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Interaction between RPD and PC

Averaging & voting of normal PC is not utilised

No voting employed: hreqt, n, p assumed as 1

Hreqave value equal to rpd_period

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RF Power Control

Thank You

Q & A