cap06 power control

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BSSPAR1: Chapter 6Power Control


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Module Objectives

• Explain the motivation for power control

• Indicate the BSS parameters required for power control in general (output power levels, fixed step sizes)

• Describe the principle steps to be executed for power control (averaging, triggering, power change step size estimation)

• Discuss the algorithms used to estimate the power change step size, when the power has to be increased / decreased due to signal level / quality

• Explain the motivation for power optimisation

• Indicate the BSS parameters required for power optimisation

• Discuss, how power control and traffic channel allocation are modified by power optimisation

• AMR Power Control is presented in chapter on AMR


• Longer service time of battery• Realization of power class• Supported by default on UL

Reduced interference on DL/UL

Activation of DL power control

powerCtrlEnabled (PENA) Y,N

Power control independent

• for DL and UL• for each call

Power Control Motivation


30 dB Range

Power classdependentrange

Attenuations

Power Values

Maximum MS output power

msTxPwrMaxGSM (PMAX1) 5..39 dBm GSM 900 TCHmsTxPwrMaxGSM1x00 0..36/32,33 dBm GSM 1800/1900 TCH (PMAX2)msTxPwrMaxCCH (TXP1) 5..39 dBm GSM 900 CCHmsTxPwrMaxCCH1x00 0..30 dBm GSM 1800 CCH(TXP2) 0..32 dBm GSM 1900 CCH

Minimum MS output power

minMSTxPower (PMIN) 5..39 dBm GSM 9000..36 dBm GSM 18000..32 dBm GSM 1900

Maximum BTS output power (by minimum attenuation)

bsTxPwrMax (PMAX1) 0..30 dB GSM 900bsTxPwrMax1x00 (PMAX2) 0..30 dB GSM 1800/1900

Minimum MS output power (by maximum attenuation)

bsTxPowerMin 0..30 dB

Power Control ParameterOutput Power Limits


Fixed increment step size

• powerIncrStepSize (INC) 2,4,6 dB

Fixed decrement step size

• powerDecrStepSize (RED) 2,4,6 dB

Desired power level can be achieved in 1 or 2 commands

Yes

Fixed step size

No

Variable step size

Power Control ParametersPower Change Step Sizes


UL Level

UL Quality <Av_RXQUAL_UL>

<Av_RXLEV_UL>

DL Level

DL Quality <Av_RXQUAL_DL>

<Av_RXLEV_DL>

POWER CONTROLUPLINK

POWER CONTROLUPLINK

THRESHOLD COMPARISON

POWER CONTROLDOWNLINK

POWER CONTROLDOWNLINK

Power control interval

powerCtrlInterval (INT) 0..31 s

Power Control StrategyMeasurement Averaging


threshold

Actual average samples

Nx samplesLess than Px samples exceed thresholdNo power change triggered

Nx samplesPx samples are equal to or exceed thresholdPower change triggeredSignal level thresholds

pcUpperThresholdLevelDL/UL (UDR/UUR) -110..-47 dBmpcLowerThresholdLevelDL/UL (LDR/LUR) -110..-47 dBm

Signal quality thresholds

pcUpperThresholdQualDL/UL (UDR/UUR) 0..7pcLowerThresholdQualDL/UL (LDR/LUR) 0..7

Number of average samples (for each threshold)

Nx 1..32Px 1..32

Power change step size estimation

Power Control StrategyTriggering


Exceeded threshold Action Reason

pcUpperThresholdLevelDL BTS power decrease Signal levelpcLowerThresholdLevelDL BTS power increase Signal levelpcUpperThresholdLevelUL MS power decrease Signal levelpcLowerThresholdLevelUL MS power increase Signal level

pcUpperThresholdQualDL BTS power decrease Signal qualitypcLowerThresholdQualDL BTS power increase Signal qualitypcUpperThresholdQualUL MS power decrease Signal qualitypcLowerThresholdQualUL MS power increase Signal quality

Power Control StrategyScenarios


pcLowerThresholdsLevelDL/UL

Power control triggeredUL: Power increase of MSDL: Power increase of BTS

RXLEV_DL/UL > pcLowerThresholdLevelDL/UL - 2 powerIncrStepSize

Yes

Fixed step size

PWR_INCR_STEP = powerIncrStepSize

No

Variable step size

PWR_INCR_STEP = pcLowerThresholdLevelDL/UL –RXLEV_UL/DL

Actual receive level RXLEV_DL/UL

Power Increase Due to Signal LevelFor MS & BTS


pcUpperThresholdsLevelDL

Power control triggeredPower decrease

Yes

Fixed step size

PWR_DECR_STEP = powerDecrStepSize

No

Variable step size

PWR_DECR_STEP = Min (RXLEV_DL –pcUpperThresholdLevelDL, 10)

Actual received level RXLEV_DL

RXLEV_DL < pcUpperThresholdLevelDL + 2 powerDecrStepSize OR

variableDLStepUse (VDLS) = No

Power Decrease Due to Signal LevelFor BTS


pcUpperThresholdsLevelUL

Power control triggeredPower decrease

Yes

Fixed step size

PWR_DECR_STEP = powerDecrStepSize

No

Variable step size

PWR_DECR_STEP = RXLEV_UL –pcUpperThresholdLevelUL

Actual received level RXLEV_UL

RXLEV_UL < pcUpperThresholdLevelUL + 2 powerDecrStepSize

Power Decrease Due to Signal LevelFor MS


pcLowerThresholdsQualDL/UL

Power control triggeredUL: Power increase of MSDL: Power increase of BTS

Actual receive quality RXQUAL_DL/UL

Variable step size based on actual quality

PWR_INCR_STEP = (1 + Max (0,QUAL)) * powerIncrStepSize

QUAL = RXQUAL_DL/UL – pcLowerThresholdQualDL/UL

Step size based on actual level

Take algorithm for power increase due to signal level

Take largest step size

Power Increase Due to Signal QualityFor MS & BTS


pcUpperThresholdsQualDL/UL

Power control triggered

Actual received quality RXQUAL_DL/UL

Actual RXLEV_DL/UL – pcLowerThresholdLevelDL/UL < 6 dB

Yes No

No power decrease

Avoid ping pong effect

Power decrease

Take algorithm for power decrease due to signal level(different for MS & BTS power decrease)

Power Decrease Due to Signal QualityFor MS & BTS with No Power Optimization


Lower Level Upper Level

Upper Quality

Lower Quality

Power decrement due to quality Power increment due to level

Power Decrease Due to Signal QualityPing Pong Effect


Power Control Summary

Lower Level Upper Level

Upper Quality

Lower Quality

No actionPower decreasedue to level

Power increasedue to quality

Power increasedue to levelor quality

Power increasedue to quality

Power decreasedue to levelor quality

Power increasedue to level

Power decreasedue to quality6 dB

Power increasedue to level

Qual 0

Qual 7

-110 dBm -47 dBm


Maximum decrement step size in dependence on signal quality

pwrDecrLimitBand0 (PD0) 0..38 dB used for quality 0pwrDecrLimitBand1 (PD1) 0..38 dB used for quality 1pwrDecrLimitBand2 (PD2) 0..38 dB used for quality 2

and worse

Enable power decrement below optimum level for UL

powerDecrQualFactor (PDF) 0,1 enabled, if set to 1

Activation of power optimisation

optimumRxLevDL (LEVD) -109..-47 dBmoptimumRxLevUL (LEV) -109..-47 dBm

Power Control ParametersPower Optimization

TRX Level

BTS Level


Power decrease step size for MS

PWR_DECR_STEP = Min (pwrDecrLimit, Max (A,B))

A = Max (0, RXLEV_UL - optimumRxLevUL)

B = (powerDecrQualFactor + Max (0,QUAL)) * powerDecrStepSize

with QUAL = pcUpperThreshold - <RXQUAL_UL>

Term A: Would bring actual receive level exactly to optimum level

Term B: Considers difference between average receive quality and threshold quality

Power decrease step size for BTS

PWR_DECR_STEP = Min [Min (pwrDecrLimit, Max (A,B)),10]

Power decrease step size for MS

PWR_DECR_STEP = Min (pwrDecrLimit, Max (A,B))

A = Max (0, RXLEV_UL - optimumRxLevUL)

B = (powerDecrQualFactor + Max (0,QUAL)) * powerDecrStepSize

with QUAL = pcUpperThreshold - <RXQUAL_UL>

Term A: Would bring actual receive level exactly to optimum level

Term B: Considers difference between average receive quality and threshold quality

Power decrease step size for BTS

PWR_DECR_STEP = Min [Min (pwrDecrLimit, Max (A,B)),10]

Power Decrease Due to Signal QualityWith Power Optimization


MAX_INTF_LEV = max (min (RXLEV_UL + msTxPrwMax - MS_TXPWR, optimumRxLevUL),RXLEV_UL + msTxPrwMin - MS_TXPWR) - cnThreshold

MAX_INTF_LEV = max (min (AV_RXLEV_NCELL (n) - rxLevBalance, optimumRxLevUL (n)),AV_RXLEV_NCELL (n) - rxLevBalance +msTxPrwMin (n) - msTxPrwMax (n)) - cnThreshold (n)

Call set up or intra cell handover

Inter cell handover

Modified maximum acceptable interference level

TCH AllocationWith Power Optimization


Optimization of MS Power LevelIn call setup

MS_TXPWR_OPT =

MsTxPwrMaxGSM(BTS) - MAX( 0,( RXLEV_UL - OptimumRxLevUL ))

• RXLEV_UL is measured during the initial signalling period of call set-up

• RXLEV_UL is the uplink signal level when the mobile station is transmitting at the maximum RF power that an MS is permitted to use on a channel in the serving cell.


Optimization of MS Power LevelIntra-BSC handover

• When the handover to be performed is an inter-cell handover, the optimisation is controlled by the parameter MS pwr opt level(n).

• When the handover to be performed is an intra-cell handover, the optimisation is controlled by the parameter optimum RX level uplink.

MS_TXPWR_OPT(n) =

MsTxPwrMaxGSM(ADJ)(n) - MAX(0,(AV_RXLEV_NCELL(n) - MsPwrOptLevel(n)))

• AV_RXLEV_NCELL(n) is the averaged downlink signal level of the adjacent cell (n)

• MsPwrOptLevel(n) (POPT) is set for each adjacent cell

MS_TXPWR_OPT = MsTxPwrMaxGSM(BTS) -

MAX( 0,(AV_RXLEV_UL_HO+(MsTxPwrMaxGSM(BTS)-MS_TXPWR)-OptimumRxLevUL) )

• OptimumRxLevUL (LEV) is set for every TRX

Inter-Cell

Handover

Intra-Cell

Handover


AMR Power Control

Exceeded threshold Action ReasonAMR Power Control FR PC Lower Threshold DL Rx Qual

BTS power increase Poor DL signal quality

AMR Power Control FR PC Lower Threshold UL Rx Qual

MS power increase Poor UL signal quality

AMR Power Control FR PC Upper Threshold DL Rx Qual

BTS power decrease Good DL signal quality

AMR Power Control FR PC Upper Threshold UL Rx Qual

MS power decrease Good UL signal quality

AMR Power Control HR PC Lower Threshold DL Rx Qual

BTS power increase Poor DL signal quality

AMR Power Control HR PC Lower Threshold UL Rx Qual

MS power increase Poor UL signal quality

AMR Power Control HR PC Upper Threshold DL Rx Qual

BTS power decrease Good DL signal quality

AMR Power Control HR PC Upper Threshold UL Rx Qual

MS power decrease Good UL signal quality

AMR FR

AMR HR

Details in chapter on AMR


AMR Progressive Power Control

• AMR PPC provides mechanism to change quality thresholds depending on used power level so that it favours increase of power with low power levels and avoid increase of power with higher power levels. Following results are striven by this:

• Better power distribution - introducing less interference to the network

• Better quality distribution - yielding to better speech codec distribution

Details in chapter on AMR

cap06 power control

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