EGPRS Downlink Power Control

GSM/EDGE BSS, Rel. RG20(BSS), Operating Documentation, Issue 07

Feature description

RG301666: (E)GPRS Downlink Power Control

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Issue 01Approval Date 2011-08-18

Confidential

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Id:0900d805808a061aConfidential

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Table of contentsThis document has 18 pages.

1 Introduction to the feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.1 Software requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.2 Hardware requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.1 Functional details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5 System impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115.1 Relations to other features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

6 User interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126.1 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126.2 MML commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.3 Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.4 Measurements and counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

7 Activating and configuring the feature . . . . . . . . . . . . . . . . . . . . . . . . . . 157.1 Activating the (E)GPRS Downlink Power Control feature . . . . . . . . . . . 167.2 Deactivating the (E)GPRS Downlink Power Control feature . . . . . . . . . 17

8 Terms and Abbreviations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 Z. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

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List of tablesTable 1 Software requirements for different network elements . . . . . . . . . . . . . . 7Table 2 Hardware requirements for different network elements . . . . . . . . . . . . . . 7Table 3 Parameters for the feature (E)GPRS Downlink Power Control . . . . . . . 12Table 4 New Counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

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RG301666: (E)GPRS Downlink Power Control Introduction to the feature

Id:0900d805808a05f6Confidential

1 Introduction to the featureThe feature RG301666: (E)GPRS Downlink Power Control is introduced to decrease the interference in the system that is caused due to progressive introduction of packet switched (PSW) services in GSM networks.

(E)GPRS Downlink Power Control feature assists in controlling the downlink transmit power on (E)GPRS timeslots. The power control in DL transmission is done on a block-by-block basis depending on the receivers channel conditions. That is, if an MS is in good radio conditions, the DL transmit power for this MS can be reduced. And if the MS is in bad radio conditions, then the DL transmit power for this MS can be increased. DL transmit power is reduced in such a way that the MSs throughput is not negatively impacted, or at least not impacted significantly. This not only reduces the interference in the radio network, but also reduces the BTS Power consumption.

This feature is controlled by BSC level ON/OFF license key.

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Benefits

2 BenefitsThe feature (E)GPRS Downlink Power Control provides the following benefits to the operator.

Transmit power reduction helps in reducing the interference in the network and hence the mobiles experience better radio conditions. Thus, the spectral efficiency in the network is improved.

The reductions in the DL transmit power results in less BTS power consumption. DL transmit power control for EGPRS maintains voice quality when the data usage

grows up.

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RG301666: (E)GPRS Downlink Power Control Requirements


3 RequirementsFollowing are the requirements for the feature (E)GPRS Downlink Power Control:

3.1 Software requirementsThe (E)GPRS Downlink Power Control feature requires the following Software:

3.2 Hardware requirementsThe (E)GPRS Downlink Power Control feature requires the following Hardware:

Network element Required software release

BSC S15 EP2.1

BTS BTS Plus - Gemini 2.1 buildTable 1 Software requirements for different network elements

Network element Required hardware

BSC PCU2

BTS Any of the following BTS site types:

UltraSite Flexi Edge Flexi Multiradio BTSplus

Table 2 Hardware requirements for different network elements

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Functional description

4 Functional descriptionIn the existing Abis L1 interface the DL PCU (master) data frames contain a Downlink Power Control field which indicates the DL power level to BTS. Currently PCU sets this field based on PMAX (= maximum power level on the TRX) and the value remains the same unless the parameter value is changed by the operator.

In the feature (E)GPRS Downlink Power Control PCU controls the DL transmit power with the same Downlink Power Control field but the field value is now changed on a DL RLC block-by-block basis.

4.1 Functional detailsThe feature (E)GPRS Downlink Power Control can be activated on a segment level.

Once the feature is activated, PCU starts to apply the (E)GPRS DL Power Control algo-rithms for the DL TBFs.

GPRS DL Power Control algorithmThe GPRS DL Power Control algorithm controls the DL transmission power level of the GPRS DL TBFs. In the beginning of the DL TBF, the data transmission is started with the default power level (user configurable) and then the power level is either decreased or increased based on the I_LEVEL measurements received in the Packet Downlink Ack/Nack (PDAN) messages.

The default DL transmit power level is determined by the DL PC Default Power Reduction parameter which determines the default power reduction from the maximum power level (PMAX).

PCU uses the default DL transmit power for the DL TBF until the first PDAN message is received from the MS.

The I_LEVEL, measured by the MS, tells what is the interference level on the data channels with respect to the C_VALUE measured on the BCCH carrier. In other words, the I_VALUE tells the channel quality in terms of Carrier signal / Interference signal level (C/I) on the BCCH carrier (C/I(BCCH)). With the help of this variable, we can estimate MS channel quality of the DL transmission on the TRX where the MS is allocated. Based on the C/I(MS) value PCU decides whether the power level should be reduced, increased or kept the same. C/I(MS) can be determined by the following formula:

C/I(MS) = MAX{ C/I(BCCH) Non_BCCH_Layer_Offset(BTS) PR(TBF) ; 0 dBm}.

Where Non_BCCH_Layer_Offset is a BTS existing parameter which determines whether the predefined offset margin is used when evaluating the signal level of the non BCCH layer and PR(TBF) is the TBF's current power reduction.

If C/I(MS) is larger than DL PC C/I Target parameter value and if PCU has not changed the power level for the TBF since the PDAN was polled (the time interval between two subsequent power changes should be at least RLC RTT), then PCU reduces the power level of this DL TBF by 2 dBm. That is, the power reduction, PR(TBF), is increased by 2 dBm as follows:

PR(TBF) = MIN{ PR(TBF) + 2 dBm, DL PC Window Size }.

If C/I(MS) is smaller than DL PC C/I Target parameter value and if PCU has not changed the power level for the TBF since the PDAN was polled (the time interval between two subsequent power changes should be at least RLC RTT), then PCU increases the power level of this DL TBF. That is, the power reduction, PR(TBF), is reduced as follows:

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RG301666: (E)GPRS Downlink Power Control Functional description


PR(TBF) = MAX{ PR(TBF) [DL PC C/I Target C/I(MS)], 0 dBm }.

If PCU does not receive a valid I_LEVEL measurement in the PDAN message, then the TBFs power level is not changed.

Note that by these formulas the GPRS DL Power Control algorithm tries to keep the mobiles C/I conditions on the given target level.

EGPRS DL Power Control algorithmThe EGPRS DL Power Control algorithm controls the DL transmission power level of the EGPRS DL TBFs. Similar to GPRS, the data transmission is started with the default power level (user configurable) but in EGPRS the power level is either decreased or increased based on the 8-PSK MEAN_BEP measurements received in the EGPRS Packet Downlink Ack/Nack (EPDAN) messages.

The default DL transmit power is determined by the DL PC Default Power Reduction parameter which determines the default power reduction from the maximum power level (PMAX).

PCU uses the default DL transmit power for the DL TBF until the first EPDAN message is received from the MS.

The 8-PSK MEAN_BEP, measured by the MS tells about the channel quality of the DL transmission on the TRX, where the MS is allocated. Based on the received BEP mea-surements PCU decides whether the power level should be reduced, increased or kept the same.

If 8-PSK MEAN_BEP is larger than DL PC PSK8 BEP Target parameter value and if PCU has not changed the power level for the TBF since the EPDAN was polled (the time interval between two subsequent power changes should be at least RLC RTT), then PCU reduces the power level of this DL TBF by 2 dBm. That is, the power reduction, PR(TBF), is increased by 2 dBm as follows:

PR(TBF) = MIN{ PR(TBF) + 2 dBm, DL PC Window Size }.

If 8-PSK MEAN_BEP is smaller than DL PC PSK8 BEP Target parameter value and if PCU has not changed the power level for the TBF since the EPDAN was polled (the time interval between two subsequent power changes should be at least RLC RTT), then PCU increases the power level of this DL TBF. That is, the power reduction, PR(TBF), is reduced as follows:

PR(TBF) = MAX{ PR(TBF) [(int)( (DL PC PSK8 BEP Target 8-PSK MEAN_BEP + 1) / 3 ) x 2 dBm], 0 dBm }.

If 8-PSK MEAN_BEP equals to DL PC PSK8 BEP Target parameter value, then the TBFs power level is not changed.

Note that by these formulas the EGPRS DL Power Control algorithm tries to keep the mobiles BEP measurement on the given target level.

Relation to PMAX and PMIN parametersThe existing Max Power Level parameters (Bs Tx Pwr Max and BS Tx Pwr Max1x00) define the maximum power level (PMAX) as an attenuation from the peak power of the TRX.

Similarly the existing Min Power Level parameter (BS Tx Pwr Min) defines the minimum power level (PMIN) as an attenuation from the peak power of the TRX.

Since the (E)GPRS DL Power Control algorithm operates within the limits of PMAX and PMIN, the DL PC parameters must satisfy the following rules:

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Functional description

Bs Tx Pwr Max + DL PC Window Size

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RG301666: (E)GPRS Downlink Power Control System impacts

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5 System impactsThis section describes the interaction of (E)GPRS Downlink Power Control feature with other features.

5.1 Relations to other features BTS2013: Baseband (BB) hopping

(E)GPRS DL Power Control feature is activated by the PCU on BCCH TRX when BB Hopping is enabled else the feature is disabled by the PCU on BCCH TRX.

BSS21507: Flexible MCPA TX Power PoolingIn the Flexible MCPA TX Power Pooling feature BTS reduces the PS transmit power by 2 dBm. BTS can do so even if the DL PC feature is enabled.

BSS20958: Energy saving mode for BCCH TRXIn the Energy Saving Mode for BCCH TRX feature BTS reduces the power on BCCH TRX when BB hopping is disabled. However, since BTS does not reduce power on PDTCH channels and since PCU is not applying the (E)GPRS DL Power Control feature on BCCH TRXs when BB hopping is disabled, there is no relation.

BSS20088: Dual Transfer ModePCU applies the (E)GPRS DL Power Control algorithm to DTM TBFs but the power reduction for DTM TBFs should not be larger than 10 dBm.

BSS212288: Downlink Dual Carrier (DLDC)PCU applies (E)GPRS DL Power Control algorithm to DLDC TBFs in such a way that BEP measurements for C1 and C2 are used as an input in the EGPRS Power Control algorithm and then the result, PR(TBF), is applied on both carriers (C1 and C2).

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User interface

6 User interfaceThis chapter is divided into the following sections: Parameters MML commands Alarms Measurements and counters

6.1 ParametersThe following table show the parameters implemented for the feature (E)GPRS Downlink Power Control. The parameters are subject to change.

Name Object Description Range Default value

DL PC C/I Target BSC With this parameter user is able to define the target C/I value for GPRS TBFs. The decision to increase or decrease the DL power level is done against this parame-ter.

0...30 dB, step 1 dB 15 dB

DL PC 8PSK BEP Target BSC With this parameter user is able to define the target 8-PSK BEP value for EGPRS TBFs. The decision to increase or decrease the DL power level is done against this parameter.

0...31, step 1 29

GPRS DL PC Enabled BTS-SEG

With this parameter user is able to activate and deactivate the (E)GPRS DL Power Control feature on a segment level.

GPRS DL PC Disabled (N), GPRS DL PC Enabled (Y)

GPRS DL PC Disabled (N)

DL PC Window Size POC With this parameter user is able to define the window within which the DL transmit power can be varied on the PDTCH chan-nels.

The existing Max Power Level parame-ters (like Bs Tx Pwr Max) define the maximum power level (PMAX) as attenu-ation from the peak power of the TRX. Hence the power attenuation on PDTCH channels can vary within the window of [PMAX; PMAX + DL PC Window Size].

0...10 dBm, step 2 dBm

8 dBm

Table 3 Parameters for the feature (E)GPRS Downlink Power Control

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RG301666: (E)GPRS Downlink Power Control User interface


6.2 MML commandsThe following MML commands are used to handle the feature: The EEM command for modifying the DL PC C/I Target (PCCI) and DL PC

8PSK BEP Target (PCPSK) parameters. The EEO command for displaying the DL PC C/I Target(PCCI) and DL PC

8PSK BEP Target (PCPSK) parameters. The EQV command for modifying the GPRS DL PC Enabled (DLPC) parameter. The EQO command for displaying the GPRS DL PC Enabled (DLPC) parameter. The EUC command for creating the DL PC Window Size(PCWS) and DL PC

Default Power Reduction (PCPOW) parameters with default values. The EQM command for modifying the DL PC Window Size (PCPWS) and DL PC

Default Power Reduction (PCPOW) parameters. The EUO command for displaying the DL PC Window Size (PCPWS) and DL PC

Default Power Reduction (PCPOW) parameters.

6.3 AlarmsThe (E)GPRS Downlink Power Control feature does not introduce any new alarms.

6.4 Measurements and countersThe following measurements and counters are utilized by the feature RG301666: (E)GPRS Downlink Power Control.

DL PC Default Power Reduction

POC With this parameter user is able to define the default power reduction on the PDTCH channels.

PCU uses the default power reduction (that is, the power attenuation in DL direc-tion is PMAX + DL PC Default Power Reduction) in the beginning of the DL TBF until the channel quality measurements are received from MS. This parameter also sets the maximum power reduction level (that is, the power attenuation in DL direction is at maximum PMAX + DL PC Default Power Reduction) if the DL RLC block carries USF to some other MS (not the one that is receiving the DL data).

0...10 dBm, step 2 dBm

4 dBm

Name Object Description Range Default value

Table 3 Parameters for the feature (E)GPRS Downlink Power Control (Cont.)

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User interface

Counters for: 072 Packet Control Unit Measurement

Counter Number

DL PC RLC/MAC BLOCKS SENT 072267

DL PC REDUCTION STEP SUM 072268

Table 4 New Counters

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RG301666: (E)GPRS Downlink Power Control Activating and configuring the feature


7 Activating and configuring the featureThis chapter provides the procedures to operate (E)GPRS Downlink Power Control feature.

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Activating and configuring the feature

7.1 Activating the (E)GPRS Downlink Power Control featurePrerequisiteTo operate the feature, the license for the feature (E)GPRS Downlink Power Control must be installed.

Following are the steps to activate the feature

1 (E)GPRS DL Power Control feature licence is installed and feature state is changed to ON or CONF using the command W7M. ZW7M:FEA=3460:ON;

2 Check the license status of the feature with the command W7IZW7I:FEA,FULL:FEA=3460;

3 Enable the parameter GPRS DL PC ENABLED using the command EQV.ZEQV:SEG=:DLPC=Y:;

g The feature gets activated with default values for feature related parameters. The parameter values can be changed.End

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RG301666: (E)GPRS Downlink Power Control Activating and configuring the feature


7.2 Deactivating the (E)GPRS Downlink Power Control featurePrerequisiteThe feature (E)GPRS Downlink Power Control deactivates when the licence expires or when the feature state is set (by user) to OFF.

1 Disable the parameter GPRS DL PC ENABLED using the command EQV.ZEQV:SEG=:DLPC=N:;;

2 Turn the license of the feature to OFF using the command W7MZW7M:FEA=3460:OFF;

3 Check the license status of the feature using the command W7IZW7I:FEA,FULL:FEA=3460;

End

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Terms and Abbreviations

8 Terms and Abbreviations

0 ZBB Baseband

BCCH Broadcast Control Channel

BEP Bit Error Probability

C/I Carrier signal level / Interference signal level

DL Downlink

DLPC Downlink Power Control

DTM Dual Transfer Mode

EGPRS Enhanced General Packet Radio Service

EPDAN EGPRS Packet Downlink Ack/Nack message

GPRS General Packet Radio Service

MS Mobile Station

PDAN Packet Downlink Ack/Nack message

PCU Packet Control Unit

PDTCH Packet Data Traffic Channel

PMAX Maximum transmit power level determined by the existing parameter: BS TX pwr min.

PMIN Minimum transmit power level determined by the existing parameters: BS TX pwr max, BS TX pwr max1x00.

PR Power Reduction

RFM Radio Frquency Module

RLC Radio Link Control

RTT Round Trip Time

TBF Temporary Block Flow

TSL Time Slot

USF Uplink State Flag

RG301666: (E)GPRS Downlink Power Control Table of contentsList of tables1Introduction to the feature2Benefits3Requirements3.1Software requirements3.2Hardware requirements

4Functional description4.1Functional details

5System impacts5.1Relations to other features

6User interface6.1Parameters6.2MML commands6.3Alarms6.4Measurements and counters

7Activating and configuring the feature7.1Activating the (E)GPRS Downlink Power Control feature7.2Deactivating the (E)GPRS Downlink Power Control feature

Terms and Abbreviations0 Z

Documents

EGPRS Downlink Power Control