08 OEO107030 LTE ERAN6.0 Power Control Feature ISSUE1.00

LTE eRAN6.0 Power Control Feature

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LTE systems use the Orthogonal Frequency Division Multiple Access (OFDMA) technique on the downlink and the Single Carrier Frequency Division Multiple Access (SC-FDMA) technique on the uplink. With these techniques, the subcarriers of UEs in a cell are orthogonal. Power control compensates for path loss and shadow fading and counteracts interference between cells. In LTE systems, power control is performed on eNodeBs and UEs.

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Downlink power control is achieved through fixed power assignment or dynamic power control.

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Fixed power assignment 

Fixed power assignment is applicable to the cell-specific reference signal, synchronization signal, PBCH, PCFICH, and the PDCCH and PDSCH that carry common information of the cell. Users configure fixed power based on channel quality. The configured power must meet the requirements for the downlink coverage of the cell.

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Dynamic power control 

Dynamic power control is applicable to the PHICH and the PDCCH and PDSCH that carry dedicated information sent to UEs. Dynamic power control lowers interference, expands cell capacity, and increases coverage while meeting users' QoS requirements. However, these channels can also support fix power assignment, and in fact, this is our recommendation because the AMC function can also meet the requirement of QoS



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The cell-specific reference signal is transmitted in all downlink subframes. The signal serves as a basis for downlink channel estimation, which is used for data demodulation.

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The power for the cell-specific reference signal is set through the ReferenceSignalPwr parameter, which indicates the Energy Per Resource Element (EPRE) of the cell-specific reference signal.

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PB indicator the power ratio between type B symbol and type A symbol, which is specified by 3GPP protocol Pb

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Symbol B/ Symbol A 1 ANT port

2 or 4 ANT ports

0

1

5/4

1

4/5

1

2

3/5

3/4

3

2/5

1/2

Related command: MOD PDSCHCFG



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Pb determine the RS occupation of total power, Pb=1 indicate the RS power is 9.4% of total power



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The synchronization signal is used for cell search and system synchronization. There are two types of synchronization signals, the Primary Synchronization Channel (P-SCH) and the Secondary Synchronization Channel (S-SCH).

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The offset of the power for the P-SCH and S-SCH against the power for the cell-specific reference signal is set through the SchPwr parameter.



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On the PBCH, broadcast messages are sent in each frame. The messages carry the basic system information of the cell, such as the cell bandwidth, antenna configuration, and frame number.

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The offset of the power for the PBCH against the power for the cell-specific reference signal is set through the PbchPwr parameter.

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The PCFICH carries the number of OFDM symbols used for PDCCH transmission in a subframe. The PCFICH is always mapped to the first OFDM symbol of each subframe.

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The power for the PCFICH is set through the PcfichPwr parameter, which indicates an offset of the power for the PCFICH against the power for the cell-specific reference signal.





Parameters

Description

PcfichPwr

Indicates the offset of the PCFICH transmit power relative to the reference signal power

PbchPwr

Indicates the offset of the PBCH transmit power relative to the reference signal power.

SCH power

Indicates the offset of the transmit power for the cell synchronization signals relative to the reference signal power.

DbchPwr

Indicates the offset of the transmit power for broadcast information on the PDSCH channel relative to the reference signal power.

PchPwr

Indicates the offset of the transmit power for the paging information on the PDSCH channel relative to the reference signal power.

RaRspPwr

Indicates the offset of the transmit power for the random access responses on the PDSCH channel relative to the reference signal power.



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Power control for the PHICH is set through the DlPcAlgoSwitch parameter

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When the PhichInnerLoopPcSwitch parameter under DlPcSwitch is set to ON, the transmit power for the PHICH is periodically adjusted to adapt to change in path loss and shadow shading according to the difference between the estimated SINRRS and SINRTarget.

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When the switches PhichInnerLoopPcSwitch under the DlPcSwitch parameter are set to OFF, the power for PHICH is set through the PwrOffset parameter, which indicates an offset of the power for the PHICH related to the RS power



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When PDCCH carry the following dedicate info, power control should be performed to ensure the receive reliability 

Uplink scheduling information (DCI format 0)

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Downlink scheduling information (DCI format 1/1A/1B/2/2A)

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PUSCH/PUCCH TPC commands (DCI format 3/3A)

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Power control for the PDCCH is set using the DlPcAlgoSwitch parameter.

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When the PdcchPcSwitch parameter under DlPcAlgoSwitch is set to ON, the transmit power for the PDCCH is periodically adjusted according to the difference between the measured BLER and BLERTarget. If the measured BLER is greater than BLERTarget, transmit power is increased. Otherwise, transmit power is decreased.

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When the PdcchPcSwitch parameter under DlPcAlgoSwitch is set to OFF, the PDCCH uses fixed power assignment. In this case, the offset of the power for the PDCCH against the power for the cell-specific reference signal is set using the DediDciPwrOffset parameter.



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The presentation of PDCCH power 

Regarding power control for the PDSCH, the OFDM symbols on one slot can be classified into two types. Above table shows the OFDM symbol indexes within a slot where the ratio of the EPRE to the EPRE of RS is denoted by ρA or ρB.

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Power control for the PDSCH determines the EPREs of different OFDM symbols using ρA and ρB. ρA determines the power offset against the power for the RS when there is no reference signal on the PDSCH, and ρB determines the power offset against the power for the cell-specific reference signal when there is a reference signal on the PDSCH.



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Power control mechanism for the PDSCH is related with the following 2 switchs

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DlIcicSwitch: switch for the downlink inter-cell interference coordination (ICIC).

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DlPcAlgoSwitch: switch for the PDSCH power control

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If : 

DL ICIC is used, then the PDSCH power control is disabled, and PDSCH power is setting by the follow command

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DLIcicAlgoSwith is off, and PdschPaAdjSwitch is on, system perform power control

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DLIcicAlgoSwith is Off, and PdschPaAdjSwitch is off, PDSCH power is setting by the follow command





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Be different from DL power control , UL power control is very important for system 

Reduce the interference for the edge cell user if ICIC is not applicable

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Reduce transmit power for UE to save power consumption



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Description of each parameters: 

PCMAX : The maximum transmit power of UE, 23dBm is the default value that

designed in specification 

Po_pre: The target power expected by the eNodeB when the requirements for the

preamble detection performance are met and the PRACH preamble format is 0. The initial value of is set through the PreambInitRcvTargetPwr parameter. 

PL: The downlink path loss estimated by the UE. This value is obtained based on

the Reference Signal Received Power (RSRP) measurement value and the transmit power for the cell-specific reference signal. The Alpha filtering factor for filtering the RSRP measurement values is set through the FilterRsrp parameter. 

 prea mble :

The offset of the power for the current preamble format against

preamble format 0. 

N pre: Number of times that the preamble of the UE is sent before the random access

procedure is successfully completed. 

 step :

The ramping step in power ramping of the preamble. This value is set

through the PwrRampingStep parameter.



Parameters

Description

PwrRampingStep

Indicates the power ramping step for preamble transmission. If access through the PRACH fails after several attempts, the power ramping step needs to be increased to ensure successful access of the UE.

PreambInitRcvTa rgetPwr

Indicates the preamble initial RX target power.

FilterRsrp

Indicates the alpha filtering coefficient used by the UE during RSRP measurement for path loss estimation



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Description of each parameters 

i: The subframe number

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PCMAX : The maximum transmit power of UE, 23dBm is the default value that designed in specification

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M PUSCH (i) : The PUSCH transmission bandwidth(RB number) for the this subframe P o _ PUSCH : The receive power expected by the eNodeB. It is determined by the

eNodeB and reflects the receive power expected by the eNodeB when the requirements for the PUSCH demodulation performance are met. The calculation formula is as follows: P o _ PUSCH 

 P  o _ NOMINAL _ PUSCH

P o _ UE _ PUSCH

P o _ NOMINAL _ PUSCH : is the transmit power for the PUSCH expected by the eNodeB when the correct PUSCH demodulation is ensured. It is set through the P0NominalPUSCH parameter.

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P o _ UE _ PUSCH : is the offset of the power for the UE against . This value reflects the impact of the UE level, service type, and channel quality on the transmit power for the PUSCH.

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 : is the path loss compensation factor. is set using the PassLossCoeff parameter. PL: same meaning & setting as PRACH power control



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TF (i )

:is the offset of the power for the current MCS format against the reference

MCS format. If the DeltaMcsEnabled parameter is set to disable, ΔTF(i) is 0. Otherwise, the impact of ΔTF(i) is considered. 

MPR K S

TF (i)  10log10 ((2

PUSCH

 1)  offset

f (i ): is the adjustment of the PUSCH transmit power of the UE. This value is

obtained based on the TPC information on the PDCCH.


)


Parameters

Description

PassLossCoeff

Indicates the compensation factor for path loss. It is used in UL power control

P0NominalPUSCH

Indicates the nominal P0 value of the PUSCH



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When the InnerLoopPuschSwitch parameter under UlPcAlgoSwitch is set to ON, the eNodeB estimates the transmit power density of the UE and then periodically adjusts the transmit power for the PUSCH to adapt to change in the channel environment based on the difference between the estimated transmit power density and the target transmit power density. If the estimated transmit power density is greater than the target transmit power density, the eNodeB sends a TPC command, ordering a decrease in the transmit power. If the estimated transmit power density is smaller than the target transmit power density, the eNodeB sends a TPC command, ordering an increase in the transmit power.



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When the CloseLoopSpsSwitch parameter under UlPcAlgoSwitch is set to ON, the transmit power for the PUSCH is periodically adjusted to adapt to change in the channel environment based on the difference between the measured IBLER and IBLERTarget. If the measured IBLER is greater than IBLERTarget, the eNodeB sends a TPC command to the UE, ordering an increase in transmit power. If the measured IBLER is smaller than IBLERTarget, the eNodeB sends a TPC command to the UE, ordering a decrease in the transmit power.



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Description of each parameters 

P 0 _ PUCCH : is the receive power expected by the eNodeB. It s determined by the

eNodeB and is the receive power expected by the eNodeB when the requirements for the PUCCH demodulation performance are met. The calculation formula is as follows:

P o _ PUCCH 

 P o _ NOMINAL _ PUCCH 

P o _ UE _ PUCCH

h n CQI , n HARQ : is determined by the PUCCH format. nCQI is the number of information bits of the CQI, and it reflects the impact of the number of CQI bits of the PUCCH on the power. nHARQ is the number of information bits of HARQ, and it reflects the impact of the number of HARQ signaling bits of the PUCCH on the power. It is defined in protocol.

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 F _ PUCCH ( F ) :

reflects the transmission format of the PUCCH on the transmit

power. It is set using the DeltaFPUCCHFormat1, DeltaFPUCCHFormat1b, DeltaFPUCCHFormat2 , DeltaFPUCCHFormat2a, and DeltaFPUCCHFormat2b parameters. 

g (i ) : is the adjustment of the transmit power of the UE's PUCCH, and it is

obtained based on the TPC information on the PDCCH.



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PDCCH power control configuration use the same command as PDSCH configuration.



Parameters

Description

P0NominalPUCCH

Indicates the nominal P0 value of the PUCCH

DeltaFPUCCHFormat1

Indicates the Delta value corresponding to PUCCH format 1

DeltaFPUCCHFormat1b

Indicates the Delta value corresponding to PUCCH format 1b

DeltaFPUCCHFormat2

Indicates the Delta value corresponding to PUCCH format 2

DeltaFPUCCHFormat2a

Indicates the Delta value corresponding to PUCCH format 2a

DeltaFPUCCHFormat2b

Indicates the Delta value corresponding to PUCCH format 2b



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When the InnerLoopPucchSwitch parameter under UlPcAlgoSwitch is set to ON, the transmit power for the PUCCH is periodically adjusted to adapt to change in the channel environment based on the difference between the measured SINR and SINRTarget. If the measured SINR is greater than SINRTarget, the eNodeB sends a TPC command to the UE, ordering an increase in the transmit power. If the measured SINR is smaller than SINRTarget, the eNodeB sends a TPC command to the UE, ordering a decrease in transmit power.



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Parameters Description 

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M SRS

: is the transmission bandwidth of the SRS

P SRS _ OFFSET : is the offset of the SRS power against the PUSCH power. This value is

set through the PsrsOffsetDeltaMcsDisable or PSrsOffsetDeltaMcsEnable parameters based on different DeltaMcsEnabled values.






08 OEO107030 LTE ERAN6.0 Power Control Feature ISSUE1.00

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