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5G NR Uplink Power Control Procedure | Power Control in 5G NR

This page describes 5G NR Uplink Power Control Procedure used between UE and gNB. The uplink power control procedure determines transmit power of the different uplink physical channels (PUCCH, PUSCH) or signals (SRS, PRACH). The equations and IEs (Information Elements) are also mentioned.

Introduction:
In wireless systems it is often required to either increase or decrease the transmit power of UE or mobile device. This is known as uplink power control. Transmit power is increased to meet required SNR or BER at the gNB (or base station or eNB). Transmit power is decreased to minimize co-channel interference of the 5G system. There are two types of power controls i.e. open loop power control and closed loop power control. Refer Open loop power control vs Closed loop power control >> for more information.

• ConfiguredGrantConfig IE defines "powerControlLoopToUse" field.
• The IE Alpha defines possible values for uplink power control.
• In 5G NR, power control procedure has been modified to work for all the numerologies or subcarrier spacing/other system parameters.
• The term 2μ in following equations support different 5G NR numerologies >>. The μ ranges from 0 to 5 to support various NR numerologies.
• There is field called "TPC command" which indicates how much power should be reduced or increased. This is mentioned below in the table.

PUSCH | Physical Uplink Shared Channel

Following equation-1 mentions various parameters needed in order to control the power of PUSCH channel.

PUSCH power control

Following power control IE (Information Element) is used by RRC for PUSCH.

PUSCH-PowerControl ::=      SEQUENCE {
tpc-Accumulation     ENUMERATED { disabled }
msg3-Alpha      Alpha
p0-NominalWithoutGrant     INTEGER (-202..24)
p0-AlphaSets      SEQUENCE (SIZE (1..maxNrofP0-PUSCH-AlphaSets)) OF P0-PUSCH-AlphaSet
pathlossReferenceRSToAddModList     SEQUENCE (SIZE (1..maxNrofPUSCH-PathlossReferenceRSs)) OF PUSCH-PathlossReferenceRS

pathlossReferenceRSToReleaseList     SEQUENCE (SIZE (1..maxNrofPUSCH-PathlossReferenceRSs)) OF PUSCH-PathlossReferenceRS-Id

twoPUSCH-PC-AdjustmentStates      ENUMERATED {twoStates}
deltaMCS      ENUMERATED {enabled}
sri-PUSCH-MappingToAddModList      SEQUENCE (SIZE (1..maxNrofSRI-PUSCH-Mappings)) OF SRI-PUSCH-PowerControl
sri-PUSCH-MappingToReleaseList      SEQUENCE (SIZE (1..maxNrofSRI-PUSCH-Mappings)) OF SRI-PUSCH-PowerControlId
}

P0-PUSCH-AlphaSet ::=      SEQUENCE {
p0-PUSCH-AlphaSetId      P0-PUSCH-AlphaSetId,
p0      INTEGER (-16..15)
alpha      Alpha
}

P0-PUSCH-AlphaSetId ::=      INTEGER (0..maxNrofP0-PUSCH-AlphaSets-1)


PUSCH-PathlossReferenceRS ::=     SEQUENCE {
pusch-PathlossReferenceRS-Id      PUSCH-PathlossReferenceRS-Id,
referenceSignal      CHOICE {
ssb-Index      SSB-Index,
csi-RS-Index      NZP-CSI-RS-ResourceId
}
}

PUSCH-PathlossReferenceRS-Id ::=      INTEGER (0..maxNrofPUSCH-PathlossReferenceRSs-1)


SRI-PUSCH-PowerControl ::=      SEQUENCE {
sri-PUSCH-PowerControlId      SRI-PUSCH-PowerControlId,
sri-PUSCH-PathlossReferenceRS-Id      PUSCH-PathlossReferenceRS-Id,
sri-P0-PUSCH-AlphaSetId      P0-PUSCH-AlphaSetId,
sri-PUSCH-ClosedLoopIndex      ENUMERATED { i0, i1 }
}

SRI-PUSCH-PowerControlId ::=      INTEGER (0..maxNrofSRI-PUSCH-Mappings-1)

BetaOffsets ::=      SEQUENCE {
betaOffsetACK-Index1      INTEGER(0..31)
betaOffsetACK-Index2      INTEGER(0..31)
betaOffsetACK-Index3      INTEGER(0..31)
betaOffsetCSI-Part1-Index1      INTEGER(0..31)
betaOffsetCSI-Part1-Index2      INTEGER(0..31)
betaOffsetCSI-Part2-Index1      INTEGER(0..31)
betaOffsetCSI-Part2-Index2      INTEGER(0..31)
}

PUCCH | Physical Uplink Control Channel

Following equation-2 mentions various parameters needed in order to control the power of PUCCH channel.

PUCCH power control

Following power control IE (Information Element) is used by RRC for PUCCH.


PUCCH-PowerControl ::=    SEQUENCE {
deltaF-PUCCH-f0    INTEGER (-16..15)
deltaF-PUCCH-f1    INTEGER (-16..15)
deltaF-PUCCH-f2    INTEGER (-16..15)
deltaF-PUCCH-f3    INTEGER (-16..15)
deltaF-PUCCH-f4    INTEGER (-16..15)
p0-Set   SEQUENCE (SIZE (1..maxNrofPUCCH-P0-PerSet)) OF P0-PUCCH
pathlossReferenceRSs   SEQUENCE (SIZE (1..maxNrofPUCCH-PathlossReferenceRSs)) OF PUCCH-PathlossReferenceRS
twoPUCCH-PC-AdjustmentStates   ENUMERATED {twoStates}
...
}

P0-PUCCH ::=   SEQUENCE {
p0-PUCCH-Id   P0-PUCCH-Id,
p0-PUCCH-Value   INTEGER (-16..15)
}

P0-PUCCH-Id ::=    INTEGER (1..8)

PUCCH-PathlossReferenceRS ::=   SEQUENCE {
pucch-PathlossReferenceRS-Id   PUCCH-PathlossReferenceRS-Id,
referenceSignal   CHOICE {
ssb-Index   SSB-Index,
csi-RS-Index   NZP-CSI-RS-ResourceId
}
}

SRS | Sounding Reference Signal

Following equation-3 mentions various parameters needed in order to control the power of SRS signal.

SRS power control

SRS-config IE uses "srs-PowerControlAdjustmentStates" field.

PRACH | Physical random access channel

Following equation-4 mentions various parameters needed in order to control the power of PRACH channel. PREAMBLE_POWER_RAMPING_STEP field is used during "Random Access Preamble transmission".

PRACH power control

Following is the contents of random access response grant field.

5G NR Random Access Response Grant Fields

Following table mentions meaning of TPC command field in dB value.


TPC command value (in dB)
0 -6
1 -4
2 -2
3 0
4 2
5 4
6 6
7 8


The total UE transmit power is defined as the sum of the linear values of UE transmit powers for PUSCH, PUCCH, PRACH, and SRS. Also refer uplink timing control procedure >> used in 5G NR.

References

• Section 7: uplink power control in 3GPP TS 38.213 V15.2.0 (2018-06), (Release 15)
• 3GPP TS 38.331 V15.2.0 (2018-06), (Release 15), RRC protocol specification


5G NR Numerology | 5G NR Terminology


5G NR Control channels | 5G NR Traffic Channels | 5G NR Reference Signals and sequences


5G TECHNOLOGY RELATED LINKS

This 5G tutorial also covers following sub topics on the 5G technology:
5G basic tutorial
5G Frequency Bands
5G millimeter wave tutorial
5G mm wave frame
5G millimeter wave channel sounding
Difference between 4G and 5G
5G testing and test equipments
5G network architecture
5G NR Physical layer
5G NR MAC layer
5G NR RLC layer
5G NR PDCP layer

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