Uplink power controlV15.11.0

Uplink power control determines the power for PUSCH, PUCCH, SRS, and PRACH transmissions. It reduces intra-cell and inter-cell interference, as well as the UE power consumpition.

Power control is based on pathloss. A UE maintains at most 4 pathloss estimates per serving cell for all PUSCH/PUCCH/SRS transmissions.

Definition: PUSCH/PUCCH/SRS/PRACH transmission occasion i:
a slot index within a frame with system frame number SFN, a first symbol S within the slot, and a number of consecutive symbol L.

Uplink power control has the general formula of , where

  • PCMAX is the UE configured maximum output power.
  • P0 is a pre-configured received power target assuming full pathloss compensation.
  • α between 0 and 1 is the fractional power control factor.
    • α = 0 means no pathloss compensation, i.e. all UEs transmit at the same power
    • α = 1 means full pathloss compensation, which tries to achieve same received power for all UEs
  • Δ is a closed loop power control component which allows base station to adjust the transmit power at UE. This is based on Transmit Power Control (TPC) command from Downlink Control Information (DCI) on the PDCCH.

Generic Uplink Power Control Example

PCMAX [dBm]P0 [dBm]αPathloss [dB]Ptx [dBm]Prx [dBm]
0.0 dBm-100.0 dBm

Power control for Physical Uplink Shared Channel (PUSCH)

If a UE transmits a PUSCH on active UL BWP b of carrier f of serving cell c using parameter set configuration with index j and PUSCH power control adjustment state with index l, the UE determines the PUSCH transmission power PPUSCH,b,f,c(i,j,qd,l) in PUSCH transmission occasion i as:

  • j=0: MSG3 in random access, or PUSCH when 0-PUSCH-AlphaSet is not provided.
  • j=1: Configured grant.
  • j=2 to 31: Dynamic grant.
: provided by higher layers, corresponds to the total power reamp-up requested by higher layers from the first to the last random access preamble: the bandwidth of the PUSCH resoure assignment expressed in number of RBs for the first PUSCH transmission on active UL BWP b: the power adjustment of first PUSCH transmission on active UL BWP b
ParameterDetails
PCMAX,f,c(i)the UE configured maximum output power defined in TS 38.101 for carrrier f of serving cell c in PUSCH transmission occasion i.
P0_PUSCH,b,f,c(j)nominal UE transmit power, represents the transmit power when allocated a single Resource RB with 15kHz subcarrier spacing and 0 dB pathloss.
P0_PUSCH,b,f,c(j) = P0_NOMINAL_PUSCH,f,c(j) + P0_UE_PUSCH,b,f,c(j), where j∈{0,1,...,J-1}

P0_NOMINAL_PUSCH,f,c(j)j = 0 = P0_PRE + ΔPREAMBLE_MSG3:
j = 1 = p0-NominalWithoutGrant from PUSCH-PowerControl, or P0_NOMIMAL_PUSCH,f,c(0) if not provided.
j ≥ 2= p0-NominalWithGrant from PUSCH-ConfigCommon, or P0_NOMINAL_PUSCH,f,c(0) if not provided. It's a cell specific power level applicable to all UEs within the cell.
P0_UE_PUSCH,b,f,c(j)j = 0 = 0
j = 1= p0 from p0-PUSCH-Alpha in ConfiguredGrantConfig that provides an index P0-PUSCH-AlphaSetId to a set of P0-PUSCH-AlphaSet, which is defined in PUSCH-PowerControl, for active UL BWP b of carrier f of serving cell c.
j ≥ 2= a set of p0 in P0-PUSCH-AlphaSet indicated by a respective set of p0-PUSCH-AlphaSetId for active UL BWP b of carrier f of serving cell c. It's a UE specific offset to adjust individual UE performance.
μnumerology, μ of {0, 1, 2, 3} corresponds to subcarrier spacing of {15, 30, 60, 120} kHz. Higher numerology has wider bandwidth, hence requires higher power.
the bandwidth of the PUSCH resource assignment expressed in number of resource blocks for PUSCH transmission occasion i on active UL BWP b of carrier f of serving cell c.
αb,f,c(j)j = 0 = msg3-Alpha from Alpha in PUSCH-PowerControl, or 1 if not provided.
j = 1 = alpha from p0-PUSCH-Alpha in ConfiguredGrantConfig providing an index P0-PUSCH-AlphaSetId to a set of P0-PUSCH-AlphaSet for active UL BWP b of carrier f of serving cell c.
j ≥ 2 = a set of alpha in P0-PUSCH-AlphaSet indicated by a respective set of p0-PUSCH-AlphaSetId for active UL BWP b of carrier f of serving cell c.
PLb,f,c(qd)downlink pathloss estimate in dB calculated by the UE using reference signal (RS) index qd for the active DL BWP, of carrier f of serving cell c.
PLb,f,c(qd) = referenceSignalPower – higher layer filtered RSRP
, where referenceSignalPower is provided by higher layers, and RSRP is defined in TS 38.215 for the reference serving cell and the higher layer filter configuration provided by QuantityConfig for the reference serving cell.
referenceSignalPowerno periodic CSI-RS reception = ss-PBCH-BlockPower in ServingCellConfigCommon or ServingCellConfigCommonSIB.
with periodic CSI-RS reception = ss-PBCH-BlockPower, or SSB transmission power + powerControlOffsetSS in NZP-CSI-RS-Resource. powerControlOffsetSS = 0 dB if not provided.
ΔTF,f,b,c(i)= 0 if the PUSCH transmission is over more than one layer, else,
= , where KS is provided by deltaMCS in PUSCH-PowerControl for each UL BWP b of each carrier f and serving cell c.
BPRE (Bits per resource element)PUSCH with UL-SCH data = , where C is a number of transmitted code blocks, Kr is a size for code block r, and NRE is a number of resource elements determined as
, where
is a number of symbols for PUSCH transmission occasion i on active UL BWP b of carrier f of serving cell c
is a number of subcarriers excluding DM-RS subcarriers and phase-tracking RS samples in PUSCH symbol j,
PUSCH without UL-SCH data (CSI only) = , where Qm is the modulation order and R is the target code rate.
fb,f,c(i,l)tpc-Accumulation not provided = is the PUSCH power control adjustment state
tpc-Accumulation is provided =
MSG3 = , where l = 0
δmsg2,b,f,cTPC command value from MSG2
ΔPrampup,b,f,ccorresponds to the total power ramp-up applied to random access preamble

Table 7.1.1-1: Mapping of TPC Command Field to absolute and accumulated values
TPC command fieldAccumulated [dB]Absolute [dB]
0-1-4
10-1
211
334

PUCCH, SRS and PRACH to be added