Some special regulations about NR Tx power backoff in 38.101 (3GPP 38.101协议关于NR发射功率回退的一些特殊的说明合集)_nr各rb数下的功率回退

Configured transmitted power calculation is well specified in clause 6.2.4. But I would like to illustrate some special power backoff requirements which are easily neglected. (Configured transmitted power 在6.2.4章节给出了明确的公式。通常情况下，考虑Ppowerclass, MPR, AMPR等参数就能算出最终的power要求，不过有些特别的功率回退要求容易被忽略。本节意在介绍一些特殊的power backoff 要求。)

Contents：

1. Lower tolerance reduction
   1.1 Lower tolerance reduction in edge channel bandwidth
   1.2 1.2 Lower tolerance reduction for some FDD bands
2. MPR tweak
   2.1 MPR for Pi/2 BPSK DFT-OFDM
   2.2 delta MPR (∆MPR)
   2.3 More MPR by almost contiguous RB allocation
3. Delta P_powerclass (∆P_powerclass)
   3.1 ∆P_powerclass in case 1
   3.2 ∆P_powerclass in case 2
   3.3 ∆P_powerclass in case 3 (SUL)
   3.4 ∆P_powerclass in case 4 (SRS-AS)
   3.5 ∆P_powerclass in case 5

1. Lower tolerance reduction

1.1 Lower tolerance reduction in edge channel bandwidth

Here is the raw description:

NOTE 3: Refers to the transmission bandwidths confined within F_{UL_low} and F_{UL_low} + 4 MHz or F_{UL_high} – 4 MHz and F_{UL_high}, the maximum output power requirement is relaxed by reducing the lower tolerance limit by 1.5 dB.

1.2 Lower tolerance reduction for some FDD bands

Here is the raw description:

NOTE 4: The maximum output power requirement is relaxed by reducing the lower tolerance limit by 0.3 dB

2. MPR tweak

2.1 MPR for Pi/2 BPSK DFT-OFDM

Here is the raw description:

NOTE 1: Applicable for UE operating in TDD mode with Pi/2 BPSK modulation and UE indicates support for UE capability powerBoosting-pi2BPSK and if the IE powerBoostPi2BPSK is set to 1 and 40 % or less slots in radio frame are used for UL transmission for bands n40, n41, n77, n78 and n79.
The reference power of 0 dB MPR is 26 dBm.

*NOTE 2: Applicable for UE operating in FDD mode, or in TDD mode in bands other than n40, n41, n77, n78 and n79 with Pi/2 BPSK modulation and if the IE powerBoostPi2BPSK is set to 0 and if more than 40 % of slots in radio frame are used for UL transmission for bands n40, n41, n77, n78 and n79. *

2.2 delta MPR (∆MPR)

Please note that ∆MPR calculation should be considered as addition instead of subtraction for the final MPR, i.e. (MPR+∆MPR).(在最大允许发射功率计算的过程中，最终的MPR应该加∆MPR而不是减去，即(MPR+∆MPR))

• If the relative channel bandwidth ≤ 4% for TDD bands or ≤ 3% for FDD band, the ∆MPR is set to zero.
• If the relative channel bandwidth > 4% for TDD bands or > 3% for FDD bands, the ∆MPR is defined in Table 6.2.2-3.

Where relative channel bandwidth = 2*BW_Channel / (F_{UL_low} + F_{UL_high})

n28 (FDD) 703 MHz – 748 MHz
n83 (SUL) 703 MHz – 748 MHz
n40 (TDD) 2300 MHz – 2400 MHz
n97 (SUL) 2300 MHz – 2400 MHz

This requirement seems specific to band n28, n83, n40, n97 as if you look at the NR operating bands , there are more other bands meeting above requirement. (这条要求看起来像是针对于band n28, n83, n40, n97，因为还有很多其他的NR bands符合relative channel bandwidth > 4% for TDD bands or > 3% for FDD bands的情况)

2.3 More MPR by almost contiguous RB allocation

First of all, it must be CP-OFDM waveform. The RB allocation can be regarded as almost contiguous allocation (ACA) when below condition is met:

N_{RB_gap} / (N_{RB_alloc} + N_{RB_gap} ) ≤ 0.25

MPR is increased by below method for ACA:

CEIL{ 10 log₁₀(1 + N_{RB_gap} / N_{RB_alloc}), 0.5 } dB

where CEIL{x,0.5} means x rounding upwards to closest 0.5dB.(意思是向上取0.5 比如CEIL{1.2, 0.5}=1.5 )

BTW, this requirement is also applicable to A-MPR.

3. Delta P_powerclass (∆P_powerclass)

Below is the formula of configured transmitted power and corresponding description of ∆P_powerclass. (specified in 6.2.4 Configured transmitted power)

有点难读，不过可以拆分梳理成下面几点

3.1 ∆P_powerclass in case 1

ΔP_PowerClass = 3dB for a power class 2 capable UE,
ΔP_PowerClass = 6dB for a power class 1.5 UE

• (P-max indicated的情况) when P-max of 23 dBm or lower is indicated; or
• (maxULdc absent的情况) when the field of UE capability maxUplinkDutyCycle-PC2-FR1 is absent and the field of UE capability maxUplinkDutyCycle-PC1dot5-MPE-FR1 is absent and the percentage of uplink symbols transmitted in a certain evaluation period is larger than 50%; or
• (maxULdc-pc2 not absent的情况) when the field of UE capability maxUplinkDutyCycle-PC2-FR1 is not absent and the percentage of uplink symbols transmitted in a certain evaluation period is larger than maxUplinkDutyCycle-PC2-FR1 as defined in TS 38.306 (The exact evaluation period is no less than one radio frame); or
• (maxULdc-pc1.5 not absent的情况) when the field of UE capability maxUplinkDutyCyclePC1dot5-MPE-FR1 is not absent and half the percentage of uplink symbols transmitted in a certain evaluation period is larger than maxUplinkDutyCycle-PC1dot5-MPE-FR1 as defined in TS 38.306 (The exact evaluation period is no less than one radio frame). （注意，maxUplinkDutyCyclePC1dot5-MPE-FR1这里对dutycycle的要求是half）

3.2 ∆P_powerclass in case 2

ΔP_PowerClass = 3dB for a power class 1.5 capable UE

• (P-max indicated的情况) when P-max of between 23 dBm and 26 dB is indicated; or
• (maxULdc absent的情况) when the field of UE capability maxUplinkDutyCycle-PC2-FR1 is absent and the field of UE capability maxUplinkDutyCycle-PC1dot5-MPE-FR1 is absent and the percentage of uplink symbols transmitted in a certain evaluation period is between 25% and 50%; or
• (maxULdc-pc2 not absent的情况) when the field of UE capability maxUplinkDutyCyclePC2-FR1 is not absent and the percentage of uplink symbols transmitted in a certain evaluation period is between maxUplinkDutyCycle-PC2-FR1 and maxUplinkDutyCycle-PC2-FR1/2 as defined in TS 38.306 (The exact evaluation period is no less than one radio frame); or
• (maxULdc-pc1.5 not absent的情况) when the field of UE capability maxUplinkDutyCycle-PC1dot5-MPE-FR1 is not absent and the percentage of uplink symbols transmitted in a certain evaluation period is larger than maxUplinkDutyCycle-PC1dot5-MPE-FR1 as defined in TS 38.306 (The exact evaluation period is no less than one radio frame).

3.3 ∆P_powerclass in case 3 (SUL)

ΔP_PowerClass = 3dB

when the UE is configured with SUL configurations and the requirements of default power class are applied as specified in sub-clause 6.2C.1 on the band where UE indicates power class 2;

3.4 ∆P_powerclass in case 4 (SRS-AS)

ΔP_PowerClass = 3dB

is applied during SRS transmission occasions with usage in SRS ResourceSet set as ‘antennaSwitching’ with configured SRS resources in each SRS resource set(s) consisting of one SRS port when PC2 capable UE with txDiversity-r16 capability or PC1.5 capable UE further indicates SRS-TxSwitch capability ‘t1r2’ or ‘t1r4’ or ‘t1r1-t1r2’ or ‘t1r1-t1r2-t1r4’;

3.5 ∆P_powerclass in case 5

0 dB otherwise;

Reference:

3GPP TS 38.101-1 version 17.8.0 Release 17 ETSI TS 138 101-1 V17.8.0 (2023-01)