Content for TR 38.835 Word version: 18.0.1

1… 4… 5… 6 A B… B.1.2 B.1.3 B.1.4 B.1.5 B.1.6 B.1.7 B.1.8 B.1.9 B.1.10 B.2… B.2.2 B.2.3 B.2.4 B.2.5 B.2.6 B.2.7 B.2.8 B.2.9 B.2.10 B.2.11 B.2.12 B.2.13 B.2.14 B.2.15 B.2.16 B.2.17 B.2.18 C…

B.1.5 Soft HARQ-ACK enhancements
...

B.1.5 Soft HARQ-ACK enhancements p. 27

This clause captures the capacity performance evaluation results of soft HARQ-ACK enhancements. HARQ allows to recover transport blocks that are not successfully decoded by means of retransmissions. It can be leveraged to use MCS close to what the radio channel can support while maintaining high reliability. The gNB chooses the MCS for a transmission based on its knowledge of the channel conditions, but it cannot always precisely predict how they evolve.

The performance of Baseline HARQ-ACK (scheme 5.1 in Tables B.1.5-1,2,3) has been compared against different schemes with soft HARQ-ACK. Particularly, the following schemes, with soft HARQ-ACK, have been evaluated:

Scheme 5.2: Soft HARQ-ACK indicating delta MCS: UE provides enhanced HARQ-ACK feedback beyond the single bit ACK/NACK status in the form of a Delta MCS based on PDSCH decoding. The soft HARQ-ACK feedback uses SINR measurements done on each TB and link curves obtained from link level simulations. Then the information the UE feeds back to the gNB is an estimation of how far the experienced SINR is from the SINR that would allow a reliable decoding of the TB.
Scheme 5.3: Soft HARQ-ACK indicating number of redundant transmissions: 2-bit soft-HARQ feedback is reported by the UE and used by the gNB scheduler. The 2-bit soft-HARQ feedback represents 4 states: ACK, and NACK with n=1, 2, or 3, where "n" indicates how many redundant transmissions are requested by the UE.

The performance results are reported in Table B.1.5-1, Table B.1.5-2, Table B.1.5-3 in terms of the ratio of satisfied users.

Table B.1.5-1: FR1, DL, InH, VR/AR at 60 FPS

Source	Tdoc Source	Scheme	TDD format	SU/MU-MIMO	Data rate (Mbps)	PDB (ms)	Capacity (UEs/cell)	C1=floor (Capacity)	% of satisfied UEs when #UEs/cell = C1	Notes
Source [Qualcomm]	R1-2210003	5.2*	DDDSU	MU-MIMO	60	10	2.93	2	97.7%	Note 1
					45		5.4	5	92.3%
					30		8.96	8	95%
Source [Qualcomm]	R1-2210003	5.1*	DDDSU	MU-MIMO	60	10	0	0	N.A.	Note 1
					45		4.5	4	93.1%
					30		8.5	8	92.9%
Source [Qualcomm]	R1-2210003	5.2**	DDDSU	MU-MIMO	60	10	2.1	2	91.25%	Note 1
					45		4.1	4	91%%
					30		7.8	7	93.5%
Source [Qualcomm]	R1-2210003	5.1**	DDDSU	MU-MIMO	60	10	0	0	N.A.	Note 1
					45		0	0	N.A.
					30		0	0	N.A.
Source [Qualcomm]	R1-2210003	5.2***	DDDSU	MU-MIMO	60	10	1.17	1	91.25%	Note 1
Source [Qualcomm]	R1-2210003	5.1***	DDDSU	MU-MIMO	60	10	0	0	N.A.	Note 1
Source [ZTE]	R1-2203607	5.2***	DDDSU	MU-MIMO	60	10	3.3	3	93%	Note 1
Source [ZTE]	R1-2203607	5.1***	DDDSU	MU-MIMO	60	10	0	0	N.A.	Note 1
NOTE 1: BS antenna parameters: 32TxRUs, (M, N, P, Mg, Ng; Mp, Np) = (4,4,2,1,1:4,4) * gNB processing delay k3 (from HARQ feedback to retransmission) = 4 slots gNB processing delay k3 (from HARQ feedback to retransmission) = 6 slots * gNB processing delay k3 (from HARQ feedback to retransmission) = 8 slots

Table B.1.5-2: FR1, DL, DU, VR/AR at 60 FPS

Source	Tdoc Source	Scheme	TDD format	SU/MU-MIMO	Data rate (Mbps)	PDB (ms)	Capacity (UEs/cell)	C1=floor (Capacity)	% of satisfied UEs when #UEs/cell = C1	Notes
Source [Qualcomm]	R1-2210003	5.2*	DDDSU	MU-MIMO	60	10	4.6	4	94.5%	Note 1
					45		7.5	7	93%
					30		11.9	11	94.1%
Source [Qualcomm]	R1-2210003	5.1*	DDDSU	MU-MIMO	60	10	0	0	N.A.	Note 1
					45		6.6	6	92.2%
					30		11.3	11	91.3%
Source [Qualcomm]	R1-2210003	5.2**	DDDSU	MU-MIMO	60	10	2.8	2	92.9%	Note 1
					45		5.5	5	92.4%
					30		10.4	10	92%
Source [Qualcomm]	R1-2210003	5.1**	DDDSU	MU-MIMO	60	10	0	0	N.A.	Note 1
					45		0	0	N.A.
					30		0	0	N.A.
Source [Qualcomm]	R1-2210003	5.2***	DDDSU	MU-MIMO	60	10	2	2	90.1%	Note 1
Source [Qualcomm]	R1-2210003	5.1***	DDDSU	MU-MIMO	60	10	0	0	N.A.	Note 1
Source [Futurewei]	R1-2208377	5.1****	DDDUU	MU-MIMO	45	10	8.4	8	91%	Note 1
Source [Futurewei]	R1-2208377	5.3****	DDDUU	MU-MIMO	45	10	7.9	7	90%	Note 1
NOTE 1: BS antenna parameters: 64TxRUs, (M, N, P, Mg, Ng; Mp, Np) = (8,8,2,1,1:4,8) gNB processing delay k3 (from HARQ feedback to retransmission) = 6 slots * gNB processing delay k3 (from HARQ feedback to retransmission) = 8 slots **** UE processing delay and gNB processing delay = 10 slots

Table B.1.5-3: FR1, DL, UMa, VR/AR at 60 FPS

Source	Tdoc Source	Scheme	TDD format	SU/MU-MIMO	Data rate (Mbps)	PDB (ms)	Capacity (UEs/cell)	C1=floor (Capacity)	% of satisfied UEs when #UEs/cell = C1	Notes
Source [Futurewei]	R1-2208377	5.1****	DDDUU	MU-MIMO	45	10	6.2	6	90.3%	Note 1
Source [Futurewei]	R1-2208377	5.3****	DDDUU	MU-MIMO	45	10	6.1	6	91.3%	Note 1
NOTE 1: BS antenna parameters: 64TxRUs, (M, N, P, Mg, Ng; Mp, Np) = (8,8,2,1,1:4,8) **** UE processing delay and gNB processing delay = 10 slots

Based on the evaluation results in Table B.1.5-1, Table B.1.5-2, Table B.1.5-3 the following observations can be made:

For FR1, DU, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 30Mbps, 10ms PDB, 60 FPS, with MU-MIMO and 64TxRU, it is observed from Source [Qualcomm] that the capacity is increased from 11.3 UEs per cell with baseline HARQ-ACK to 11.9 UEs per cell with soft HARQ-ACK indicating delta MCS based on PDSCH decoding and k3=4 slots (capacity gain is 5%). For InH scenario, the results show similar trend.
For FR1, DU, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 45Mbps, 10ms PDB, 60 FPS, with MU-MIMO and 64TxRU, it is observed from Source [Qualcomm] that the capacity is increased from 6.6 UEs per cell with baseline HARQ-ACK to 7.5 UEs per cell with soft HARQ-ACK indicating delta MCS based on PDSCH decoding and k3=4 slots (capacity gain is 14%). For InH scenario, the results show similar trend.
For FR1, DU, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 60Mbps, 10ms PDB, 60 FPS, with MU-MIMO and 64TxRU, it is observed from Source [Qualcomm] that the capacity is increased from 0 UEs per cell with baseline HARQ-ACK to 4.6 UEs per cell with soft HARQ-ACK indicating delta MCS based on PDSCH decoding and k3=4 slots. For InH scenario, the results show similar trend.
For FR1, DU, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 30Mbps, 10ms PDB, 60 FPS, with MU-MIMO and 64TxRU, it is observed from Source [Qualcomm] that the capacity is increased from 0 UEs per cell with baseline HARQ-ACK to 10.4 UEs per cell with soft HARQ-ACK indicating delta MCS based on PDSCH decoding and k3=6 slots. For InH scenario, the results show similar trend.
For FR1, DU, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 45Mbps, 10ms PDB, 60 FPS, with MU-MIMO and 64TxRU, it is observed from Source [Qualcomm] that the capacity is increased from 0 UEs per cell with baseline HARQ-ACK to 5.5 UEs per cell with soft HARQ-ACK indicating delta MCS based on PDSCH decoding and k3=6 slots. For InH scenario, the results show similar trend.
For FR1, DU, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 60Mbps, 10ms PDB, 60 FPS, with MU-MIMO and 64TxRU, it is observed from Source [Qualcomm] that the capacity is increased from 0 UEs per cell with baseline HARQ-ACK to 2.8 UEs per cell with soft HARQ-ACK indicating delta MCS based on PDSCH decoding and k3=6 slots. For InH scenario, the results show similar trend.
For FR1, DU, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 60Mbps, 10ms PDB, 60 FPS, with MU-MIMO and 64TxRU, it is observed from Source [Qualcomm] that the capacity is increased from 0 UEs per cell with baseline HARQ-ACK to 2 UEs per cell with soft HARQ-ACK indicating delta MCS based on PDSCH decoding and k3=8 slots. For InH scenario, the results show similar trend.
For FR1, InH, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 60Mbps, 10ms PDB, 60 FPS, with MU-MIMO, it is observed from Source [ZTE] that the capacity is increased from 0 UEs per cell with baseline HARQ-ACK to 3.3 UEs per cell with soft HARQ-ACK indicating delta MCS based on PDSCH decoding and k3=8 slots.
For FR1, DU, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 45Mbps, 10ms PDB, 60 FPS, with MU-MIMO and 64TxRU, it is observed from Source [Futurewei] that the capacity is decreased from 8.4 UEs per cell with baseline HARQ-ACK to 7.9 UEs per cell with soft HARQ-ACK indicating how many redundant transmissions are requested by the UE (capacity drop is -6%).
For FR1, UMa, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 45Mbps, 10ms PDB, 60 FPS, with MU-MIMO and 64TxRU, it is observed from Source [Futurewei] that the capacity is decreased from 6.2 UEs per cell with baseline HARQ-ACK to 6.1 UEs per cell with soft HARQ-ACK indicating how many redundant transmissions are requested by the UE (capacity drop is -2%).