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.1.2 Cooperative MIMO via DL interference probing based on SRS enhancement
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B.1.2 Cooperative MIMO via DL interference probing based on SRS enhancement p. 21

This clause captures the capacity performance evaluation results for cooperative MIMO in TDD with downlink interference probing via SRS and precoding via bi-directional training (BiT). In TDD system, channel UL-DL reciprocity is utilized to obtain DL channel state information for improved performance of single-cell (non-cooperative) MU-MIMO. However, inter-cell interference is still the bottleneck that limits further capacity improvement.

The performance of MU-MIMO with zero forcing precoding (scheme 2.1 in Tables B.1.2-1,2) has been compared against Cooperative MIMO with DL interference probing (scheme 2.2 in Tables B.1.2-1,2).

Scheme 2.2:

Cooperative MIMO with DL interference probing via SRS and precoding via bi-directional training (BiT), is the scheme where SRS triggering and transmission are enhanced to directly reflect DL interference spatial information (utilizing UL-DL reciprocity). Each gNB performs its own (MU) scheduling and instructs the scheduled UEs to sound on the scheduled PRBs. Then by TDD reciprocity, a gNB seeing strong UL interference from a certain spatial direction on the SRS resources (for example, via estimating the UL spatial covariance matrix of interference signals) implies that in DL transmission the gNB will cause strong interference to UE(s) in that direction. The gNB can then adjust the precoding for DL interference avoidance during the PDSCH transmissions. Each gNB measures the corresponding UL SRS resources and adjusts its DL precoding accordingly to achieve multi-cell DL interference coordination/avoidance in a distributed way, and hence the so-called 'Bi-directional Training' (BiT).

The performance results are reported in Table B.1.2-1 and Table B.1.2-2 in terms of the ratio of satisfied users.

Table B.1.2-1: FR1, DL, DU, VR/AR and Cloud Gaming 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	2.1	DDDSU	MU-MIMO	45	10	12.2	12	90%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDSU	MU-MIMO	45	15	17.4	17	94%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDSU	MU-MIMO	45	10	16.9	16	91%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDSU	MU-MIMO	45	15	21.7	21	92%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDSU	MU-MIMO	30	10	21.7	21	91%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDSU	MU-MIMO	30	15	27.1	27	91%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDSU	MU-MIMO	30	10	25.8	25	91%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDSU	MU-MIMO	30	15	30.1	30	91%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDUU	MU-MIMO	45	10	8	8	90%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDUU	MU-MIMO	45	15	12.7	12	96%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDUU	MU-MIMO	45	10	13.1	13	90%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDUU	MU-MIMO	45	15	16.9	16	95%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDUU	MU-MIMO	30	10	13.7	13	92%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDUU	MU-MIMO	30	15	21.5	21	93%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDUU	MU-MIMO	30	10	19.9	19	93%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDUU	MU-MIMO	30	15	25.6	25	93%	Note 1
NOTE 1: BS antenna parameters: 64TxRUs, (M, N, P, Mg, Ng; Mp, Np) = (8,8,2,1,1:4,8).

Table B.1.2-2: FR1, DL, UMa, VR/AR and Cloud Gaming 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	2.1	DDDSU	MU-MIMO	45	10	7	7	90%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDSU	MU-MIMO	45	15	9.7	9	93%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDSU	MU-MIMO	45	10	9	9	90%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDSU	MU-MIMO	45	15	11.6	11	92%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDSU	MU-MIMO	30	10	11.4	11	94%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDSU	MU-MIMO	30	15	14.2	14	91%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDSU	MU-MIMO	30	10	13.2	13	92%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDSU	MU-MIMO	30	15	16	16	90%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDUU	MU-MIMO	45	10	5.2	5	90%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDUU	MU-MIMO	45	15	6.8	6	94%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDUU	MU-MIMO	45	10	6.6	6	93%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDUU	MU-MIMO	45	15	9.4	9	91%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDUU	MU-MIMO	30	10	8.8	8	90%	Note 1
Source [Futurewei]	R1-2208377	2.1	DDDUU	MU-MIMO	30	15	11.4	11	94%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDUU	MU-MIMO	30	10	10.4	10	92%	Note 1
Source [Futurewei]	R1-2208377	2.2	DDDUU	MU-MIMO	30	15	13.3	13	93%	Note 1
NOTE 1: BS antenna parameters: 64TxRUs, (M, N, P, Mg, Ng; Mp, Np) = (8,8,2,1,1:4,8).

Based on the evaluation results in Table B.1.2-1 and Table B.1.2-2, 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, 64TxRU and DDDSU, it is observed from Source [Futurewei] that the capacity is increased from 21.7 UEs per cell with MU-MIMO and zero forcing precoding to 25.8 UEs per cell with Cooperative MIMO via SRS enhancements (capacity gain is 19%). For 15ms PDB, the capacity gain is 11%. For UMa 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, 64TxRU and DDDSU, it is observed from Source [Futurewei] that the capacity is increased from 12.2 UEs per cell with MU-MIMO and zero forcing precoding to 16.9 UEs per cell with Cooperative MIMO via SRS enhancements (capacity gain is 39%). For 15ms PDB, the capacity gain is 24%. For UMa scenario, the results show similar trend.
For FR1, UMa, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 45Mbps, 10ms PDB, 60 FPS, with MU-MIMO, 64TxRU and DDDSU, it is observed from Source [Futurewei] that the capacity is increased from 7 UEs per cell with MU-MIMO and zero forcing precoding to 9 UEs per cell with Cooperative MIMO via SRS enhancements (capacity gain is 28%). For 15ms PDB, the capacity gain is 19%.
For FR1, DU, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 30Mbps, 10ms PDB, 60 FPS, with MU-MIMO, 64TxRU and DDDUU, it is observed from Source [Futurewei] that the capacity is increased from 13.7 UEs per cell with MU-MIMO and zero forcing precoding to 19.9 UEs per cell with Cooperative MIMO via SRS enhancements (capacity gain is 45%). For 15ms PDB, the capacity gain is 19%.
For FR1, UMa, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 30Mbps, 10ms PDB, 60 FPS, with MU-MIMO, 64TxRU and DDDUU, it is observed from Source [Futurewei] that the capacity is increased from 8.8 UEs per cell with MU-MIMO and zero forcing precoding to 10.4 UEs per cell with Cooperative MIMO via SRS enhancements (capacity gain is 18%). For 15ms PDB, the capacity gain is 16%.
For FR1, DU, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 45Mbps, 10ms PDB, 60 FPS, with MU-MIMO, 64TxRU and DDDUU, it is observed from Source [Futurewei] that the capacity is increased from 8 UEs per cell with MU-MIMO and zero forcing precoding to 13.1 UEs per cell with Cooperative MIMO via SRS enhancements (capacity gain is 64%). For 15ms PDB, the capacity gain is 33%.
For FR1, UMa, DL, with 100MHz bandwidth for VR/AR single-stream traffic model, 45Mbps, 10ms PDB, 60 FPS, with MU-MIMO, 64TxRU and DDDUU, it is observed from Source [Futurewei] that the capacity is increased from 5.2 UEs per cell with MU-MIMO and zero forcing precoding to 6.6 UEs per cell with Cooperative MIMO via SRS enhancements (capacity gain is 27%). For 15ms PDB, the capacity gain is 38%.