R1-2600119
discussion
Discussion on aspects of downlink-based CSI acquisition for 6GR
From Spreadtrum
Summary
This document from Spreadtrum provides 18 proposals and 12 observations on downlink CSI acquisition for 6G Radio, covering a unified CSI framework, CSI-RS design with up to 128 ports, and AI/ML-based CSI solutions including compression/feedback (JSCC/JSCM) and low-overhead CSI-RS with model generalization analysis.
Position
Spreadtrum proposes a unified CSI acquisition framework design that associates a CSI report configuration with a channel measurement configuration and/or an interference measurement configuration, supporting multiple scenarios including early CSI for candidate cells. They propose studying both NW-controlled and UE-initiated CSI reporting, and consider PUSCH-only based CSI reporting for all time domain behaviors in 6GR. For CSI-RS design, they support up to 128 ports per single CSI-RS resource and propose PN sequence with UE-specific seed with component RE pattern aggregation. On AI/ML, they present technical case showing JSCC/JSCM performance gains over SSCC especially at low SNR but propose postponing two-side model work until NR standardization completes. They prioritize low overhead CSI-RS for 6GR Day 1 AI use case, presenting evaluation results showing less than 5% SGCS loss with 87% frequency domain and 75% spatial domain RS overhead reduction, while noting spatial domain generalization across deployment scenarios needs further study due to approximately 28% SGCS loss.
Key proposals
- Proposal 1 (Sec 2.1.1): Strive to design a unified CSI acquisition framework supporting multiple scenarios (sTRP BM/CSI, mTRP BM/CSI, mTRP calibration, early CSI during RA procedure, early CSI for candidate cells) and study inclusion of early CSI for candidate cells.
- Proposal 3 (Sec 2.1.1): Study both NW controlled beam/CSI reporting and UE-initiated CSI reporting.
- Proposal 5 (Sec 2.1.2): Study mechanism to support dynamic port on/off switching for channel measurement RS.
- Proposal 7 (Sec 2.1.2): DMRS-based CSI reporting is considered as low priority in 6G day-1.
- Proposal 9 (Sec 2.1.3): Consider PUSCH-only based CSI reporting for all supported time domain behaviors in 6GR.
- Proposal 12 (Sec 2.1.3): Regarding PMI, strive to design a unified codebook for all use cases.
- Proposal 13 (Sec 2.2): Regarding the number of ports for a single CSI-RS resource, support up to 128.
- Proposal 14 (Sec 2.2): For CSI-RS sequence design, consider PN sequence with UE specific seed as starting point.
- Proposal 15 (Sec 2.2): Consider CSI-RS RE pattern as aggregated by one or multiple component RE patterns.
- Proposal 16 (Sec 2.3): Given that the standardization work for the two-side model has not yet been completed, JSCC/JSCM can be postponed until the work in NR is completed.
- Proposal 17 (Sec 2.4.2.2): For spatial domain reduction, the generalization performance of AI/ML model in various deployment scenarios needs further study.
- Proposal 18 (Sec 2.4.2.2): Prioritizing low overhead CSI-RS for 6GR Day 1 AI use case.