R1-2601815
discussion
Discussion on aspects of uplink-based CSI acquisition for 6GR
From Spreadtrum
Spreadtrum's prior position on
10.5.3.2
at
RAN1#124
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Proposes limiting 6GR Day1 SRS study to {1,2,3,4} antenna ports, noting 8-port devices lack commercial deployment despite NR support. Recommends reusing Zadoff-Chu sequences as the SRS baseline and studying cross-slot SRS features beyond 14 symbols for both CSI acquisition and velocity estimation in sensing. For AI-based SRS, asserts that antenna switching enhancement should remain NW implementation without spec impact (Observation-2), while prioritizing frequency hopping overhead reduction with Sub-case A where the NW-side model predicts full-bandwidth channel information from sparse SRS transmissions. Prefers a unified uplink RS design aggregating communication, positioning, and sensing functions, and proposes studying simplified single-step offset indication for aperiodic SRS timing determination.
Summary
This Spreadtrum contribution presents 14 proposals and 4 observations on 6G SRS design, addressing antenna port configurations, transmission schemes, AI-based overhead reduction, and integration with sensing. The document covers baseline SRS features inherited from NR alongside new study areas for 6GR including wideband transmission, cross-slot operation, and ZP SRS for CJT interference mitigation.
Position
Spreadtrum recommends focusing 6GR Day1 SRS design on {1,2,3,4} antenna ports rather than >8 ports, citing lack of commercial 8-port device deployment despite NR Rel-18 support. They propose reusing NR baselines including Zadoff-Chu sequences, periodic/SP/aperiodic time-domain behavior, and the antenna switching/codebook/non-codebook/BM usage set. They present technical case for studying TD-OCC for capacity enhancement, ZP SRS for CJT interference mitigation via reserved non-transmitted REs in PUSCH, and unified uplink RS design for integrated communication and sensing. On AI/ML, they argue AI-based SRS antenna switching is purely NW implementation with no spec impact, while AI-based SRS frequency hopping overhead reduction shows 7.5-17.9% SGCS gain and requires only minor SRS configuration changes.
Key proposals
- Proposal 1 (Sec 2): {1,2,3,4} antenna-port SRS can be studied in 6GR day1.
- Proposal 2 (Sec 2): The usages set {antenna switching, codebook/non-codebook, BM} can be set as a baseline for 6GR SRS study.
- Proposal 5 (Sec 2): Study wide band transmission for SRS, e.g., 200MHz.
- Proposal 6 (Sec 2): Study the cross-slot feature for SRS in 6GR day1.
- Proposal 7 (Sec 2): Study simplified offset indication methods for aperiodic SRS.
- Proposal 8 (Sec 2): Solutions to improve SRS coverage can be studied in 6GR, e.g., partial sounding.
- Proposal 9 (Sec 2): Solutions to minimize SRS interference can be studied in 6GR, e.g., comb offset randomization, cyclic shift randomization, etc.
- Proposal 10 (Sec 2): Study the feasibility of TD-OCC for aim of capacity enhancement.
- Proposal 11 (Sec 2): Study the feasibility of ZP SRS in 6GR.
- Proposal 12 (Sec 2): Unified uplink RS design for communication and sensing is preferred.
- Proposal 13 (Sec 2): Study the sounding scheme under DL400MHz & UL200MHz, FFS other DL CBW values in range 200~400MHz.
- Proposal 14 (Sec 3.2): Prioritizing SRS overhead reduction with Sub-case A for 6GR AI use case with the following subcase: SRS overhead reduction for frequency hopping.
- Proposal 3 (Sec 2): Support periodic/SP/aperiodic SRS for 6GR.
- Proposal 4 (Sec 2): Use Zadoff-Chu sequence as a start point for SRS in 6GR.