R1-2601870
discussion
Discussion on other aspects of CSI acquisition and channel tracking
From ZTE
Summary
This ZTE contribution contains 7 Observations and 7 Proposals across two main technical areas: joint DL/UL CSI acquisition and reference signal design for tracking in 6G. The document argues for compressed covariance reporting and AI/ML-based CSI-RS/SRS fusion while opposing IPN reporting and 512 TXRU configurations, and proposes DMRS-based tracking schemes to replace dedicated periodic TRS.
Position
ZTE proposes studying joint CSI-RS and SRS based CSI acquisition in 6GR, supporting compressed covariance report for DL CSI acquisition by reconstructing channel covariance matrix from UE-reported indices and quantized values of top-L diagonal elements. They oppose the 512 TXRUs antenna configuration, arguing its feasibility for practical commercial deployment is highly limited due to processing complexity, power consumption, and engineering construction costs. They present a technical case against IPN reporting, citing redundancy with existing CQI reports that include DL interference and noise information for MCS determination under SRS-based CSI acquisition, and limited benefit of scalar reporting without spatial domain information. For RS tracking, ZTE proposes studying DMRS-based tracking schemes (including PDSCH DMRS and DMRS-only) as alternatives to dedicated periodic TRS, and requires that 6GR RS for tracking accommodate one port transmitted from all TRPs in CJT-mTRP scenarios to achieve a ~20% spectrum efficiency gain over 5G-NR TRS at SNR=-7dB.
Key proposals
- Proposal 1 (Sec 2.1.1): Study joint CSI-RS and SRS based CSI acquisition in 6GR.
- Proposal 2 (Sec 2.1.2): Study the following aspects of evaluation for covariance report: Interference modelling, Periodicity of both covariance reporting and SRS transmission.
- Proposal 3 (Sec 2.1.2.1): Support compressed covariance report for DL CSI acquisition in 6GR.
- Proposal 4 (Sec 2.2.1): The RS for tracking should be introduced in 6GR to better support multi-TRP coordinated and high-mobility (e.g., HST) scenarios, where the design should at least consider the following aspects: Tracking performance, RS overhead, NW and UE implementation complexity, NW and UE energy consumption.
- Proposal 5 (Sec 2.2.2.1): Study the following candidates for fine time and/or frequency tracking in 6GR to reduce RS overhead and NW energy consumption caused by configuring dedicated periodic TRS as in 5G-NR: Scheme-1: DMRS based tracking, Scheme-2: AP-TRS based tracking (standalone), Scheme-3: Combination of TRS based and DMRS based schemes.
- Proposal 6 (Sec 2.2.2.2.1): 6GR RS for tracking (e.g., DMRS based) should accommodate the mechanism of one port transmitted from all TRPs to achieve time and/or frequency domain tracking in CJT-mTRP scenario.
- Proposal 7 (Sec 2.2.2.2.2): At least the following parameters and corresponding candidate values should be evaluated for determining time and/or frequency structure of RS for tracking (e.g., DMRS based) in 6GR: Frequency domain parameters (Bandwidth: {partial BW, full BW}; Density: {2, 3}; Frequency pattern: FD-OCC), Time domain parameters (Number of slots: {1, 2}; Number of symbols: {2, FFS: [3], [4]}; Symbol interval: {4, FFS: other values e.g., 6, 7, 9, 11}; Time-domain behavior: aperiodic or on-demand).