R1-2600134
discussion
6GR CSI: Aspects of Uplink-based CSI Acquisition
From InterDigital
Summary
This document presents InterDigital's views on uplink-based CSI acquisition for 6G, containing 9 Observations and 9 Proposals. The contribution covers SRS framework evolution, new UE implementations, codebook design, antenna switching, and UE-initiated triggering mechanisms.
Position
InterDigital proposes retaining all NR SRS usages ('codebook', 'nonCodebook', 'antennaSwitching', 'beamManagement') and all time-domain behaviors ('aperiodic', 'semi-persistent', 'periodic') as baseline for 6GR. They propose supporting at least 1, 2, 3, 4, and 8 SRS ports and studying increases beyond 8 TX ports for higher-capability UEs such as FWA and multi-panel devices. They propose a low-overhead adaptable UL codebook design that adapts to UE deployment environments, diverse form factors, and dynamic port obstruction from user handling—contrasting with NR's fixed equal-spaced precoder codebooks. They propose studying SRS-based DL CSI acquisition that considers UE antenna coherency capabilities across different TX chains, citing throughput degradation from amplitude/phase imbalances. They propose studying UE-initiated aperiodic SRS triggering mechanisms informed by UE-side channel measurements, power control, BSR, and CLI. They propose studying multi-port SRS for CLI and self-interference estimation to support advanced duplex operations including SBFD.
Key proposals
- Proposal 1 (Sec 2.1): Support all usages of SRS, i.e., 'codebook', 'nonCodebook', 'antennaSwitching', 'beamManagement' for 6GR.
- Proposal 3 (Sec 2.2): Support at least 1, 2, 3, 4 and 8 SRS ports for 6GR.
- Proposal 4 (Sec 2.2): Study increasing the number of SRS ports to serve higher capability UEs if more than 8 TX ports are supported.
- Proposal 5 (Sec 2.2): Study SRS design and operation to counter the loss incurred due to UE distance and interference in 6GR.
- Proposal 6 (Sec 2.2): Study SRS design and operation to support multi-port based CLI and/or self-interference estimation for advanced duplex operation (e.g., SBFD) in 6GR.
- Proposal 7 (Sec 2.3): Support a low overhead adaptable codebook design that can be adapted to UE deployment and transmission environment, a diverse set of UE form factors, and potential port obstruction resulted from user handling.
- Proposal 8 (Sec 2.4): Study SRS-based DL CSI acquisition considering UE antenna coherency.
- Proposal 9 (Sec 2.5): Study UE-initiated aperiodic SRS transmissions to assist CSI acquisition.
- Proposal 2 (Sec 2.1): Support all time domain behaviors defined in NR, i.e., 'aperiodic', 'semi-persistent', 'periodic' for 6GR.