R1-2601906
discussion
Aspects of downlink-based CSI acquisition
From TCL
Summary
TCL's contribution (25 proposals) covers a comprehensive 6G CSI acquisition framework spanning template-based configurations, enhanced CSI-RS design with up to 256 ports, codebook simplification and downloadable codebooks, UE-initiated and adaptive CSI reporting, early CSI acquisition for mobility and state transitions, CSI prediction with AI/ML, and joint source-channel coding for CSI compression.
Position
TCL proposes studying template-based CSI measurement and reporting configurations to replace RRC semi-static configuration with predefined standardized templates that enable batch parameter adjustment and state transition signaling, targeting reduced RRC reconfiguration delay and air interface signaling overhead. For CSI-RS design, TCL supports up to 256 antenna ports in the first 6G release with two options for study: single CSI-RS resource carrying all ports or multi-resource aggregation, and requires prioritizing larger CDM groups (e.g., CDM16) with single-PRB occupancy as the baseline design approach. TCL proposes eliminating periodic CSI-RS resource configurations entirely in 6GR, supporting only semi-persistent and aperiodic behaviors, with semi-persistent configurations refined to achieve periodic-equivalent functionality for UE energy savings. For codebook design, TCL selects Rel-19 Type-I or Rel-16 eType-II as baseline codebooks and requires an unified codebook structure across all antenna ports to avoid Rel-15's bifurcated design for different port counts, while also proposing a downloadable method where gNB transmits partial or full precoding matrix information to reduce UE-side CSI calculation complexity and reporting overhead. TCL proposes studying UE-initiated and event-triggered CSI reporting for all CSI quantities, adaptive CSI reporting including dynamic adaptation of reporting periodicity and overhead, early CSI acquisition for inter-cell mobility/terminal state switching/carrier state switching, frequency/spatial domain CSI prediction using low-overhead CSI-RS patterns (uniform, non-uniform, cyclic), and CSI compression with JSCC/JSCM including evaluation of CRC-free versus CRC-attached HARQ mechanisms.
Key proposals
- Proposal 1 (Sec 2.1): For 6G, support the study of template-based CSI measurement and reporting configurations to optimize configuration flexibility and reduce signaling overhead.
- Proposal 2 (Sec 2.2.1): For the maximum CSI-RS antenna ports, support up to 256 antenna ports for the first release in 6GR.
- Proposal 4 (Sec 2.2.2): For CSI-RS with a large number of antenna ports, implementation via aggregation of larger CDM groups shall be prioritized, and occupancy within a single PRB shall be used as the baseline.
- Proposal 5 (Sec 2.2.3): Study the mechanism of references signal sharing among multiple UEs based on UE demand.
- Proposal 6 (Sec 2.3.1): For 6GR, semi-persistent and aperiodic time-domain behaviors of CSI-RS resource configurations should be supported. Semi-persistent CSI-RS resource configurations can be further refined to achieve the same functionality as periodic CSI-RS configurations.
- Proposal 7 (Sec 2.3.2): For 6G NR CSI-RS, it is proposed to study the dynamic adaptation of CSI-RS parameters, e.g., number of antenna ports, periodicity, resource density, power offset.
- Proposal 8 (Sec 2.4.1): For simplifying codebook type in 6GR, support Rel-19 Type-I or Rel-16 eType-II codebook as the baseline codebooks.
- Proposal 10 (Sec 2.4.2): For unified fixed codebook design in 6GR, study the downloadable method for transmitting CSI parameters on the gNB side to assist the UE side in CSI calculation and reporting.
- Proposal 13 (Sec 2.5): For CSI reporting procedures, it is proposed that UE-initiated or event-triggered CSI reporting mechanisms should be studied for all types of CSI reporting quantities.
- Proposal 14 (Sec 2.6.1): For 6GR, early trigger CSI measurement and reporting should be considered for inter-cell mobility management, and further study can be expended to M-TRP CJT scenarios.
- Proposal 15 (Sec 2.6.2): For 6GR, early trigger CSI measurement and reporting should be considered for terminal state switching, further study can combine with energy saving state switching.
- Proposal 17 (Sec 2.7.1): Initiate the study of adaptive CSI reporting given the advantages of overhead reduction, timeliness, scalability, and reduced network load.
- Proposal 18 (Sec 2.7.1): RAN1 could study the following technical approaches for adaptive CSI reporting: network-configured CSI reporting configurations with UE selection, UE-initiated CSI reporting configuration request, and UE-autonomous CSI reporting configuration determination.
- Proposal 20 (Sec 2.7.2): For 6GR CSI reporting, dynamic adaptation of CSI reporting should be studied, e.g. CSI reporting periodic, CSI reporting overhead.
- Proposal 24 (Sec 2.9): RAN1 gives priority to studying CSI compression with JSCC/JSCM for 6GR MIMO.