R1-2509139
discussion
Overview of 6GR air interface
From KT
Summary
This document from KT Corp. provides an overview of the 6GR air interface, presenting 3 observations and 4 main proposals across four technical areas: bandwidth adaptation, spectrum utilization, coverage, and multi-RAT spectrum sharing. The contributions aim to capture lessons learned from 5G NR and propose study directions for 6GR design.
Position
KT proposes studying a simplified BWP concept for 6GR that avoids excessive BWP-specific RRC configurations (e.g., CORESET/SS, PUCCH resources per BWP) and mitigates physical layer issues including HARQ-ACK initialization and configured scheduling release during BWP switching. They propose studying a new SCMC (Single Cell with Multi-CCs) concept for spectrum utilization where multiple component carriers operate as a single logical cell, extending PCell-limited functions such as synchronization, RLM, RRM, PUCCH, and PRACH across aggregated cells. For coverage, they propose reusing NR techniques including TBoMS, joint channel estimation, and repetitions while studying cross-slot scheduling by extending SLIV-based symbol-level signaling across slot boundaries. For MRSS, they propose two multiplexing options—signal/channel sharing of SSB and CSI-RS, and rate-matching using layered signaling (RRC RE-level bitmap, MAC CE RB-level activation, DCI RB/symbol-level triggering) with conditional SCS information inclusion to handle differing numerologies between 5G and 6G.
Key proposals
- Observation 1 (Sec BWP-related RRC configuration): 5G NR BWP framework was designed to allow excessive RRC configurations, which resulted in unnecessary latency during RRC reconfiguration.
- Observation 2 (Sec BWP switching): 5G NR BWP switching negatively impacts the physical layer, causing issues such as long BWP switching delay, ambiguity between UE and gNB, and initialization of HARQ-ACK/configured scheduling.
- Observation 3 (Sec Multi-RAT spectrum sharing): Legacy DSS rate-matching (e.g., RateMatchPatternLTE-CRS) is LTE CRS-centric and lacks support for 5G NR dynamic RS (e.g., aperiodic/semi-persistent CSI-RS) and SCS misalignment, leading to inefficient resource avoidance in MRSS with differing numerologies.
- Proposal 1 (Sec BWP switching): From a UE power saving perspective, the basic BWP concept should be studied for 6GR by avoiding excessive RRC configurations and negative impacts by BWP switching.
- Proposal 2 (Sec Spectrum utilization and aggregation): RAN1 to study spectrum utilization and aggregation by considering flexibility, resource management, and signaling efficiency.
- Proposal 3 (Sec Overall coverage): RAN1 to study coverage enhancement for 6GR by identifying Day-1 targets and applying both reused NR techniques (e.g., repetitions, TBoMS, joint channel estimation) and new approaches such as cross-slot scheduling.
- Proposal 4 (Sec Multi-RAT spectrum sharing): RAN1 to study dynamic multiplexing of 5G NR UE and 6GR UE both in time and frequency domains for MRSS with Option 1 (sharing of 5G NR signal/channel, e.g., SSB and CSI-RS) and Option 2 (rate-matching around 5G NR signal/channel).
- Proposal 4 Option 2-1 (Sec Multi-RAT spectrum sharing): Study how existing configuration mechanisms (e.g., RE-level bitmap for RS resource reservation) can be extended or reused to indicate reserved 5G NR resource positions to 6G UEs via RRC-level configuration.
- Proposal 4 Option 2-2 (Sec Multi-RAT spectrum sharing): Consider dynamic signaling methods (e.g., RB-level indication through MAC/DCI) to support time/frequency domain multiplexing and rate-matching adaptation for dynamic RS receptions (e.g., semi-persistent or aperiodic CSI-RS).