R1-2508736
discussion
Numerology and frame structure for 6GR air interface
From Huawei
Summary
This Huawei/HiSilicon document proposes 10 technical positions and 1 observation for the 6GR numerology and frame structure study. The proposals cover subcarrier spacing for sync signals (single 120kHz SCS in FR2-1), 6GR frame structure design including TDD flexibility, SBFD, flexible DL/UL pairing, scheduling timing units, and physical resource definitions.
Position
Huawei proposes a single SCS of 120kHz for 6GR sync signals and other channels/signals (except PRACH) in FR2-1 to reduce UE blind search during initial cell search. For frame structure, they advocate reusing NR's DL/UL/flexible/SBFD symbol types with both cell-specific and UE-specific RRC configuration, while urging study of a simplified SFI indication framework that avoids slot-level SFI complexity by using fewer long-term slot formats. They require native support for semi-static BS-side SBFD with time-frequency domain subband-level TDD UL/DL configuration, and propose further study of flexible SBFD subband bandwidth changes via DCI or MAC CE mechanisms, including a flexible subband mechanism analogous to flexible symbols in NR. Huawei further proposes studying flexible DL/UL pairing that decouples DL and UL carriers across different bands, and time-domain scheduling with flexible duration and location using a unified mapping type that replaces NR's separate mapping type A and type B schemes.
Key proposals
- Proposal 1 (Sec Numerology/SCS): RAN1 assumes same SCS between 6GR Sync signals and other channels/signals (except PRACH) in FR2-1, i.e., only 120kHz in FR2-1.
- Proposal 2 (Sec Frame Structure/Flexibility of TDD): DL symbols, UL symbols, flexible symbols and SBFD symbols should be kept. FFS the use cases of flexible symbols.
- Proposal 3 (Sec Frame Structure/Flexibility of TDD): Cell-specific RRC configuration and UE-specific RRC configuration should be used in 6GR to configure the frame structure of the UEs.
- Proposal 4 (Sec Frame Structure/Flexibility of TDD): Transmission direction indication in TDD should be studied in 6GR taking into consideration the realistic variation in DL/UL traffic. E.g., RAN1 study and design a simplified SFI indication framework.
- Proposal 5 (Sec Frame Structure/SBFD): Semi-static BS side SBFD should natively be supported.
- Proposal 6 (Sec Frame Structure/SBFD): Time-frequency domain configuration, e.g., subband-level TDD UL/DL configuration, shall be further considered.
- Proposal 7 (Sec Frame Structure/SBFD): Flexible SBFD change in terms of subband bandwidth can be further studied in 6GR.
- Proposal 8 (Sec Frame Structure/Flexible pairing of DL and UL): 6GR frame structure configuration considering flexible uplink and downlink paring should be studied.
- Proposal 9 (Sec Frame Structure/Timing unit for scheduling): Time-domain scheduling in 6GR with flexible duration and flexible location should be further studied.
- Proposal 10 (Sec Frame Structure/Frequency-domain physical resources): 6GR defines CRB and PRB similar to NR.