R1-2508685
discussion
Discussion on 6G frame structure
From Xiaomi
Summary
Xiaomi's contribution R1-2508685 presents 11 proposals for 6G frame structure design, focusing on simplified numerology (single per band), streamlined duplex modes, simplified slot format, efficient Multi-RAT Spectrum Sharing (MRSS) with 5G NR, and dedicated ISAC CP length considerations. The document argues against over-optimization seen in 5G NR dynamic TDD designs.
Position
Xiaomi proposes continuing 5G NR numerologies (15 × 2^k kHz) for 6G but requires a single numerology per band to simplify UE behavior, avoiding multiple BWPs with different SCS. They oppose gNB-side dynamic SBFD, UE-side SBFD, and gNB full duplex for 6G Day 1, supporting only FDD, TDD, HD-FDD on UE side, and gNB-side semi-static SBFD. They require simplifying 6G slot format design by dropping DCI format 2_0 for dynamic slot indication and oppose UE-dedicated TDD UL/DL configuration (tdd-UL-DL-ConfigurationDedicated), supporting only cell-level configuration. For MRSS, they require time-domain boundary alignment and frequency-domain resource grid alignment between 5G and 6G, reusing NR-LTE rate-matching. They propose to align sensing and communication on sub-frame level but study a longer CP length for sensing to handle larger delay spread in monostatic and bi-static scenarios.
Key proposals
- Proposal 1 (Sec 2.1): Continue using SCS of 15 × 2^k kHz for 6G.
- Proposal 2 (Sec 2.1): Support a single numerology for each band for 6G.
- Proposal 5 (Sec 2.2): 6GR should support FDD, TDD, HD-FDD on UE side and gNB side semi-static SBFD; no support of gNB side dynamic SBFD, UE side SBFD or gNB side full duplex.
- Proposal 6 (Sec 2.3): Simplify 6G slot format design and avoid over-optimization.
- Proposal 7 (Sec 2.3): Support only cell level TDD UL/DL configuration for 6GR.
- Proposal 8 (Sec 2.4): For MRSS, align 6G frame/slot/symbol boundaries with 5G NR in time domain and align numerology, Point A, and resource grid in frequency domain.
- Proposal 9 (Sec 2.4): Reuse RE-level and RB-level rate-matching mechanisms specified for NR-LTE coexistence for 5G-6G coexistence.
- Proposal 10 (Sec 2.5): Align sensing and communication on sub-frame level.
- Proposal 11 (Sec 2.5): Study a CP length longer than for communication to guarantee sensing performance with large coverage.
- Proposal 3 (Sec 2.1): For around 7GHz, maximum 200MHz channel bandwidth is supported for a UE.
- Proposal 4 (Sec 3): For around 7GHz, aggregating two 200MHz bandwidth carriers via CA framework to adapt 400MHz spectrum is supported.