R1-2508682
discussion
6GR air interface design overview
From Xiaomi
Summary
This 3GPP RAN1 contribution from Xiaomi provides a comprehensive overview of 6G radio physical layer design, covering scalable design, coverage, minimum bandwidth, BWP, NR-6G coexistence, spectrum aggregation, sync signals, NTN, and sensing across 24 proposals and 8 observations.
Position
Xiaomi proposes that 6G initial access and coverage enhancement frameworks should be commonly applicable to all device types with scalable performance. They require MCL as the coverage performance metric, citing comparability with 5G targets and independence from carrier frequency. They oppose studying 3 MHz smallest maximum UE bandwidth for low-tier devices, arguing it cannot achieve meaningful complexity reduction versus 5 MHz while requiring substantial system design changes. For BWP, they propose enhancements targeting switching latency reduction, reliability improvement, and simplification by reducing per-BWP parameter proliferation. They propose reusing NR's RE-level and RB-level rate-matching mechanisms for 5G-6G coexistence under MRSS. For spectrum aggregation, they propose studying flexible DL/UL carrier pairing to break tight linkage, aggregating fragmented spectrums as single serving cells, and allowing up to two scheduling cells per scheduled cell for PDCCH offloading. For sensing, they propose prioritizing four specific deployment-scenario combinations and require a unified design of sensing and communication with mandatory ISAC support for basic functionality.
Key proposals
- Proposal 1 (Sec 2.1): 6G initial access should be designed to be commonly applicable to all 6G device types.
- Proposal 3 (Sec 2.2): MCL is used as 6G coverage performance metric.
- Proposal 6 (Sec 2.3): For smallest maximum UE BW for at least one low-tier device type supported by 6GR framework from physical layer perspective, further study the following Option 2/3/4: Opt 2: 5 MHz with 15 kHz SCS, Opt 3: 10 MHz with 30kHz SCS, Opt 4: 20 MHz.
- Proposal 9 (Sec 2.4): BWP operation can be further enhanced in 6GR. At least the following aspects can be considered: Reduction on BWP switching latency, Enhancement for BWP switching reliability, Simplification for BWP switching, Improve system performance during BWP switching, BWP operation for energy saving.
- Proposal 10 (Sec 2.5): For MRSS, in time domain, 6G frame boundary, slot boundary and symbol boundary should be aligned with 5G NR; in frequency domain, same numerology, same Point A and same resource grid should be aligned between 5G and 6G.
- Proposal 12 (Sec 2.6): For 6GR, RAN1 should study to solve the pain points of the existing technologies of spectrum utilization and aggregation on top of existing CA/multi-carrier technologies.
- Proposal 17 (Sec 2.7): The default SSB periodicity should be studied by taking NES, UE cell search latency, and UE cell search complexity into account. The default SSB periodicity should be no larger than X, e.g., X = 40 ms.
- Proposal 18 (Sec 2.8): During 6G NTN discussion, holistic NTN support in day 1 needs to be targeted with the delivery of essential features addressing versatile commercial needs in synchronization with TN under the harmonized design principle according to the lessons learned from NR/IoT NTN.
- Proposal 21 (Sec 2.9): To support the most important near future applications with a feasible evaluation effort, Rel-20 prioritizes following combinations of target type and deployment scenario: 1 UAV sensing scenario UMa-AV, 1 human sensing scenario InH, 1 automotive sensing scenario Urban grid, 1 AGV sensing scenario InF.
- Proposal 23 (Sec 2.9): RAN1 should strive for a unified design of sensing and communication, with mandatory support of ISAC at least for basic functionality.
- Proposal 5 (Sec 2.3): Do not consider the smallest maximum BW of 3MHz for 6G devices.
- Proposal 14 (Sec 2.6): For 6GR, RAN1 should study flexible pairing of DL and UL carriers to accommodate different DL and UL service requirements.
- Proposal 16 (Sec 2.6): For 6GR, RAN1 should study the scheduling mechanism to allow up to two scheduling cells for a scheduled cell for PDCCH offloading.
- Proposal 20 (Sec 2.8): Multi-Satellite Coordination based on efficient cell/cell group management needs to be considered for 6G NTN day 1 thanks to its data rate improvement and service continuity benefit.