R1-2508560
discussion
Overview of 6GR air interface
From NEC
Summary
This NEC contribution for the 3GPP RAN1 6GR study provides a comprehensive overview of physical layer design principles across 12 technical areas, containing 22 numbered proposals and 5 observations. The document emphasizes a 'lean' design philosophy that limits configuration flexibility, proposes Day 1 support for diverse device types including LPWA, and introduces concepts like single-cell operation with non-contiguous spectrum and two-stage DCI.
Position
NEC proposes a lean 6GR design philosophy that explicitly limits configuration flexibility by restricting the number of supported options per function and special cases in the specification, learned from 5G NR's over-designed flexibility. The company requires 200MHz channel bandwidth in FR1 with 30kHz SCS, arguing comparable complexity between a single 8k FFT and dual 4k FFTs with frequency shifting. NEC introduces a single-cell operation concept for non-contiguous frequency resources, proposing to logically unify fragmented spectrum under one serving cell rather than relying on the 5G CA model, and requires studying initial access signals design (SSB/PBCH/SIB) and resource allocation for this paradigm. For initial access, NEC proposes simplifying the SSB-RO mapping mechanism by eliminating the three-layer concept of mapping cycle, association period, and association pattern period, and requires native support of repetition on PDCCH/PDSCH for SIB1, OSI, paging and Msg1/2/3/4/5 from Day 1. NEC proposes studying two-stage DCI for multi-carrier and PXSCH scheduling to reduce DCI size and PDCCH blind detection complexity caused by the many DCI formats and RNTI scrambling types in 5G NR. On MRSS, NEC proposes reusing existing 5G NR initial access signals (SSB, PRACH) and reference signals (CSI-RS) for 6GR UEs in co-located deployments, with rate matching of 6GR transmissions around 5G NR signals.
Key proposals
- Proposal 2.1.1 (Sec 2.1): 6GR design should consider the trade-off between configuration flexibility and complexity in real deployment. Over-designed configuration flexibility should be avoided, e.g., limit the number of supported options for a function, limit the number of special cases to be handled by the specification.
- Proposal 2.2 (Sec 2.2): 6GR scalable design should support LPWA use cases, which should support channel bandwidth from 3 MHz (same as NR) and UE type(s) with/without reduced bandwidth 5 or lower MHz. Narrow channel bandwidth of 300 kHz should be out of scope of the scalable design of 6GR.
- Proposal 2.3 (Sec 2.3): Coverage enhancement feature should be considered in 6GR Day 1, 6G UE should support repetition of physical signals and physical channels and UL dynamic waveform switching.
- Proposal 2.4 (Sec 2.4): 6GR supports 200MHz channel bandwidth in FR1 with 30kHz subcarrier spacing.
- Proposal 2.5 (Sec 2.5): 6GR study an efficient frequency resource management method on fragmented spectrum, at least including single cell operation with non-contiguous frequency resources, resource allocation aspects, initial access channels and signals design with non-contiguous frequency resources, UE capability aspects, and carrier aggregation enhancement.
- Proposal 2.6 (Sec 2.6): In the 6GR initial access study, consider specification simplification compared to 5G NR (e.g., simplified PRACH resource configuration and SSB-RO mapping mechanism), further improving power efficiency, scalable and forward-compatible design for diverse device types, and native coverage performance improved mechanism (e.g., native support of repetition on PDCCH/PDSCH for SIB1, OSI, paging and Msg1/2/3/4/5).
- Proposal 2.7.1 (Sec 2.7): Study two-stage DCI at least for multi-carrier scheduling, and one or multiple PXSCH scheduling.
- Proposal 2.8 (Sec 2.8): 6GR consider to study the following enhancement of SBFD: gNB dynamic SBFD, UE SBFD, gNB FD (partial overlapped SBFD).
- Proposal 2.9 (Sec 2.9): Study tight interworking for spectrum sharing between 6GR and 5G NR, at least including reusing of 5G NR initial access channels and signals for a 6G UE to connect to the 6G cell, rate matching of 6GR transmissions around 5G NR signals and channels, reusing 5G NR Reference Signals for 6GR channel measurements, dynamic allocation of 5G NR and 6GR radio resources within MRSS, both TDM and FDM multiple access types, and guard band for FDM MRSS.
- Proposal 2.10.1 (Sec 2.10): The 6GR frame structure design shall incorporate inherent flexibility to optimize spectrum efficiency for both TN (multipath-rich) and NTN (LOS-dominant) channel characteristics without requiring fundamentally different designs.
- Proposal 2.11.1 (Sec 2.11): Study a unified framework for AI/ML for 6GR, ensuring high performance, security, and adaptability to all use cases in 6G, including unified data collection framework, unified LCM framework, and unified and dynamic AI processing capability among multiple AI/ML functionalities as well as non-3GPP applications.
- Proposal 2.12 (Sec 2.12): In the 6GR ISAC study, all sensing modes should be studied including collaborative sensing mode and multi-static sensing mode, the study should extend beyond UAV use case to smart home, smart factories, and public transportation, and should consider both sensing-assisted communication and communication-assisted sensing.