R1-2508462
discussion
On 6G frame structure
From Ericsson
Summary
Ericsson's contribution contains 3 observations and 9 proposals covering numerology, duplexing, and frame configuration for 6G Radio. The document argues for a simplified 15 kHz-only SCS for FDD below 6 GHz, removal of 60 kHz SCS for 15 GHz, deprioritization of complex duplexing schemes like dynamic SBFD and gNB FD, removal of SFI-based operation, and introduction of new 'Mixed DL/UL' and 'None' resource types in the frame structure.
Position
Ericsson proposes limiting 6GR FDD bands below sub 6 GHz to only 15 kHz SCS, citing MRSS coexistence with 5G and IODT testing constraints. They oppose supporting 60 kHz SCS for around 15 GHz, presenting link-level simulation results showing 120 kHz SCS is inferior to 30 kHz/60 kHz under 300ns delay spread, and arguing 60 kHz would have no other frequency range market. They require removal of SFI-based operation (DCI 2_0) from the 6G duplexing study, arguing the UE procedures in TS 38.213 Clause 11.1.1 for determining slot format using dynamic SFI are highly complex and SFI has not been deployed. They propose deprioritizing gNB dynamic SBFD and gNB FD for communications use-cases, citing Rel-18 agreements on increased CLI and implementation complexity, and require that any new duplexing scheme such as UE SBFD demonstrate clear measurable gains over alternatives like cross-band carrier aggregation with independent TDD patterns before adoption. They propose studying two new resource types for 6GR frame configuration: 'Mixed DL/UL' to natively support SBFD and dynamic TDD without inheriting NR flexible symbol complexity, and 'None' to explicitly reserve time-frequency resources for guard periods and services like ISAC.
Key proposals
- Proposal 1 (Sec 2.1): For FDD bands below sub 6 GHz, support only 15 kHz SCS.
- Proposal 3 (Sec 2.1): Do not support 60kHz subcarrier spacing for around 15 GHz.
- Proposal 4 (Sec 2.1): Support only the normal CP for communication purposes in 6GR.
- Proposal 5 (Sec 2.2): For Dynamic TDD, the key lesson learned is the high complexity of SFI operation using DCI2_0. Remove SFI-based operation from the 6G duplexing study.
- Proposal 6 (Sec 2.2): RAN1 to deprioritize gNB dynamic SBFD and gNB FD for communications use-cases in the 6GR duplexing study.
- Proposal 7 (Sec 2.2): New duplexing schemes for 6G (such as UE SBFD) should be studied in a holistic manner and must demonstrate clear, measurable performance gains with reasonable complexity compared to other solutions/technologies before being adopted.
- Proposal 8 (Sec 2.3): For 6GR, study frame format configurations incorporating a 'Mixed DL/UL' resource type that natively supports flexible time-frequency configurations, enabling both traditional duplexing modes, dynamic TDD, and advanced duplexing modes such as SBFD.
- Proposal 9 (Sec 2.3): For 6GR, study frame format configurations incorporating a 'None' resource type that natively supports flexible configuration of time-frequency resource reservation, that would explicitly represent symbols or resources reserved for guard periods and other non-scheduling purposes or new services like ISAC.
- Proposal 2 (Sec 2.1): SSB uses the same SCS as PDxCH.
- Observation 3 (Sec 2.1): For the channel models in the 3GPP scenarios UMa and UMi, without beamforming, the delay spread is larger than 300ns for 15%-20% of the cases.