R1-2508472
discussion
Overview of 6GR air interface
From Thales
Summary
Thales and co-signatories present 7 proposals and 1 observation advocating for native NTN integration in the 6G radio design from the outset, emphasizing that 5G's late NTN addition led to non-optimized adaptations. The document details specific technical aspects requiring early harmonization, including waveform design, frame structure, GNSS-independent operation, and support for all orbit types from VLEO to GSO.
Position
Thales requires NTN-specific considerations be integrated into the 6G radio design from the initial 6G specification in Release 21, citing the lesson from 5G NR that late NTN addition necessitated non-optimized adaptations. They propose studying waveform design, frame structure, channel coding, MCS, and AI/ML with NTN challenges such as high Doppler shifts (up to 24.23 ppm for VLEO), large/variable RTT (up to 541.46 ms for GSO), and low SNRs as primary design drivers. They define detailed reference deployment scenarios across five orbit types with specified altitudes (300 km VLEO to 35,786 km GSO), maximum beam footprint sizes ([<250] km), and service link minimum elevation angles (10°). They require the physical layer to operate independently of GNSS, support PAPR reduction for OFDM-based satellite downlink, achieve ultra-low BLER of 10^-6 without HARQ to avoid latency from long propagation delays, and extend SSB periodicity up to 320 ms for beam hopping.
Key proposals
- Proposal 1 (Introduction): NTN-related technical considerations should be addressed early in the 6G study, including in waveform design, frame structure, channel coding, MCS, AI/ML, and evaluation assumptions, considering high Doppler, large/variable RTT, low SNRs, and compatibility across VLEO, LEO, MEO, and GEO orbits.
- Proposal 2 (Potential building blocks): RAN1 studies should identify technical aspects affected by NTN characteristics, including at least time/frequency synchronization, FFS on pre-compensation of RTT/Doppler, GNSS-independent physical layer, PAPR reduction for NTN DL, frame structure, coverage enhancements, ultra-low BLER avoiding HARQ, beam hopping with extended SSB periodicity, duplexing mode, NTN propagation impairments, positioning/navigation/timing, and 6G NTN coexistence with IoT-NTN or NR-NTN in the same beam.
- Proposal 3 (Orbits): The 6G radio interface/access shall be defined to support all practical NTN deployment scenarios described in terms of orbits and related service link characteristics, including VLEO (300 km), medium LEO (600 km), high LEO (1200 km), MEO (8000 km), and GSO (35,786 km) with earth-fixed steerable beams.
- Proposal 4 (Payloads and feeder links): The 6G radio interface/access shall be defined to support all NTN payload types including transparent, semi-transparent (RU), regenerative with full BS, and regenerative with functional BS split (RU+DU).
- Proposal 5 (Duplexing mode): The 6G radio interface/access shall be defined to support all duplex modes at UE and network level, including full-duplex FDD, half-duplex FDD, and TDD, with specific payload types for each.
- Proposal 6 (6GR UE): The 6G radio interface/access shall be defined to support all NTN capable UE types including smartphones/IoT with omnidirectional antennas operating up to ~7 GHz, and vehicle/building/vessel/aircraft mounted devices with directional antennas across all satellite frequency bands, with specified antenna gain, transmit power, noise figure, and ground speed parameters.
- Proposal 7 (Positioning, Navigation and Timing): The 6G radio interface/access shall be defined to provide high-accuracy and resilient positioning without GNSS service.