R1-2601848
discussion
On NTN specific requirements and design for GNSS based operation in 6GR
From Nokia
Nokia's prior position on
10.7.1
at
RAN1#124
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Requires that all 6G devices support GNSS for NTN operation and that 6G systems support NTN from day one with maximum similarity to the terrestrial network (TN) design, insisting NTN-specific features must only be introduced when strictly necessary. Opposes the Rel-18 network verified UE location feature unless it is accurate, trustworthy, and has mandatory UE support. Proposes studying extended PDSCH/PUSCH transmission duration to combat HARQ stalling, and studying concurrent SIB1 and NTN access essential SIB scheduling to improve initial access latency and reliability. Calculates TDD efficiency losses of 14-31% for LEO orbits and therefore requires that 6G NTN studies focus on FDD duplex mode.
Summary
Nokia's contribution to the 3GPP RAN1 #124bis meeting on 6G NTN discusses GNSS-based operation requirements, proposing 21 specific technical recommendations and 2 observations. The document argues for maximum harmonization between terrestrial (TN) and non-terrestrial (NTN) 6G designs, with NTN-specific features introduced only when strictly necessary, and proposes studying solutions for HARQ stalling, SIB scheduling, beam management, and dynamic scheduling offsets.
Position
Nokia requires that all 6GR NTN capable devices support accurate pre-compensation (GNSS-based or via detailed prior geo-location), and that the 6GR system supports NTN from day one with maximum similarity to TN design. They propose that network-verified UE location features be considered only with mandatory UE support and adequate accuracy. Nokia opposes simultaneous multi-satellite UE connections for CA or multi-orbit operation due to timeline and frequency offset complexity. They propose integrating the k_offset_UE component into the UL scheduling grant (TDRA table) to replace MAC-CE based adjustment, citing latency, reliability, and signaling overhead drawbacks of the current approach. Nokia recommends studying extended PDSCH/PUSCH transmission duration to address HARQ stalling without increasing soft buffer memory, and proposes concurrent scheduling of SIB1 and NTN access essential SIB information to reduce initial access latency. They argue that NTN studies for 6GR should focus exclusively on FDD duplex mode, presenting technical analysis showing 14-31% resource loss for TDD operation at LEO orbits of 600-1200 km.
Key proposals
- Proposal 1 (Sec Introduction): All 6GR NTN capable devices are expected to support accurate pre-compensation (i.e. GNSS-based or based on detailed geo-location) to facilitate 6GR NTN based operation.
- Proposal 4 (Sec Considerations on learnings from NR over NTN work): NTN operation in 6GR system shall strive for maximum similarity to the 6GR TN system.
- Proposal 8 (Sec 6GR NTN link budget): Consider our input to the link budget template in the attached document.
- Proposal 10 (Sec 6GR NTN and GNSS-based/resilient operation): UEs that can guarantee to perform sufficiently accurate pre-compensation based on prior knowledge of geo-location may consider themselves as able to connect to the 6GR system as if they were GNSS-enabled.
- Proposal 11 (Sec Considerations on NTN specific SIB in 6GR NTN): RAN1 to study mechanisms for concurrent scheduling of SIB1 and NTN access essential SIB system information.
- Proposal 12 (Sec Considerations on HARQ processing in 6GR NTN): Study extended duration of PDSCH and/or PUSCH transmissions targeting the problem of HARQ stalling in NTN.
- Proposal 13 (Sec Timing relationships with large RTT): Integrate at least the k_offset_UE component into the UL scheduling grant (e.g. in the TDRA table) to allow for more dynamic and efficient adjustment of the UE scheduling offset(s).
- Proposal 15 (Sec Coverage target): Coverage enhancement solutions arising from NTN requirements should also be applicable to TN without modifications.
- Proposal 16 (Sec Physical layer aspects of multi-satellite operation): RAN1 does not support simultaneous UE connections to multiple satellite, neither for CA nor for multi-orbit.
- Proposal 17 (Sec Aspects related to Multiple beams per satellite): RAN1 should study aspects relevant to RAN1, such as broadcast information and beam management, to facilitate the coexistence of wide and narrow beams.
- Proposal 18 (Sec Aspects related to satellite having more beam footprints than simultaneously active beams): 6GR for NTN to define different CORESET0 periodicities based on defined SSB periodicities.
- Proposal 21 (Sec Duplex mode): NTN studies for 6GR should focus on FDD.