R1-2600128
discussion
Discussion on 6GR NTN specific requirements and design for GNSS based operation
From Spreadtrum
Summary
Spreadtrum provides 2 observations and 13 proposals on 6G NTN design, focusing on leveraging 5G NTN legacy solutions as a starting point while promoting unified TN/NTN designs where applicable. The document covers synchronization, timing, initial access, coverage, capacity, signaling overhead, beam management, duplexing, and energy efficiency.
Position
Spreadtrum proposes reusing 5G NTN legacy solutions as the starting point for UL frequency synchronization and UL timing advance maintenance in 6G. They require unified TN/NTN design for cell search procedure, coverage features, HARQ process number/HARQ-ACK feedback disable, maximum SSB index count (Lmax), and cell DTX/DRX mechanism. They propose studying longer SSB periodicity (160ms or larger values) for NTN with limited simultaneously active beams, and support FDD and HD-FDD for 6G day-1 NTN. They propose studying OCC-based UL capacity increase with OCC schemes, OCC length, and UL channels (PRACH, Msg3, CG-based SDT), with NTN study first and conclusions applied to TN. They propose studying TN energy-saving technologies first, then adapting results to NTN considering time/frequency synchronization, timing relationship, and beam hopping.
Key proposals
- Proposal 1 (Synchronization): For UL frequency synchronization, legacy solution in 5G NTN can be as the starting point.
- Proposal 3 (Timing relationship): For the timing definitions involving DL-UL timing interaction, similar as 5G NTN, additional timing delay (e.g., Koffset and/or Kmac) configured by network can be studied.
- Proposal 5 (Initial access): For NTN with limited number of simultaneously active beams, longer periodicity (e.g., 160ms or larger values) of sync signal(s) for initial access can be studied.
- Proposal 6 (Coverage): Coverage features to meet coverage target can be uniformly discussed in the corresponding sections of the 6GR signal/channels design, which are applicable to NTN and TN.
- Proposal 8 (Capacity/throughput): For 6GR, increasing UL capacity through OCC can be studied with aspects including OCC schemes, OCC length, and UL channel(s) applied OCC (e.g., PRACH, Msg3, CG based SDT); study can be conducted first in NTN section with conclusions applied to TN.
- Proposal 9 (Signaling overhead): Study signaling overhead in aspect of mobility management, scheduling, etc.
- Proposal 10 (Beam management/beam hopping): On beam hopping in NTN, cell DTX/DRX mechanism can be considered for RRC idle/inactive mode and RRC connected mode, which should be unified design for NTN and TN.
- Proposal 11 (Beam management/beam hopping): On the maximum number of SSB indexes (i.e., Lmax), unified design for NTN and TN should be considered and it should be uniformly discussed in initial access section.
- Proposal 12 (Duplexing): Support FDD and HD-FDD in 6G day-1.
- Proposal 13 (UE/NW energy efficiency): Energy-saving technologies (for UE and/or network) can be studied in the TN first. Then, all the study results of energy-saving technologies will be adapted to NTN with considering time/frequency synchronization, timing relationship, and beam hopping.
- Proposal 4 (Initial access): Cell search procedure should be unified design for TN and NTN, which should be uniformly discussed in initial access section.
- Proposal 7 (Capacity/throughput): HARQ process number and HARQ-ACK feedback disable can be uniformly discussed in 10.5.4.3 section (i.e., HARQ related Aspects), which are applicable to for NTN and TN.
- Proposal 2 (Synchronization): For UL timing advance maintenance, legacy solution in 5G NTN can be as the starting point.