R1-2601781
discussion
6G Synchronization Acquisition and Beam Measurement
From FUTUREWEI
FUTUREWEI's prior position on
10.5.1.1
at
RAN1#124
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Proposes extending 5G NR network energy saving techniques for 6G by removing backward compatibility constraints. Requires replacing frequent SSB/SIB1 transmissions with infrequent periodic transmissions up to 160ms for any SSB type (CD-SSB and NCD-SSB). Proposes a light Sync Signal structure with sequence-based design for indicating UL WUS configuration, beam/Sync Signal index, and LSBs of SFN, arguing this enables on-demand request of MIB/SIB1 in standalone cells and allows the BS to use a low-power transmitter. For paging, proposes clustering/grouping of legacy Paging Frames in time domain via frequency domain multiplexing to align cell DTX/DRX with UE DRX. Requires adoption from day one of duty-cycled operations and DL WUS of OFDM-based sequence with at least Rel-17 PEI functionality replacement, citing that DL WUS coverage comparable to a 6GR control channel is achievable when using the standard 6GR UE Noise Figure rather than relying on OOK waveform limitations.
Summary
This document presents 7 proposals and 15 observations covering synchronization/system information and paging transmission/monitoring for 6G Radio. It advocates for longer default SSB/SIB1 periodicity combined with light sync signals and on-demand mechanisms for network energy saving, along with paging frame clustering/grouping aligned with cell DTX/DRX and adoption of DL WUS of OFDM-based sequence as baseline UE energy saving mechanisms.
Position
Futurewei proposes supporting basic 6GR SSB design with bandwidth larger than 3MHz at 15KHz SCS, rejecting the ≤3MHz option as degrading PBCH detection performance and coverage compared to 5G NR's 3.6MHz SSB bandwidth. They propose defining a light sync signal structure consisting of at least PSS with lightweight sequence indication and optionally SSS to compensate for longer default SSB periodicity while maintaining cell search complexity. They propose on-demand Sync signal/SIB1 request in standalone cells using sequence-based indication of UL-WUS configuration, beam/Sync Signal index, and/or LSBs of SFN, with UL WUS design limited to a small number of OFDM sequences and listening occasions to enable low-power BS receiver operation. They propose clustered provisioning of cell-common signaling with frequency domain multiplexing of paging frames for aligned cell DTX/DRX and UE DRX, combined with DL-WUS grouping/subgrouping indication. They propose adoption from day one of DL WUS of OFDM-based sequence replacing Rel-17 PEI functionality and supporting dynamic POs as baseline UE energy saving mechanisms, citing achievable coverage comparable to 6G PDCCH when considering standalone DL WUS not reliant on OOK waveform.
Key proposals
- Proposal 1 (Sec 3.1): Support the design of basic 6GR sync signal structure (SSB) for initial access assuming bandwidth larger than 3MHz with 15KHz SCS, which is applicable to any spectrum allocations with adjustment, if applicable.
- Proposal 2 (Sec 3.2): Define a 6GR light sync signal structure which consists of at least primary synchronization signal(s) and lightweight sequence(s) indication(s), and optionally secondary synchronization signal(s).
- Proposal 3 (Sec 3.2): Consider the longer periodicity for 6GR SSB and SIB1 combined with light sync signal(s) (e.g., PSS with lightweight sequence indication and optionally SSS) and on-demand sync signal/SIB1 (in any cell type and for UEs in any RRC state) for network energy saving with minimal impact on UE cell search complexity and access latency.
- Proposal 4 (Sec 3.2): Consider network energy efficiency by adoption of on-demand Sync signal/SIB1 request in standalone cells utilizing sequence-based indication of UL-WUS configuration, beam/Sync Signal index, and/or LSBs of SFN, and UL WUS design based on limited number of sequences and UL WUS listening occasions.
- Proposal 5 (Sec 4.1): Consider realizing aligned design of cell DTX/DRX and UE duty cycled operations (i.e., IDRX and/or eDRX) using clustered provisioning of cell-common signaling, e.g., with frequency domain multiplexing, for improved network energy saving without sacrificing UEs performance (e.g., paging latency) and power saving.
- Proposal 6 (Sec 4.1): Consider PFs clustering/grouping combined with grouping information indication by DL-WUS and/or paging messages multiplexing in frequency domain as an approach for aligned Cell DTX/DRX and UE DRX.
- Proposal 7 (Sec 4.2): Consider the adoption from day one of DL WUS of OFDM based sequence with at least PEI functionality replacement and dynamic POs as baseline UE energy saving mechanisms in 6G.