R1-2600198
discussion
Discussion on Synchronization acquisition and beam measurement for 6GR
From OPPO
Summary
OPPO presents 30 proposals and 11 observations on 6G Radio synchronization, SSB structure, energy efficiency, and initial access procedures. The document covers SSB design parameters, sync raster interaction, PBCH optimization, SSB periodicity/adaptation, on-demand SIB1/paging, coverage evaluation methodology, and beam measurement.
Position
OPPO proposes that 6GR SSB design use binary m-sequence/Gold sequence with length 127, matching NR, and requires orthogonal sequences if RAN4 does not separate sync raster points in MRSS spectrum. They propose a more compact PBCH payload (≤56 bits with CRC) and evaluate PBCH bandwidth ranges of [12-15] RBs and [16-20] RBs, showing number of RBs dominates performance. OPPO argues that extending default SS periodicity beyond 20ms proportionally increases UE search latency and power consumption, requiring mitigation via sparser sync raster or two-step cell search with high-priority sync raster points. They support SSB period adaptation up to 160ms for non-standalone cells, cell-triggered on-demand SS rather than SSB, and UE-triggered OD-SSB with a Discovery Signal for measurement and synchronization. OPPO proposes studying OD-SIB1 independent of Cell-A by compressing configuration into PBCH, and evaluates UE-triggered cell wake-up achieving 47-53% NES gain for BS Cat.1 and 30-35% for Cat.2 in low load.
Key proposals
- Proposal 1 (Sec 2.1): If sync raster points for 6GR cannot be sufficiently separated from those for 5GR, 6GR sync signal structure should be designed to prevent 5G UE from decoding 6GR PBCH.
- Proposal 2 (Sec 2.2): RAN1 should proceed with down selection between Opt1 and Opt2 agreed in RAN1#123 for minimum spectrum allocation of 3MHz with 15kHz SCS.
- Proposal 3 (Sec 2.3): Performance of 6GR sync signal should be better or at least not worse than 5G SSB, and SSB detection should be improved for cell-edge UE without undermining cell center UEs or sacrificing resource efficiency.
- Proposal 5 (Sec 2.4): For any introduced NES scheme on SSB, approach(es) to neutralize the negative impact if any to UE should be introduced at the end.
- Proposal 7 (Sec 3.1): PSS/SSS sequence length of 127 should be considered for 6GR.
- Proposal 9 (Sec 3.2): The decoding performance of 6GR PBCH should enable the coverage in around 7GHz comparable to that of Rel-15 NR Msg3 in 5G mid-band.
- Proposal 14 (Sec 3.4): For evaluation of candidate 6GR SSB structure, use parameters in Table 5, baseline 5G SSB, PSS/SSS length 127, PBCH BW [12-15] or [16-20] RBs, payload ≤56 bits, 4-6 OFDM symbols.
- Proposal 15 (Sec 4): If default SS period larger than 20ms is used, approaches should be introduced to ensure total time for initial cell search comparable to 5G.
- Proposal 18 (Sec 5): SSB period adaptation by transmitting SSB with a variety of periodicities up to 160ms should be supported in 6GR day 1 for non-standalone cell.
- Proposal 21 (Sec 5): For UE-triggered OD-SSB, study cell discovery/measurement, time/frequency synchronization for UL-WUS transmission, and provisioning of related configuration information.
- Proposal 25 (Sec 6): Study to support OD-SIB1 with and without relying on Cell-A.
- Proposal 26 (Sec 7): Both uniformly distributed PO configuration and clustered PO configuration should be considered in 6GR study.
- Proposal 28 (Sec 8): For sync signal/channel coverage evaluation, use MPL as metric with Target MPL = MPL of Rel-15 NR Msg3 + pathloss difference, following a 3-step methodology.
- Proposal 29 (Sec 9): Study an initial CORESET similar to CORESET#0 for scheduling PDSCH carrying system information before RRC connection setup.