R1-2600112
discussion
Discussion on 6GR synchronization acquisition and beam measurement
From Spreadtrum
Summary
Spreadtrum/UNISOC provides 33 proposals and 5 observations on 6GR synchronization acquisition and beam measurement, advocating NR initial access procedures as the baseline while introducing enhancements for coverage, energy efficiency, and AI-based beam prediction. The document covers SSB structure, periodicity, sequence design, PBCH content, RMSI delivery, paging, on-demand signals, sync signal-less operation, cell DTX/DRX, and beam management across both idle and connected modes.
Position
Spreadtrum proposes that NR initial access procedures serve as the baseline for 6GR design with specific evolutionary enhancements. They argue that reducing 6GR sync signal bandwidth by a small margin does not significantly reduce sync raster entries but seriously degrades SSB receiving performance, and present evaluation results showing only 6% additional NES gain when extending SSB periodicity from 40ms to 80ms under zero load. They require same SCS between 6GR PSS/SSS and other channels/signals (except PRACH) for a given band across all frequency ranges, opposing different SCS for SSB versus other channels in FR2-1. They propose studying beam prediction for initial access (Sub-use case D) leveraging AI/ML experience from NR BM-Case 1 for both SSB spatial prediction (Set B subset of Set A) and beam refinement prediction (Set B different from Set A). They support introducing cell DTX/DRX operation in idle state and on-demand sync signals for both single-cell and multi-cell deployments, with NR SSB-less solutions as starting points for sync signal-less operation.
Key proposals
- Proposal 1 (Sec 2): NR initial access procedure should be a starting point for 6GR initial access design.
- Proposal 4 (Sec 3.1): A single unified SSB structure design needs to be defined to meet all the supported deployment scenarios: single/multiple cells/carriers/TRPs/beams, frequency ranges, TN and NTN.
- Proposal 6 (Sec 3.2): 5G NR m-sequence could be the base sequence for 6GR PSS/SSS.
- Proposal 9 (Sec 3.3): In order to balance UE experience and network energy-saving requirements, 40ms SSB periodicity for initial access can be a starting point.
- Proposal 11 (Sec 3.4): For frequency domain, Opt1 is adopted for 6GR SSB design for initial access by assuming 5MHz with a 15kHz SCS.
- Proposal 13 (Sec 3.5): SSB burst set in NR should be inherited to 6GR and the maximum number of SSB index (i.e., the value of Lmax) can be further studied and evaluated together with SSB coverage requirement.
- Proposal 15 (Sec 3.6): At least SFN, half-frame-index (if necessary), SSB index, SSB subcarrier offset, RMSI PDCCH configuration, and DL DMRS position should be carried by 6GR PBCH.
- Proposal 17 (Sec 3.7): Coverage enhancements for RMSI delivery should be considered in 6GR day1 and NR time domain repetition scheme can be considered as the starting point.
- Proposal 22 (Sec 4.1): On-demand SSB for Scell can be considered in 6GR Day1, and the legacy NR solution can be considered as the starting point.
- Proposal 24 (Sec 4.1): For 6GR idle mode, two cases of on-demand sync signal(s) for sync and initial access in multiple cells/carriers deployment can be studied: Case 1 with no always-on sync signals in non-anchor/capacity carriers, Case 2 with always-on sync signal with longer periodicity in non-anchor/capacity carriers.
- Proposal 26 (Sec 4.3): Time domain (e.g., periodicity), spatial domain (e.g., actually transmit SSB index), and power domain (e.g., power allocation) aspects can be studied and evaluated for 6GR sync signals adaptation.
- Proposal 28 (Sec 4.4): For 6GR RRC idle mode, sync signal-less operation for the non-anchor/capacity carriers/NES cells can be studied and NR SSB-less solution can be considered as the starting point.
- Proposal 29 (Sec 4.5): Enhanced cell DTX/DRX operation compared with NR in RRC connected state and cell DTX/DRX operation in idle state need to be studied.
- Proposal 31 (Sec 5.2): In 6GR RRC CONNECTED mode, at least SSB and CSI-RS can be studied for RRM measurement for L3 mobility.
- Proposal 33 (Sec 6.1): Beam prediction for 6GR initial access (Sub-use case D) should be studied.