R1-2600032
discussion
On synchronization acquisition and beam measurement
From Nokia
Summary
This Nokia Tdoc for the 6GR study item presents 28 proposals and 36 observations covering the design of synchronization signals, broadcast channels, mobility measurements, and AI/ML in initial access. The document's technical focus spans synchronization raster definition, PSS/SSS sequence design, PBCH combining, on-demand system information delivery, beam management, and measurement frameworks for 6GR.
Position
Nokia proposes studying ZC sequence-based designs for PSS to exploit robustness against frequency offset, contrasting with NR's m-sequence approach and noting ZC sequences require fewer frequency hypotheses for reliable correlation peak strength. They propose studying a single PSS sequence to reduce initial cell selection complexity by a factor equal to the number of frequency hypotheses and synchronization raster points. For SSS, they propose Gold sequences as baseline, while noting these sequences lose their autocorrelation/cross-correlation properties under frequency offset, requiring the UE to have sufficient synchronization for IDLE mode measurements. They propose studying on-demand SIB1 delivery in both stand-alone and non-stand-alone scenarios, extending beyond Rel-19's multi-cell limitation. For FR2-1, they require 240kHz SCS SS/PBCH support to halve the time-domain footprint and increase cell spectral efficiency, with numerical analysis showing 2-12% DL resource gain depending on channel bandwidth and FDM assumptions. They propose studying AI/ML in initial access by fully reusing Rel-19 AIML beam management models for spatial-domain and temporal-domain DL Tx beam prediction.
Key proposals
- Proposal 1 (Sec 3): RAN1 to study the time and frequency allocation of 6GR SS/PBCH assuming at least 5MHz (for 15kHz SCS) bandwidth and considering initial cell selection complexity.
- Proposal 2 (Sec 3.2): For 6GR assume that initial synchronization signal(s) need to be able to carry information on the physical cell ID, at least 1008 IDs.
- Proposal 3 (Sec 3.2): For 6GR study, assume that at least two initial synchronization signal types, PSS and SSS, are supported in hierarchical manner.
- Proposal 4 (Sec 3.3): RAN1 should study the benefit of single PSS sequence to reduce the initial cell selection complexity.
- Proposal 5 (Sec 3.3): RAN1 should consider ZC sequence based designs for PSS sequence design due to its robustness against frequency offset.
- Proposal 6 (Sec 3.3): RAN1 to consider Gold sequence as a baseline for SSS sequence design.
- Proposal 11 (Sec 3.5): 6GR PBCH design should enable PBCH combining by avoiding time variant payload.
- Proposal 14 (Sec 3.7.1): For frequencies around 7 GHz, study the maximum number of SS/PBCH positions (beams) to be supported.
- Proposal 15 (Sec 3.7.2): For frequency ranges using 120kHz SCS, 240kHz SCS SS/PBCH should be supported for 6GR to enable smaller time domain footprint of SS/PBCH transmissions providing higher cell spectral efficiency.
- Proposal 16 (Sec 4.1): Study the support of on-demand SIB1 (RMSI) delivery considering both stand-alone and non-stand-alone scenarios.
- Proposal 17 (Sec 5): Study additional on-demand synchronization signals for facilitating UE synchronization for paging reception.
- Proposal 19 (Sec 6.1): Study synchronization signal (SS), as measurement signal for mobility in all RRC states.
- Proposal 21 (Sec 6.1): Study NZP-CSI-RS as mobility measurement signal at least in CONNECTED MODE.
- Proposal 27 (Sec 6.4): Study Radio Link Monitoring for 6GR.
- Proposal 28 (Sec 7): RAN1 should consider studying AI/ML in initial access and RA procedures by fully reusing AIML models evaluated for Rel19 AIML beam management use cases (BM-Case1: Spatial-Domain DL Tx Beam Prediction and BM-Case2: Temporal-Domain DL Tx Beam Prediction).