R1-2600045
discussion
On the design of WUS with OFDM based sequence
From Nokia
Summary
This Nokia contribution discusses 6G WUS (Wake-Up Signal) design aspects, focusing on OFDM-based sequences, energy-efficient processing assumptions, and information mapping schemes. It contains 7 proposals and 14 observations covering CFO assumptions, RX chain configurations, sequence family selection, subgroup mapping, and coverage targets.
Position
Nokia proposes assuming a more stringent residual CFO of 1 ppm for the EE processing state, arguing that SSB-based calibration during active states can maintain this accuracy from initial cell search. They require the minimum number of RX chains for 6G WUS reception to depend on RRC state and frequency range, noting that deep/ultra-deep sleep states justify single RX chain operation due to lack of channel state information and CFO accuracy. Nokia proposes exploring m-sequence and Gold sequence families as alternatives to Zadoff-Chu for 6G WUS, while requiring evaluation of sequences based on auto correlation peak prominence, low cross correlation performance, and receiver complexity. They propose studying both direct subgroup-specific sequence mapping (codepoint scheme) and segmented bitmap mapping to OFDM sequences, noting that controlling the number of segments allows the design to mimic either scheme. Nokia also proposes striving for WUS coverage equivalent to paging PDCCH coverage at aggregation levels 8 and 16.
Key proposals
- Proposal 1 (Sec CFO Assumption): RAN1 should assume residual CFO of 1 ppm for EE processing state for efficient 6G WUS signal design.
- Proposal 2 (Sec RX chains): The minimum number of RX chains assumed for 6G WUS reception shall depend on the RRC state and the operating frequency range, i.e., FR1, FR1-2, or FR2.
- Proposal 3 (Sec Sequence Family): Unlike 5G, where Zadoff-Chu sequence is overlaid on OOK, RAN1 shall explore the possibility of other sequence families, such as m-sequence, Gold sequence, can be considered for 6G WUS.
- Proposal 4 (Sec Sequence Family): RAN1 shall evaluate sequences, if any, using the following KPIs, namely, auto correlation peak prominence, low cross correlation performance, and the receiver complexity to generate and correlate multiple sequences.
- Proposal 5 (Sec Information Mapping and Subgroups): RAN1 shall study direct mapping of a specific sequence to a subgroup and a sequence indicating the wake-up of all subgroups.
- Proposal 6 (Sec Information Mapping and Subgroups): RAN1 shall study bitmap scheme with segmented bits mapped to a specific sequence.
- Proposal 7 (Sec Coverage and System Overhead): RAN1 shall strive to achieve the WUS coverage same as that of paging PDCCH coverage (AL8 and AL16).