R1-2600028
discussion
On remaining aspects of channel coding in 6GR
From Nokia
Summary
This document presents Nokia's views on 6G channel coding, containing 6 proposals and 2 observations. It addresses LDPC extensions for data rates beyond NR range, polar code enhancements for control channels, and the retention of 5G block codes for small block lengths in 6G.
Position
Nokia proposes defining the boundary between NR-range and beyond-NR-range data rates using the maximum TBS supported in 5G NR Rel-15 per carrier. For LDPC extensions beyond NR range, Nokia requires any new base graph to preserve the QC-LDPC dual-diagonal structure and sub-matrix construction from 5G, citing encoding efficiency advantages from avoiding matrix B inversion. Nokia presents technical evidence that reusing BG1 with an optimized puncturing pattern (puncturing columns 0 and 26 instead of the first two systematic columns) yields 0.2–0.44 dB gain at low MaxIts (e.g., 5 iterations) and reduces average normalized decoding iterations, positioning this as a candidate when reducing MaxIts is a design objective. For polar codes, Nokia questions the necessity of UCI payloads beyond NR range and proposes that any extension should design segment counts based on code rate and information length, with SCL decoding at list size 8 or 16 as the baseline receiver. Nokia requires block codes for small block lengths (≤11 bits) to remain identical to 5G, arguing minimal gain exists even under ML decoding.
Key proposals
- Proposal 1 (Sec 2.1): To facilitate the discussion on the data rate beyond NR range for the study of LDPC extension, RAN1 to consider discussing the max TBS supported in 5G NR Rel-15 per carrier.
- Proposal 2 (Sec 2.2.1): For LDPC extensions beyond 5G NR data rate range, in case an additional BG is studied, it should keep the same design principles as for 5G BGs, i.e. using QC-LDPC with dual-diagonal structure and sub-matrices construction as per 5G design principle.
- Proposal 3 (Sec 2.2.2): If reducing the MaxIts is a design objective for the study of LDPC extension for very high data rate, RAN1 to consider reusing BG1 with optimized puncturing pattern as one candidate for further study.
- Proposal 4 (Sec 3.1): For the study of UCI segmentation for UCI payload beyond NR range, the number of segments should be designed by taking into account the code rate and information length as well as the encoding and decoding complexity.
- Proposal 5 (Sec 3.1): For 6G polar codes evaluation, a baseline receiver should use successive cancellation list (SCL) decoding with a list size of 8 or 16. The key performance metrics for this evaluation are the overall and undetected error probabilities.
- Proposal 6 (Sec 3.2): For 6G, block codes for small block lengths should be kept the same as in 5G.
- Observation 1 (Sec 2.2.2): For data rate beyond NR range, reusing BG1 with enhanced puncturing pattern can enhance performance and reduce complexity at low number of iterations, especially when average number of iterations is considered.
- Observation 2 (Sec 3.1): NR range of UCI payload is sufficient for 6G needs. Any extension beyond NR range should be well justified, taking into account further inputs from other agenda items.