R1-2508982
discussion
FL summary#2 for 6G channel coding
From ZTE
Summary
This document is the RAN1#123 meeting facilitator (FL) summary #2 for the 6G channel coding study item, moderated by ZTE and Apple. It compiles over 53 observations and 15+ formal proposals from numerous companies on evaluation methodologies, LDPC data channel coding extensions, control channel coding (Polar), and coding chain enhancements. The FL proposes a core set of evaluation metrics (BLER, complexity, throughput/latency), outlines six candidate LDPC extension options for higher throughput, and presents draft agreements for DCI/UCI beyond NR range including segmentation and interleaver modifications.
Position
ZTE, as co-moderator of this FL summary, presents an aggregated and balanced view of all contributing companies' positions on 6G data and control channel coding, without advocating a single definitive technical solution. They observe broad support across multiple sources for evaluating LDPC extensions via Option 1 (fast convergence/reduced iterations) and Option 2 (increased lifting size up to 2x or 4x), noting their own contributions that new BG design can achieve 2.25x–3.6x decoding throughput of 5G BG1 with SNR loss no more than 0.21dB and computational complexity only 0.28–0.45 times that of 5G. They propose standardized evaluation assumptions including layered BP decoding with 2–20 iterations and reversed order, target BLER at 10^-2 and 10^-4, and a common template for reporting SNR and complexity. For control channel coding, they capture extensive company inputs on Polar code extensions beyond NR range for DCI and UCI, noting majority support (>16 sources) for reusing NR Polar code within NR range and diverse options for beyond NR range including more than 2 segments, D-CRC interleaver redefinition, and higher modulation order.
Key proposals
- Proposal 3.1.1-1-v2 (Sec 2.1.1.3): For the evaluation study of potential 6G data channel coding scheme(s) for higher throughput than 5G with acceptable performance-complexity tradeoff, at least BLER performance, complexity, and decoding throughput/latency should be reported. Area efficiency and energy efficiency can be additionally reported with detailed definitions.
- Proposal 3.1.2-1-v2 (Sec 2.1.2): For the study of 6G LDPC extension for higher throughput, evaluation assumptions include AWGN channel, QPSK baseline modulation with other orders reportable, company-reported code rate and information block size, target BLER of 10^-2 and 10^-4, and layered BP decoding with 2–20 iterations and reversed decoding order.
- Proposal 3.2-1-v2 (Sec 2.2): For the study of LDPC code for higher throughput, six options can be considered (individually or combined): (1) Fast convergence LDPC, (2) Increased maximum lifting size to [2 or 4]*384, (3) Optimized parallelism/orthogonality, (4) Increased systematic columns, (5) Reduced edges in BG, (6) Implementation-based solutions. The LDPC code is quasi-cyclic (QC-LDPC), with FFS on using 5G BG(s) or a new BG.
- Proposed conclusion 3.2-2-v2 (Sec 2.2): Companies are encouraged to provide LDPC BG(s) and PCM(s) in an Excel spreadsheet and report required SNR and complexity for target BLER along with decoding algorithm assumptions. The template will be further discussed.
- Proposal 3.2-3-v1 (Sec 2.2): Study whether/how to optimize the error floor performance for LDPC code.
- Proposal 3.2-4-v1 (Sec 2.2): Study whether/how to enhance LDPC for 6G low complexity/power scenarios.
- Proposal 3.3-1-v1 (Sec 2.3): For 6G data channel coding chain enhancements, proponents are encouraged to provide details and expected spec impact of inter-code block coding and bit interleaver enhancement, evaluation metrics including BLER/throughput, and evaluation assumptions.
- Offline proposal 1 (Sec 1): For Polar code design for UCI with payload size larger than NR range (>1706 bits), options identified include more than 2 segments, PAC code, Polar encoding based on N/2 Polar sequence for length-N Polar code, and higher modulation order.
- Offline proposal 2 (Sec 1): For Polar code design for DCI with payload size larger than NR range (>140 bits), options identified include segmentation, removing D-CRC interleaver, defining a D-CRC interleaver for larger DCI size, PAC code, 2-stage DCI, using 1024-length Polar sequence for DL, and higher modulation order.
- Proposal 4.3-1-v2 (Sec 4.3): For 6G small UCI channel coding, study options including use of 5G RM code, enhanced coding scheme including rate matching, and use of sequence. FFS on the range of small UCI (e.g., 3–11 bits).
- Proposal 4.5-1-v1 (Sec 4.5): For 6G control channel coding chain enhancements, proponents are encouraged to provide details and expected spec impact, evaluation metrics (BLER, throughput), and evaluation assumptions (channel type, resource allocation, MCS, channel estimation, antenna configuration).
- Proposal 4.6.1-1-v1 (Sec 4.6.1): For evaluation of 6G control channel coding, at least BLER performance, FAR, complexity, early termination, and DCI RNTI false alarm should be considered.
- Proposal 4.6.2-1-v1 (Sec 4.6.2): Evaluation assumptions for 6G control channel coding include AWGN channel, QPSK modulation (other UL orders reportable), UL code rates from 1/12 to 5/6, DL coded bit length as 108*[1,2,4,8,16], SCL decoding with list size=8, and company-reported information block lengths with specified ranges for UL and DL.