QC LDPC Bit Mapping with Cyclic Block Permutation for BICM
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Solution Overview
Problem
In bit-interleaved coding and modulation (BICM) systems using quasi-cyclic low-density parity-check codes (QC LDPC codes) and quadrature amplitude modulation (QAM), existing methods lack an efficient method to optimize cyclic block permutations and non-uniform constellations for improved communication performance across different code rates, leading to suboptimal bit error rates and signal-to-noise ratios.
Innovation Solution
The proposed solution involves executing a cyclic block permutation for codewords generated based on QC LDPC codes, mapping bits to non-uniform constellations, and selecting these permutations and constellations based on the code rate, specifically defining cyclic block permutations and non-uniform 64-PAM constellations for 6/15, 7/15, and 8/15 code rates to optimize communication performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cyclic block permutations and uniform constellations are used in BICM systems, then the system structure is simple and easy to implement, but the communication performance (bit error rate and signal-to-noise ratio) is suboptimal
Solution Approach 1:
The patent applies local quality by using non-uniform constellations where different constellation points have different distances from the origin, creating local variations in signal strength and robustness. This allows bits mapped to more robust constellation points to have higher reliability, improving overall communication performance while maintaining a relatively simple system structure.
Solution Approach 2:
The patent changes the parameter of constellation uniformity by transitioning from uniform QAM constellations to non-uniform constellations. This parameter change enables differential encoding where cyclic block importance levels are matched with constellation robustness levels, thereby improving bit error rate performance without significantly increasing system complexity.
2Reliability
If cyclic block permutations are optimized for each code rate, then bit error rate performance is improved, but the complexity of selecting and managing different permutations increases
Solution Approach 1:
The patent optimizes cyclic block permutations specifically for different code rates (6/15, 7/15, 8/15) to match the importance levels of cyclic blocks with the robustness levels of constellation points. This parameter optimization for each code rate improves bit error rate performance while the patent manages complexity by providing specific permutation patterns for each code rate rather than requiring dynamic optimization.
Data Source
AI summary
A communication method includes executing a cyclic block permutation for a codeword generated based on a quasi-cyclic parity-check code including a repeat-accumulate quasi-cyclic low-density parity-check code, where the cyclic block permutation is permutation of cyclic blocks within the codeword, and mapping each bit of the codeword for which the cyclic block permutation is executed to any one of constellation point of a non-uniform constellation.