QC LDPC Bit Mapping With Cyclic Permutation by Code Rate
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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 different code rates, leading to suboptimal communication performance.
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 enhance communication performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bit interleavers are used in BICM systems with QC LDPC codes, then the system structure is simple, but communication performance is suboptimal due to lack of optimization for different code rates
Solution Approach 1:
The patent implements dynamic selection of cyclic block permutation patterns and non-uniform constellation configurations based on the code rate being used. Different code rates (e.g., 1/3, 2/3, 3/4) have pre-defined optimal permutation patterns and constellation configurations stored in lookup tables. The system dynamically switches between these configurations according to the selected code rate, achieving optimized communication performance for each code rate without requiring complex real-time optimization algorithms.
Solution Approach 2:
The patent changes key parameters including the cyclic block permutation pattern, non-uniform constellation configuration, and mapping rules based on the code rate. By varying these parameters according to the code rate, the system achieves optimal performance for each specific code rate scenario. This parameter-based optimization approach allows the system to adapt to different code rates while maintaining a relatively simple overall structure through pre-defined configurations.
2Reliability
If standard uniform constellations are used, then the mapping is simple, but bit error rate performance is suboptimal compared to non-uniform constellations
Solution Approach 1:
The patent employs non-uniform constellations where different regions of the constellation diagram have different properties. Specifically, the constellation points are distributed non-uniformly with higher density in certain regions and lower density in others, optimized for the specific code rate being used. This local variation in constellation quality allows the system to achieve better bit error rate performance by matching the constellation characteristics to the error correction capabilities of the QC LDPC code for each code rate.
Solution Approach 2:
The patent changes the constellation parameters including point distribution, spacing, and configuration based on the code rate. Different code rates have pre-defined optimal non-uniform constellation configurations stored in lookup tables. By varying these constellation parameters according to the code rate, the system achieves optimal bit error rate performance for each specific code rate scenario while maintaining manageable complexity through pre-defined configurations.
3Reliability
If cyclic block permutation is optimized for each code rate, then communication performance improves, but the complexity of selecting and managing different permutations increases
Solution Approach 1:
The patent performs preliminary optimization and stores the optimal cyclic block permutation patterns for different code rates in pre-defined lookup tables during the design phase. When the system operates, it simply retrieves the appropriate permutation pattern from the lookup table based on the selected code rate, rather than performing complex real-time optimization. This preliminary action approach achieves optimal frame error rate performance for each code rate while keeping the operational complexity low through simple table lookup and retrieval operations.
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.