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 fail to optimize cyclic block permutations and non-uniform constellations to achieve optimal communication performance across various code rates and noise conditions.
Innovation Solution
The proposed method involves executing a cyclic block permutation for codewords generated based on QC LDPC codes, mapping bits to non-uniform constellations, and selecting permutations and constellations based on specific code rates, such as 6/15, 7/15, and 8/15, to optimize communication performance. This includes using tables to define cyclic block permutations and non-uniform 64-PAM constellations for 4096-QAM constellations, ensuring optimal bit interleaving and demapping.
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 communication performance is suboptimal across various code rates and noise conditions
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, matching the varying importance levels of different cyclic blocks in QC-LDPC codes.
Solution Approach 2:
The patent changes the parameter of constellation uniformity to non-uniformity, transforming the traditional uniform QAM constellation into a non-uniform constellation where symbol distances vary. This parameter change enables optimization of bit error rate performance by aligning constellation robustness with cyclic block importance levels.
2Reliability
If cyclic block permutations are optimized for specific code rates, then bit error rate performance is improved, but the system loses adaptability to different code rates
Solution Approach 1:
The patent implements dynamics by making the cyclic block permutation and constellation selection adaptive to the code rate. Instead of using fixed permutations, the system dynamically selects appropriate permutations and non-uniform constellations based on the specific code rate being used, allowing optimization for each code rate while maintaining overall system versatility.
Solution Approach 2:
The patent achieves universality by developing a framework that works across multiple code rates (6/15, 7/15, 8/15) with specific optimized permutations and constellations for each. This multi-functional approach allows the same BICM system structure to achieve optimal performance across different operating conditions.
3Reliability
If non-uniform constellations are introduced to match cyclic block importance levels, then transmission reliability is enhanced, but constellation design and selection complexity increases
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, matching the varying importance levels of different cyclic blocks in QC-LDPC codes.
Solution Approach 2:
The patent applies preliminary action by pre-defining specific non-uniform constellation designs and cyclic block permutations for different code rates. This preliminary preparation eliminates the need for real-time optimization during operation, reducing implementation complexity while maintaining optimal performance.
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.