QC-LDPC Bit Interleaving for Spatial-Multiplexed Constellation Mapping
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Solution Overview
Problem
Communication systems using bit-interleaved coding and modulation (BICM) with quasi-cyclic low-density parity-check (QC-LDPC) codes face challenges in optimizing the mapping of codeword bits onto constellation words, particularly in spatial-multiplexing systems, which affects reception performance.
Innovation Solution
An interleaving method that applies bit permutation to codeword bits based on QC-LDPC codes, ensuring each constellation word is composed of bits from multiple cyclic blocks, with pairs of bits having the same robustness, to improve the mapping onto spatial-multiplexing blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bit mapping is used without optimized interleaving, then the system structure remains simple, but reception performance deteriorates due to suboptimal mapping of codeword bits onto constellation words
Solution Approach 1:
The interleaver divides the codeword bits into multiple segments corresponding to different cyclic blocks, and maps these segments to different spatial-multiplexing blocks and constellation words. This segmentation allows systematic optimization of bit mapping while maintaining manageable complexity through structured organization of the interleaving process
Solution Approach 2:
The interleaving scheme dynamically adapts the mapping of codeword bits to constellation words based on the spatial-multiplexing configuration and modulation scheme. The mapping relationships are adjusted according to system parameters such as the number of transmit antennas and modulation order, enabling optimized reception performance under varying operational conditions
2Reliability
If bits from a single cyclic block are mapped to each constellation word, then the mapping process is simple, but reception performance deteriorates due to lack of diversity in bit sources
Solution Approach 1:
The interleaver segments the codeword into multiple cyclic blocks and distributes bits from different cyclic blocks across different constellation words within spatial-multiplexing blocks. This segmentation ensures that each constellation word receives bits from diverse sources, improving reliability through diversity while maintaining structured mapping
Solution Approach 2:
The interleaving scheme applies different mapping strategies to different local regions of the codeword structure. Specifically, it ensures that bits from the same cyclic block are grouped together in certain positions while bits from different cyclic blocks are distributed to different constellation words, creating locally optimized mapping patterns that enhance overall reception performance
3Reliability
If robust bit pairs are not properly grouped from common cyclic blocks, then the interleaving process is simpler, but signal reliability deteriorates due to mismatched bit pairing
Solution Approach 1:
The interleaver ensures that bit pairs with the same robustness are extracted from common cyclic blocks, creating locally optimized pairings within the overall interleaving structure. This local quality control maintains signal reliability by ensuring that paired bits share similar error characteristics while the overall structure remains manageable through systematic extraction patterns
Data Source
AI summary
Bit permutation to bits of a codeword is performed such that: at least one spatial-multiplexing block is made up of bits from B/2 different cyclic-blocks; each constellation word of the at least one spatial-multiplexing block is made up of bits from Bt/2 different cyclic blocks, Bt being the number of bits of the constellation word; and each of the bit pairs of the constellation word is made up of bits from a common one of the Bt/2 different cyclic blocks.