QC-LDPC Shift Values With Rate-Specific ACE Constraints
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Solution Overview
Problem
Existing solutions for constructing parity-check matrices in LDPC codes face challenges in avoiding harmful cycles, particularly in high-rate parts of rate-compatible LDPC codes, where ACE constraints for full parity-check matrices allow harmful cycles with low connectivity, and it is difficult to find cyclic shifts that fulfill tough ACE constraints for large cycles.
Innovation Solution
A lifting method is introduced that applies different approximate cycle extrinsic message degree (ACE) constraints for different code rates and cycle lengths, optimizing ACE constraints for each shift size separately to ensure short cycles have higher connectivity than longer cycles, and specifying separate constraints for systematic and parity bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single ACE constraint is applied to the full parity-check matrix, then the construction process is simple, but harmful cycles with low connectivity are allowed in high-rate parts
Solution Approach 1:
The patent segments the parity-check matrix into different rate parts (full matrix and high-rate submatrix) and applies different ACE constraints to each segment. This allows the full matrix to have a relaxed constraint while the high-rate part has a stricter constraint, eliminating harmful cycles in the critical high-rate region without over-constraining the entire matrix.
Solution Approach 2:
The patent applies different quality standards (ACE constraints) to different local regions of the parity-check matrix. The high-rate submatrix receives a stricter ACE constraint (ηACE_high) compared to the full matrix constraint (ηACE_full), ensuring that the critical high-rate portion has superior cycle properties while maintaining overall construction efficiency.
2Reliability
If tough ACE constraints are applied to avoid harmful cycles, then cycle connectivity improves, but it becomes difficult to find cyclic shifts that satisfy the constraints
Solution Approach 1:
The patent applies the strict ACE constraint only partially to the high-rate submatrix rather than to the entire parity-check matrix. This partial application of excessive constraint (stricter than necessary for the full matrix) ensures harmful cycles are avoided where they matter most, while maintaining feasibility of finding valid cyclic shifts.
3Reliability
If different ACE constraints are applied for different code rates, then harmful cycles are avoided in high-rate parts, but the constraint design becomes more complex
Solution Approach 1:
The patent divides the parity-check matrix into two segments (full matrix and high-rate submatrix) and assigns different ACE constraints to each. This segmentation approach systematically manages the complexity by clearly defining which constraint applies to which portion, making the dual-constraint design more tractable and implementable.
Data Source
AI summary
According to some embodiments, a method for use in a wireless transmitter of a wireless communication network comprises encoding information bits using a purity check matrix (PCM) and transmitting the encoded information bits to a wireless receiver. The parity check matrix (PCM) is optimized according to two or more approximate cycle extrinsic message degree (ACE) constraints. In some embodiments, a first portion of the PCM is optimized according to a first ACE constraint and a second portion of the PCM is optimized according to a second ACE constraint.