LDPC Code Structure With BCH Outer Coding for Reduced Memory
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Solution Overview
Problem
Low Density Parity Check (LDPC) codes are not widely deployed due to their complexity, high storage requirements, and computational load, making them inefficient for high data rate communication systems.
Innovation Solution
The approach involves generating LDPC codes with a reduced memory requirement by using an outer Bose Chaudhuri Hocquenghem (BCH) code and restricting the parity check matrix to a triangular form, facilitating simple encoding and decoding processes while minimizing storage and processing resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LDPC codes are implemented using traditional encoding techniques with generator matrices, then coding performance approaches the Shannon limit, but storage requirements become prohibitively large due to the need to store very large non-sparse matrices
Solution Approach 1:
The patent segments the LDPC code structure into outer BCH code and inner LDPC code components. The parity check matrix is divided into sub-matrices with specific structures (triangular forms) that can be stored efficiently. This segmentation allows the system to maintain the error correction performance of full LDPC codes while reducing storage requirements by exploiting the structured sub-matrices.
Solution Approach 2:
The patent applies local quality by imposing specific structural constraints on different parts of the parity check matrix. Certain sub-matrices are required to be in triangular form or have specific sparsity patterns. This local structuring enables efficient encoding and storage while maintaining overall code performance, as the structured regions provide the necessary properties for reduced complexity operations.
2Reliability
If LDPC codes use large block sizes to achieve effectiveness, then coding performance improves, but computational load and complexity of the encoding and decoding processes increase significantly
Solution Approach 1:
The patent segments the encoding process into two distinct stages: first encoding with the outer BCH code, then encoding with the inner LDPC code using the structured parity check matrix. This segmentation allows each encoder to operate independently with reduced complexity, avoiding the need to implement the full LDPC encoding operation which would be computationally intensive for large block sizes.
Solution Approach 2:
The patent changes the structural parameters of the parity check matrix by enforcing triangular forms and specific sparsity patterns on sub-matrices. These parameter changes transform the encoding operation into a simpler process that requires fewer computational resources while maintaining the ability to handle large block sizes effectively.
3Reliability
If LDPC codes are deployed in bandwidth-constrained satellite systems, then communication reliability improves, but the high storage and processing requirements create implementation challenges
Solution Approach 1:
The patent segments the code structure into outer BCH and inner LDPC components with structured parity check matrices. This segmentation enables implementation in satellite systems by reducing the storage requirements for code parameters and simplifying the processing requirements, making the system more feasible for deployment in bandwidth-constrained satellite communication environments.
Solution Approach 2:
The patent applies local structural constraints to the parity check matrix sub-matrices, requiring triangular forms in specific regions. This local structuring reduces the computational complexity of encoding and decoding operations, making the implementation more suitable for satellite systems with limited processing capabilities while maintaining communication reliability.
Data Source
AI summary
An approach is provided for generating Low Density Parity Check (LDPC) codes. An LDPC encoder generates a LDPC code with an outer Bose Chaudhuri Hocquenghem (BCH) code. For a rate 3/5 code, the approach provides a degree profile that yields reduced memory requirements for storage of the edge values without significantly affecting the performance with respect to an “unmodified” rate 3/5 code. The relevant parameters for the reduced memory LDPC codes are as follows: q=72, nldpc=64800, kldpc=nBCH=38880, kBCH=38688. The above approach has particular application in digital video broadcast services over satellite.