QC-LDPC Encoder Structure for Higher-Girth HARQ Decoding
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Solution Overview
Problem
Current channel coding techniques for digital communication systems, particularly in GLDPC codes for IR-HARQ schemes, face challenges in achieving high data throughput with efficient encoding and decoding resources, and are limited by short cycles in Tanner graphs which can lead to error floors and decoding convergence issues.
Innovation Solution
The development of a protomatrix-based encoder for generating a generalized QC-LDPC code with a triangular structure, where the number of second columns is twice the number of second rows, and the use of Cordaro-Wagner component codes to derive additional parity bits, along with iterative selection of shift values to optimize girth and extrinsic message degree, facilitates improved encoding and decoding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LDPC codes are used for channel coding, then encoding and decoding operations can be performed, but short cycles in Tanner graphs lead to error floors and decoding convergence issues
Solution Approach 1:
The patent segments the LDPC code structure by introducing a protomatrix that defines a triangular submatrix structure. This segmentation approach divides the Tanner graph into structured components with minimum cycle length constraints, eliminating short cycles while maintaining overall code functionality and improving decoding convergence.
Solution Approach 2:
The patent changes structural parameters of the LDPC code by enforcing a minimum cycle length of 8 in the Tanner graph and using a protomatrix with specific triangular structure. This parameter change eliminates harmful short cycles that cause error floors, thereby improving reliability without excessive complexity increase.
2Reliability
If GLDPC codes are used to improve error correction performance, then decoding reliability increases, but encoding and decoding resource requirements increase
Solution Approach 1:
The patent applies local quality by using Cordaro-Wagner component codes specifically at check nodes where they provide maximum benefit. This localized application of component codes improves error correction performance at critical points without requiring complex GLDPC structures throughout the entire code, thus balancing reliability improvement with resource constraints.
Solution Approach 2:
The patent introduces dynamics by using rate-compatible punctured GLDPC (RC-PGLDPC) codes that allow flexible adaptation of code rate and structure based on channel conditions. This dynamic approach enables the system to optimize between error correction performance and resource usage depending on actual transmission requirements.
3Measurement precision
If iterative decoding is used to improve convergence, then decoding accuracy increases, but computational complexity and time increase
Solution Approach 1:
The patent applies preliminary action by pre-optimizing the protomatrix structure and shift values before decoding operations. The triangular structure with minimum cycle length 8 is predetermined to facilitate faster convergence, reducing the number of iterative decoding steps required while maintaining high decoding accuracy.
Solution Approach 2:
The patent substitutes traditional mechanical iterative decoding approaches with optimized message-passing algorithms on the structured protomatrix. The predefined triangular structure with specific shift values enables more efficient message passing that converges faster than conventional iterative decoding methods.
Data Source
AI summary
Provided is an encoder, a decoder, a computer-readable medium and methods of forward error correction channel encoding/decoding within a HARQ scheme, based on a generalized quasi-cyclic low-density parity-check code comprising a Cordaro-Wagner component code.