Rate-Compatible LDPC Puncturing for H-ARQ Decoding Reliability
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Solution Overview
Problem
Current rate-compatible low-density-parity check (LDPC) codes for hybrid automatic repeat request (H-ARQ) applications face challenges in achieving high rates due to variable information block sizes and high degrees of punctured nodes, making them unsuitable for high-throughput communications.
Innovation Solution
The method involves generating high-rate codes from low-rate codes through regular-irregular puncturing, where a subset of codeword bits is punctured to obtain a desired code from a preceding code, optimizing protographs using progressive edge growth and density evolution to maximize girth and extrinsic cycle information, and employing random or progressive node puncturing to achieve flexible rate compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If regular puncturing is used to generate high-rate codes from low-rate codes, then code rate is improved, but decoding performance deteriorates due to high degrees of punctured nodes
Solution Approach 1:
The patent applies local quality by differentiating between systematic nodes and non-systematic nodes in the LDPC code structure. Systematic nodes are preserved with lower degrees to maintain decoding performance, while non-systematic nodes can be punctured more freely to achieve higher code rates. This localized differentiation resolves the contradiction by protecting critical nodes while allowing rate adaptation.
Solution Approach 2:
The patent segments the LDPC code into systematic bits and parity bits, with further segmentation of parity bits into different degree categories. This segmentation allows selective puncturing of high-degree non-systematic nodes while preserving low-degree systematic nodes, thereby achieving high code rates without sacrificing decoding performance.
2Adaptability or versatility
If variable information block sizes are used to achieve rate compatibility, then adaptability is improved, but code structure complexity increases
Solution Approach 1:
The patent creates a universal LDPC code structure where a single parent code can generate multiple child codes with different rates through systematic puncturing rules. The same base graph and node degree distribution serve multiple rate requirements, eliminating the need for separate code designs for different rates and thereby reducing overall system complexity.
Solution Approach 2:
The patent achieves rate compatibility by changing the puncturing parameter (number of punctured bits) while keeping the fundamental code structure, node degrees, and decoding algorithm unchanged. This parameter-based rate adaptation maintains structural simplicity while providing flexibility for different transmission conditions.
3Productivity
If high-degree nodes are punctured to achieve high rates, then code rate is improved, but error correction capability deteriorates
Solution Approach 1:
The patent applies local quality by assigning different protection levels to different nodes based on their degrees and types. Low-degree systematic nodes receive protection from puncturing to maintain error correction capability, while high-degree non-systematic nodes are candidates for puncturing to achieve high rates. This selective approach resolves the contradiction between rate and reliability.
4Device complexity
If fixed code rate is used to simplify implementation, then device complexity is reduced, but adaptability to channel conditions is worsened
Solution Approach 1:
The patent introduces dynamics by enabling the code rate to adapt to channel conditions through selective puncturing of the parent code. The system can dynamically adjust the number of punctured bits based on channel quality, transitioning from low-rate modes in poor conditions to high-rate modes in good conditions, while maintaining a unified code structure for simplified implementation.
Data Source
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AI summary
In one embodiment the present patent application comprises a method and apparatus to generate high- rate codes from low- rate codes, comprising puncturing a subset of codeword bits, wherein the step of puncturing a subset of codeword bits comprises regular-irregular puncturing where the puncturing pattern will be as regular as possible with respect to the preceding code.