Punctured LDPC Channel Decoding for Flexible Codeword Lengths
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Solution Overview
Problem
Current LDPC code systems, such as DVB-S2, are limited to only two codeword lengths, which restricts their extendibility and flexibility, particularly in high-order modulation communication systems where various codeword lengths are required to support different data rates, and storing separate parity-check matrices for each length reduces memory efficiency.
Innovation Solution
A method and apparatus that utilize puncturing and shortening techniques to generate LDPC codes with varying codeword lengths from a given parity-check matrix, allowing for efficient support of different codeword lengths without the need for additional stored information, by selectively not transmitting specific bits and using the structural characteristics of the LDPC code to maintain decoding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate parity-check matrices are stored for each codeword length, then decoding performance is maintained, but memory efficiency deteriorates
Solution Approach 1:
The patent applies universality by designing a single parity-check matrix that can serve multiple codeword lengths through puncturing and shortening operations. The base parity-check matrix of size 16200×64800 can generate various codeword lengths (16200, 64800, and intermediate lengths) by selectively puncturing columns and shortening rows, eliminating the need to store separate matrices for each length while maintaining decoding performance.
2Adaptability or versatility
If puncturing is applied to generate various codeword lengths, then flexibility and extendibility are improved, but reliability of information bits deteriorates due to increased irregularity
Solution Approach 1:
The patent applies local quality by carefully selecting which columns to puncture and which rows to shorten based on their local properties. The puncturing pattern is designed to maintain uniform distribution of punctured columns across different column groups, and the shortening operation selectively removes rows with specific characteristics. This localized optimization ensures that the irregularity introduced by puncturing is distributed evenly, preventing concentration of errors and maintaining information bit reliability.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing the puncturing and shortening patterns for different codeword lengths. The base parity-check matrix is designed with specific structural properties that enable predictable and controlled puncturing/shortening operations. By preparing these patterns in advance, the system can quickly switch between different codeword lengths without real-time optimization, maintaining both flexibility and reliability.
3Device complexity
If only two fixed codeword lengths are supported, then system complexity is reduced, but adaptability to different data rates deteriorates
Solution Approach 1:
The patent applies dynamics by introducing configurable puncturing and shortening parameters that can be adjusted based on the required data rate. The system maintains a single base parity-check matrix but dynamically modifies its effective size through controlled puncturing (column removal) and shortening (row removal). This dynamic adaptation allows the system to support various codeword lengths between 16200 and 64800 bits, providing flexibility for different data rates while keeping the underlying matrix structure fixed and simple.
Data Source
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AI summary
The invention relates to a method and apparatus for a channel decoding using a Low-Density Parity-Check (LDPC) code, the method comprising: demodulating a signal transmitted from a transmitter; determining position of the punctured parity bits by estimating information about a predetermined order of parity bit sets to be punctured and the number of parity bit sets ; and decoding data using the positions of the punctured parity bits, wherein determining position of punctured parity bits comprises, determining a number of parity bits to be punctured; determining a number of parity bit sets to be punctured based on the determined number of parity bits to be punctured; and acquiring a predetermined order of parity bit sets, wherein the predetermined order of parity bit sets to be punctured is determined as 6, 4, 13,9,18,8,15,20,5,17,2,22,24,7,12,1,16,23,14,0,21,10,19,11,3, when a codeword length is 16200 and an information length is 7200.