LDPC Parity-Bit Puncturing 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 supporting various data rates required for adaptive communication systems and broadcast services, and storing separate parity-check matrices for each codeword length reduces memory efficiency.
Innovation Solution
The method involves using shortening or puncturing techniques to generate LDPC codes with different codeword lengths from a given LDPC code, specifically applying a puncturing pattern that maximally suppresses irregularity in reliability during decoding by leveraging the structural characteristics of the DVB-S2 LDPC code, allowing for efficient support of various codeword lengths without the need for additional storage or new parity-check matrices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate parity-check matrices are stored for each codeword length, then code performance is optimized, 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 operations. The base matrix with 16200 columns can generate codes of various lengths (e.g., 16200, 13140, 10800, 8100, 5400, 4050, 3240, 2700, 1350, 1080, 900, 675, 450, 300, 225, 150, 75) by selectively puncturing columns, eliminating the need to store separate matrices for each length while maintaining code performance.
Solution Approach 2:
The patent employs parameter changes by modifying the effective codeword length through controlled column puncturing of the base parity-check matrix. By varying the number and positions of punctured columns, the system dynamically adjusts the code length parameter while reusing the same underlying matrix structure, thus optimizing memory usage without sacrificing code performance.
2Device complexity
If only two fixed codeword lengths are supported, then system complexity is reduced, but adaptability deteriorates
Solution Approach 1:
The patent applies dynamics by enabling the LDPC code system to adaptively support multiple codeword lengths from a single base matrix through puncturing. The system can dynamically select different effective lengths (16200 down to 75) based on communication requirements, transforming a static two-length system into a dynamic multi-length system without proportionally increasing complexity.
Solution Approach 2:
The patent uses segmentation by dividing the base parity-check matrix into column groups that can be selectively punctured. The matrix is organized such that columns can be removed in structured patterns, allowing the system to generate various codeword lengths by segmenting and removing specific portions while maintaining the integrity of the remaining code structure.
3Adaptability or versatility
If puncturing is applied to generate variable codeword lengths, then flexibility is improved, but decoding reliability may deteriorate due to irregularity
Solution Approach 1:
The patent applies local quality by carefully selecting which columns to puncture based on their positions and connections in the Tanner graph. The puncturing pattern is designed to maintain local structural properties that are favorable for decoding, such as preserving girth-4 cycles and avoiding excessive puncturing in locally dense regions, thereby maintaining decoding reliability while achieving flexibility.
Solution Approach 2:
The patent uses copying by replicating the base parity-check matrix structure across different codeword lengths. Instead of creating entirely new matrices for each length, the system copies and selectively removes columns from the base matrix, preserving the fundamental structural properties that ensure reliable decoding while adapting to different length requirements.
Data Source
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AI summary
An apparatus and a method for channel encoding using a Low-Density Parity-Check (LDPC) code, the method comprising: determining a number of parity bits for puncturing; determining a number of parity bit sets based on the number of parity bits for puncturing, each of the parity bit sets being formed by parity bits at a predetermined interval; and puncturing parity bits based on the number of parity bit sets and a predetermined order of parity bit sets to be punctured, wherein the predetermined order of parity bit sets is determined as 6, 4, 18, 9, 13, 8, 15, 20, 5, 17, 2, 24, 10, 22, 12, 3, 16, 23, 1, 14, 0, 21, 19, 7, 11.