Long LDPC Code Structure for Fixed-Length 7/8 Encoding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The implementation of different LDPC codeword lengths for various code rates in wireless communication systems, such as IEEE 802.11ay, leads to inefficiencies in blocking and de-blocking processes, particularly for the 7/8 LDPC code rate, which results in increased redundancy and complexity due to puncturing processes that alter the codeword length from 1344 bits to 1248 bits, disrupting consistency with lower rate codes.
Innovation Solution
A high rate 7/8 long LDPC code is developed with a consistent codeword length of 1344 bits, achieved by modifying the generator matrix through a two-step lifting process and applying a lifting matrix to maintain compatibility with lower rate codes, thereby simplifying encoding and reducing redundancy in single carrier blocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different LDPC codeword lengths are used for different code rates, then code rate adaptability is improved, but implementation complexity and redundancy increase
Solution Approach 1:
The patent applies universality by designing a unified LDPC encoding apparatus that can handle multiple code rates (1/2, 5/8, 3/4, 7/8) using the same codeword length of 1344 bits. The encoder structure remains consistent across different code rates, with only the information bit length varying, thereby reducing implementation complexity while maintaining code rate adaptability.
Solution Approach 2:
The patent changes the parameter of codeword length from variable (different for each code rate) to fixed (1344 bits for all code rates). This parameter change simplifies the encoder design and reduces complexity, as the same encoding apparatus can be used for all code rates by simply adjusting the information bit length K while keeping N=1344 constant.
2Productivity
If puncturing process is applied to achieve high code rate, then code rate is improved, but redundancy and complexity in blocking processes increase
Solution Approach 1:
Instead of using puncturing to achieve high code rates, the patent extracts only the necessary parity bits for each specific code rate while maintaining a fixed codeword length of 1344 bits. For example, for 7/8 code rate, only 168 parity bits are generated (1344-1176), eliminating the need for complex puncturing and de-blocking operations.
3Device complexity
If consistent codeword length is used for different code rates, then implementation complexity is reduced, but code rate flexibility may be limited
Solution Approach 1:
The patent introduces dynamic adaptability within the fixed-length framework by allowing the information bit length K to vary according to the desired code rate, while the codeword length N remains fixed at 1344 bits. This dynamic adjustment of K enables flexible code rate selection (1/2, 5/8, 3/4, 7/8) without compromising the simplicity of the fixed-length encoder design.
Data Source
AI summary
Methods and devices are disclosed for encoding source words and decoding codewords with LDPC matrices, comprising: receiving a 1×K source word row vector ū; and generating a 1×N codeword vector c=ū·G, wherein G is a K×N generator matrix derived from a parity check matrix Hl; and wherein Hl is derived from a base parity check matrix H by summing different rows in the base parity check matrix H to obtain an intermediate parity check matrix, and applying a lifting matrix to the intermediate base parity check matrix to obtain Hl.