Structured LDPC Decoding with Shortening and Puncturing
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Solution Overview
Problem
Existing data communication technologies face challenges in efficiently encoding and decoding transmissions across a wide range of code word lengths and code rates, particularly in wireless broadband communications, due to the complexity and inefficiency of conventional LDPC encoding techniques and the need to handle a large number of code combinations specified by standards like IEEE 802.16e.
Innovation Solution
The implementation of a system that allows for the extension of a subset of available code word lengths by applying techniques such as shortening and puncturing, while maintaining excellent performance and avoiding interference between these methods, to achieve precise code rate selection and efficient hardware realization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a subset of code word lengths is used to generate all required code word lengths through shortening and puncturing, then device complexity is reduced, but manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The code word length parameter is segmented into a base length from a subset and adjustment parameters (shortening and puncturing amounts). Instead of implementing all possible code word lengths directly, the system segments the parameter space and generates required lengths through controlled modifications of base lengths, reducing implementation complexity while maintaining precision through mathematical relationships.
Solution Approach 2:
The system changes parameters (shortening amount S, puncturing amount P) applied to base code words from the subset to generate target code words with specific lengths and rates. By controlling these parameter changes precisely, the system achieves accurate code rate selection while using fewer base code definitions, resolving the contradiction between complexity reduction and precision maintenance.
2Adaptability or versatility
If shortening and puncturing techniques are applied to extend code word lengths, then adaptability increases, but device complexity increases
Solution Approach 1:
The system uses universal base code words from a limited subset that can serve multiple purposes. Through shortening and puncturing operations, these base codes can generate multiple target code words with different lengths and rates. This multi-functionality approach increases adaptability while avoiding the need to implement separate dedicated code structures for each code rate, thereby limiting the increase in device complexity.
Solution Approach 2:
The system performs preliminary selection of base code words from a subset and pre-determines the shortening and puncturing parameters needed to achieve target code rates. By preparing and organizing these parameters in advance, the system enables flexible adaptation to different code requirements without requiring complex real-time decision logic, thus increasing adaptability while managing device complexity.
3Manufacturing precision
If all required code word lengths are implemented directly, then manufacturing precision is maintained, but loss of time increases
Solution Approach 1:
Instead of implementing all required code words directly, the system creates target code words by copying base code words from a subset and applying transformations (shortening and puncturing). This copying approach maintains manufacturing precision because the base codes are carefully designed and verified, while significantly reducing development time by avoiding the need to design and verify every individual target code from scratch.
4Quantity of substance
If a subset of code word lengths is used, then memory requirements are reduced, but reliability may be affected
Solution Approach 1:
The system uses shortening and puncturing operations as intermediary mechanisms to bridge the gap between the limited subset of base code words and the full range of required target code words. These intermediary transformations allow the system to achieve diverse code specifications from a compact base set, reducing memory requirements while maintaining reliability through the mathematical properties of LDPC codes and careful selection of transformation parameters.
Data Source
AI summary
A communications transceiver for transmitting and receiving coded communications, with the coding corresponding to a low-density parity check code, is disclosed. A set of available code word lengths and code rates are to be supported by the transceiver. These available code word lengths and code rates are implemented as a subset of starting code word lengths, which are length-reduced by shortening and puncturing selected bit positions in the starting code word length to attain the desired one of the available code word lengths and code rates. The bit positions to be shortened and punctured are selected in a manner that avoids interference between the shortened and punctured bit positions, and that attains excellent code performance.