A kind of LT code encoding and decoding method and system

Abstract

The invention discloses an LT code encoding and decoding method and system. According to the method, a traditional Gaussian approximation tracking mean value method is modified into a mode of trackinga check node and outputting an error rate by a variable node, an obtained error rate result is closer to actual code word performance compared with a traditional Gaussian approximation (tracking meanvalue) method, and the coding and decoding precision is improved; the bit error rate result obtained by adopting the method is basically consistent with the discrete density evolution result, but thecomplexity is greatly reduced, and compared with a Monte Carlo simulation method, the method is shorter in time consumption, and the coding and decoding efficiency is improved. In addition, by meansof the method, the target bit error rate can be directly set during degree distribution optimization, it is guaranteed that a result obtained through optimization (namely code words with the optimizeddegree distribution) meets the target bit error rate under the condition that the code rate is as large as possible (namely code word cost is low), and therefore the degree distribution function optimized through the method has good bit error rate performance.

Description

technical field [0001] The invention relates to the technical field of digital communication, in particular to an LT code encoding and decoding method and system. Background technique [0002] Luby proposed the first practical fountain code-LT code (Luby Transform, Ruby Transform code) in 2002. The LT code was originally applied to binary erasure channels (BEC). The decoder only needs to receive a certain number of encoded packets to successfully restore the original data. It has the characteristics of no fixed code rate and low encoding and decoding complexity. . Later, people extended LT codes to wireless noise channels (such as AWGN (Additive White Gaussian Noise) channels, fading channels), and found that there is a higher error floor. In order to solve this problem, a high bit rate codeword is concatenated before the LT encoder, which can greatly reduce the error floor. This concatenated code is also called Raptor code. The outer code of the Raptor code usually choos...

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Problems solved by technology

[0004] The purpose of the present invention is to provide an LT code encoding and decoding method and system to solve the problems of long time consumption, high complexity or insufficient precision in the existing LT code performance analysis method

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