Research On LDPC Long Code Encoding And Recognition Technology

In non-cooperative conditions,especially in the field of communication confrontation,we need to analyze the coding type and parameters of the received data so that the receiver can react effectively.And under the premise of unknown or known part of the prior knowledge,the channel encoding recognition technology identifies the channel coding parameters from the received data,which makes the research of the technology have important application value and practical significance.In this thesis,we studied the blind identification method of low density parity check(LDPC)codes in channel coding.Due to the long code length,the existing algorithm has a low recognition rate and high computational complexity for LDPC long code blind recognition under low SNR conditions.In order to solve these problems,this thesis proposes an improved LDPC long code fast blind recognition algorithm based on previous research,which amplifies the characteristic parameters of logarithmic likelihood ratio of check relations,and improves the recognition rate under low SNR condition by using the distribution characteristics of LLR information and using the mean square feature.At the same time,considering the characteristics of a peak feature when the recognition is correct,in this thesis,we propose that the coding parameters of the coded data are identified at this time as long as the peak value satisfies our preset threshold under the premise of recognition rate is not affected,which effectively avoids the existing literature traversing the entire set of encoding parameters,and greatly reduces the amount of identification algorithm.Furthermore,in order to solve the problem that the long LDPC code recognition rate is not high under the high bit rate condition,this thesis proposes a parity matrix thinning algorithm to further reduce the nonzero elements in the high bit rate parity check matrix,which makes the peak feature more prominent,and thereby improving the recognition rate under high bit rate conditions.Theoretical analysis and computer simulation results show that the proposed algorithm can improve the recognition rate of LDPC codes with low SNR and high bit rate,and greatly reduce the computational complexity of LDPC codes,which implement fast blind identification of LDPC long codes.