Research On Bits Flipping Two-phase Decoding Algorithm Of QC-LDPC Codes Based On Trapping Sets

LDPC(Low-Density-Parity-Check) code is a coding method with aperformance closed to Shannon limit, which has become the main technology andhot researching in field of channel coding and especially in field of wirelesscommunications in recent years, and currently has been widely used in satellitedigital video, optical communications, audio broadcasting and deep spacecommunications. It’s hard to avoid the trapping sets problem in constructing LDPCcode, which is the reason of error-floor in high SNR(signal-to-noise ratio) regionduring decoding, that the BER(bit error rate) decreases very slowly with theincreasing of signal-to-noise ratio, and it hinders the further increase of codeperformance. Now more and more communicating applications need lower BER tomeet the higher requirements of the applications, so it become one of the problemwith research value to improve decoding algorithm in order to reduce theerror-floor.In order to reduce error-floor and aspire after lower BER, we analyse andimprove the decoding algorithm of LDPC code based on trapping sets to correcttrapping sets error during decoding. By analysis of the trapping sets pattern, thispaper research and improve a new bits flipping two-phase iterative decodingalgorithm, which can correct the trapping sets error and further reduce theerror-floor of the LDPC code and approach the code performance limit in aneffective way.This paper designs the LDPC code bits flipping two-phase decoding algorithmsimulation system by structure several quasi-cyclic LDPC(QC-LDPC) code ofdifferent code length and code rate using the quasi-diagonal cyclic of the checkmatrix and pick out four codes for using. By simulation of the bits flippingtwo-phase decoding, this paper analysis the performance and the improvement ofbits flipping two-phase decoding in different kind of trapping set. The bits flippingtwo-phase decoding algorithm researched by this paper can achieve higherprobability of correcting the trapping sets error and improve the performance ofthe iterative decoding algorithm.The bits flipping two-phase decoding can correct more errors than thetraditional iterative decoding, it can achieve lower error-floor in high SNR regionand decoding with lower BER, which make it possible to meet some new practicalapplications of lower BER requirements.