Research On Construction And Decoding Algorithm Of Quasi-cyclic LDPC Codes

In this paper, the methods to design the construction methods of quasi cycle LDPC codes and reduce the complexity of decoding algorithm with low encoding complexity are studied.QC-LDPC is a kind of construction codes.It's BER and error platform is similar to random LDPC, the implementation of coding is simple and practicable.In the study of LDPC codes construction, the traditional design methods are compared and introduced.Then the construction methods of QC-LDPC codes in the Galois Field are proposed and discussed. In this paper, the algorithm simulation and comparison are based on Matlab simulation.The simulation results show that the proposed construction methods have linear encoding complexity, no 4 cycle in Tanner and are suitable for constructing the middle and short LDPC codes with excellent performance.Nonbinary LDPC has strong ability of sudden error correction, and significantly improved BER performance, but it has high complexity decoding. To solve this problem in this paper, the Sum-Product algorithm of nonbinary LDPC codes is summarized at first. A simplified decoding algorithm for LDPC codes over high order Galois field is proposed to reduce the complexity of traditional sum-product algorithm. On this basis, it given the high order modulation based on gaussian channel of combining the coding modulation system simulation. The simulation results show that the algorithm of this paper decreases LDPC code of structure and decode the problem of high complexity; it increases bandwidth utilization, and with data rate increased several times, is also ensure the data reliable transmission in high modulation.