Design And Implementation Of LDPC Encoder And Decoder Based On FPGA

Low density parity check code is a coding scheme that approaches the Shannon limit.As one of the important candidates for third-generation channel coding,LDPC has the advantages of low error layer and excellent error correction performance.At present,LDPC has been selected as the data channel coding standard in 5 G-eMBB scenario,and is widely used in deep space communication,optical communication,wireless communication systems.This paper focuses on the LDPC encoder and decoder and the FPGA implementation of frame synchronization.The main contents of the research are as follows.(1)Aiming at the problems of high complexity,long coding delay and low applicability of existing coding algorithms,an improved coding algorithm was proposed.The proposed encoding algorithm uses the generation matrix to complete the encoding.Compared with other encoding algorithms,it is simple to implement and can select different encoding parallelism degrees according to different FPGA resources.Finally,based on this encoding algorithm,the hardware implementation structure of FPGA is improved,the steps required for hardware encoding are reduced.(2)Aiming at the problems of the traditional frame synchronization algorithm based on LDPC,such as difficult hardware implementation,long synchronization delay and low reliability,this paper proposes a soft decision frame synchronization algorithm based on the idea of LDPC decoding.When the frame synchronization error rate is 1E-3,the proposed algorithm has a performance improvement of 0.9dB compared with the traditional synchronization algorithm.And with the increase of synchronization codeword length,the advantage of performance gap continues to increase,with FPGA implementation is simple,fast synchronization advantages.(3)The decoder is implemented based on the normalized minimum sum decoding algorithm,and an indoor wireless optical communication system with a line rate of 40Mbps is built using a PPM modulation format.A wireless optical communication link experiment was conducted on the LDPC codewords used in this paper.The experimental results show that LDPC can improve the receiver sensitivity by about 8dB compared with the RS coding scheme communication system under the condition that the communication rate of 40Mbps and the bit error rate is no higher than 1E9.