Research And Optimization On Encoding And Decoding Of Ldpc Codes

With the increasing demands for channel capacity, transmission distance and speed of the optical communication system, relying on fiber itself low-loss characteristics has been very difficult to satisfy the system requirements for low bit error rate,so it is very necessary to introduce an effective and reliable forward error correction(FEC) techniques into the system. Low-density parity-check codes(LDPC) was used by the optical communication system for FEC with its excellent error correction performance and low decoding complexity.By analyzing its efficient coding methods and more excellent decoding scheme, this research is expected to provide solutions for the LDPC codes used in optical communication system.Firstly, detailed theoretical analysis and program implementation are given base on the encoding and decoding algorithm of LDPC codes, then the corresponding advantages and disadvantages of the algorithm are listed by analyzing the simulation results, and the Min-Sum Algorithm(MSA) is proved to be the most suitable for practical application through the comprehensive analysis of the performance and complexity of different decoding algorithms. In order to make further improvement on the decoding performance on condition that it would not increase the decoding complexity, this paper presents two improved decoding algorithms base on MSA although the modified MSA its decoding performance is very close to the BP decoding algorithm. Finally, three methods about performance analysis and design optimization are proposed to analyze whether the designed LDPC codes meets the requirements of communication systems or not, which in turn guide the design and construction of LDPC codes.