LDPC Code Encoding And Decoding Research And Its Application In Optical Communication

Beginning in the1970s, fiber optic communication has been in development at an alarming rate, and make it difficult to imagine the transmission bandwidth to provide for the communication network that we rely on today. It becomes the most important in the information network transmission, and for the explosive growth of information flow provides a spacious, smooth delivery platform. Increasingly important communication status requires the more demanding requirements for the reliability of communication.Low Density Parity Check (Low Density Parity Check, LDPC) code is a hot research field of channel coding, and it has excellent performance approaching Shannon limit. In long code LDPC exceeds the outstanding performance of Turbo codes, and LDPC has a very low error floor. Because of these advantages, the LDPC codes have been considerable developed in the field of wireless communications, and was elected as the fourth-generation mobile communication standard of choice. However, the research and application in the field of optical communications has great potential to be tapped, that is the article based on and expanded.The analysis of the LDPC code is commenced based on the DQPSK optical communication system. Firstly, this article describes the development of optical fiber communication course, which leads to a forward error correction technology in the importance of optical fiber communication; described LDPC code research and application status and development trend. Secondly, discussed the composition of the communication system and the basic channel coding theoretical knowledge, involving the development of error correction technology, the establishment of the channel model, linear block codes, and shannon’s channel coding theoiy.Then introduced the basic concepts of the LDPC codes, covering a bipartite graph, regular and irregular LDPC Code, girth and some important concepts; analyzed common coding methods, studied how to construct the LDPC check matrix, and analyzed the pros and cons of the various constructors and applicable occasions; delved into a variety of decoding algorithms of LDPC codes, based on normalized minimum sum algorithm proposed an improved decoding algorithm, made the performance and complexity comparison and simulation for each algorithm,come to the conclusion there a0.2dB’s performance improved algorithm than the normalized least and algorithms.; built optical communication DQPSK modulation and demodulation platform, deduced the DQPSK signal decoding initialization formula for the optical communication in detail, that is critical for us to decode correctly, do the simulation and analysis about the decoding algorithms in the platform, and discussed the impact of the iterations number to the decoding performance, LDPC code length impact on performance; realized the MATLAB-based multi-core parallel computation.