Coding Scheme And Properties Of LDPC Codes In Space Optical Communication System

Space optical communication technology has good secrecy, information capacity, high transmission rate, network flexible, low cost and many other advantages.It cause more attention of researchers and businessmen in many applications. But on the other hand, laser propagation in atmosphere, its performance is influenced by the atmospheric effect, background noise, and many other interference factors, resulting in lower error performance, This limits the space optical communication technology's application. Therefore,study coding scheme which has good error performance, simple implementation, has important practical significance to the application of space optical communication technology.In the error correction coding areas, low density parity code (LDPC) has advantages of approximate shannon limit, has flexible structure, describing simple,low decoding complexity, parallel decoding etc. It is suitable for application in space optical communication system which has large capacity and high rate.The thesis firstly introduces the basic principle of LDPC code, structure of the check-up matrix and and coding method coding method.From its own structure, we simulation and analysis the influence factors of LDPC code such as the minimum distance, code value, code length, degree distribution. Study the LDPC's decoding algorithm. Study the influence factors of the spatial channel, and build spatial light channel model. Study and simulation the performance of OOK, PPM, DPIM modulation technology in the space optical communication system. The results show that the comprehensive performance of DPIM is better, suitable for application in space optical communication system. Then put forward a coding scheme based on theπ-rotating LDPC codes in pace optical communication system. Use matlab to simulation and analyze its performance. Make comprehensive simulation ofπ-LDPC code combining the OOK, DPIM, the results show that theπ-rotating LDPC code coding scheme combining DPIM modulation technology, effectively cut the ber of space optical communication system, and the system performance is getting a better ascend.