Research On Channel Codec Algorithms In Deep Space Communications For CCSDS

Due to the very low SNR, in deep space communications, to ensure the reliabilityof communication becomes one of emphasis and difficulty. An effective means to solvethis problem is the use of channel codec technology. LDPC and Turbo codes are twoexcellent codes, and have been used in CCSDS standard. In this thesis, the codecalgorithms of both codes were analyzed, focusing on their application in deep spacecomunications, and their performance were compared through simulation.Firstly, the LDPC encoding and decoding algorithms were studied. Based on theoverview of LDPC codes, several commonly used LDPC encoding and decodingalgorithms were analyzed, the focus was on the QC-LDPC encoding, the min-sumdecoding, and improved algorithms. The application in deep space communication ofLDPC codes was also discussed.Secondly, the Turbo decoding algorithms were studied. This section focus onanalysis of MAP algorithm, Log-MAP algorithm and improved algorithms. And Turbocoder and decoder used in deep space communication were discussed.Finally, LDPC codes and Turbo codes recommended in CCSDS standard weresimulated by MATLAB, their decoding performance under different conditions werecompared respectively. And the performance of these two codes, such as the encodingefficiency, the encoding and decoding complexity and the data transmission rate, etc.were compared and analyzed.Overall, after a lot of theory study and understanding, this thesis focuses on thealgorithm inference of LDPC code and Turbo code, especially the simulation of thecodes, which has a strong.guiding significance for the application.