Research On Low Complexity Algorithms And Applications Of TURBO Decoding

Turbo code was proposed by French scholar C.Berrou and others in 1993.Once it came out,it was widely used because of its excellent performance close to Shannon limit.For deep space communication,because channel coding needs to overcome the low signal-to-noise ratio of long distance transmission and the fading effect of transmission environment,the Consultative Committee for Space Data System(CCSDS)chose Turbo code as the channel coding standard for satellite and deep space communications.The application scenario of this project is MIMO-SCFDE communication system based on ultra-long distance transmission,which has the characteristics of long transmission distance and long transmission time.Therefore,CCSDS standard structure is adopted in the research of Turbo decoder.Turbo code has excellent performance,but its decoding structure is too complex.So this topic mainly focuses on the low complexity decoding scheme of Turbo code and focuses on a simplified algorithm based on SOVA algorithm.Firstly,in order to reduce the computational complexity,the research of this topic starts with finding the maximum likelihood path quickly and reducing the number of branch paths,and obtains a SOVA decoding scheme with lower complexity.Secondly,this low-complexity algorithm is applied to Turbo codes based on CCSDS standard,and the Turbo equalization scheme is pioneered in MIMO-SCFDE communication system based on ultra-long distance transmission.The low-complexity Turbo decoder and equalizer are used to iteratively transmit mutual information to enhance the system's ability to resist fading and interference.Finally,after full performance simulation and complexity analysis,the C language fixed-point program of the simplified algorithm is developed to facilitate the subsequent application of the algorithm on DSP or ARM.The low-complexity Turbo decoding algorithm studied in this paper has about 0.3dB inferiority in decoding performance compared with Log-MAP algorithm,but it has a significant reduction in computation and storage compared with the traditional Log-MAP algorithm and SOVA algorithm.Under the condition of high signal-to-noise ratio,the storage is reduced by more than 50%.Moreover,Turbo equalization scheme is applied to MIMO-SCFDE system,and the application value of the low complexity Turbo decoder in ultra-long distance transmission is further verified by link level simulation.