Research and realization of TURBO Codec in the space laser communication

Adopting Forward Error Correction (FEC), technologies for the laser communication system such as encode, interleaving, decode have been discussed in detail in the system. TURBO code is applied in this system which can reduce the system BER effectively. We make a detailed analysis of principle and performance of encoder, interleaver and decoder. Meanwhile, we compare their performance and computational complexity in three algorithms: MAP, Log-MAP and Max-log-MAP. Besides, principle and process of Max-log-MAP decoding algorithm are emphatically discussed. On this basis, a TURBO codec with fixed frame length was designed based on Max-logMAP decoding algorithm and FPGA technique. MATLAB simulation shows BER of codec at different bit rates and with different length of frame can reach to the order of 10^-5~10^-6.