The Design Of CCSDS Turbo Decoder Based On TI DSP

Since C. Berrou proposed Turbo code in1993, Turbo had been the channel coding standard of more and more wireless communication organizations because of its perfect performance. With the development of3G and4G,Turbo code has proved its significant value. As the transmission distance is very long and the channel condition is harsh in the field of deep space communication, CCSDS (Consultative Committee for Space Data Syatems)group has set Turbo code as the channel coding standard.As decoding algorithm of Turbo code is iterative MAP (Maximum A Posteriori), the decoding complexity is always very high. In order to reduce the delay of decoding, the implementation is achieved in FPGA and accelerators in most cases. Because of the expensive price of FPGA and the specificity of accelerators, we proposed a method to implement Turbo decoding in TI DSP. As we know, TI has been the most famous company in the domain of DSP, because it launched some kinds of DSP with high performance successfully. TI TMS320C6678is selected to implement CCSDS Turbo decoder.This dissertation first introduces the structure of encoding and decoding of Turbo code, and mainly focus on CCSDS Turbo code. Then the decoding algorithm of Turbo code is derived in detail which is always called BCJR, and the LOG-MAP and MAX-LOG-MAP are introduced based on BCJR. The performance of Turbo code is discussed in theory, and simulation results are given. As interleavers are important in Turbo code, the designs of several interleavers are introduced. Iterative soft demodulation methods are also discussed in the next. Then We introduce software pipelining of TI DSP with practical examples. We propose several optimization technologies in detail from the perspective of efficiency. At last we introduce key methods to optimize the delay of Turbo decoder based on TI DSP and realize the Turbo decoder with high speed which can reach the peak throughput of13Mbps and meet the requirements of real-time signal processing.