The Design And Implementation Of CCSDS Turbo Decoder Based On Xilinx FPGA

Shannon channel coding theory,which requires random coding and long code length,gives the ideal performance of channel encoding,and proves the existence of efficient and reliable encoding.While the theory only proves the existence of the ideal encoding,it did not give a specific encoding method.Turbo code was proposed in 1993.It utilizes the condition of random coding and decoding of Shannon channel coding theory,and has obtained the performance near to Shannon theoretic limit.In the field of deep space communication,the transmission distance is so long and the channel condition is harsh,so CCSDS(Consultative Committee for Space Data Systems)group has set Turbo code as the channel coding standard.In the SC-FDE(Single-Carrier Frequency Domain Equalization)remote wireless communication system,CCSDS standard Turbo code is used as the channel encoding.In this paper,we implement the decoder based on Virtex-6 FPGA(Field Programmable Gate Array)Xilinx hardware platform.Considering the high complexity of Turbo decoding algorithm,the logic resource and storage resource consumed by hardware implementation,this paper designs and implements a kind of serial Turbo decoder.In this paper,the structure of Turbo codes is analyzed,and the decoding algorithms like MAP are derived.Then the decoding performance of Turbo codes is studied by means of the floating-point simulation platform,and the calibration of the Turbo decoder is analyzed.Then the paper introduces the improved modulo algorithm,in which non extension algorithm is adopted to reduce the complexity of decoding.Then this paper presents the architecture of serial Turbo decoder based on FPGA.In order to reduce the decoding delay,the forward and backward decoding scheme is adopted.Also the dual buffer structure and ping pong operation are adopted to reduce the decoding complexity of reading and writing the path metric.The hardware resource consumption using modulo algorithm is given in the end of this paper.The implementation of the CCSDS standard Turbo code has effectively reduced the hardware resource consumption and has been successfully applied to the SC-FDE remote wireless communication system.