Design And Implementation Of Effective Algorithm Of Iterative Receiver For SCCC In Space Communications

Because of large fluctuations in channel, strong uncertainty in SNR and other issues inspace communication process, Consultative Committee for Space Data Systems hasdeveloped CCSDS131.2-B-1coding standard with SCCC.27codewords with different codelengths and modulation formats are provided in this standard, can adaptive SNR accordingto the channel information fed back to the receiver. And then the receiver selects an kind ofappropriate coding and modulation scheme to send data to reduce the transmission BER.SCCC is similar to Turbo codes, but it is serial concatenation of two RSC which is differentfrom parallel concatenation of Turbo. The extremely low error floor makes SCCC is idealfor low BER requirement scene.This paper elaborates the evolution and history of convolution code and its decodingalgorithm, introduces the principle of common encoder, modulation-demodulation andrelated decoding algorithm including SISO decoding structure which is based on MAPdecoding algorithm, Log-MAP decoding algorithm, Max-Log-MAP and improved decodingalgorithm. Besides, SOVA (Soft Output Viterbi Algorithm) is introduced too. The decodingperformance and implementation complexity are compared to above decoding algorithm.This paper simulates SISO decoder based on different decoding algorithm in floating-point and fixed-point, analysis the diversity and performance loss of quantify to differentalgorithm, describes the issues that may occur during fixed-point implementation andcompares the differences between different implementations. Finally, a kind of decodingscheme with high performance and low resource consumption is identified.In the end, the paper selects eight codewords in CCSDS standard to achieve theencoding process which can adaptive switching the encoding mode. Based on the eightcodewords, SISO decoders by linear approximation Log-MAP decoding algorithms isimplemented in hardware. High-speed parallel iterative receiver up to120-channel isprovided, details of the design of each module are described thoroughly in this paper.