Research On The Application Of SPINAL Code In Deep Space Communications

Deep Space Communication system has large transmission distance between space nodes span, resulting in large link loss, severe signal attenuation and limited transmission capacity of channel. In order to ensure transmission capacity of communication system, the key lies in the use of high-gain channel coding technology. Deep space communications research has always been focus on excellent performance channel coding. Turbo code and LDPC code are representatives of a series of advanced coding technology, and also widely used in deep space communication channel coding so far, but these fixed rate codes can’t adapt to deep space channel with characteristics of tine-varying and large link loss. Spinal code is proposed in 2012, a newly rateless code which essentially achieves capacity over both AWGN and BSC channels. In ground mobile communication system, compared to traditional high-gain fixed-rate coding(such as LDPC codes), improved rateless codes such as Raptor codes, Strider codes and so on. Spinal codes can obtain better performance in a wide range of SNRs. The characteristics of high coding gain, low complexity, rateless show that Spinal code has enormous applied potential for deep space communication. Considering that deep space scene has relatively unique characteristics compared to ground mobile communications, Spinal code still has many aspects need to be studied in depth when applies to deep space communication. This paper focus on applying Spinal code into deep space communication, studying the issue of suitable coding-decoding parameter combinations, constellation mapping method and different working mode selection of Spinal code in deep space communication.This paper begins with a brief introduction and analysis of deep space research status of traditional and rateless code technology, elaborates the base principle of Spinal code, show the advantages of Spinal code by contrast with the performance of traditional LDPC codes in deep space communication. On this basis, I have been deeply studied on time complexity and performance of different encoding and decoding parameters of Spinal code, determined appropriate parameters for deep space scene, made optimization recommendations according to simulation results. Next, considering that nonlinear characteristics and high spectral efficiency requirements for deep-space channel, studied the matching modulation for Spinal code, comparative focus on the performance of 16-APSK, 16-QAM, 16-PSK modulation for Spinal code, give suggestions for suitable modulation scheme. Finally, since Spinal code can be applied to both analog channels and digital channels, this paper comparative studied the performance of Spinal code over analog channels and digital channels with hard and soft demodulation, and given the working mode recommendation. In the digital channel mode, when Spinal code applies soft information, this paper proposes an efficient method for Spinal codes to make use of soft information which generated by soft demodulation.Research results show that Spinal code has great development prospects for deep space communication: using short code length of 256, 512 bits design, coupled with 16-APSK modulation codes in analog channel mode, the performance is far superior to the traditional LDPC code that has high complexity. Spinal code can get performance closer to Shannon limit under different SNRs(eg, When SNR is 4 d B, Spinal code can achieve rate higher than LDPC for 0.446 bits/symbol).