Research On Low-complexity High-performance Spinal Codes For Deep Space Communications

Deep space communication has characteristics of large transmission distance,large floating delay and serious link loss.In order to ensure the effective transmission,it is necessary to adopt the high-performance channel coding technology suitable for deep space channel.Some advanced fixed-rate codes are widely used in deep space communication channel coding so far,but it can't adapt to the deep space channel with dynamic change and limited feedback resources.The rateless codes can fit complex and changeable deep-space channel state without feedback,and it becomes one of the hotspots in deep space communication research.As a type of newly invented rateless codes in 2012,Spinal codes are provably characterized by capacity achieving over both binary symmetric channel and additive white gaussian noise channel.Compared with the widely used fixed-rate codes and other rateless codes,Spinal codes can achieves excellent performance over a wide range of SNRs.These show that Spinal codes have great research potential and development value for deep space communication.Firstly,this paper introduces the basic principle of Spinal codes,and analyzes the performance advantage of Spinal codes by comparing with other excellent codes.On this basis,I have been determined the direction of research and deeply studied on two aspects of complexity and performance.Then,in order to achieve low complexity and improve the performance,I optimize Spinal codes from three aspects: decoding algorithm,coding transmission mode and transmission system structure.The following shows specific research contents.(1)In order to reduce the current high decoding complexity,a novel low complexity decoding algorithm named sliding feedback decoding(SFD)for Spinal codes is proposed.Spinal decoding is the procedure of constructing the decoding tree for node searching.Due to the interference of redundant nodes,the decoder needs to search for some unnecessary error decoding paths,resulting in increasing the decoding complexity.The SFD uses sliding window and feedback node to exclude such interference.Through sliding window selecting nodes and feedback node determining the decoding path,the SFD scheme can get lower decoding complexity while ensuring successful decoding.Compared with other decoding algorithms,SFD can significantly reduce the decoding complexity without any harming to the performance.(2)In order to improve the performance and achieve the ideal rate performance,a new punctured coding is proposed.According to the characteristics of Spinal coding and the basis of successful decoding,I propose an irregular "inverted triangle" punctured coding.The results show that this punctured coding exhibits a higher gain performance advantage with increasing SNR than other punctured coding,and it has a lower application complexity.(3)In order to obtain the dual advantage of complexity and performance,a scheme concatenated with RS codes and Spinal codes is carried out in deep space communication.The message is sequentially encoded by RS codes and Spinal codes in cascaded system,which effectively enhances the system's resistance to burst interference and random interference.The interleaving technique introduced in cascaded system can realize the parallel processing of information and facilitate the transmission of long code information.The proposed scheme,especially the interleaving scheme,can have a lower complexity under the premise of better performance,and solve the problem that the transmission of long information needs long time.