Research On Application Of Distributed Rateless Codes In Deepspace Communication

With the accelerated pace of deep space exploration of human, The range of human exploration of the universe becomes wider and wider, the distance of both sides of communications are very far, meanwhile a variety of noise affect the normal communication in complex channel of the deep space with the limited equipment and energy, so communications in the deep space require more reliability and efficiency than communications on earth. M.Luby successfully made a kind of data transmission named fountain code who meets that requirement.Fountain code is rateless erasure codes that are very efficient as the data length grows. It can continuously generate encoded symbol in the encoding process, the number of encoded symbols can be adjusted according to the communication requirements for transmission. Destination node can successfully decode when it receives a little more than the number of information bits. It has low complexity encoding and decoding algorithm with no feedback which guarantees the reliability and efficiency of data transmission in the deep space, but also modified LT codes has better performance in the multi-source model of a single relay.In this paper, the background of deep space communications departure, we introduce the characteristic of deep space communications and the process of encoding and decoding of fountain code with details. According to the characteristics of fountain codes, we get the result of simulation and extractedsimple common multi- source single- relay communication model from deep space communications network model. From multi- source single- relay communication model, with deconvolving the robust soliton distribution, we do the research of the encoding algorithm of distributed LT codes and the simulation performance. According to the number of the encoded symbol that makes decoding successful, this paper verify that distributed LT code more efficient than traditional LT code. Consider that it is common in data transmissions that some information is more important than others, we propose a simple yet constructive scheme called prioritized protection to send high priority data reliably and efficiently using LT codes with this fact and do the simulation of its performance. Then using this scheme in the multi- source single- relay communication model, we can get distributed prioritizedLT codes, it has a better performance than distributed LT codes. Finally, we modify the degree distribution of LT codes, we get the performance of some different degree distribution of LT codes comparing to RSD. According the deconvolving of the robust soliton distribution, similarly we get a new kind LT codes named distributed scale-free LT codes.