Fountain Codes And Their Application In The High-speed Mobile Communication

Fountain codes are a class of rateless linear erasure codes. It has low encoding and decoding complexity and can resume when meets interruption and has little or no feedback.As the users handoff frequnetly in the high speed network environment, we expect the receiver not have to accept data by an sort order and decoding quickly. The emergence of fountain codes provides a new way to solve the problem.Firstly, the three main patterns of fountain codes—Random linear fountain, LT code,Raptor codes —are introduced and pays more attention on the LT code. The encoding process of LT code contains selection of random degree and generating encoding packets.In the LT code, the construction of degree distribution is the critical factor in the decoding,so this thesis discuss two degree distributions in detail. The decoding algorithm is Belief Propagation. At last, the effects of degree distribution, the length of source symbols and various parameters on the decoding performance of LT code are compared.In order to improve the decoding success rate of LT code, an optimized encoding and decoding scheme based on original algorithm is proposed. The results show that LT codes with optimized algorithm can improve success rate compared with traditional algorithm.A coded cooperation scheme in high-speed mobile communication based on fountain code is discussed in final. First, we introduce the relay cooperation transmission model based on fountain code and the influences of the number of relay nodes on transmission time and energy consumption when relay nodes work on asynchronous and synchronoustransmission protocols is analysised mainly during data transmission. Then, applying fountain code in the high speed environment. In the light of defects of ordinary transmission, asynchronous transmission mode of fountain code is adopted in the transmission process of track relays to train. We do theoretical deduction of the process and compared to the transmission without fountain codes, the coded cooperation using fountain code do improve the system transmission performance.