No Rate Decoding And Ldpc Incremental Redundancy Code In The Application Of Relay System Research

Rateless codes have recently attracted extensive attension due to their advantages,such as flexible code rate, few feedback requirements and low encoding and decodingcomplexity, etc. And the cooperative relay systems also are hot topic due to theirabilities of improving system capacity and coverage. In this paper, we first study thedecoding of rateless codes and two corresponding modified decoding algorithm forBDRC (Binary Determinstic Rateless Codes) codes and LT (Luby Transformation)codes are proposed. Then we investigate the incremental redundancy (IR) codingscheme for the cooperative relay system. The specified major work are listed as follows:Firstly, we introduce the classical encoding and decoding algorithms as well as theIR(Incremental Redundency) transmission scheme, and investigate the performances ofthree kinds of rateless codes over packet erasure channel, including BDRC codes, LTcodes, and Raptor codes by computer simulation.Secondly, two novel decoding methods are designed for two kinds of ratelesscodes: binary deterministic rateless codes (BDRC) and LT codes. The traditionaldecoding algorithms for the two codes discard the erroneous packets that may onlycontain few erroneous bits, which will cause the waste of bandwidth. The noveldecoding methods adopt the packet combining technology to find the potential positionsof the erroneous bits in the erroneous packets and correct them, which will acceleratethe collection of the correct packets for the traditional decoding methods. And thesimulation results show that the proposed decoding methods outperform the traditionaldecoding methods for both BDRC codes and LT codes.Furthermore, we study the IR coding scheme for the cooperative relay system. Inthe proposed scheme, the IR packets are generated based on the initial LDPC codes andtransmitted cooperatively by the source and the relay. The IR packets at the relay is inthe form of soft information and generated by soft encoding in order to get bettertradeoff between the system transmission efficiency and the error propogation. GaussianAproxiamtion is also used to optimize the degree distribution of the check matrix of the IR codes to further improve the performance of the joint codes.At last, we conclude the study and give some possible future work of rateless codesin the wireless communication systems.