Lt Code Combined With The Differential Modulation Of The Simulation Study

Luby Transform(LT) codes are new emerging rateless codes for error control, which is the first practical implementation of Fountain codes. LT codes have a good performance in unknown Network/channels, for its rateless property. Thus, it is suitable in wireless fading scenario. We combined the LT codes with differential binary phase shift keying(DBPSK). Widely simulates are preformed to get insight for future research.In the first chapter, this article will show some knowledge of the background of the coding, which will lead the direction of the following content.The second chapter introduces the LT codes with relevant contents. First, introducing the BEC(Binary Erasure Channel), which is used for simulating the Network channel. Then the original of the LT codes, Fountain codes, will be shown, and Fountain codes are rateless codes, thus they can generate infinite length of the encoding symbols which is encoded randomly from all the source. The process of the encoding and decoding of the LT codes will be shown then, and Tanner graph will be introduced at last because the decoding of the LT codes is base on Tanner graph.In the chapter three, the aim of this thesis, LT-DBPSK, will be introduced. At first, the motivation of the system LT-DBPSK will be shown, which explains why combining LT codes with DBPSK. The system LT-DBPSK will use the believable propagation(BP) algorithm, which is used in LDPC-type codes, thus this algorithm will be explained in the chapter. Then the RA (Repeat Accumulate) codes will be given, because these codes have the resemble construction with LT-Differential codes and comparing with LT codes with modulation is a good way. At last, the graph of encoding of the system LT-DBPSK will be proposed at first, and the process of the encoding also will be analyzed. Then the decoding of this system will be proposed too, and here using the Tanner graph,the concrete algorithm will be shown in this chapter, and also some prove of the algorithm will be given, which will help acknowledge the system LT-DBPSK explicitly.The fouth chapter is about the simulation result of the system LT-DBPSK. At first, the specific condition of the simulation will be shown, including the length of the source, the encoding rate, SNR(Signal-to-Noise Ratio), channel vector, the chosen degree distribution function. The simulation will work in the BSC(Binary Symmetric Channel), comparing RA code with LT-Differential; and work in the AWGN, comparing LT-DBPSK with RA-BPSK; and work in Rayleith block fading channel, comparing LT-DBPSK with RA-BPSK; and work in Rayleith block fading channel, comparing two different degree distribution function. Because the RA code is not rateless code, thus LT-DBPSK has constant encoding rate when it is comparing with RA code. The comparing about the two different degree distribution function is base on the rateless property. At last, the conclusion of the simulation result will be shown. The result gives some good performance of LT-DBPSK which is used in wireless communications.The last chapter of this thesis will give the conclusion about the recent result, and also propose the future work.