Performance Analysis And Design Of Fountain Codes

Digital Fountain Code is proposed as a new channel coding scheme for the application characteristics of large scale data distribution and reliable broadcasting, which is concerned by academics and industry in recent years. In order to improve the error-correcting ability of Fountain Codes, in this paper we propose an improved pre-coding design, which is based on the analysis of Fountain Code structure and performance of encoding and decoding. We also show the research on Unequal Error Protection strategy of Fountain Code for some multimedia applications.As a basic research of this paper, first we introduce the basic concepts and principles of Digital Fountain Code, including channel models, definitions, and characteristics. Then three kinds of typical Fountain Code-Tornado code, LT code and Raptor code were highlighted. We give a comprehensive description of their encoding and decoding algorithms, and also some analysis for their performance.Raptor code consists of pre-code and LT code, therefore a good pre-coding design is of great significance. We select a kind of capacity-approaching LDPC code ensembles to construct the pre-code of Raptor code, which is given by two different designs of degree distribution, and we further verify our work with simulations. The simulation results indicate that when overheadγ=1.15, the bit error rate of Raptor code is less than 10-5, which provides a good performance and a certain significance to the actual design and application.Finally, from need of unequal error protection in some multimedia applications, Using LT code as an example, this paper provides analysis and research for implementation of unequal error protection fountain code, proposes an improved method. The simulation results show that the improved method of UEP achieves better performance than the original method when the receiver gets fewer coding symbols.