Research On Unequal Error Protection Transmission Sheme Based On Distributed Fountain Codes

In current wireless communications networks, as there are so many users and channel resources are limited, multi services are transmitted through one single channel. These services often have different reliability and timeliness requirements. In order to improve the transmission efficiency, the best method is to ensure that all the business data are transmitted according to their own service quality requirements.As a kind of rateless codes, fountain codes can configure channel resources flexibly to ensure that all the data are transmitted efficiently and reliably. To overcome the long transmission delay, complex propagation path and limited channel resources in wireless communications networks, unequal error protection based on fountain codes are studied in this paper. The main work is as follows:First, the fundamentals of fountain codes are introduced. The specific encoding and decoding algorithms of fountain codes are introduced and analyzed. Typical degree distribution functions are introduced and complexity analysis and performance comparison are performed.Second, analysis technique of fountain code is studied, including the asymptotic analysis and finite length analysis. The similarities and differences of the And-Or tree technique and BP decoding algorithm are analyzed. The limitations of ERS function are analyzed. The decoding performance of maximum likelihood decoding algorithm is analyzed, and the upper and lower bound of error rate are derived. In-depth analysis about the Ideal Soliton Distribution is provided, deriving the average degree of the remaining output symbols, which contributes to the optimization of Ideal Soliton Distribution.Finally, fountain codes with unequal error protection property are studied. The encoding schemes of current rateless codes with UEP property are studied. Asymptotic analysis and simulations are performed. A new coding scheme is proposed to provide unequal error protection for distributed rateless codes. This coding scheme can be applied when multi-sources symbols share a single relay and the relay has no knowledge of their importance levels. The coding principle is presented. Asymptotic analysis and experimental results prove this coding scheme viable.