Research On P2P Reliable Storage Based On LT Codes

Digital Fountain Codes is considered as an important breakthrough in the field ofcommunication network. Initially, it was designed for Binary Erasure Channel (BEC).The main feature is rateless, which means that the number of coded symbols that isproduced by encoder is limited and flexible. Decoder can restore source data when itreceives sufficient number of coded symbols. Therefore, no matter how great thedeleting probability of Erasure Channel is, encoder can produce an endless stream ofcoded symbols until decoder can restore source data. Based on this feature, DigitalFountain Codes can approach Shannon limit performance in the Erasure Channels.LT Codes has so many features, such as low decoding complexity, great errorcorrection ability, rate-less and many other advantages, making it suitable in distributedstoring, multi-point parallel downloads, wireless broadcast and multicast and so on. Inthis paper, LT Codes becoming a new hotspot in the field of robust distributed datastorage.The main tasks of this paper are listed as follows:1. Firstly, the paper briefly outlines the knowledge of P2P System and P2PStoring System. Then, describes the classification of P2P Storing System and itsarchitecture. Finally, analyze the advantages and the disadvantages of P2P StoringSystem.2. In the second place, the paper describes theoretical and basic principles ofDigital Fountain Codes. After understanding the basis of theoretical ideas of Fountaincodes, analyze the coding and decoding algorithm and code construction method deeply.This paper uses LT Codes Distribution Function and various decoding methods, do alarge number of simulation experiments of coding and decoding of LT Codes, andchoose the most suitable LT Code in a P2P Storing System.3. In this section, two methods of theoretical analysis are used in P2P StoringSystem as redundancy scheme：coding redundancy mode and replication mode, thestudy lead to a conclusion that P2P Storing System can get better availability by usingcoding redundancy mode.4. In the simulation of the P2P Storing System, the paper test the performance byusing fountain codes instead of using replication, then, analyze the reason why codingredundancy mode can obtain better system availability. The final result shows that: By using coding redundancy mode can reduce design complexity, and avoid disadvantagesof using retransmission in the feedback mechanism, in addition, which improves therobustness, data storage efficiency, ensure reliable data storage and efficient access,finally, enhance the transmission efficiency of the entire network, capacity androbustness.