Research On The Key Technologies For Wireless P2P Files Sharing Systems

Along with the development of the communication technologies and the prosperity of Internet applications, traditional service providing pattern of Server/Client in application layer could not fulfill massive accessing requirements. Then a series of commercial services based on P2P (peer-to-peer) networks have achieved huge success with equal communicating positions among entities. Users and terminals are connected by virtual links and provided with direct end-to-end serving. They play both server and client roles in the networks to share various kinds of data, storage space, computing capacities and other resources. Depending on P2P, thousands of users all around the world could enjoy instant communication, online movie and music, files searching, distributed computing and many other entertaining and academic activities. The most popular application is P2P files sharing systems, which support looking for target files among numerous databases and encourage abundant users to offer help to others with their own resources.Wireless communication technologies make people may access to networks anywhere and anytime. Relative service demand from wireless users has also increased. Existing P2P files sharing systems are all designed for wired networks, which need further revisions to adapt to wireless environment. Underlying transmission condition changes result in obvious influence on upper layers, such as random moving of users, unreliable wireless links, energy-limited terminals, increasing failure risk of nodes and frequent topology changes. Although researchers have proposed many algorithms in wireless P2P area, it mainly focuses on resource discovering, security schemes, incentive methods and other hot fields, lacking thorough analysis on sharing procedure and scalablity. This thesis would concentrate on the key steps of files sharing in wireless P2P system, combining existing research results with wireless transmission environments, proposing effective, flexible and reliable approaches from several important respects. The main contributions of the thesis are listed as follows:1. Proposing effective network architecture for wireless P2P files sharing systems. Abundant nodes are organized by hybrid layers, with head nodes and ordinary nodes shouldering respective responsibilities. The shared files are stored in the database for fuzzy and multiple-keys lookup. Relative running and maintaining schemes are also designed for scalable and reliable requirements.2. Designing the P2P resource discovering algorithm matching the proposed network architecture. Remote links are introduced into the routing table to construct a man-made small-world network. The looking up request is forwarded not only to neighbor heads, but also to remote clusters. This may greatly improve the files discovering efficiency, decreasing overhead and enhance the system performance.3. Proposing the optimal files holder selection criteria used in wireless P2P files sharing systems, always-optimally-coordinated rule (AOC), to replace the traditional min-hops rule designed for wired networks. Based on the through consideration on wireless environment, the new AOC algorithm may adjust the evaluating stress to different cases. Fuzzy knowledge combination theory is introduced to construct the mathematic model, and the concrete procedure of the algorithm is realized. It may adapt to various P2P resource discovering protocols with good improvement on successful transmission rate and files transmission time compared to min-hop-based algorithm.4. Designing a novel path failure recovery scheme for wireless files transmission in P2P networks. Loosely-connected groups are organized to realize quick detecting and recovering for failed next-hop nodes. In order to decide the most proper backup node, periodic information collection and failure risk evaluation are carried out by all the nodes in the group. Fuzzy cognitive maps theory is introduced to set up the node failure risk model for wireless P2P files sharing and deduce the evaluating rule. It has been proved that the new scheme could work with various routing protocols to provide successful file transmission among nodes with good scalable and flexible behavior.