Research On Wireless P2P Overlay Model And Key Technologies Based On Cayley Graphs

Recently, with the development of wireless communication technology quickly and the processing capability of mobile devices increasingly, users of the mobile devices can access wireless networks services anywhere and anytime, which brings an advantageous opportunity for P2P applications extending into wireless networks. However, the practical characteristics of wireless networks, such as dynamic topology, restricted link transmission bandwidth, limited processing capability of wireless nodes, and so on, which resulted in that the existed P2P technologies designed on the Internet may not be applicable to wireless networks easily. Therefore, how to extend the P2P technology into wireless networks widely by considering the particular nature of wireless networks, and taking full advantage of wireless networks, is becoming an urgent research task.Cayley graph is a method of constructing graphs using algebra groups, thus people can analyze constructional characteristics and design correlative algorithms of Cayley graphs by using mature algebra graphs theories. In particular, due to symmetry, vertex transitivity, low degree, low diameter, perfect embeddability, high fault tolerance, simple routing algorithms, and other excellent properties of network models based on Cayley graphs, therefore, researches on the key technologies in the P2P networks by using the method of algebra graphs theories has high theoretical significance and applied value. The following three issues based on Cayley graph are studied in this paper:1. According to particular characteristics of wireless mesh networks, and by using semi-direct product of two groups in the algebra groups theories, a wireless P2P overlay model which is based on Cayley graph, is presented in this paper. A simple approach that P2P overlay network depends upon nodes’neighborhood in the physical network topology, is used during designing P2P overlay networks, then, topology consistency between the overlay network and the physical network is kept well. In addition, the method of cross-layer in wireless networks is also used in the proposed routing algorithm, then, the 1-hop broadcast communication occurring in wireless networks is utilized adequately during searching resources in an distributed way, which speed up the lookup operations by exploiting the information that is available at the MAC layer evidently. Simulation results show our proposed P2P network can achieve optimal performance of searching resources under dynamic wireless network condition.2. The non-uniform distribution of resource objects stored at a peer node, the heterogeneity nature of nodes’capabilities and the dynamic character of wireless networks, which are resulted in load imbalance issue in dynamic structured P2P networks. By using perfect embeddability of Cayley graphs, a binary-tree based load balancing model which is constructed on top of the hypercube P2P overlay network is presented in this paper. Then, collecting load and capacity information of nodes, making the decision of load balancing and transferring the overloaded loads can be finished in each balancing domain independently. By using of the balancing domain in the proposed model, therefore, the operation of load balancing can be implemented in each balancing domain in a distributed and parallel way. Simulation results show that the proposed scheme achieves load balancing under dynamic wireless network condition, and the load movement cost is reduced greatly during the process of load balancing.3. Aim at the bad availability and other existed problems of wireless P2P networks, and by using powerful storage and processing capability of wireless mesh routers, an adaptive management model of resource replicas which is based on Cayley graph in wireless P2P networks, is proposed in this paper. According to the dynamic feature of resource popularity and nodes’load state, the proposed model can adjust the number of resource replicas adaptively in the P2P networks. Besides, by using multiple-adjacency code theories and construction character of Cayley graphs, the proposed model can place the known number of resource replicas onto the appropriate nodes perfectly in the P2P networks, then, access hops between the resource requester node and the offering resource nodes are greatly reduced. Simulation results show that the proposed model has perfect adjustable capability, and yields improvement on the availability, fault tolerance and scalability under dynamic wireless network environment in the P2P network.