Mobile Ad Hoc Networks Selfish Behavior Characteristics And Coping Strategies

Mobile Ad hoc Networks(MANET) is a collection of mobile hosts with wireless transceivers. It is a multihop and instant self-organization network without the aid of any established infrastructure or centralized administration.In such a network,each mobile node acts not only as a host but also as a router. MANET works properly rely on the cooperation of all the participating nodes in routing and forwarding. Actually, detecting routes and forwarding packets consumes battery energy, memory and bandwidth, in order to preserving their own resources, some selfish nodes simply does not cooperate in network operation.In this dissertation , the character of MANET is investigated and its security is researched. The effect of selfish behavior in global network performance is analyzed by simulation with NS2, and the experiment results indicates that the selfish behavior is the hidden trouble of mobile Ad Hoc network routing protocol. Guaranteeing cooperation in each node is the essential security demand of MANET. There are two approaches to deal with selfish nodes according to their mechanism implementing. The first approach uses a virtual currency tries to give a motivation for participating in the network function; another system is based on the reputation mechanism.Against the disadvantage of existing strategy of nodes occupy a lot of storage space and communications resources, a cluster-based reputation evaluation scheme(CBRES) is proposed combing with the characteristics of clustered hierarchical networks. Firstly, the advantage of using clustering network structure in reputation evaluation scheme is expounded, some typical clustering algorithms are introduced, an improved k-hop cluster-based algorithm is proposed and its performance is analyzed,the experiment shows that the performance of the improved clustering is better than that of the original one in the number of clusters, load balancing and uniform distribution of the nodes. It is more appropriate to evaluate the reputation.Lastly, design this CBRES in detail and an analysis of the proposed scheme is also presented, the use of simple experiment has proved that the average performance of the CBRES has the advantage over the CORE mechanism in the case of existing selfish nodes. A performance evaluation shows the proposed scheme reduce consumption of resources and communication costs; raises the accuracy of the reputation evalution;debases the negative impact brought by node mobility and limits network nodes randomly change the status.