Research On Cooperation In Opportunistic Network Based On Evolutionary Game Theory

With rapid development of wireless communications technology, many short-range wireless smart devices are emergying in recent years, and wireless adhoc techonology is widely used in many scenarios, among which opportunistic network has been concerned more and more frequently. Opportunistic network is kind of mobile adhoc network, while differs from traditional network, it's not necessary that there must exist a complete communication path between source and destination nodes. Instead, it ultilizes the movement of nodes to seek the possible communication chances to transmit the messages by hops. Using―Store-Carry-Forward‖routing method to realize communication, this technology can solve the traditional problem about intermittent connection base on network deployment range, wireless technology limitation, dynamic of moving nodes and different seperation of network.In opportunistic network, it is assumed that all nodes in the network are willing to cooperate with each other to forward the message as relay. While in real scenarios, this assumption might easily be violated due to the limitation of processing and calculating ability, memory size and battery. Normally, each node will behave according to network condition in order to maximize its profits.In this paper, according to social and biological features of self-organize behavior, we introduce evolutionary game theory as the tool in order to analyze the cooperation between nodes. Differing from tranditional game theory, evolutionary game theory dose not require the wholly rational determination and perfect information. Because in opportunistic network, it is impossible to acquire perfect information due to highly dynamic movement of nodes, in result nodes can not behave totally rationally. And different kinds of nodes are not well mixed, and the chances to meet each other are not homogeneous distribution, each node only competes in a game with the nodes in its transmission range. Thus, it is necessary to further introduce evolution graph theory to address the cooperation problem in consideration of space topology of network.In this cooperation model, each node in the network is represented by a vertex of the graph. The edges denote node pairs are in mutual transmission range. First, we should establish the payoff matrix for each node; each node can use any one of n strategies according to its payoff; finally the whole network will stay in a relativly stable state. We can obtain the distribution and evolution of cooperation behaviors accordingly in order to investigate the survival ability of the network under specific configurations. We also implement related simulations combining the opportunistic movement model in our system; ultimately we can offer theoritical support to opportunistic network design and related deployment issues in real world.