The Research Of Routing Algorithm In Opportunistic Networks

In the multi-hop wireless network,the movement and sparse distributing of the nodes and obstacles will cause the network splits and communication interruption,which resultes in the degradation of network performance.Opportunistic network appears as a new network type to solve these problems.The mobile nodes in the opportunistic network make the communication using the stochastic contact with each other.The communication is extended from the"store-forward"to"store-carry-forward".The thesis does some research on the node mobility model and opportunistic forwarding in the opportunistic newwork.The research and analysis about the node mobility model play a significant role in the evaluation of the performance of the opportunistic routing protocols.The thesis makes the comparative analysis in the AODV(Ad hoc On-Demand Distance Vector Routing) routing protocols between the random mobility and uniform mobility model respectively from the three metric parameters, successful delivery rate, the average latency and routing overhead.In random waypoint, the nodes move towards the central districts as the time goes by and far away the border areas, this results in the steady state distribution of the nodes over the disk is not uniform, in uniform mobility model, it's difficult to determine the mean value of the migration length.For the above problems, the paper presents a the mobility model in which the distance of the node in every moving period has the uniform distribution regarding the network diameter.The experimental results show the delivery ratio has been promoted meanwhile the network latency and the routing expenses have been reduced.The key problem of the research on opportunistic network is the route forwarding,and the base problems about the route design include how to choose the forward sets,the forwarding priority, avoiding the redundancy forwarding and so on.Against the discharge of the node congestion caused by flooding infectious forwarding of the epidemic routing algorithm. This paper improves the epidemic routing algorithm from the view of the use of average forwarding number of packets to control the congestion. It's the main idea that the packets are sorted according to the ascending order of the forwarding number of packets in the buffer queue.If the the forwarding number of packets is equal,packets will be sorted according to the packet TTL(Time To Live) value,that is,the packet which has the smaller TTL value is arrangeed in front of the large ones.In last the nodes send these packets according to their sequence stored in the cache. If the number of packet forwarding number is greater than or equal to the average forwarding, we believe that the packet may arrive at its destinations and it will be deleted to free up buffer space.This paper conducts the performance evaluation from the three parameters, average number of forwarding packets ,delivery rate, end to end delay between the joint congestion control of epidemic routing and epidemic routing algorithm.Simulation results show that the improved epidemic routing to improve the packet delivery ratio and reduce the end to end delay and the average forwarding number of packet.