Research On Opportunistic Routing And Congestion Avoidance Strategy For VANET

As an important part of intelligent transportation system, Vehicular Ad hoc Network(VANET) can be applied to solve the traffic congestion and safety problems in cities. However, due to the high mobility of vehicles and the complexity of communication environment, it is difficult to maintain the stable communication links between vehicle terminals, which severely limits the application of vehicular ad hoc networks. Opportunistic transmission is based on the "storage-carry-forward" method, the communication in opportunistic networks takes place on the establishment of opportunistic contacts among mobile nodes, without availability of end-to-end message routing paths. The specialty of “Delay Tolerant” can meet the demand of VANET.As the distance between the sender and the receiver increases, the probability of message transmission between them decreases, this paper proposes an Adaptive Opportunistic Routing based on Geography for VANET(AORG). As the distance between the sender and the receiver increase, the network is divided into opportunity forwarding area, greedy forwarding area and restricted forwarding area. Each node switches to different routing strategies in each area respectively. AORG leverages the knowledge of the geography position, motion vector to choose a node that has a greater opportunity to transmit message.In opportunistic networks, congestion occurs at any time when the sum of demand exceeds available capacity. This paper proposes a Status-aware Congestion Avoidance Strategy for Vehicular Opportunistic Networks(SCSV). Each node sets aside some safety buffer before advertising the receive buffer space. Upon sending messages to an intermediate node for forwarding, each node checks the receive buffer space of intermediate node to see if they can contain the message. To adapt the advertised receive buffer space to varying network conditions, we propose to adjust the advertised receive buffer space based on message drops and node status.This paper uses VanetMobiSim and NS2 simulation software to make a simulation of the routing protocol AORG and congestion avoidance strategy SCSV. The result shows that AORG and SCSV have a better network performance.