Improvement And Simulation Of On-Demand Routing Pprotocol In Vehicular Ad Hoc Networks

Vehicular Ad Hoc Networks (VANET) is one of the specific applications of Mobile Ad Hoc Networks. Because of the vehicular nodes that constitute the network with high mobility, the network topology changes sharply, the links between the vehicular nodes disconnect frequently, and the performance of routing protocol is severely damaged. Therefore, how to improve the stability of routing protocol and enhance the quality of vehicular communication system have become a hot spot of VANET research. In this paper, we study routing protocol of VANET, and introduce an improved V-SARP (Stability AODV Routing Protocol for VANET), which optimizes is based on Global Position System equipment.Because node mobility model is the basis for routing protocol simulation, first of all, we abstract the motion characteristics of real vehicles and establish use the vehicular mobility model by using the VanetMobiSim traffic simulation software. Secondly, through analyzing AODV protocol and combining with the advantages of VANET, we propose an enhanced V-SARP protocol. V-SARP uses two new mechanisms as follows:(1) RREQ message forwarding restriction algorithm, the algorithm limits the number of forwarding nodes by judging the reliability of network node, in order to restrict the flooding which caused by broadcasting RREQ messages and reduce the protocol overhead; (2) the optimal routing selection mechanism, the routes establishing by using this mechanism have the longest expiration time, which ensures the stability of the network to achieve higher packet delivery ratio. As a result of the changes, original local repair mechanism of AODV protocol is no longer applicable for V-SARP, we add request_repair and reply_repair messages to modify the local repair process. Finally, we respectively simulate AODV and V-SARP protocol in low-load or high-load urban and highway vehicular situation, through using the documents generated by VanetMobiSim as the input scenarios to NS-2 platform.The experimental results show that, compared with the AODV protocol, although V-SARP protocol increase the end-to-end delay with little, it can increase the packet delivery ratio and reduce the protocol control overhead. Accordingly, V-SARP protocol has advantages in ensuring network robustness and data transmission. It is more suitable for heavy load and high speed vehicular communication systems.