Research On AODV Routing Protocol For Vehicular Ad Hoc Networks

In recent years, with the development of Intelligent Transportation System, vehicle ad-hoc network becomes popular in the field of the network communication technologies. VANET is a special kind of MANET(Mobile Ad hoc Network) which applied on vehicle communication, and has its own characteristics, such as high-speed mobile nodes, frequently changing Topology et al. Because of these features, the reliability and stability of network are affected. According to the characteristics of the vehicle network, designing a suitable network routing protocol is the focus of current research.This paper at first summarizes the structure and characteristics of VANET, and then analyzes the routing protocols applied to VANET, especially AODV. AODV is an on-demand routing protocol which is specially designed for MANET and widely used in VANET. In order to enhance the link stability of VANET, this paper proposes two new improved protocols on the basis of AODV.One of the improved routing protocols is SV_AODV(on ad hoc on-demand distance vector with speed variance). To avoid establishing a route between the vehicles very different from each other in speed and direction, nodes update their routing tables according to the speed variance of the paths in SV_AODV. The simulation results from the Network Simulator Version 2 prove that SV_AODV performances well in the case of fast moving of nodes, it can be applied to urban vehicular ad hoc networks.Another enhanced routing protocol is L_AODV(on ad hoc on-demand distance vector with link expiration time). L_AODV uses the priority nodes judging mechanism in routing discovery phase to prevent the flooding caused by RREQ messages, and uses the break link avoiding mechanism in routing maintenance phase to decrease the rate of the packet loss. The two mechanisms are both carried out by calculating link expiration time. The simulation results from the Network Simulator Version 2 prove that L_AODV performances well in VANET, especially in the dense and fast motion VANET.