Research On Routing Protocols In Vanet For City Scenarios

Vehicular Ad-hoc Networks (VANETS) has attracted considerable attention recently since it serves as the basic supporting technologies of Intelligent Transportation Systems (ITS). VANETS is a kind of Mobile Ad-hoc Networks (MANETS) under special scenarios. Hence it have some inherent characteristic, such as frequently topology changes, limited and predictable mobility traces, a mass of nodeset. At the same time, the above characteristics of VANETS has brought new challenges to the design of routing protocols under city scenarios, with more critical requirements to path stability, communication overhead, end-to-end delay.This paper firstly surveys different types of routing protocols in VANETs with comparison of the advantages and disadvantages of them. Then the current achievements of the vehicle mobility trace prediction are introduced. A prediction mechanism on vehicle mobility is proposed to calculate mobility metrics in the future time slot through mobility parameters, based on which the future anchor point position of a vehicle can be predicted. In addition, this paper also proposes an improved VANET routing protocol, PEAP (Predicted and efficiently Anchor based Routing protocol), under city scenario. It models the city scenario into a graph in which the streets is abstracted as edges, and the intersection is modeled as vertex and a transmit anchor. The routing discovery process is designed to acquire the anchor list, according to which the forwarding nodes are found and data is delivered. The mobility prediction mechanism is used to solve the walk around problem and routing selection. At last, the proposed routing protocol is simulated in the Network Simulation Software NS2, routing performance under different node density and different speed are validated. The comparison between the PEAP with the prediction mechanism and the pure EAP without prediction proves that the prediction mechanism presented in this paper played a key role in improve the routing performance. In addition, compared with other classical routing protocols, PEAP takes a relatively longer waiting time for routing decision while achieved better performance on path selection in both quality and efficiency.