Research Of VANET Routing Protocols In Urban Road Environments

Vehicular Ad hoc Network (VANET) is considered a special type of Mobile Ad hoc Network (MANET). Its importance is particularly observable in the design and implementation of Intelligent Transportation Systems (ITS). Because VANET characteristically has high node speed, building blocking signal transmission, trajectory predictability etc., and its routing algorithms face many challenges. This article focuses on researching position-based routing protocols in urban road enviroments. The main contributions of this paper can be outlined as follows:Firstly, because of high moving speed, sparse vehicular density, and direction of movement, the GPSR (Greedy Perimeter Stateless Routing) protocol usually leads to wrong packet forwarding decisions in VANET. Consequently, a routing protocol named Traffic Information Aware Based on GPSR (TIAB-GPSR) algorithm is hereby proposed. In order to improve packet delivery ratio, moving direction and "lifetime" used to filter hopeless candidates; then incorporate speed, vehicular density etc. to select the optimal next hop node.Additionally, for the routing breaking in the intersection, some further research on combining V2V (Vehicle to Vehicle) and V2I (Vehicle to Infrastructure) are implemented, static infrastructural nodes are deployed in intersections to build hybrid VANET environment. In order to make the algorithm feasible under this hybrid VANET environment, TGPSR-WI algorithm is proposed. This algorithm works on the principle that when static infrastructural nodes exist in neighboring list, the neighbor with nearest distance to destination will be selected as the next hop; otherwise, TIAB-GPSR algorithm is used to determine the optimal host.Finally, MOVE is used to build three kinds of typical urban simulation scenarios and export network simulator scripts which supported in NS-2. NS-2is used to comparatively study AODV, DSDV and GPSR under these typical simulation urban area scenarios. Packet delivery rate, average end-to-end delay and the first-packet-received time under different packet sizes and vehicle numbers used as the performance metrics to evaluate those three routing algorithms. TIAB-GPSR and TGPSR-WI protocols are simulated using NS-2under the Grid map simulation scenario, and then compared with traditional GPSR and GPSR-L algorithms respectively when packet delivery rate, average end-to-end delay are used as the performance metrics. Experimental results indicate that under the V2V environment, the TIAB-GPSR alogorithm shows better performance. Meanwhile, under the hybrid VANET environment, the performance of three routing algorithms improved greatly, the TGPSR-WI algorithm still has advantage.