Research On Position-based Routing Protocol In Urban VANET

Nowadays, with the development of Intelligent Transport System (ITS), Vehicular Ad-hoc Network (VANET) has become a popular communication technology, and has a bright future. VANET can improve the traffic situation in some aspects like cooperative driving and safety warning, providing access service of Internet simultaneously. However, in urban scenario, vehicles run at a high speed and change their directions frequently, resulting in the unstable network topology of VANET. Applied in VANET, the topology-based routing protocol plays a poor performance, meanwhile the effect of many position-based routing protocol at present is not ideal. To a large extent, routing technology, an important part of VANET, determines the overall performance of the network. Therefore, it is necessary for us to design a reliable and real-time routing protocol specifically, which improves the data transmission efficiency.Considering the complex network environments and the special application background, we propose a Position and Traffic-Information based Routing protocol (PTIR), which makes routing decisions based on the positions of vehicles and the collected traffic information. In PTIR, the nodes are divided into vehicle nodes and intersection nodes:the vehicle node locates the position of its current road, and the intersection node needs to collect the traffic information using the clustering principles and the multicast technology. During the data forwarding process, it is essential for data packets passing through a series of intersection nodes. As a result, the signal interference of obstacles like buildings in urban scenarios can be avoided, which reduces the end-to-end packet loss rate as well. PTIR selects the candidate road with the help of position and traffic information. Between two intersections PTIR uses the improved greedy forwarding strategy, which focuses on the location prediction, and solve the position error problem in many existing routing protocols.Finally, the simulations of PTIR are conducted by NS2 with different packets sending rates and vehicle density. The results show that, compared with GPSR, PTIR provides higher packet delivery ratio and lower packet latency, which demonstrates PTIR is more suitable for high packet sending rates and vehicle density in urban environment.