The Research Of Routing Protocol For Urban VANET

Vehicular ad hoc networks realize the communication between the car and the car and between the car and the infrastructure by short distance communication technology. It is a special kind form of mobile ad hoc networks. But compared with the traditional mobile ad hoc networks, Vehicular ad hoc networks has its unique characters, such as vehicle node moves at a rapid speed, network topology changes frequently, have a higher demands on the end-to-end delay et al,which bring great challenges to the design of the vehicular ad hoc networks routing protocol. Vehicular ad hoc networks mainly have two application scenarios: the highway and the urban environment. Especially in urban environment, where many tall and dense buildings are located in and the vehicle node's mobility is constrained by the road. It makes the communication environment more complex. Therefore, how to design a stable and efficient routing protocol combines with the characteristics of the vehicular ad hoc networks in the urban environment is one of the focuses of the study of the VANET.This paper firstly classifies the existing routing protocol in vehicular ad hoc networks, and introduces some typical routing protocol and analyses their strengths and weaknesses. Then in view of the problem that the existing routing protocol without considering the density of the vehicle nodes and its distribution in the road section and the global information in the urban environment, the paper proposed a routing protocol which is based the traffic information of the road section(TIR), the protocol measures whether the node distribution is uniform by calculated the standard deviation of the vehicle nodes on every road section, as well as considers the global information by analyzing the performance of all the sections and the intersections in the routing, then select the optimal path for data transmission. Simulation results show that the proposed TIR protocol effectively increases the data delivery ratio, and significantly reduces the end to end delay, which is better than other existing VANET routing protocol.In addition, according to the exact demands to the end-to-end delay of some information in urban environment, this paper propose a real-time routing protocol(RRP), which established the calculation model of the section delay and the crossing delay by setting terminal intersection. Considering the local section delay, as well as considering the global delay to the terminal intersection of the destination node, then the source node selects the path with the shortest delay for data transmission. Simulation results show that the proposed TIR protocol effectively increases the data delivery ratio, and significantly reduces the end to end delay and routing overhead which is better than other existing VANET routing protocol.