IDM Model Based Routing Protocol Research For Vehicular Ad Hoc Networks

In the research of broadcast routing for vehicular ad hoc networks, multi-hop broadcast is often adopted in message transmission for the limited communication range of nodes. Because of the characteristic of highly dynamic change in topological structure, the transmission reliability decreases sharply with the increase of hops. It becomes difficult to meet the requirements for the reliability and timeliness of message transmission. Therefore, it is the key and difficult point of the research for vehicular ad hoc networks to ensure the reliability of transmission and fast delivery of information. In addition, it takes a high cost to build a real massive scene to verify the performance of protocol. Therefore, simulation becomes an indispensable means for protocol research. However, only with the mobile simulation scenarios that are based on a high real mobile model, the simulation results of routing protocol could be meaningful and valuable.Aimed at the existing problems of ignoring the characteristics of driver behavior and the traffic heterogeneity in the design of algorithm and the method to build the model in the intelligent driving model(IDM) which is widely used in research of vehicular ad hoc networks, we propose an improved algorithm firstly, which realizes the description of disparate following-patterns for vehicles under disparate traffic conditions. Subsequently, with the introduction of estimation bias, reaction time and vehicle model factor, the enhanced mobility model can better simulate the moving behavior of vehicles. By integrating the enhanced mobility model into the traffic simulator whose name is VanetMobiSim, we get the simulation results. It shows that the enhanced mobility model can simulate the stimulate-reaction process and following behavior of vehicles preferably. Finally, combined with the network simulation software, we verify that the accident factor has an effect on the performance of protocols with the accident scene produced by the enhance model.At the same time, an adaptive broadcast protocol that is based on distance and speed(ABP-DS) is proposed base on the distance based adaptive broadcast protocol for adapting to the characteristics of vehicular ad hoc networks preferably. Furthermore, disparate relay forwarding strategies for section scene and intersection scene are designed. In section scene, the adaptive forwarding priority partition mechanism is proposed by considering the factors of mobility of the nodes and the width of road, which can reduce the transmission delay in sparse network region and the collision probability in dense network region. In intersection scene, for reducing the influence of obstacles on packet transmission, an improved forwarding algorithm that is based on the distance to the intersection center is proposed. What is more, the power exponential function is introduced which can reduce the average waiting time effectively. In addition, to solve the existed misjudgment problem of the adaptive routing that is based on distance in the intersection model a routing recovery strategy is proposed. Finally, by introducing the packet based forwarding confirmation mechanism the transmission reliability of routing is improved in the premise of no extra control overhead. The simulation results show that the ABP-DS protocol has a good performance in average packet coverage ratio, proportion of forwarding nodes, average broadcast delay and broadcast overhead, which proves the effectiveness of the proposed algorithm.