NS2-Based Simulation And Study Of Vehicular Networking Wave Networking Services Protocol

The main research of the thesis concentrates on Networking Services protocol of WAVE (Wireless Access in Vehicular Environment) communication technology. The main purpose of the research for the protocol is to solve the problem of traffic jam warning under urban roads. The vehicles can inform the following vehicles through WAVE communication technology when traffic jam occurs. WAVE technology provides an approach to communicate between vehicles and roadside facilities for intelligent transportation systems.First of all, thesis analyzes the application prospects of WAVE technology. According to low latency and long communication distance characteristicses of WAVE technology, thesis analyzes the possible scenarios of WAVE technology. Finally, we select the traffic jam warning under urban roads as the main scene of the thesis and analyze the communication performance requirements of this scene, including communication delay, communication distance and communication reliability. According to the three requirements, the thesis analyzes the meetment situations of Networking Services protocol for these requirements, the analysis finds that Networking Services protocol can meet the communication delay requirement, but we need to improve the protocol in terms of reliability and communication distance.WAVE communication transmits in a single-hop broadcasting way, which makes only nodes within the transmission range of source node can receive messages and limits the transmission range of WAVE communication, which makes the protocol can not meet the need of communication distance for traffic jam warning. In order to solve this problem, the thesis introduces multi-hop broadcasting routing algorithm. Taking into account the simple flooding broadcasting routing algorithm may produce excessive amount of redundant data, resulting in broadcasting storms. The thesis analyzes several broadcasting routing algorithms proposed currently:simple flooding, distance based, area based, neighbor node information based. By comparing the advantages and disadvantages of the several algorithms, the thesis improves broadcasting routing algorithm based on the distance, making it more suitable for WAVE communication. The new algorithm introduces decreasing distance threshold mechanism and forwarding confirming mechanism to increase the reliability of communication.In order to demonstrate the performance of the improved broadcasting routing algorithm, the thesis implements the protocol module and algorithm module in NS2. We compare the performance of the new algorithm with ordinary flooding algorithm by NS simulation experiments. We can verify the improvement of the reliability and the communication distance by the experiments. By comparing the packet delivery ratio, the average end to end delay and the forwarding ratio under different number of nodes and different speeds, we finally proved that the new algorithm can significantly reduce redundant data packets and restrain broadcasting storm. In addication, the communication reliability of the new algorithm can maintains a high level.