Performance Analysis And Simulation Of Vehicular Communications In Intelligent Transport System

Nowadays the Internet of Things is emerging and concepts like Intelligent Earth, Intelligent City are coming out very quickly. Intelligent Transport is one of them under the same background. In vehicular communication networks, the mainly adopted protocol stack is IEEE WAVE. It consist of802.1lp,1609.0～1609.4and so on, altogether protocols. They specify the standards of different layers in communications. This protocol stack focuses on the unstable and fast changing network topology of vehicles and the special mechanisms to guarantee communication qualities in such environment.In the thesis, the current research and development of the Internet of things and intelligent transport system is briefly:ntroduced in the first part. Then related background knowledge of IEEE WAVE protocol stack and intelligent transport system is stated. Based on the former information, the thesis then analyzes the challenges short range and long range communications in the architecture of vehicular networks. The short range communication is used to support safety messages which affect the safety of vehicles travelling on road. Due to the CSMA and channel switching mechanisms in the media access control layer of the protocols, safety messages may cause waste of channel resources when vehicle density is low. On the other hand, when the vehicle density is high, safety messages may not be sent out before the channel switch comes. So, in order to deal with the CSMA feature of contending, we propose a mechanism using buses to help propagate safety messages among vehicles. We use buses as the carrier of safety messages, which changes the original broadcasting method and effectively improves the efficiency of safety message broadcast. In terms of channel switching, we propose a uniform switching mechanism based on vehicle densities. As to long range communications, original multi-hop mechanism causes long delays. We set forth the new mechanism of using buses as the long range communication media, making use of their feature of having stable routes and large coverage. In the end, NS-3network simulator and SUMO traffic simulator are employed to realize multiplatform simulation which is very close to real world scenarios, improving the reliability of the results.