Research On Simulation Platform And Routing Protocol For Vehicular Ad Hoc Networks In Urban Scenarios

As an extension of IEEE802.11standards, IEEE802.11p is an excellent solution and specially developed for vehicular wireless communications in Intelligent Transport System. Recently, VANET has attracted much attention and been a research hotspot. The communication environment and network architecture in VANET are different from other wireless communication systems. As a critical part, routing protocol plays a very important role in VANETs. In this paper, we investigate the simulation platform and routing protocol for VANETs in urban scenarios. We build an urban scenario simulation platform with IEEE802.11p based on OPNET and VanetMobiSim, and evaluate the performance of IEEE802.11a and IEEE802.1lp, then propose an improved routing protocol.We first analyze the characteristics, structure, application, access technology and different mechanisms of routing protocols for VANETs, and then introduce the IEEE802.11p physical layer and MAC layer technology. Secondly, we build an IEEE802.11p module based on existing IEEE802.11a node model in OPNET to evaluate VANETs with IEEE802.11p technology. Thirdly, we develop an integrated simulation platform for VANETs based on VanetMobiSim and OPNET, where VanetMobiSim is responsible for generating traffic data while OPNET is in charge of simulating protocols in different scenarios. Based on the integrated simulation platform, IEEE802.11a and IEEE802.11p are compared. In addition, we investigate AODV, DSR and GRP routing protocols thoroughly by extensive simulations. Simulation results show that GRP which uses geographical location information is more suitable for VANETs.Furthermore, in order to improve the performance of GRP, we analyze the neighborhood division and hierarchical method in GRP. After extensive simulations, a mathematical model about relationship between GRP neighborhood size and vehicle numbers is presented for a given network scale, which is helpful to provide a theoretical foundation to choose the neighborhood size of GRP. After an in-depth analysis of GRP, especially its next hop selection, aiming at its two drawbacks in next hop selection, some improvements have been provided accordingly and a new improved geographical routing protocol (IGRP) is presented, which jointly considers distance and hierarchical factor and takes full advantage of neighborhood division to choose a more suitable neighbor as next hop. Simulation results show that IGRP can improve the performance in packet delivery, network delay, routing hops and backtrack number. Therefore, it is much better than GRP for a VANET with an urban environment.