Research On Position-based Routing Protocol In Urban Vehicular Ad-hoc Networks

Vehicular Ad-Hoc Networks (VANET) is built up among moving vehiclesequipped with the wireless communication module without any pre-installedinfrastructure. With the growing demand for intelligent traffic management, intelligenttraffic assist and vehicular application and service, VANET has become a hot spot inthe field of Intelligent Transportation System. As a kind of Mobile Ad-Hoc Networks(MANET), VANET has all characteristics of MANET, such as dynamic topology,limited transmission bandwidth, distributed control and multi-hop communication.Consider the vehicle moving at high speed in urban environment, VANET has its owncharacteristics, such as topology changes frequently, channel conditions are veryunstable, vehicle nodes are distributed unevenly, transportation systems affect nodemovement behavior. Routing protocol, as one of the key technologies of VANET, isimportant to determine the performance of VANET. In order to guarantee informationeffective transmission, it is necessary to design a proper routing protocol which couldsatisfy the characteristics of VANET.Since position-based routing protocols do not need to maintain global routinginformation and complete data forward based on a small amount of local information,it has the strong compatibility on VANET in urban environment. Therefore, this studyproposes an improved GPSR that is a position-based routing protocol. The improvedGPSR is more suitable for VANET.This thesis classifies the common routing protocols, compares and analyzes thedifferent type of routing protocols with several classic instances, and draws theconclusion that position-based routing protocol, such as GPSR, is more suitable forVANET in urban environment. Then this thesis analyzes the rule of vehicle movementin the city, points out the defects of classic GPSR protocol. A new GPSR based on thepriority direction is presented to deal with the defects. The new GPSR takes intoconsideration of the rule of vehicle movement in Greedy Forwarding. A node choosesthe next hop according to the neighbor node’s priority that is determined by thevehicle moving direction. Meanwhile, to decrease the computational complexity ofnode, the new GPSR designs the Greedy Forwarding into two parts, one is the GreedyForwarding at crossroad, the other is the Greedy Forwarding at straight road. At last,this thesis compares several network simulation tools and traffic simulation tools, and chooses NS2and VanetMobSim to make simulation experiments between theimproved GPSR and classic GPSR. It is concluded that the improved GPSR has betteradaptability in VANET in urban environment compared by average end-to-end delay,packet drop rate, throughput and normalized routing load.