Geographical Position-Based Routing Mechanism Research In VANET

VANET(Vehicle Ad hoc Network) is one of the most promising technology in ITS(Intelligent Transportation System). It plays a crucial role in auxiliary driving, early warning of traffic accidents, Internet services and so on. VANET is a special application of MANET(Mobile Ad hoc Network) in the field of transportation, it’s main features are: vehicles move with a high speed, so topology changes fast and frequent; vehicles move around the road, so the movement of vehicles is regular; vehicles are equipped with GPS, so they can get their location information timely, and so on. Due to these features of VANET, we can’t simply use MANET’s routing protocols to VANET.Therefore, it’s important and difficult to design a suitable routing protocol which can improve the efficiency of VANET’s routing.First, through the analysis of topology-based routing protocol and geographical position-based routing protocol, this thesis concluded that the geographical position-based routing protocol is more suitable for VANET.Second, the current geographic position-based routing protocols are assumed that they already know the position of destination node, and do not give a clear method to get the position of destination node, so, this thesis put forward a method which is based on position service to get the position of destination node.Then aiming at the shortcomings of several kinds of typical geographic position-based routing protocols, this thesis put forward a geographical position-based routing protocol which is suitable for urban. This routing protocol’s name is TLGR(Two hops Limited Greedy Routing).TLGR routing protocol can be divided into three parts: the optimal path selection, the two hops limited greedy forwarding strategy and the repair strategy which is based on direction priority.The optimal path selection use electronic map, combine the length of roads and the density of road traffic information to choose a optimal path which is a crossing nodes sequence from source node to destination node, it is used to solve the problem that the urban construction affect the quality of communication. The two hops limited greedy forwarding strategy choose next hop by knowing two hops neighbor nodes’ position information, it can effectively predict routing holes so as to avoid routing hole, it is used to solve the problem that GPSR and GPCR’s greedy forwarding strategy easily and frequently occur routing holes.The repair strategy which is based on direction priority is used when the two hops limited greedy forwarding strategy failed,it is used to reduce the algorithm complexity of GPSR and GPCR’s repair strategy.Finally, this thesis use SUMO which is a traffic simulation software to build a simple urban traffic scene, and use NS3 which is a network simulation software to simulate four kinds of routing protocols. These four kinds of routing protocols are TLGR, GPSR, GPsrJ+ and ROGRP. GPSR, GPsrJ+ and ROGRP are three kinds of typical geographical position-based routing protocol. This thesis evaluates these four routing protocols by calculating the packet delivery ratio and average end-to-end delay.The result shows that, compared with other three routing protocols, TLGR’s packet delivery ratio has been greatly improved, it’s average end-to-end delay has also been improved.