Research Of Relay Selection Scheme Vehicular Ad Hoc Networks

As a new wireless communication system, Vehicular Ad Hoc Network becomes an active research area in recent years. One of the most important applications of VANET is the security application, so how to broadcast emergency messages to vehicles is the urgent problem. Relay selection algorithm will affect the broadcast system performance very seriously. A Good algorithm should have a low delay but a high deliver rate.The research of this article focuses on the relay selection schemes in VANET. VANET is a special ad hoc network and owns some unique characters, so firstly, this paper introduce the characters and application in these two networks. The application scene in VANET can be classified into three types:vehicle-to-infrastructure(V2I), vehicle-to-vehicle(V2V) in high way, vehicle-to-vehicle in city. In order to analyze the algorithms performance, make some reasonable assumptions and simplification. The broadcast relay selection schemes can be classified into two methods. This paper deeply research three neighbor knowledge based methods:Greedy scheme, Primary and candidate relays cooperative work scheme, Opportunistic broadcast. These schemes are simulated using NS2 on the high way and city scene separately. On the high way scene, they all have a good performance on delay, delivery rate and overhead, but in the other scene, the existing of the obstacle result in a steep descent at the delivery ratio. Chapter five gives a greedy forward optimizing scheme. In this scheme, the vehicle at the crossing can select several relay nodes from different roads to forward the messages for it. The simulation shows that the optimizing scheme can increase the delivery rate effectively, with nearly the same overhead.When there are 300 nodes in the city scene, with the optimizing scheme, 45% of the nodes can receive the messages. Comparably, with the primary and candidate relays cooperative work scheme, only 29% of the nodes receive the message.This paper provide a greedy forward optimizing scheme in city scene, it can increase the delivery rate about 15%. But still now, on one scheme can provide the satisfactory result. So this paper can be the basic of the further research for relay selection scheme in vehicular network...