The Research On Data Transmission Technology In Vehicular Ad Hoc Networks

Vehicular Ad Hoc Network (VANET) is composed by vehicle and roadside infrastructure integrating ad hoc network, wireless LAN (WLAN) and cellular technology to achieve intelligent inter-vehicle communications and improve road traffic safety and efficiency. The main goal of VANET is using vehicles on the city road to construct a self-organization, easy to deploy, low cost, and open architecture inter-vehicle communications network. VANET technology can implement a variety of application such as traffic accident alarm, traffic assistance, traffic information querying, internet accessing, and so on. Because of the hybrid network architecture, fast-moving characteristics of the node, and new application scenario, so VANET is essentially different from traditional self-organization network. Therefore, VANET pose many unique networking research challenges, and the design of an efficient routing protocol for VANET is very crucial.In this thesis, through investigating and analyzing of the routing protocols in Vehicular Ad Hoc Networks, we sum up their main ideas and advantages as well as disadvantages. Aim at the problems faced by Vehicular Ad Hoc Networks in urban, we present a routing algorithm for VANET based on geographic location. Meanwhile, according to consideration of the Hello Beacon’s delivery mechanisms have effect on geographic location-based routing algorithm, we also present an adaptive beaconing mechanism. The main contributes of this thesis are as follows:1) This thesis presents a routing algorithm for VANET based on geographic location. Because of the shortcoming of geographic location-based routing algorithms when handling routing hole. For instance, the right-handed rule simply not suited to urban environment, carry and forward mechanism can not handle the routing hole actively, it just simply wait for the next hop node’s appearance, and pre-estimate optimal route mechanism ignore the routing hole when delivering data packet. And therefore, this thesis presents a routing algorithm, combines the idea of source routing and geographic location-based routing algorithms, can handle routing hole actively. Also, the algorithm improves the intersection-node’s direction forwarding mechanism and ensures accuracy of the next hop node.2) This thesis presents an adaptive Hello Beacon rate adjusting mechanism. Because of the existing Hello Beacon rate using in routing algorithm is fixed, and do not consider status of the node and its neighborhood node. So, this thesis presents an adaptive Hello Beacon rate adjusting mechanism which consideration of the node’s speed and the number of its neighborhood node.Finally, we compare the performance of proposed routing algorithm and DSR、GPSR using network simulator NCTUns. The simulation results of the research prove that:in city environment, when node moves at max speed of lOm/s, the proposed routing algorithm presented in this paper is feasible and superior to the DSR and GPSR in the aspect of end to end delay and packet delivery; meanwhile, comparing with fixed Hello Beacon rate, the mechanism presented in this thesis reduced the channel load and optimized the performance of geographic location-based routing algorithm.