Research On Position-based Broadcast Algorithms In Vehicular Ad Hoc Networks

With the increasing number of cars and the continuous development of new vehiculartechnologies, road safety has become a main issue for governments and car manufacturers. Theurgent needs of road safety made the Vehicular Ad hoc Network (VANET) emerge as one of theimportant research areas of intelligent transportation systems. VANET can provide a wide variety ofapplications and services, and many applications need to be implemented by broadcastingtechnology. However, due to the special nature of VANET, traditional broadcast protocol does notapply to the vehicular network, so the design of an effective and suitable broadcast protocol forVANET is significant.Most broadcast algorithms always have large delay and they are not so reliable, in order toovercome these problems, existing broadcast algorithms of VANET are intensively studied and amulti-candidates-based adaptive broadcast algorithm called MCAB is proposed in this thesis. Thealgorithm is divided into broadcast of an intersection and broadcast of a single road, and multiplevehicles are selected as the forwarding candidates to reduce the time of retransmission by sourcevehicle, and an adaptive broadcast mechanism according to the vehicle’s position (intersection orroad) is adopted, so that there is a great deal of flexibility in MCAB.When the broadcast algorithm of an intersection is adopted, the number and ID of forwardingcandidates are decided by sender, and different broadcast mechanisms are adopted in line with thevehicle’s density of an intersection, it replaces the function of repeater in most broadcast algorithmsand reduces the cost of hardware facilities. When the broadcast algorithm of a single road isadopted, in contrast to the intersection broadcast, the forwarding candidates are decided byrecipients, and different broadcast mechanisms are used in both the ideal situation of uniformdistribution and the actual situation of random distribution of vehicles, especially the method ofclassification for vehicles in the situation of random distribution has a good performance inreducing delay. And the acknowledgment mechanism is also taken by MCAB in order to ensure thereliability of broadcast while reducing delay.Finally, the proposed algorithm is simulated and analyzed by NS2network simulator andVanetMobiSim traffic simulator. The simulation results show that MCAB has better reliability andlow transmission delay compared with existing multi-hop broadcast algorithms.