Earticle

Roadside Unit (RSU) in Vehicular Ad-hoc Network (VANET) is an essential unit usually placed at intersections to collect and analyze traffic data given from smart vehicles. Due to the costs of RSU setup, effective RSU allocation is one of important issues in VANET. In this paper, we provide an optimal RSU allocation algorithm with a concept of intersection-connectivity between intersections. We initially find optimal RSU candidate intersections which can cover the entire intersections, in the meantime minimizing the overlapped transmission coverage of RSUs. Then we repeatedly eliminate RSU candidates by the value of intersection-connectivity between RSU candidate intersections. The intersection-connectivity between two intersections is basically measured by the number of vehicles with the same moving pattern such that pass through both intersections. Thus, a high value of intersection-connectivity between two intersections stands for that the traffic information obtained at one intersection can be carried-and-forwarded to the other intersection with a high probability by those vehicles. With this feature, we repeatedly remove RSUs having high intersection-connectivity with its neighbors. Finally, we provide simulated analyses of our algorithms using real urban roadmaps of JungGu and Seochogu in Seoul. We analyze how our algorithms work in different types of roadways with real traffic data, and find the optimal number and positions of RSUs in these areas.