On characterization of the traffic hole problem in Vehicular Ad-hoc Networks

Data delivery in Vehicular Ad Hoc Networks (VANETs) is based on the vehicles on the roads. However, the distribution of vehicles could be affected by some external means. For example, the traffic light or pedestrian signal could block the traffic flow moving onto a road. Thus, a gap between vehicles will appear at the entrance of the road, where the distance is larger than the communication range of the vehicles. We term it as a traffic hole, which not only affects the forwarding opportunities in VANETs, but also affects the performance of data delivery on the road, even under heavy traffic. In this paper, we model and analyze the traffic hole problem to characterize the pattern of traffic holes in VANETs. Then we discuss its influence on the data delivery in VANETs, and propose to utilize the backward traffic to mitigate the traffic hole problem. We conduct intensive simulations for discussing the traffic hole problem in VANETs. The simulation results imply that signal operations can affect the performance of data delivery in VANETs, and suggest that the backward traffic can mitigate the traffic hole problem.