Event Notification in VANET With Capacitated Roadside Units

Many future vehicular ad hoc network (VANET) applications will be event driven and will require events of different types to be delivered to moving vehicles within some specified time. In this paper, we propose a publish-subscribe based event notification framework that uses roadside units (RSUs) to deliver events to vehicles that subscribe to them within the validity periods of both the subscriptions and the events. Each RSU can disseminate only a finite number of events at a time and has a cost associated with it. Two scheduling problems to schedule the dissemination of events from RSUs are formulated. The first problem aims to maximize only the number of subscriptions that are matched to some events. The second problem, in addition to maximizing the number of subscriptions matched, also aims to minimize the total cost of disseminating the events. We have designed offline and online algorithms for the problems that a service provider can execute to schedule event disseminations from the RSUs. Detailed simulation results are presented to show that the algorithms are able to match a high percentage of subscriptions with low average event dissemination cost for some realistic city traffic scenarios.