Query-response geocast for vehicular crowd sensing

Modern vehicles are essentially mobile sensor platforms collecting a vast amount of information, which can be shared in vehicular ad hoc networks. A prime example of a resulting vehicular crowd sensing application might be the search for a parking spot in a specific geographic area. The interested vehicle sends a corresponding query into the destination area-a technique known as geocast. As the query originator, however, is likely to have moved relatively far away from the location from where the query was started by the time the response arrives, an efficient routing approach towards the originator is required. In this paper, we extend the Breadcrumb Geocast Routing (BGR), a georouting protocol for vehicular networks that is able to close this functional gap. We introduce several performance improvements. In particular, we focus on further reducing both the delivery delay and network overhead and on the dynamic adaption of breadcrumbs to the street layout, node density and other scenario-specific parameters. Extensive simulations in four different urban scenarios show a significant improvement on BGR, especially in terms of delivery delay, which can be reduced by an average of 24%. Breadcrumb Geocast Routing Version 2 (BGR2) thus not only avoids up to 93% of the traffic overhead of Epidemic, but increases the delivery rate of the underlying georouting protocol significantly from about 48% to almost 100% even in difficult scenarios. In sum, it is shown that BGR2 and breadcrumbs in general are a feasible and efficient approach for the routing of query responses to moving nodes via geocast, enabling a variety of vehicular crowd sensing applications.