A Data Dissemination Protocol for Vehicles with Temporary Cellular Network Inaccessibility

The cellular network coverage in sparsely populated and mountainous areas is often patchy. That can be a significant impediment for services based on connections between vehicles and their environment. In this paper, we present a method to reduce the waiting time occurring when a vehicle intends to send a message via a cellular network but is currently in a dead spot without sufficient coverage. We use a hybrid network approach combining cellular network access with ad-hoc networks between vehicles that are nearby. In particular, we introduce a data dissemination protocol that allows the vehicles connected through an ad-hoc network to find out which one will most likely leave the dead spot first. Messages can then be sent to this vehicle that forwards them as soon as it regains cellular network access. Further, we developed an initial implementation of this protocol using the technology WiFi Direct that is realized on many mobile phones. Implementation details of the prototype as well as analysis results regarding data transmission time limits of fast driving vehicles are discussed in the article as well.