ExTra: Expediting file transfers through optimized inter-vehicle communication

In the realm of cooperative Intelligent Transportation Systems, vehicles are able to communicate with each other and with the available telecommunications infrastructure to support various safety-related services, traffic-efficiency solutions, and a wide variety of infotainment applications. As the number of mobile devices and information they need to exchange steadily increases, this will further strain mobile networks. It is for that reason that communication over wireless local area networks (WLANs) is becoming the primary means of transporting data to/from vehicles. However, due to their limit range WLANs only offer intermittent connectivity, and due to node mobility the established connections are only available for a short period of time. The present paper investigates how inter-vehicle communication can help minimize the upload/download delivery times in the context of delay tolerant traffic and intermittent communication. To do so, each vehicular station distributes part of its message to neighboring nodes prior to accessing the infrastructure. In turn, vehicles transmit their buffered messages when passing by the infrastructure terminals to complete the file transfer. This paper presents a thorough study of the aforementioned strategy providing a mathematical framework and optimized forwarding techniques. Performance results validate the applicability of the proposed solution.