Feasibility of content dissemination between devices in moving vehicles.

ABSTRACTWe investigate the feasibility of content distribution between devices mounted in moving vehicles using commodity WiFi. We assume that each device stores content in a set of files, and that each file has a version number. When two devices come into wireless range, they attempt to synchronize the latest versions of any files they have in common. This is challenging because connections are often short-lived and have variable link quality. Prior work demonstrates that current protocols perform badly under these conditions. To motivate this work, we use the example of Personal Navigation Devices (PNDs), or SatNavs, where the content to be exchanged includes maps and points-of-interest files. We describe a protocol enabling devices in vehicles to identify and exchange content of shared interest. We evaluate the protocol using a small vehicular testbed in two urban locations and on a highway with a closing speed of 140MPH. We investigate the effects of using 802.11a versus 802.11g, placing the antenna inside or outside the vehicle, and varying the packet size. We transfer up to 70MB in the urban settings and 7MB on the highway.