Cabernet- Vehicular Content Delivery Using Wi-Fi

Cabernet is a system for delivering data to and from moving vehicles using open 802.11 (Wi-Fi) access points encountered opportunistically during travel. Using open Wi-Fi access from the road can be challenging. Network connectivity in Cabernet is both fleeting (access points are typically within range for a few seconds) and intermittent (because the access points do not provide continuous coverage), and suffers from high packet loss rates over the wireless channel. On the positive side, Wi-Fi data transfers, when available, can occur at broadband speeds. In this paper, we introduce two new components for improving open Wi-Fi data delivery to moving vehicles: The first, Quick Wi-Fi, is a streamlined client-side process to establish end-to-end connectivity, reducing mean connection time to less than 400 ms, from over 10 seconds when using standard wireless networking software. The second part, CTP, is a transport protocol that distinguishes congestion on the wired portion of the path from losses over the wireless link, resulting in a 2× throughput improvement over TCP. To characterize the amount of open Wi-Fi capacity available to vehicular users, we deployed Cabernet on a fleet of 10 taxis in the Boston area. The long-term average transfer rate achieved was approximately 38 Mbytes/hour per car (86 Kbit/s), making Cabernet a viable system for a number of non-interactive applications.