DSRelay: A scheme of cooperative downloading based on dynamic slot

People´s growing dependency on the Internet makes them want to access the network anytime and anywhere, even while driving cars. Although 3G or 4G networks can be used to achieve this goal, roadside APs have the advantages of low cost and high bandwidth. At present, however, APs cannot cover all the areas, which cause intermittent connectivity. In this paper, we propose the DSRelay, a scheme of cooperative downloading. Unlike some studies that multiple cars download files from the Internet and different cars deliver different blocks of files like a P2P network, our work concentrates on the request of downloading respectively. Making use of the characters of the limited communication range of WIFI network, DSRelay schedules the Dark Areas (DA) out of AP coverage areas. If a mobile client leaves an AP coverage area without finishing its downloading, using the proposed scheme, APs calculate meeting time and communication duration between client car and other registered cars, and choose a series of cars to carry data client needed so that the data can be transmitted to it at different slot in DA. Also, we analyze the influence of change of car speed and a corresponding solution is presented. This scheme utilizes DAs for extending the downloading areas of the client as much as possible. Simulation results indicate the benefits of the proposed scheme in terms of increasing throughput and reducing delay.