MaxCD: Efficient multi-flow scheduling and cooperative downloading for improved highway drive-thru Internet systems

摘要

The limitation of existing wireless wide area networks, coupled with the delay tolerant property of many non-realtime applications (e.g. email, file download) enables drive-thru networking, which depends on roadside units (RSUs) to provide vehicular users with intermittent Internet access service. Focusing on the downlink service, MaxCD - a joint multi-flow scheduling and cooperative downloading protocol is proposed in this paper with the goal of maximizing the amount of data packets that can be downloaded per drive-thru. Based on the macro-level opportunistic scheduling and node cooperation, the best wireless link(s) (with the highest data rate) between the RSU and vehicular users can always be utilized. On the other hand, the advantage of opportunistic overhearing due to the broadcast nature of wireless medium is also exploited to reduce packet retransmission times, so as to further increase the effective data rate. Since the store-carry-forward delivery manner is adopted for the cooperators to avoid introducing interference to the in-range data communication, a multi-channel collision-free relay mechanism is designed to address the reliable and fast data exchange issue when the vehicular users are outside the service area of the RSU. Our theoretical analysis vindicates the performance gain of the cooperation and extensive simulations demonstrate the efficiency of MaxCD.