Abstract-To address the goal of providing drivers on highways with guaranteed arrival times, we propose a traffic management system that combines virtual slots with semiautonomous driving to shape traffic and prevent congestion. Two algorithms that address aligning vehicles into slots and efficient merging from three to two lanes are proposed. Furthermore, an implementation and evaluation of these algorithms using the VISSIM traffic simulator is presented. Our initial results indicate that a slot-based system has the potential to be used to guarantee arrival times and provide a significant overall increase in efficiency when compared against a human driving model.

No abstract

Vehicular networks suffer from fundamental reliability problems, which preclude basing safety-critical decisions on the expected outcome of communication. To enable safe, distributed decision making, reliable feedback on the success of communication is of critical importance. In this paper, we address the problem of end-to-end acknowledgement of geocast, in order to allow an application to know to which vehicles its geocast messages were successfully transmitted. Acknowledgements are gathered in a wave of fixed velocity to obtain results with a predictable delay. Acknowledgements are aggregated into larger messages and aggregators are selected using consistent hashing to increase the probability of acknowledgements from different vehicles being forwarded to the same aggregator. The source is found using a combination of a sink tree towards its original position, which is overlaid on the road network, and position updates by the source. We show that the algorithm is effective under various traffic conditions on a simulated highway.

Abstract. BitTorrent users and consumer ISPs are often pictured as having opposite interests, with end-users aggressively trying to improve their download times, while ISPs throttle this traffic to reduce their costs. However, inefficiencies in both download time and quantity of long-distance traffic originate in BitTorrent randomly selecting peers to interact with. We show that biasing the link selection allows one to reduce both median download times by up to 32% and long-distance traffic by up to 16%. This optimization can be deployed by modifying only the BitTorrent trackers. No external infrastructure nor specialized client-side software deployment is necessary, thereby facilitating the adoption of our technique.

Geographic group communication is a promising technique for collaborative driving applications. While oneway, geographic broadcast (geocast) is well-studied in vehicular networks, there has been little work to address the challenging reliability problems that arise. Not only do vehicular networks experience highly variable packet loss, but communication failures are difficult to detect. The presence of vehicles in an area and thus the set of vehicles that is supposed to receive a geocast, changes continuously. Without an expectation of the vehicles that should respond to queries, communication failure cannot easily be distinguished from absence. This requires a cross-layer approach, exploiting communication, sensing and driving rules. In this paper, we propose a membership service that provides group views for geographic areas as a building block to reliable geocast. We specify the semantics of the service and discuss different ways of implementing it. Finally, we show how it can be used for safe, collaborative driving.