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This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in IEEE Vehicular Networking Conference, 2011. , 2011-11-14

{This paper presents GeoVCom, a robust geocast protocol for vehicular networks. GeoVCom allows a vehicle to send geocast messages to all vehicles in a given geographical area without the sender having any knowledge about which vehicles are present in that area. GeoVCom is ad hoc, scalable and can handle communications under a wide variability of traffic load. We investigate the performance of GeoVCom in both simulation and real world tests using an implementation running on smart phones. Our field deployment and simulation results show that the number of transmissions per geocast message is kept low, significantly outperforming conventional flooding algorithms and at the same time maintaining a high (over 90%) success rate.}

This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in Submitted to IEEE Conference on Network Protocols. , 2011-10-17

{An important but relatively less studied class of network layer protocol for wireless sensor networks is geocast. It allows a sensor node to send messages to all nodes in a given geographical area without the sender node having any knowledge about which nodes are present in that area. Developing a robust geocast protocol for practical sensor networks poses several challenges. Geocast messages should be reliably delivered to the destination area in the presence of unreliable wireless links, a typical characteristic of practical sensor network deployments. The protocol should minimize the number of radio transmissions and avoid control traffic to save energy, which is a scarce resource in sensor networks. The protocol should be robust against a wide range of network densities. This paper presents the design, implementation, and evaluation of SGcast --- a reliable, robust, and energy-efficient geocast protocol that achieves these goals. For a wide range of experiments conducted using networks of real sensor nodes and simulations, we show that compared to a recent geocast protocol, SGcast achieves up to 11.08x reduction in energy consumption and up to 2.17x improvement in successful delivery of geocast messages to the destination area, while being extremely robust against a wide variability in network densities. }