A measurement study of inter-vehicular communication using steerable beam directional antenna

We provide a measurement study of a single vehicle-to-vehicle (V2V) link using 802.11b as the link layer technology. Our goal is to investigate practical usage of steerable beam directional antennas to improve V2V communications. We conduct extensive experiments using commercially available phased-array antennas mounted on cars in two different environments -- suburban roads and highways, with various drive patterns. It is observed that directional beamforming improves the link SNR significantly, that translates to significant range improvements. However, to achieve this performance gain both antenna beams must be steered appropriately in the right direction. We observe that often the best beams indeed point directly to each other (called `LOS beams'), in spite of various sources of reflections that could be present in the environment. We develop and evaluate a simple beam steering approach that uses LOS beams for communication. We present experimental data, demonstrating the performance gains (in terms of SNR and PHY-layer data rates) achieved by this approach. While we have studied a single V2V link, this method can be extended to a multihop V2V network.