We design, implement, and evaluate a vehicular communication system that improves uplink connectivity through multi-lobe beam pattern switching on a smart antenna. Directionality and base station-diversity are two well-known, independently developed mechanisms for improving the uplink connectivity of mobile clients. In this paper, we highlight that a system combining both mechanisms can achieve significant improvement in performance with multi-lobe beams that strike a tradeoff between

more »

... lity and diversity. This is in contrast to the mere steering of narrow beams used in conventional smart antenna systems. For tractability at vehicular speeds, our R2D2 system searches through a limited set of beam patterns with different numbers of lobes, and includes a two-stage algorithm that uses both runtime adaptation and cached candidate patterns. We design and evaluate several variants of run-time adaptation that tune the number and angle of lobes in the beam, and the bit rate. The design of these algorithms is guided by both analysis and real-world measurements with a smart antenna system mounted on a vehicle. These measurements with our prototype implementation show that R2D2 can achieve an uplink throughput increase of up to 154% over pure beamsteering and 45% over pure basestation diversity. Figure 1 : Different beam configurations for communication between clients and the receivers. B1 uses directionality with a single receiver, B2 uses diversity with all visible receivers, and B3 uses a combination of directionality and diversity with a subset of the visible receivers.