Precise vehicle positioning is the fundamental technology in vehicle platooning, for sensing the driving environment, detecting hazards, and determining driving strategies. While radars offer robust performance in extreme weather, the positioning error of up to 1.8 m could be insufficient for platoons with vehicle spacings of a few meters. In contrast, LiDARs provide great accuracy, but its high cost hinders its penetration in the commercial market. To this end, this paper presents MatrixLoc, utilizing a projector as the headlight and a customized light sensor array as the receiver to achieve low-cost and centimeterlevel relative vehicle positioning in both longitudinal and lateral axes, along with bearing information. MatrixLoc leverages differential phase shift keying (DPSK) modulation to create a fringe pattern, enabling single-shot positioning. Accurate positioning is achieved by analyzing the observed space-varying frequency and demodulated phase information. Real-world driving results demonstrate that MatrixLoc achieves centimeter-level positioning accuracy, with a positioning error of 30 cm and a bearing error of 9 degrees at a distance of 20 m.

Connected autonomous vehicles have boosted a high demand on communication throughput in order to timely share the information collected by in-car sensors (e.g., LiDAR). While visible light communication (VLC) has shown its capability to offer Gigabit-level throughput for applications with high demand for data rate, most are performed indoors and the throughput of outdoor VLC drops to a few Mbps. To fill this performance gap, this paper presents RayTrack, an interference-free outdoor mobile VLC system. The key idea of RayTrack is to use a small but real-time adjustable FOV according to the transmitter location, which can effectively repel interference from the environment and from other transmitters and boost the system throughput. The idea also realizes virtual point-to-point links, and eliminates the need of link access control. To be able to minimize the transmitter detection time to only 20 ms, RayTrack leverages a high-compression-ratio compressive sensing scheme, incorporating a dual-photodiode architecture, optimized measurement matrix and Gaussian-based basis to increase sparsity. Real-world driving experiments show that RayTrack is able to achieve a data rate of 607.9 kbps with over 90% detection accuracy and lower than 15% bit error rate at 35 m, with 70 - 100 km/hr driving speed. To the best of our knowledge, this is the first working outdoor VLC system which can offer such range, throughput and error performance while accommodating freeway mobility.