mmFlower: A Low-Cost mmWave Tracking System for Industrial Robot via Mechanically Reconfigurable Reflector

Millimeter-wave (mmWave) communication has great potential for high rates and low latency but suffers from severe non-line-of-sight (NLOS) blockage and high cost of beam alignment. These problems exacerbate for mobile industrial robots. Most existing methods use reconfigurable intelligent surfaces (RIS) to change the channel environment, whose practical applications are hindered by high cost. This article introduces low-cost mmFlower, consisting of an array of 3-D-printing reflector units whose orientation can be adjusted mechanically. We first construct a theoretical reflection model, bridging the mechanical parameters and communication metrics. mmFlower works in two modes according to whether it needs real-time reconfiguration. On the one hand, based on our uniform-received signal strength (RSS) projection algorithm, mmFlower remains static and reshapes mmWave into arbitrary projection trajectory along the robot movement. It maximizes mmWave allocation to the more frequently visited areas and realizes seamless mmWave coverage. On the other hand, mmFlower can dynamically track mmWave pencil beams on robots, providing higher reflection gain. Extensive evaluations in an airplane assembly factory show the superiority of mmFlower on reflection gain (supporting up to 1.8 Gb/s in NLOS), flexibility to different trajectories of robots, robustness to deployment deviation, etc.