Real-Time Underwater Visible Light Mobile Communication with an Extended Distance Using Dynamic Counting Threshold

The capability of real-time mobile communication is highly desirable for underwater applications. However, there have been few reports on the underwater visible light communication (UVLC) systems with the ability to move, as their distance of reach is limited to a few meters and often rely on offline signal processing. In this paper, we propose a dynamic counting threshold (DCT)-based system for real-time underwater mobile communication to extend the reach beyond traditional adaptive feedback threshold (AFT)-based system. In the experiments, we achieved real-time underwater mobile communication at 2.0 Mb/s with a distance of reach up to 60 m under tap-water conditions. The proposed DCT-based system achieved a dynamic range of 15 m, representing a 5.8-fold improvement over the AFT-based system. In addition, we also demonstrate the real-time video transmission, showing that the receiver can move at a speed of 0.35 m/s while maintaining a BER below the FEC threshold at the same time.