Global Positioning of Underwater Nodes Using Airbome-formed Visual Light Beams and Acoustic Ranging

In many applications of underwater networks, surface nodes cannot be employed for security and logistical reasons. For these scenarios an airborne unit ought to reach the underwater nodes directly from the air in order to provide commands to and configure the network. In particular, the airborne unit should facilitate localizing the underwater nodes and enable the establishment of a global coordinate system. Visible Light Communication (VLC) stands out as a prime choice for communication across the air-water interface. Using VLC, an underwater node uses the light intensity to infer proximity of the beam incident point. When receiving a sufficient number of VLC transmissions, prior work could localize the underwater nodes. However, such an approach requires very fine-grained area coverage, especially in shallow water environments, which is not practical in many application scenarios. This paper tackles such a limitation by introducing a novel Hybrid Airborne-Enabled Underwater Localization (HAUL) method. HAUL leverages knowledge of the underwater network topology in the localization process. Specifically, both acoustic ranging and light intensity measurements are used to estimate the node's global coordinates. HAUL is validated through extensive MATLAB simulations, demonstrating its effectiveness in calculating accurate positions.