Global positioning of underwater nodes using airborne-formed visual light beams

The global coordinates of underwater nodes are determined by measuring their relative location to anchors with known GPS (Global Positioning System) positions. These anchors are conventionally provisioned through the deployment of either tethered or floating devices that communicate with the underwater nodes. However, such deployment imposes tardiness and logistical complications and does not suit emerging and covert application scenarios. This paper fills the gap by introducing a novel framework for Global Underwater Localization using Airborne light Beams (GULAB). GULAB utilizes Visible Light Communication (VLC) beams from an airborne unit. By projecting airborne light beams onto a gridded surface area and encoding each beam with location metadata, GULAB forms virtual anchors with known GPS coordinates. Upon receiving an airborne VLC transmission, an underwater node assesses its proximity to the virtual anchor through the received light intensity and depth sensing. The underwater node then applies multilateration to accurately estimate its global coordinate based on all received VLC transmissions. GULAB utilizes both normal and tilted light beams to boost underwater coverage. The simulation results confirm the effectiveness of GULAB in terms of localization accuracy and coverage for both stationary and mobile underwater nodes.