Performance Analysis of UAV-Assisted RF-UOWC Systems
Tijana Devaja, Milica Petkovic, Marko Beko, Dejan Vukobratovic
TL;DR
This work analyzes a UAV-assisted, relay-aided downlink over a dual-hop RF-UOWC channel, combining RF links from a hovering UAV to surface buoys with underwater optical wireless links from buoy to underwater devices. Best-relay selection among N buoys and fixed-gain AF relaying are used to optimize the downlink reliability, with end-to-end performance quantified by the outage probability. The authors derive a closed-form outage expression that integrates the RF Rayleigh fading statistics with a mixture Exponential–Generalized Gamma turbulence model for UOWC, including pointing errors. Numerical results reveal how relay count, bubble-induced turbulence, water salinity, pointing errors, and UAV/buoy geometry influence outage, highlighting moderate turbulence as favorable and illustrating design trade-offs for practical deployments. The findings inform the deployment of hybrid RF-UOWC networks in underwater environments, emphasizing the importance of channel modeling and relay positioning for reliable connectivity.
Abstract
This paper introduces a relay-assisted solution for downlink communications in a mixed system of Radio Frequency (RF) and Underwater Optical Wireless Communications (UOWC) technologies. During the initial downlink phase, data transmission occurs via RF link between hovering Unmanned Aerial Vehicle (UAV) and the floating buoys at the water surface. As fixed buoy acts as amplify-and-forward relays, the second UOWC link represents downlink signal transmission from the floating buoy to the underwater device. Best relay selection is adopted, meaning that only the buoy with the best estimated RF-based UAV-buoy channel will perform signal transmission to an underwater device. Analytical expression for the outage probability is derived and utilized to examine the system's performance behaviour for various UOWC and RF channel conditions.