Performance Evaluation and Optimization of UAV-Based Hybrid Dual-Hop FSO/UOWC Systems

This article considers an unmanned aerial vehicle-based hybrid dual-hop free-space optical (FSO)/underwater optical wireless communication (UOWC) system with a decode-and-forward relay, where the FSO channel is influenced by atmospheric loss, turbulence, pointing error, and angle-of-arrival fluctuation, and the UOWC channel is affected by oceanic path loss, turbulence, and pointing error. Using direct detection and heterodyne detection, we obtain tractable analytical expressions of the outage probability (OP) and bit error rate (BER), respectively. We then derive asymptotic bounds of the OP and BER to reveal more insights into the effects of various parameters. As an extension, we also analyze the system performance over a more general channel model. After that, we consider a serial multirelay-based hybrid FSO/UOWC system, and jointly optimize the relay number and the relay distance vector to obtain a tradeoff between system cost and OP performance. Numerical results are provided to validate the accuracy of the derivations and the superiority of the proposed optimization scheme. We also discuss the influences of various parameters on system performance.