Secrecy Outage Analysis of Two-Hop Decode-and-Forward Mixed RF/UWOC Systems

The secrecy performance is analyzed for a two-hop mixed radio frequency (RF)/underwater wireless optical communication (UWOC) system using a decode-and-forward (DF) relay. All RF and UWOC links are modeled by the α-μ and exponential-generalized Gamma distributions, respectively. We first derive the expressions of a lower bound of secrecy outage probability in closed-form, and these expressions are used to derive asymptotic expressions in simple functions at high signal-to-noise ratio. Moreover, based on the asymptotic expressions, we can numerically determine a suboptimal transmit power for a wide variety of RF and UWOC channel conditions. All analyses are validated using Monte Carlo simulation.