Physical Layer Security of Hybrid FSO-mmWave Communications in Presence of Correlated Wiretap Channels

Hybrid Free-Space Optical (FSO) and millimeter Wave (mmWave) systems have emerged as a promising candidate for high data rate wireless transmissions due to the unique complementary properties against the different channel and environment conditions. Consequently, in this study, we investigate the hybrid FSO-mmWave systems from a physical-layer security point of view in the presence of a hybrid type eavesdropper, where the communication between two legitimate peers takes place over both FSO and RF links simultaneously. We examine practical scenarios to eavesdrop the legitimate communication and discuss the effects of random radio power of mmWave link and optical irradiance of FSO link on the probability of achieving a secure transmission. The impact of the fundamental physical layer parameters on the secrecy performance of the hybrid system is analyzed by obtaining closed-form derivations of the probability of strictly positive secrecy capacity (SPSC) for correlated wiretap channels.