Secrecy Probability of a NOMA based FSO-RF Network with Amplify-and-Forward Relaying

In this paper, the secrecy performance from the perspective of secrecy outage probability(SOP) for a free space optical-radio frequency (FSO-RF) network with an amplify-and-forward (AF) relaying under the wiretapping of an eavesdropper is investigated. Specifically, a superimposed signal of two users is first transmitted from a source (S) to a relay (R) over an FSO link, and then converted by R into an electrical one and broadcasted to their corresponding users over the RF links, while an eavesdropper is overhearing this transmission. In addition, the information transmission in both hops is incorporated with a non-orthogonal multiple access technique. Assuming the FSO and the RF links undergo Gamma-Gamma fading and Nakagami-$m$ fading respectively, the analytical expression for SOP is first obtained and then verified with simulation results.