In this study, two novel multi-hop relay-assisted hybrid FSO/RF communication systems are presented and compared. In these structures, RF and FSO links, at each hop, are parallel and send data simultaneously. This is the first time that in a multi-hop hybrid FSO/RF structure, detect and forward protocol is used. In the first structure, at each hop, received signals with a higher signal-to-noise ratio are selected. However, in the second structure, at each hop, received FSO and RF signals are separately detected and forwarded and selection is done only at the last hop. Considering FSO link in negative exponential atmospheric turbulence and RF link in Rayleigh fading, for the first time, closed-form expressions are derived for outage probability (Pout) and bit error rate of the proposed structures. MATLAB simulations are provided to verify derived expressions. Results indicate that the structure with the selection at each hop has better performance than the structure with a selection at the last hop.

Keywords