Employing Non-Orthogonal Multiple Access for A Dual-Hop Relaying System With FSO/RF Links

The system performance is studied in the context of dual-hop relay systems using mixed free-space optical/ radio frequency (FSO/RF) links. Two destinations need assistance from relay associated with FSO link connecting a source node. The heterodyne detection or direct detection is necessary for detecting signal in the first hop. In the second hop, the relay relying on the non-orthogonal multiple access technique to support multiple users through an RF link. The high-speed backhauling related to FSO is suitable to design hybrid system for applications in high dense users environment. The FSO link is modeled by the M distribution in the presence of pointing errors, while the RF link is modeled by Rayleigh fading. To provide system performance analysis, we present closed-form formulas of the outage probability. Furthermore, we find that performance gap among two users mainly depend on power allocation factors and transmit signal-to-noise ratio (SNR) at the source. Finally, we conduct Monte Carlo simulation results to corroborate the derived formulas.