Multi-User Mixed FSO-RF Systems with Aperture Selection under Poisson Field Interference

In this paper, we study the performance of mixed free space optical (FSO)-radio frequency (RF) multi-user relay network with aperture selection and opportunistic user scheduling in the presence of Poisson field interference. The considered system includes multiple optical sources (apertures), one amplify-and-forward (AF) relay, and multiple users. The source is connected with the relay node through FSO links and the relay is connected with the users through RF links with a Poisson field interference at the users. The FSO-RF channels are assumed to follow Málaga- M κ - μ fading models with pointing errors on the FSO links. Exact closed-form expressions are derived for the outage probability and average symbol error probability (SEP). Moreover, the system performance is studied at the high signal-to-noise ratio (SNR) regime, where an approximate expression for the system outage probability is derived, in addition to deriving the system diversity order and coding gain. Then, the optimum source and relay transmission powers and relay position are determined to minimize the system asymptotic outage probability. The Monte-Carlo simulations are provided to validate the achieved exact and asymptotic results.