  In this paper, we provide a global framework analysis of a dual-hop mixed
Radio Frequency (RF)/Free Space Optical (FSO) system with multiple
branches/relays wherein the first and second hops, respectively, consist of RF
and FSO channels. To cover various cases of fading, we propose generalized
channels' models for RF and FSO links that follow the Nakagami-m and the Double
Generalized Gamma (DGG) distributions, respectively. Moreover, we suggest
Channel State Information (CSI)-assisted relaying or variable relaying gain
based Amplifiy-and-Forward (AF) amplification. Partial relay selection with
outdated CSI is assumed as a relay selection protocol based on the knowledge of
the RF CSI. In order to derive the end-to-end Signal-to-Interference-plus-Noise
Ratio (SINR) statistics such as the Cumulative Distribution Function (CDF), the
Probability Density Function (PDF), the higher order moments, the amount of
fading and the Moment Generating Function (MGF), the numerical values of the
fading severity parameters are only valid for integer values. Based on these
statistics, we derive closed-forms of the outage probability, the bit error
probability, the ergodic capacity and the outage capacity in terms of Meijer-G,
univariate, bivariate and trivariate Fox-H functions. Capitalizing on these
expressions, we derive the asymptotic high SNR to unpack valuable engineering
insights of the system performance. Monte Carlo simulation is used to confirm
the analytical expressions.
