  In this work, we present a global framework of a dual-hop RF/FSO system with
multiple relays operating at the mode of amplify-and-forward (AF) with fixed
gain. Partial relay selection (PRS) protocol with outdated channel state
information (CSI) is assumed since the channels of the first hop are
time-varying. The optical irradiance of the second hop are subject to the
Double-Weibull model while the RF channels of the first hop experience the
Rayleigh fading. The signal reception is achieved either by heterodyne or
intensity modulation and direct detection (IM/DD). In addition, we introduce an
aggregate model of hardware impairments to the source (S) and the relays since
they are not perfect nodes. In order to quantify the impairment impact on the
system, we derive closed-form, approximate, upper bound and high
signal-to-noise ratio (SNR) asymptotic of the outage probability (OP) and the
ergodic capacity (EC). Finally, analytical and numerical results are in
agreement using Monte Carlo simulation.
