  In this work, we present a unified performance analysis of a free-space
optical (FSO) link that accounts for pointing errors and both types of
detection techniques (i.e. intensity modulation/direct detection (IM/DD) as
well as heterodyne detection). More specifically, we present unified exact
closed-form expressions for the cumulative distribution function, the
probability density function, the moment generating function, and the moments
of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission
system, all in terms of the Meijer's G function except for the moments that is
in terms of simple elementary functions. We then capitalize on these unified
results to offer unified exact closed-form expressions for various performance
metrics of FSO link transmission systems, such as, the outage probability, the
scintillation index (SI), the average error rate for binary and $M$-ary
modulation schemes, and the ergodic capacity (except for IM/DD technique, where
we present closed-form lower bound results), all in terms of Meijer's G
functions except for the SI that is in terms of simple elementary functions.
Additionally, we derive the asymptotic results for all the expressions derived
earlier in terms of Meijer's G function in the high SNR regime in terms of
simple elementary functions via an asymptotic expansion of the Meijer's G
function. We also derive new asymptotic expressions for the ergodic capacity in
the low as well as high SNR regimes in terms of simple elementary functions via
utilizing moments. All the presented results are verified via computer-based
Monte-Carlo simulations.
