In this work, the ergodic capacity performance for multipleinput/single-output (MISO) free-space optical (FSO) communications
system with equal gain combining (EGC) reception is analyzed over
gamma-gamma and misalignment fading channels, which are modeled as
statistically independent, but not necessarily identically distributed (i.n.i.d.).
Novel and analytical closed-form ergodic capacity expression is obtained
in terms of H-Fox function by using the well-known inequality between
arithmetic and geometric mean of positive random variables (RV) in order to
obtain an approximate closed-form expression of the distribution of the sum
of M gamma-gamma with pointing errors variates. In addition, we present
an asymptotic ergodic capacity expression at high signal-to-noise ratio
(SNR) for the ergodic capacity of MISO FSO systems. It can be concluded
that the use of MISO technique can significantly reduce the effect of the
atmospheric turbulence as well as pointing errors and, hence, provide significant capacity gain over the direct path link (DL). The impact of pointing
errors on the MISO FSO system is also analyzed, which only depends on
the number of laser sources and pointing error parameters. Moreover, it
can be also concluded that the ergodic capacity performance is dramatically reduced as a consequence of the severity of pointing error effects.
Simulation results are further demonstrated to confirm the analytical results
