  In this paper, a very accurate approximation method for the statistics of the
sum of M\'{a}laga-$\mathcal{M}$ random variates with pointing error (MRVs) is
proposed. In particular, the probability density function of MRV is
approximated by a Fox's $H$-function through the moment-based approach. Then,
the respective moment-generating function of the sum of $N$ MRVs is provided,
based on which the average symbol error rate is evaluated for an $N $-branch
maximal-ratio combining (MRC) receiver. The retrieved results show that the
proposed approximate results match accurately with the exact simulated ones.
Additionally, the results show that the achievable diversity order increases as
a function of the number of MRC diversity branches.
