In this study, approximate symbol probability of
error (i.e., symbol error rate) formulas are derived for both of
the M-ary phase shift keying and M-ary quadrature amplitude
modulation constellations schemes. These formulas are
obtained over slow, flat, and independent and identically
distributed Nakagami-m fading channels, where the orthogonal
space-time block codes is utilized. This approach reduces the
complexity and instability of using integrals or hyper-geometric
infinite series forms to evaluate exact symbol error rate formulas.
Numerical examples are presented to illustrate the new results.