Analysis of maximal-ratio and equal-gain diversity systems for M-ary QAM on generalized fading channels

New, simple yet very accurate closed-form expressions for calculating the symbol error probability (SER) of multilevel quadrature amplitude modulation (MQAM) in conjunction with L-fold antenna diversity on a Nakagami (1960) fading channel are presented. Both maximal-ratio (MRC) and equal-gain (EGC) predetection diversity combining techniques have been considered. The exact closed-form formula for a MRC diversity system removes the limitations of previous studies in the literature which have been limited to Rayleigh fading. Moreover, an exact analysis of EGC for MQAM has not been reported previously despite its practical interest. The exact SER is expressed as a finite-range integral. Our unified expressions are sufficiently general to handle arbitrary fading parameters as well as dissimilar mean signal strengths across the diversity branches. The generality and computational efficiency of these new formulas render themselves as a powerful tool for SER analysis in different fading conditions