Abstract: A cooperative communication scheme with equal gain combining (EGC) is presented to deal with the severe double fading channels in mobile-to-mobile (MTM) systems. Performance analysis of this scheme is addressed for the dual-hop decode-and-forward (DF) protocol. Double Nakagami-m fading is assumed for the considered MTM channels. The approximate expression of the moment-generating function (MGF) of the output signal-to-noise ratio is firstly provided by using the Padé approximation. Furthermore, the closed-form expression of the approximate symbol error rate is derived for M-phase-shift keying modulation. Simulation results show that the theoretical results match the corresponding simulation curves under various channel parameters. Compared with optimum maximum ratio combining, the performance degradation caused by EGC is about 1 dB.