The performance of the mixed radio frequency/free-space optical (RF/FSO) systems is presented based on decoding and forward relaying. A mixed RF/laser communication system model is constructed with subcarrier multilevel phase shift keying modulation. The exponentiated Weibull atmospheric turbulence channel with pointing error effect is adopted for FSO communication link and the RF link undergoes the Nakagami-m fading channel. We derive the analytical expressions for cumulative distribution function of equivalent signal-to-noise ratio. The novel mathematical presentations of outage probability and average bit-error-rate are developed based on the Meijer′s G function. The outage probability and the bit-error-rate are compared for different turbulence intensities and receiving apertures. The simulation results show that the pointing error has less effect on the outage in moderate atmospheric turbulence than in weak turbulence, the aperture averaging effect improves performance of the mixed RF/FSO communication system effectively, and the FSO channel is dominant in the mixed system.