a significant problem in multicarrier communication systems is the necessity to reduce the value of papr (peak-to-average power ratio) of transmitting signal. in this thesis we study the effect of the system parameters such as coding and modulation types on papr and ultimate ber in a mc-cdma system. in this study we consider fading channel as well as the nonlinearity of transmitter’s amplifier to show how the control of the papr in different approaches can actually affect on the overall quality of the received signal. we study some different papr reduction techniques and propose a new method of papr reduction in mc_cdma system which is based on phase perturbation after spreading process. this method follows the fact that the papr of the mc-cdma signal is highly dependent on the related phase of the subcarriers.