A method for controlling an input signal of a power amplifier is provided. The method comprise applying CFR to the input signal to obtain a processed input signal; determining a minimum CFR threshold; comparing the peak power of the power amplifier and an allowable peak power; and if the peak power is below the allowable peak power, determining a final CFR threshold by increasing the minimum CFR threshold, or if the peak power is not below the allowable peak power, reducing the average output power until peak power reaches the allowable peak power.