A method of processing an Orthogonal Frequency-Division Multiplex (OFDM) signal having a plurality of data carriers and a plurality of unused carriers is disclosed. The method comprises transforming an original frequency-domain OFDM signal into a time domain signal and simulating the effect of a non-linear amplifier on the time-domain signal to provide a potentially distorted time domain signal. The potentially distorted time domain signal is transformed into a potentially distorted frequency domain signal and at least some of any values of the data carriers in the potentially distorted frequency domain signal are restored with corresponding values from the original frequency domain signal. At least some of the unused carriers in the at least partially restored frequency domain signal are scaled with a scaling factor. The scaled frequency domain signal is transformed into a temporary time domain signal and the temporary time domain signal is analysed for the presence of a peak or near zero amplitude value that would lead to distortion by said amplifier. If the signal includes such a peak or near zero value, the scaling, transforming and analysing are repeated with an increased scaling factor.