Abstract: A cyclostationary signature is artificially created in a multi-carrier signal. In one embodiment, a multi-carrier Orthogonal Frequency Division Multiplexing (OFDM) signal is used. The approach involves mapping a set of one or more of the sub-carriers onto a second set such that any data symbols transmitted on the first set is are simultaneously transmitted on the second set. In this way, those spectral components of the signal will be identical and a spectral correlation pattern will have been created. This spectral correlation pattern comprises the cyclostationary signature. An artificial cyclostationary signature embedded in this way is continuously present in the transmitted data-carrying signal and so can be considered a type of signal watermark. By detecting and examining this watermark, a communications receiver can determine key properties of the signal and use those properties to achieve a number of critical tasks.