Peak-to-average power reduction by rotation of the time-frequency representation

Multi-carrier communication is associated with a high peak-to-average power ratio (PAPR). A new PAPR reduction method is proposed which is based on rotating the time-frequency representation of a transmit signal, prior to transmission. In general, a time-frequency rotation of a multi-carrier signal would change the signal basis, affecting the robustness of the transmit signal in fading channels. Exceptions are transmit signals constructed by (modulated) Hermite functions. The PAPR has been analyzed for transmit signals based on 64 Hermite functions. Allowing a rotation over 16 angles in time-frequency, the PAPR, which occurs with a probability of 10^-3, is reduced by 3.8 dB at the cost of an increased computational complexity and a minor loss in spectral efficiency.