Apparatus and method for reducing peak-to-average power ratio in orthogonal frequency division multiplexing communication system

An apparatus for reducing a PAPR (Peak-to-Average Power Ratio) of a transmit signal in a broadband wireless communication system, the apparatus comprising:

• a tone assignment unit for assigning information signals to remaining tones except L reserved tones that are previously appointed among N tones;
• an IFFT (Inverse Fast Fourier Transform) unit for performing an IFFT operation on the L reserved tones to which the information signals are not assigned and the (N-L) tones to which the information signals are assigned, and outputting the IFFT-ed signal to a multi-gradient algorithm unit;
• and
• the multi-gradient algorithm unit for detecting multiple peaks that are greater than a predefined reference value from an input signal generating a plurality of signals to remove the detected multiple peaks using a P-waveform having an impulse characteristic, accumulating the plurality of generated signals, and removing the peaks by adding the accumulated signal to the input signal at every iteration of detecting through removing the detected multiple peaks;
• a PAPR calculator for calculating PAPR of the signals output from the multi-gradient algorithm unit;
• and
• a controller for comparing the calculated PAPR with a predefined target PAPR,
• wherein if the calculated PAPR is less than the target PAPR, the controller outputs an output signal of the multi-gradient algorithm unit as a transmit signal, and
• wherein if the calculated PAPR is greater than the target PAPR, the controller feeds back the output signal of the multi-gradient algorithm unit to an input of the multi-gradient algorithm unit for a next iteration of detecting through removing the detected multiple peaks.