A Preprocessing Method for PAPR Reduction in OFDM Systems by Modifying FFT and IFFT Matrices

In this paper we propose an algorithm for PAPR reduction in OFDM systems, based on a modification in the IFFT matrix at the transmitter and using the inverse matrix at the receiver. In this method two columns of the IFFT matrix are replaced with a linear combination of them in order to reduce the PAPR. These columns correspond to the maximum and minimum in the sequence of absolute values for each OFDM symbol. It will be shown that we may choose more than one pair in order to reduce the PAPR more effectively. The proposed method entails less complexity at the transmitter in comparison with other PAPR reduction algorithms. It also requires less increase in SNR for the same BER compared to other methods. A trade-off between complexity and system performance can set the number of pairs of maximum and minimum processed. The only drawback of this method is that the modified IFFT matrix is not the same for all OFDM symbols; therefore some extra information about the modified matrix must be sent.