Peak Power Reduction of OFDM Signals Using Trigonometric Transforms

This paper presents a new technique, based on trigonometric transforms, to solve the peak to average power ratio (PAPR) problem associated with orthogonal frequency division multiplexing (OFDM) signals. In the proposed technique, both the in-phase and in-quadrature components of the OFDM signals after the inverse fast Fourier transform (IFFT) are transformed using either the discrete sine transform (DST) or the discrete cosine transform (DCT). It is known that both the DCT and the DST have an energy compaction property concentrating most of the signal energy in the first few samples after the application of the transform and leaving the rest of samples close to zero. This property can be exploited for PAPR reduction by interchanging the first half of samples of the in-phase component by the last half of samples of the in-quadrature component after applying the discrete transform on both of them, separately. The OFDM signal is transmitted in this format. By this process of replacement, it can be guaranteed that if either the in-phase or the in-quadrature component of the OFDM signal is large, the other will be small.