I. Introduction
Orthogonal Frequency Division Multiplexing (OFDM) is a unique multi-carrier modulation technique. In recent years, it has been used extensively in communication systems and radar systems. Due to its high spectrum efficiency and channel robust, it is becoming more and more popular in commercial and academic research. But OFDM signals still remain some limitations, one of the main drawbacks is high Peak-to-Average Power Ratio (PAPR) of time-domain signals. OFDM signals are composed of many individual sub-carriers, when the phases of output sub-carriers are identical, the peak power of the transmitted signal will be higher than the average power. High PAPR raises a higher requirement to linearity of transmit power amplifier, but many amplifiers are nonlinear and have the finite dynamic range, when the OFDM signal transmitted by a nonlinear power amplifier, it may suffers from spectral spreading and in-band distortion. While, the increase of dynamic range in a transmit power amplifier will lead to lower efficiency and higher costs. So we must try to reduce the PAPR in OFDM system.