Novel Nonlinear Companding Transform for Reduced Peak-to-Average Power Ratio in OFDM

Orthogonal Frequency Division Multiplexing (OFDM) is an excellent solution to overcome multipath effects and inter-symbol interference in high-speed mobile communication systems. However, OFDM inherently has a high Peak-to-Average Power Ratio (PAPR) that adversely affects the system. In this study, we propose a nonlinear companding transform scheme function, in order to reduce the high PAPR in OFDM signals. With the proposed scheme, the average power of the OFDM signal can be maintained nearly unchanged over the companding process by properly chosen values of the parameters of the companding function. One salient feature of the proposed scheme over error function based companding schemes is that the signal compression and expansion levels of the companding function can be adjusted independently, and thus it is easier to maintain the average power. With the aid of simulations, we prove that the proposed scheme has an outstanding PAPR reduction capability and it works well with nonlinear transmitter amplifiers as well. Moreover, we show that the BER performance of the proposed companding transform is superior to the one obtained from the error function companding.