Joint Reduction of Peak-to-Average Power Ratio and Out-of-Band Power in OFDM Systems

Abstract

The high peak-to-average power ratio is a major drawback of OFDM systems. Many PAPR reduction techniques have been proposed in the literature, among them a method that uses a subset of tones that do not carry any data, but are modulated such that the PAPR of the resulting time domain signal is minimized. Another problem of OFDM systems is the high out-of-band power caused by the sidelobes of the modulated tones. The OBP can be reduced by modulating reserved tones at the edges of the occupied spectrum so that the sidelobes of the data carriers are reduced. In this paper, we propose to consider both optimization problems jointly. This way, the amount of PAPR and OBP reduction can be significantly enhanced in comparison to a system that performs two separate optimization steps. Furthermore, the joint reduction algorithm offers more flexibility, because the relative weighting of the two optimization criteria can easily be changed, resulting in a smooth trade-off curve.