On the distribution of the peak-to-average power ratio in OFDM signals

The distribution of the peak-to-average power ratio (PAPR) in strictly band-limited orthogonal frequency-division multiplexing (OFDM) signals is studied. Assuming that the base-band OFDM signal is characterized as a band-limited complex Gaussian process, we first attempt to derive the exact distribution of the PAPR in the band-limited OFDM signals. Since this distribution cannot be expressed in a closed form, we further develop a simple closed-form approximation, based on the level-crossing rate analysis. Comparisons of the proposed distributions with those obtained by computer simulations show good agreement and convergence with an increase in the number of subcarriers.

I. Introduction

Due to its robustness against multipath fading with certain implementation advantages over single-carrier systems, coded orthogonal frequency-division multiplexing (OFDM) has become a popular technique in various high-speed wireless data transmission systems [1], [2]. One of the major drawbacks of OFDM signals (or more generally, multicarrier signals) is its waveform with a very high peak-to-average power ratio (PAPR). OFDM signals therefore cause serious problems such as a severe power penalty at the transmitter, which is prohibitive for use in portable wireless systems where the terminals are powered by battery [3]. Recently, a number of PAPR reduction schemes have been proposed to alleviate this undesirable property of OFDM signals (see, e.g., [4]–[6]).