Constant envelope OFDM phase modulation: spectral containment, signal space properties and performance

Abstract

A class of constant envelope OFDM phase modulated (OFDM-PM) signals is studied. The motivation behind OFDM-PM is to alleviate the high peak-to-average power ratio of conventional OFDM systems. Power density spectrum plots and fractional out-of-band power curves are given. For small modulation indices, the OFDM-PM signals are shown to be more spectrally contained than conventional OFDM. The signal space is studied by considering the correlation properties of the OFDM-PM signals. A performance bound on the optimum OFDM-PM receiver is compared to simulation results. Also, a sub-optimum phase demodulator receiver is analyzed and an AWGN performance approximation is compared to simulation results. It is shown that for a small modulation index and high signal-to-noise ratio, the sub-optimum receiver performs close to the optimum receiver.