Multicarrier modulations are widely used in mobile radio applications due to their adaptability to the time-frequency characteristics of the channel, thus enabling low-complexity equalization. However, their intrinsically high peak-to-average power ratio (PAPR) is a major drawback with regard to implementation issues (e.g., power amplification efficiency, regulatory constraints...). In this paper, we confirm that the PAPR can be decreased as the signaling density (i.e., spectral efficiency at fixed constellation size) increases, even in the case where symbols cannot be perfectly reconstructed using a linear system. In such a two-dimensional generalization of faster-than-Nyquist (FTN) systems, PAPR distribution models from the literature are confirmed by simulation results. Furthermore, for a fixed number of subcarriers, we show that a sufficient condition to yield the optimal PAPR distribution at the output of a critically sampled transmitter is to specify pulse shapes as tight frames. Finally, simulation are performed in the more realistic case of an oversampled transmitted signal.
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