Static cyclic prefix alignment for OFDM-based waveforms

Abstract

The cyclic prefix (CP) alignment is an appealing technique for achieving multiple goals such as peak-to-average power ratio (PAPR) reduction, out-of-band (OOB) leakage suppression, and physical layer (PHY) security. It generates a perturbation signal which is aligned with the CP duration of orthogonal frequency division multiplexing (OFDM) symbols after it passes through the channel. The original method requires exact channel state information (CSI) at the transmitter to maintain perfect alignment. However, in practice, CSI may be erroneous due to the imperfect channel estimation and aged by the time that it is available at transmitter due to mobility. Thus, the alignment signal may not be exactly aligned with CP duration with the original method and interfere the data symbols. In this study, in order to address this challenge, we propose a method, called static CP alignment, which achieves the alignment regardless of the CSI by partially using the CP duration for the alignment purpose. Unlike the original CP alignment approach, the proposed technique eliminates the need of strong frequency selective multipath channel and achieves enhancements in waveform characteristics under any medium conditions.