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Orthogonal time frequency space (OTFS) modulation has been put forward to achieve better performances over delay-Doppler channels in comparison with orthogonal frequency division multiplexing (OFDM) systems. In this letter, a nonlinear corrective active constellation expansion (NC-ACE) method is firstly proposed in OTFS waveform to achieve precise control of peak-to-average power ratio (PAPR) and BER performances due to its nonlinear compression characteristics. Compared to linear constraint of clipping and filtering process in traditional active constellation expansion (ACE) and bounded distortion ACE (BD-ACE) strategies, nonlinear compressed clipping noise is considered with a flexible curvature control coefficient. According to flexible features of NC-ACE, a bridge between optimal suppression and no reduction of PAPR performances is established in OTFS systems, where tradeoff between PAPR and BER performances can be further obtained. [ABSTRACT FROM AUTHOR]

Orthogonal time frequency space (OTFS) modulation has been proposed to achieve outstanding performances over delay-Doppler channels in comparison with orthogonal frequency division multiplexing (OFDM) systems. Particularly, transmitter and receiver structures of OTFS are same as those of asymmetric OFDM (A-OFDM) waveforms, and OTFS is simplified as A-OFDM over static multipath channels. In this letter, we propose an integrated waveform framework based on weighted-type fractional Fourier transform (WFRFT) with two-dimensional adjustable parameters and strong scalability, called as WFRFT-OTFS, which can be reduced to OTFS, A-OFDM, hybrid carrier (HC), OFDM and other waveforms. Basically, theoretical BER expressions of integrated WFRFT-OTFS framework over multipath channels with zero forcing (ZF) and minimum mean square error (MMSE) receivers are derived through fusing different waveform components and verified by simulation results. [ABSTRACT FROM AUTHOR]