Spectrally Precoded OTFS Modulation.

Rectangularly-pulsed orthogonal time frequency space (OTFS) can be efficiently signaled by a frame of orthogonal frequency-division multiplexing (OFDM) block signals and outperforms OFDM in error performance over doubly selective channels. However, due to the discontinuity in rectangular pulse, the rectangularly-pulsed OTFS suffers large power spectral sidelobes decaying as f(-2), with f being the frequency in Hertz. In this paper, spectral precoding is integrated with rectangularly-pulsed OTFS to make the compact spectrum rendering small sidelobes decaying as f(-2I-2) or faster. The characteristics of peak-to-average power ratio, achievable data rate, spectral efficiency, and error performance are also investigated for the spectrally-precoded OTFS.