Circularly Pulse Shaped Orthogonal Time Frequency Space Modulation

Abstract

Orthogonal time-frequency space (OTFS) modulation is a recently proposed waveform for efficient data transfer in high-speed vehicular scenarios. The use of rectangular pulse shape in OTFS results in high out of band (OoB) radiation, which is undesirable for multi-user scenarios. In this work, we present a circular pulse shaping framework for OTFS for reducing the OoB. We also design a low complexity transmitter for such a system. We argue in favor of orthogonal transmission for low complexity transceiver structure. We establish that frequency-localized circulant Dirichlet pulse is one of the possible pulses having this desirable unitary property, which can reduce OoB radiation significantly (by around 50 dB) without any loss in BER. We also show that our proposed pulse shaped OTFS has a lower peak to average power ratio than the conventional OTFS system.