Low Complexity Modem Structure for OFDM-based Orthogonal Time Frequency Space Modulation

TL;DR

This paper introduces a simplified, low-complexity OFDM-based OTFS system that avoids transmitter windowing, providing a more practical implementation with reduced computational requirements for handling time-varying wireless channels.

Contribution

The paper presents a discrete-time formulation of OFDM-based OTFS and derives simplified modulator and demodulator structures that are easier to implement than existing methods.

Findings

Avoids transmitter windowing in OTFS for realistic scenarios

Provides deeper insights into channel impact on OTFS

Develops simpler modulator and demodulator structures

Abstract

Orthogonal time frequency space (OTFS) modulation is a two-dimensional signaling technique that has recently emerged in the literature to tackle the time-varying (TV) wireless channels. OTFS deploys the Doppler-delay plane to multiplex the transmit data where the time variations of the TV channel are integrated over time and hence the equivalent channel relating the input and output of the system boils down to a time-invariant one. This signaling technique can be implemented on the top of a given multicarrier waveform with the addition of precoding and post-processing units to the modulator and demodulator. In this paper, we present discrete-time formulation of an OFDM-based OTFS system. We argue against deployment of window functions at the OTFS transmitter in realistic scenarios and thus limit any sort of windowing to the receiver side. We study the channel impact in discrete-time providing deeper insights into OTFS systems. Moreover, our derivations lead to simplified modulator and demodulator structures that are far simpler than those in the literature.