OTFS: A New Generation of Modulation Addressing the Challenges of 5G

TL;DR

OTFS is a novel 2D modulation scheme that leverages delay-Doppler representation to improve 5G communication by capturing channel physics, enhancing spectral efficiency, and enabling robust MIMO performance in challenging environments.

Contribution

This paper introduces OTFS, a new modulation technique that generalizes traditional methods and links radar and communication, offering improved robustness and efficiency for 5G networks.

Findings

OTFS approaches channel capacity with optimal tradeoff.

It provides high-resolution delay-Doppler channel imaging.

OTFS enables full MIMO gains in challenging 5G scenarios.

Abstract

In this paper, we introduce a new 2D modulation scheme referred to as OTFS (Orthogonal Time Frequency & Space) that multiplexes information QAM symbols over new class of carrier waveforms that correspond to localized pulses in a signal representation called the delay-Doppler representation. OTFS constitutes a far reaching generalization of conventional time and frequency modulations such as TDM and FDM and, from a broader perspective, it establishes a conceptual link between Radar and communication. The OTFS waveforms couple with the wireless channel in a way that directly captures the underlying physics, yielding a high-resolution delay-Doppler Radar image of the constituent reflectors. As a result, the time-frequency selective channel is converted into an invariant, separable and orthogonal interaction, where all received QAM symbols experience the same localized impairment and all the delay-Doppler diversity branches are coherently combined. The high resolution delay-Doppler separation of the reflectors enables OTFS to approach channel capacity with optimal performance-complexity tradeoff through linear scaling of spectral efficiency with the MIMO order and robustness to Doppler and multipath channel conditions. OTFS is an enabler for realizing the full promise of MUMIMO gains even in challenging 5G deployment settings where adaptation is unrealistic.