Orthogonal Time Frequency Space with Delay-Doppler Alignment Modulation

TL;DR

This paper introduces DDAM-OTFS, a novel waveform design combining delay-Doppler alignment modulation with OTFS to improve spectral efficiency and reduce complexity in high-mobility, high-frequency channels.

Contribution

It proposes a new DDAM-OTFS technique with two implementation schemes, enhancing OTFS performance by channel reshaping and alignment in mmWave and THz communications.

Findings

Superior spectral efficiency compared to conventional OTFS

Reduced peak-to-average power ratio (PAPR)

Effective delay-Doppler spread mitigation

Abstract

Delay-Doppler alignment modulation (DDAM) is a novel technique to mitigate time-frequency doubly selective channels by leveraging the high spatial resolution offered by large antenna arrays and multi-path sparsity of millimeter wave (mmWave) and TeraHertz (THz) channels. By introducing per-path delay and Doppler compensations, followed by path-based beamforming, it is possible to reshape the channel features with significantly reduced channel delay and Doppler spreads. This offers new degrees-of-freedom for waveform designs such as orthogonal time frequency space (OTFS), since the reshaped channel can significantly relax the constraints on OTFS parameter selection and reduce the complexity of signal detection at the receiver. Therefore, in this paper, by combing DDAM with OTFS, we propose a novel technique termed DDAM-OTFS. Two implementation schemes are introduced for DDAM-OTFS, namely path-based alignment and bin-based alignment. Simulation results are provided to demonstrate the superior performance of the proposed DDAM-OTFS in terms of spectral efficiency (SE) and peak-to-average power ratio (PAPR) compared to the conventional OTFS.