On the Doppler Squint Effect in OTFS Systems over Doubly-Dispersive Channels: Modeling and Evaluation

TL;DR

This paper investigates the Doppler Squint Effect in wideband OTFS systems, modeling its impact on channel estimation and demonstrating that accounting for DSE significantly improves performance in high-mobility scenarios.

Contribution

It introduces a novel characterization of DSE in OTFS channels and proposes an OMP-based estimation scheme that considers DSE, outperforming traditional methods.

Findings

DSE significantly affects OTFS channel estimation accuracy.

The proposed scheme effectively mitigates DSE impact.

Simulation shows improved performance over existing methods.

Abstract

Extensive work has demonstrated the excellent performance of orthogonal time frequency space (OTFS) modulation in high-mobility scenarios. Time-variant wideband channel estimation serves as one of the key compositions of OTFS receivers since the data detection requires accurate channel state information (CSI). In practical wideband OTFS systems, the Doppler shift brought by the high mobility is frequency-dependent, which is referred to as the Doppler Squint Effect (DSE). Unfortunately, DSE was ignored in overall prior estimation schemes employed in OTFS systems, which leads to severe performance loss in channel estimation and the consequent data detection. In this paper, we investigate DSE of wideband time-variant channel in delay-Doppler domain and concentrate on the characterization of OTFS channel coefficients considering DSE. The formulation and evaluation of OTFS input-output relationship are provided for both ideal and rectangular waveforms considering DSE. The channel estimation is therefore formulated as a sparse signal recovery problem and an orthogonal matching pursuit (OMP)-based scheme is adopted to solve it. Simulation results confirm the significance of DSE and the performance superiority compared with traditional channel estimation approaches ignoring DSE.