On the Characterization and Evaluation of Doppler Squint in Wideband ODDM Systems

TL;DR

This paper analyzes the Doppler squint effect in wideband ODDM systems, revealing its impact on system performance and providing theoretical characterization to improve signal processing techniques.

Contribution

It introduces a detailed analysis of Doppler squint effect in wideband ODDM systems, including explicit characterization of extra delay-Doppler dispersion.

Findings

Doppler squint causes significant delay-Doppler dispersion.

Extra DD spread and power leakage are theoretically characterized.

Numerical results confirm the importance of considering DSE.

Abstract

The recently proposed orthogonal delay-Doppler division multiplexing (ODDM) modulation has been demonstrated to enjoy excellent reliability over doubly-dispersive channels. However, most of the prior analysis tends to ignore the interactive dispersion caused by the wideband property of ODDM signal, which possibly leads to performance degradation. To solve this problem, we investigate the input-output relation of ODDM systems considering the wideband effect, which is also known as the Doppler squint effect (DSE) in the literature. The extra delay-Doppler (DD) dispersion caused by the DSE is first explicitly explained by employing the time-variant frequency response of multipath channels. Its characterization is then derived for both reduced cyclic prefix (RCP) and zero padded (ZP)-based wideband ODDM systems, where the extra DD spread and more complicated power leakage outside the peak region are presented theoretically. Numerical results are finally provided to confirm the significance of DSE. The derivations in this paper are beneficial for developing accurate signal processing techniques in ODDM-based integrated sensing and communication systems.