Multiuser OTFS Channel Parameter Estimation Toward Grid-Independent Regime

TL;DR

This paper introduces grid-independent parameter estimation techniques for multiuser OTFS channels, improving accuracy and efficiency in delay-Doppler domain estimation with a focus on robustness and computational tradeoffs.

Contribution

It develops a matrix pencil-based method for fully grid-independent delay-Doppler estimation and extends weighted MUSIC to multiuser OTFS with reduced grid dependency.

Findings

MP method achieves fully grid-independent estimation.

W-MUSIC performs better at low SNR.

MP offers higher accuracy at moderate-to-high SNR with lower complexity.

Abstract

We study channel parameter estimation for multiuser orthogonal time frequency space (OTFS) systems in the delay-Doppler (DD) domain. To enable structured parametric estimation, we adopt a multi-user pilot cyclic prefix (MU-PCP) design, which multiplexes users along the Doppler dimension while preserving a separable exponential structure. This structure facilitates high-resolution estimation of fractional delay and Doppler parameters in the multiuser setting. Building on this framework, we extend weighted MUSIC (W-MUSIC) to multiuser OTFS, providing a computationally efficient approach with mild grid dependency, and develop a matrix pencil (MP)-based method that achieves fully grid-independent delay-Doppler parameter estimation. Numerical results demonstrate the effectiveness of the proposed methods and reveal a robustness-complexity tradeoff: W-MUSIC performs better at low SNR, while MP achieves higher estimation accuracy at moderate-to-high SNR with significantly lower computational complexity.