Enhanced ToA Estimates with Positioning Reference Signal in Delay-Doppler Domain

Precise positioning plays a critical role in beyond-fifth-generation ($\mathbf{B 5 G}$) wireless networks for a wide range of indoor and outdoor applications. Conventionally, positioning accuracy can be dramatically degraded in a high Doppler environment and it may also require complex signal processing technique to accurately estimate the positioning in harsh multipath channels. Thus, this paper studies a positioning reference signal with orthogonal time-frequency space (PRS-OTFS) to enhance multi-user positioning accuracy. Firstly, multi-user PRS are designed in delay-Doppler (DD) domain and then a simple DD-domain based algorithm is proposed to estimate time-of-arrivals (ToAs) which is mainly based on an efficient energy detection in DD domain. Performance superiority of the proposed DD-domain scheme compared to conventional time-frequency based estimators is also discussed. Finally, robustness of the ToA estimation algorithm is discussed through numerical results for various channel conditions and arbitrary non-integer normalized delay-and Doppler-spread.