Beam Squint Assisted User Localization in Near-Field Integrated Sensing and Communications Systems

TL;DR

This paper leverages beam squint phenomena in near-field MIMO systems, controlled by true-time-delay lines, to enable high-accuracy user localization with reduced beam sweeping overhead in integrated sensing and communication systems.

Contribution

It introduces a method to control beam squint trajectories using TTDs and utilizes this effect for efficient user localization in near-field ISAC systems.

Findings

Effective control of beam squint trajectories using TTDs.

Achieved high-accuracy user localization with reduced beam sweeping.

Simulation confirms the proposed method's effectiveness.

Abstract

Integrated sensing and communication (ISAC) has been regarded as a key technology for 6G wireless communications, in which large-scale multiple input and multiple output (MIMO) array with higher and wider frequency bands will be adopted. However, recent studies show that the beam squint phenomenon can not be ignored in wideband MIMO system, which generally deteriorates the communications performance. In this paper, we find that with the aid of true-time-delay lines (TTDs), the range and trajectory of the beam squint in near-field communications systems can be freely controlled, and hence it is possible to reversely utilize the beam squint for user localization. We derive the trajectory equation for near-field beam squint points and design a way to control such trajectory. With the proposed design, beamforming from different subcarriers would purposely point to different angles and different distances, such that users from different positions would receive the maximum power at different subcarriers. Hence, one can simply localize multiple users from the beam squint effect in frequency domain, and thus reduce the beam sweeping overhead as compared to the conventional time domain beam search based approach. Furthermore, we utilize the phase difference of the maximum power subcarriers received by the user at different frequencies in several times beam sweeping to obtain a more accurate distance estimation result, ultimately realizing high accuracy and low beam sweeping overhead user localization. Simulation results demonstrate the effectiveness of the proposed schemes.