Near-Field Localization Based On Beam Squint of mmWave Communications

Integrated sensing and communication (ISAC) has been regarded as a key technology of 6G wireless communications, in which large-scale multiple input and multiple output (MIMO) with higher and wider frequency bands will be adopted. However, recent studies show that the beam squint phenomenon can not be ignored in the wideband MIMO system, which generally deteriorates the communications performance. In this paper, we find that with the aid of the true-time-delay lines (TTDs), the range and trajectory of the beam squint in the 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 timing overhead as compared to the conventional beam sweeping approach. Simulation results demonstrate the effectiveness of the proposed scheme.