Joint Localization and Environment Sensing by Harnessing NLOS Components in RIS-Aided mmWave Communication Systems

Abstract

This study explores the use of non-line-of-sight (NLOS) components in\nmillimeter-wave (mmWave) communication systems for joint localization and\nenvironment sensing. The radar cross section (RCS) of a reconfigurable\nintelligent surface (RIS) is calculated to develop a general path gain model\nfor RISs and traditional scatterers. The results show that RISs have a greater\npotential to assist in localization due to their ability to maintain high RCSs\nand create strong NLOS links. A one-stage linear weighted least squares\nestimator is proposed to simultaneously determine user equipment (UE)\nlocations, velocities, and scatterer (or RIS) locations using line-of-sight\n(LOS) and NLOS paths. The estimator supports environment sensing and UE\nlocalization even using only NLOS paths. A second-stage estimator is also\nintroduced to improve environment sensing accuracy by considering the nonlinear\nrelationship between UE and scatterer locations. Simulation results demonstrate\nthe effectiveness of the proposed estimators in rich scattering environments\nand the benefits of using NLOS paths for improving UE location accuracy and\nassisting in environment sensing. The effects of RIS number, size, and\ndeployment on localization performance are also analyzed.\n