A Modified NLLS Algorithm for UWB Positioning Systems with Experimental Validation

This study presents a concise background of indoor positioning technologies and is mainly focused on the functionality of UWB (Ultra-Wide Band) navigation devices and Non-Linear Least-Squares (NLLS) algorithm in position estimation applications for minimizing measurement error and effects of uncertainties. This research presents a modified NLLS equation, which is specifically formulated for indoor 3D position estimation of a Real-Time Locating System (RTLS). To confirm its validity, an experiment was conducted with a Decawave® DWM1001 kit. The position estimation obtained from NLLS is compared in detail with the built-in estimation of the kit on MATLAB® platform. For further justification and highlighting the pivotal points on the functionality of the proposed NLLS algorithm, the dataset is replaced with precise range measurements, which are verified mathematically. Subsequently, a random noise is added on top of the true values, and the XYZ position of the tag is estimated once more. The results support the effectiveness of the NLLS algorithm, and the findings of this paper can enhance the functionality and estimation performance of NLLS based RTLS units.