Analysis and Accuracy Improvement of UWB-TDoA-Based Indoor Positioning System

Abstract

Positioning systems are used in a wide range of applications which require determining the position of an object in space, such as locating and tracking assets, people and goods; assisting navigation systems; and mapping. Indoor Positioning Systems (IPSs) are used where satellite and other outdoor positioning technologies lack precision or fail. Ultra-WideBand (UWB) technology is especially suitable for an IPS, as it operates under high data transfer rates over short distances and at low power densities, although signals tend to be disrupted by various objects. This paper presents a comprehensive study of the precision, failure, and accuracy of 2D IPSs based on UWB technology and a pseudo-range multilateration algorithm using Time Difference of Arrival (TDoA) signals. As a case study, the positioning of a 4×4m2 area, four anchors (transceivers), and one tag (receiver) are considered using bitcraze’s Loco Positioning System. A Cramér–Rao Lower Bound analysis identifies the convex hull of the anchors as the region with highest precision, taking into account the anisotropic radiation pattern of the anchors’ antennas as opposed to ideal signal distributions, while bifurcation envelopes containing the anchors are defined to bound the regions in which the IPS is predicted to fail. This allows the formulation of a so-called flyable area, defined as the intersection between the convex hull and the region outside the bifurcation envelopes. Finally, the static bias is measured after applying a built-in Extended Kalman Filter (EKF) and mapped using a Radial Basis Function Network (RBFN). A debiasing filter is then developed to improve the accuracy. Findings and developments are experimentally validated, with the IPS observed to fail near the anchors, precision around ±3cm, and accuracy improved by about 15cm for static and 5cm for dynamic measurements, on average.

Ultra-Wideband-Based Time Occupancy Analysis for Safety Studies

“…In the second trial, the distance error measurement was 0.97 m for the y coordinate and 0.51 m for the x coordinate. Several factors could have contributed to the distance error observed in the second trial, including the orientation of the anchor's antennas, as suggested by Grasso et al [22]. Their study found that positioning accuracy could be improved by directing the anchor's antennas toward the center of the area being covered, resulting in distance errors of 5 cm for dynamic measurements and 15 cm for static measurements.…”

An Ultra-Wideband Indoor Localization Algorithm with Improved Cubature Kalman Filtering Based on Sigmoid Function

“…In this way, three or more localization base stations are required to determine the location of the target to be measured [16]. ,1 i d represents the difference in distance from the target M to the primary base station, and each of the secondary base stations is defined as follows (2):…”

System and Method for Reducing NLOS Errors in UWB Indoor Positioning

“…Indoor Positioning Systems (IPSs) are crucial in diverse fields, from emergency services to industrial automation [1]. The most used satellite technologies, like the Global Navigation Satellite System (GNSS) [2], are ineffective indoors due to signal attenuation caused by building materials and environmental factors [3]. Ultra-wideband (UWB) technology has been increasingly recognized as an efficacious strategy for IPSs due to its high accuracy, low transmission cost, and robustness to environmental perturbations [4].…”