A UWB-based localization system: analysis of the effect of anchor positions and robustness enhancement in indoor environments

Localization in indoor environments is a hard task because of several constraints, both in terms of multiple reflections due to wall and people moving around the localization domain. This is especially due to the communication technologies adopted to perform both ranging and positioning. In this paper, a Ultra Wide Band technology is adopted to perform localization in indoor environment, considering a square domain, by means of three fixed anchors and one mobile node. In specific applications, the object to localize is covered by a metallic shield, e.g. robots, and the localization sensor must be embedded inside the object. In this scenario, the paper proposes to solve three issues: assess nominal performance of UWB localization technology, find a way to approach it in harsh conditions, as the one above specified and a further investigation on optimal anchors' positions in the localization domain to verify sensitivity to specific set-up arrangement. First task is accomplished through an extensive measurement campaign without any obstacle; second one is solved by means of a double calibration procedure estimating anchor-to-anchor distance and online correcting the acquired data. A simulated approach that, starting from on-field measurements, verifies the role of different anchors' positions on the positioning error, completes the investigation.