Indoor static localization based on Fresnel zones model using COTS Wi-Fi

Abstract

Compared with outdoor localization using Global Positioning System (GPS), indoor localization is more complex and difficult due to the shadowing, fading and reflecting of radio. Thus, pioneers struggled for accurate device-free indoor localization and many creative schemes were proposed. However, these schemes still have defects and deficiencies. Mode-based schemes usually extract features of radio signal as fingerprints to match the target positions and signal modes. The training of features is time-consuming and labor-intensive because the fingerprints need to update every time when indoor environment changes. Model-based schemes universally establish empirical model to locate target, but the models are mostly un-robust in multiple experimental scenes. In this paper, we attempt to localize target in indoor environment based on Fresnel zones model of radio communication that could determine which elliptic region the target located in according to the phase of Channel State Information (CSI) obtained from Commercial Off-The-Shelf (COTS) Wi-Fi device. In addition, we focus on the interference on radio signal in indoor environment and propose specific solutions to remove phase offset and measurement error caused by insufficient hardware or background fluctuation. Therefore, our proposed system is more accurate compared with existing works. Results show the average error of our scheme is 33.6 cm in 47.6 m2 meeting room and 31.2 cm in 40.7 m2 office room while state-of-the-art work (MFDL) is 75 cm in 72 m2.