3-D Localization of Wi-Fi APs and BLE Beacons With Interfloor Path Loss in Multifloor Buildings

In modern urban environments with increasing numbers of high-rise buildings, accurate 3-D positioning is essential. Fingerprint-based positioning systems are widely used in such environments but require labor-intensive presurvey efforts to construct floor-by-floor radio maps. In contrast, range-based methods demand less manual effort, requiring only anchor node (AN) positions and site-specific ranging models. However, obtaining this information remains challenging in multifloor environments where interfloor signal attenuation differs significantly from the same-floor propagation. This study introduces an automated site survey procedure that jointly estimates 3-D AN coordinates and site-specific path-loss parameters, including floor penetration loss, by integrating smartphone-collected received signal strength (RSS) measurements with inertial sensor data for pedestrian dead reckoning (PDR). To address insufficient Wi-Fi coverage in real buildings, heterogeneous wireless infrastructure comprising Wi-Fi access points (APs) and Bluetooth low energy (BLE) beacons is considered, leveraging their similar 2.4-GHz propagation characteristics for unified modeling. Empirical measurements study was conducted to analyze and compare the interfloor path loss of signals from these ANs, and a cost function was formulated to jointly estimate the 3-D AN coordinates and path-loss parameters. Experimental evaluation in a real multistory building demonstrated mean absolute localization errors of 2.60 m for all ANs (1.02 m for Wi-Fi APs) with 100% floor identification accuracy. Using the estimated AN locations and path-loss models, the online range-based positioning achieves 2.51-m accuracy over a 330-m trajectory, outperforming conventional approaches by effectively utilizing interfloor signals through site-specific path-loss modeling.