Smartphone-Based Indoor Tracking in Multiple-Floor Scenarios

Abstract

With the rapid development of location-based services (LBSs), efficient and mobile-friendly localization algorithms should be designed for users to deliver a reliable LBS. In this paper, we present an algorithm with the corresponding smartphone app that enables users to calculate their locations based on representative infrastructures, such as nearby Wi-Fi access points and Bluetooth low energy (BLE) beacons subject to low-cost, rapid system deployment, and competitive location accuracy. Working under indoor multiple-floor scenarios, our app has three prominent features for estimating user locations. First, we establish a feature identifier to detect the current floor and the feasible area in which the user may walk. Second, owing to the structures of the indoor environment and the presence of different obstacles, the unpredictable variation of the received signal strength (RSS) in indoor environments is considered in the RSS-distance relationship to provide accurate location estimates. Third, with the prevalence of smartphones, we extract smartphone-inertial measurement units to learn users' behavior preferences, while collecting reference signals (e.g., Wi-Fi/BLE readings) along the pathway and input to the tracking algorithm. Then, the user's current location is displayed on the app. With this solution, we can provide an accurate location estimate with relatively low computational complexity regarding mobile device capability, while reducing labor costs from traditional fingerprint deployments. Finally, we test our tracking app in real-time multiple floor scenarios and evaluate the collected tracking data. Experimental results show that our proposed scheme achieves an average localization accuracy of more than 80% within a 2-m error bound in multiple-floor scenarios, while all areas (i.e., corridors, rooms, and stairs) were successfully identified.