Bluetooth Low Energy separate-channel fingerprinting with frequency-scanned antennas

A novel Bluetooth Low Energy (BLE) positioning system for IoT devices that employs frequency-scanned leaky-wave antennas (FSLWAs) and the fingerprinting technique is proposed in this work. This system is based on the Received Signal Strength Indicator (RSSI) fingerprinting acquired separately from each one of the three BLE advertising channels. As a main novelty, the Separate-Channel Fingerprinting (SCFP) technique is combined with FSLWAs, specifically tuned to multiplex each BLE advertising channel in a distinct direction. In this way, FSLWAs produce increased spatial resolution in separate-channel radiomaps, which results in greater localization accuracy when compared to the use of conventional monopole antennas installed usually in BLE IoT equipment. This is demonstrated with a practical example involving four BLE beacons distributed in an indoor area of 7 m x 5 m, simulating a practical environment. The proposed system combining SCFP and FSLWAs improves the mean localization error by 39 % compared to conventional monopole antennas without SCFP and 23 % compared to the use of monopoles and SCFP. The system's performance over time and its robustness to the presence of obstacles after calibration are also analyzed, showing the benefits of using SCFP with FSLWAs.