A coherent data filtering method for large scale RF fingerprint Wi-Fi Positioning Systems

Abstract

The rapid growth of mobile communication and the proliferation of smart phones have drawn significant attention to location-based services (LBS). The Wi-Fi positioning system (WPS) is a newly attractive method as a widely applicable positioning technique in LBS. In WPS, the received signal strength indication (RSSI) data of all Wi-Fi access points (APs) are measured, and stored in a huge database, as a form of radio fingerprint map. Because of the millions of APs in urban areas, radio fingerprint data are seriously contaminated. Therefore, we present a coherent filtering method for radio fingerprint data. All fingerprints used in the developed test bed are harvested from actual radio fingerprint measurements taken throughout Seoul, Korea. This demonstrates the practical usefulness of the proposed methodology.

Infrastructure Wi-Fi for connected autonomous vehicle positioning: A review of the state-of-the-art

“…With respect to wireless positioning systems (WPS), RSS radio ranging can be implemented as access point/base station (AP/BS) trilateration using path loss models or Wi-Fi fingerprinting as illustrated in Fig. 1 [24,25]. In terrestrial radio communications, propagation models are typically adopted in predicting the received power or radio coverage.…”

“…In time-of-arrival based ranging, the distance is inferred using the propagation time of the radio wave between the transmitter/initiator and the receiver/responder. The time-of-flight (ToF) is given as the arrival time of the transmitted packet also known as time-of-arrival (ToA) minus the time-of-transmission (ToT) added by the initiator [25]. In order to obtain accurate estimations of the ToA, real-time synchronization of the clocks in the participating devices is required [25,38].…”

“…The time-of-flight (ToF) is given as the arrival time of the transmitted packet also known as time-of-arrival (ToA) minus the time-of-transmission (ToT) added by the initiator [25]. In order to obtain accurate estimations of the ToA, real-time synchronization of the clocks in the participating devices is required [25,38]. However in the literature, two-way ToA or hybrid methods using phase-shifts have been adopted to avoid synchronization [39,40], as achieving real-time synchronization is challenging [38].…”

“…2. In general, delay-based ranging can be affected by uncertainties arising from clock drift, noise, multipath and relative motion [25].…”

“…From the triangulation depicted in Fig. 3, the localization error is optimized when the line joining the anchors and the device to the anchors forms an acute triangle [25].…”