Spatio-temporal (S-T) similarity model for constructing WIFI-based RSSI fingerprinting map for indoor localization

WIFI-based received signal strength indicator (RSSI) fingerprinting is widely used for indoor localization due to desirable features such as universal availability, privacy protection, and low deployment cost. The key of RSSI fingerprinting is to construct a trustworthy RSSI map, which contains the measurements of received access point (AP) signal strengths at different calibration points. Location can be estimated by matching live RSSIs with the RSSI map. However, a fine-grained map requires much labor and time. This calls for developing efficient interpolation and approximation methods. Besides, due to environmental changes, the RSSI map requires periodical updates to guarantee localization accuracy. In this paper, we propose a spatio-temporal (S-T) similarity model which uses the S-T correlation to construct a fine-grained and up-to-date RSSI map. Five S-T correlation metrics are proposed, i.e., the spatial distance, signal similarity, similarity likelihood, RSSI vector distance, and the S-T reliability. This model is evaluated based on experiments in our indoor WIFI positioning system test bed. Results show improvements in both the interpolation accuracy (up to 7%) and localization accuracy (up to 32%), compared to four commonly used RSSI map construction methods, namely, linear interpolation, cubic interpolation, nearest neighbor interpolation, and compressive sensing.postprin

Indoor location identification technologies for real-time IoT-based applications: an inclusive survey

YesThe advent of the Internet of Things has witnessed tremendous success in the application of wireless sensor networks and ubiquitous computing for diverse smart-based applications. The developed systems operate under different technologies using different methods to achieve their targeted goals. In this treatise, we carried out an inclusive survey on key indoor technologies and techniques, with to view to explore their various benefits, limitations, and areas for improvement. The mathematical formulation for simple localization problems is also presented. In addition, an empirical evaluation of the performance of these indoor technologies is carried out using a common generic metric of scalability, accuracy, complexity, robustness, energy-efficiency, cost and reliability. An empirical evaluation of performance of different RF-based technologies establishes the viability of Wi-Fi, RFID, UWB, Wi-Fi, Bluetooth, ZigBee, and Light over other indoor technologies for reliable IoT-based applications. Furthermore, the survey advocates hybridization of technologies as an effective approach to achieve reliable IoT-based indoor systems. The findings of the survey could be useful in the selection of appropriate indoor technologies for the development of reliable real-time indoor applications. The study could also be used as a reliable source for literature referencing on the subject of indoor location identification.Supported in part by the Tertiary Education Trust Fund of the Federal Government of Nigeria, and in part by the European Union’s Horizon 2020 Research and Innovation Programme under Grant agreement H2020-MSCA-ITN-2016 SECRET-72242

Extraktion von Kontextinformationen zur Analyse von Nutzerströmen

Kontextadaptive Dienste ermitteln auf Basis von Sensordaten die aktuelle Situation des Nutzers. Dabei zählt neben Zeit, Identität und Aktivität vor allem der Aufenthaltsort zu den primären Kontextinformationen. Gerade Gebäude- und Infrastrukturbetreiber haben höchstes Interesse an solchen Daten, bekommen jedoch nur selten Zugriff darauf. Eine vielversprechende Alternative stellt das Aufzeichnen und Analysieren von Bluetooth- bzw. WLAN-Signalen dar, welches sich auch ohne Einverständnis der Nutzer realisieren lässt. Einige Startup-Unternehmen bieten mit dieser Strategie bereits Kundenanalysen an, jedoch fehlen wissenschaftliche Studien über die tatsächliche Güte solcher Verfahren. Zudem stellt die Extraktion primärer Kontextinformationen eine bisher ungelöste Herausforderung dar, da die aufgezeichneten Daten ein hohes Rauschen und eine geringe Frequenz aufweisen. Die vorliegende Arbeit geht dieses Problem der Datenunsicherheit an. So wird im ersten Teil untersucht, wie und welche Informationen aus Kommunikationsdaten gewonnen werden können. Diese werden anschließend zur Berechnung von Nutzerströmen in einem realen Szenario verwendet. Mithilfe einer bekannten Grundwahrheit können erstmals belastbare Aussagen über die Güte der evaluierten Verfahren getroffen werden. Die Ergebnisse zeigen, dass sich gerade WLAN-Daten zur Nutzerstromanalyse eignen, weshalb anschließend Simulationsmodelle von WLAN-Beobachtungen entwickelt werden. Dabei wird erstmals neben der Zeit auch die Aktivität und das Endgerät berücksichtigt. Der zweite Teil beschäftigt sich mit der Extraktion der Ortsinformation aus WLAN-Daten, die von mehreren Messknoten aufgezeichnet werden. Hierbei werden zunächst geometrische Ansätze zur Platzierung solcher Knoten vorgestellt. Auf Basis der Ergebnisse werden Messknoten installiert, um Bewegungspfade mobiler Nutzer im Gebäude zu ermitteln. Es zeigt sich, dass deterministische Methoden nicht die nötige Genauigkeit liefern und probabilistische Verfahren andere Nachteile aufweisen. Deshalb wird der State-Partikel-Filter als neuartige hybride Variante vorgestellt, die im Rahmen der Evaluation bessere Ergebnisse in Bezug auf anerkannte Metriken erreicht. Im dritten Teil wird die Extraktion von Aktivitäts- und Identitätsinformationen untersucht. Hierzu wird ein modifiziertes Verfahren zur Bestimmung von Ruhe- und Bewegungsphasen vorgestellt, das im Vergleich zu verwandten Arbeiten genauer ist. Auf Basis aller verfügbaren Informationen wird schließlich zur Identitätserkennung eine Klassifizierung von Nutzerrollen durchgeführt. Anders als in bisherigen Arbeiten findet so eine komplette Extraktion primärer Kontextinformationen aus aufgezeichneten Kommunikationsdaten statt.Context-aware services mainly estimate a user's current situation using sensor data. The well-known primary types of context information are time, identity, activity, and above all, location. Building managers and infrastructure providers are particularly interested in such data. However, they hardly get access to it. A promising alternative way without requiring users' permission for data access is to observe and analyse Bluetooth as well as Wi-Fi signals. Some start-ups already apply this technique in order to offer retail analytics. However, scientific studies providing information about the real performance of such approaches are still missing. Furthermore, extracting all of the primary types of context information is still challenging, due to the fact that the recorded data suffers from high noise and low sampling rates. This work deals with the afore-mentioned problems. Hence, the first chapter investigates, how and which kind of information can be inferred from captured communication data. Subsequently, this information is used to estimate user flows in a realistic scenario. With access to a known ground truth it becomes possible for the first time to reveal the real performance of the evaluated approaches. The results indicate that Wi-Fi captures are suitable for user flow analysis. Hence, models for simulating Wi-Fi based observations are developed considering time and novel aspects such as the user's activity and the device. The second chapter deals with the extraction of location information from Wi-Fi data which is captured by several distributed monitoring units. As a first step, geometric approaches for the placement of such units are presented. Based on the achieved results, Wi-Fi monitors are deployed in order to track and estimate trajectories of mobile users. In this connection, it is shown that deterministic methods do not reach the required accuracy and probabilistic approaches suffer from different drawbacks. Therefore, the so-called State-Particle-Filter is introduced as a novel hybrid variant returning better results in terms of well-adopted metrics within the performed evaluation. In the third chapter, the extraction of activity and identity information is investigated. Therefore, a modified approach for recognition of dwell times and motion periods is introduced which is shown to be more accurate than existing techniques. Finally, on the basis of all the available information, a user role classification task is performed for identity discovery. Thus, in contrast to other works, a complete extraction of the well-known primary types of context information is realized using captured communication data and the proposed methods