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G. Retscher:
"Indoor Localization Technologies Using Wi-Fi Based on Fingerprinting and Trilateration and in Combination with RFID";
Talk: Guest Lecture at the School of Information Science and Engineering of Xiamen University, China, Xiamen (invited); 2016-10-28.

The development of indoor navigation systems has become a growing field of research interest in recent years as many applications nowadays require ubiquitous positioning in combined out-/indoor environments. There are still many unresolved challenges in such type of applications as satellite-based GNSS and GNSS-aided inertial navigation systems (INS) are capable methods for mainly outdoor navigation only. Indoor positioning can be defined as any system which attempts to provide an accurate positioning inside of a covered structure using radio waves, acoustic signals, or other sensory information collected by mobile devices. It is primarily used for real-time location of people or objects in large buildings and in closed areas/spaces. Several types of location-sensing systems exist which each have its own strengths as well as limitations. In general, localization technologies can be classified into three categories, i.e., designated technologies based on pre-deployed signal transmission infrastructure, technologies based on `signals-of-opportunity´ and technologies not based on signals. In the first categories fall systems using infrared or ultrasonic signals, magnetic fields, Ultra Wide Band (UWB), Radio Frequency Identification (RFID) or other RF-based systems. Signals-of-opportunity include RF signals not intended for positioning, for instance, Wi-Fi, digital television, mobile telephony, FM radio and others. Dead reckoning (DR) using inertial sensors (accelerometers and gyroscopes) as well as vision/camera systems belong to the third category.
This talk aims to provide an insight into the use of a prominent signal of opportunity, namely Wi-Fi. Two new approaches developed at the TU Wien - Vienna University of Technology, Austria are introduced. In the first one, localization fingerprinting is the employed positioning method. A so-called `intelligent check-point´ (iCP) concept has been developed to reduce the laborious work for the establishment of reference points and radio maps of Wi-Fi signal strength distributions located throughout the area of interest. The second approach is based on the well-known DGPS principle. We term it Differential Wi-Fi (DWi-Fi). From measurements to reference stations area correction parameters are derived and applied for positioning determination of a mobile user. Both technologies have been extensively tested in a multi-storey office building. The main findings are highlighted in this presentation. It is shown that the approaches are capable to located a user carrying a smartphone or other mobile device in complex buildings. Furthermore, the combination and integration with RFID is briefly elaborated.