112 research outputs found
Design of an adaptive RF fingerprint indoor positioning system
RF fingerprinting can solve the indoor positioning problem with satisfactory
accuracy, but the methodology depends on the so-called radio map calibrated in
the offline phase via manual site-survey, which is costly, time-consuming and
somewhat error-prone. It also assumes the RF fingerprintâs signal-spatial
correlations to remain static throughout the online positioning phase, which
generally does not hold in practice. This is because indoor environments
constantly experience dynamic changes, causing the radio signal strengths to
fluctuate over time, which weakens the signal-spatial correlations of the RF
fingerprints. State-of-the-arts have proposed adaptive RF fingerprint
methodology capable of calibrating the radio map in real-time and on-demand
to address these drawbacks. However, existing implementations are highly
server-centric, which is less robust, does not scale well, and not privacy-friendly.
This thesis aims to address these drawbacks by exploring the
feasibility of implementing an adaptive RF fingerprint indoor positioning
system in a distributed and client-centric architecture using only commodity
Wi-Fi hardware, so it can seamlessly integrate with existing Wi-Fi network and
allow it to offer both networking and positioning services. Such approach has
not been explored in previous works, which forms the basis of this thesisâ main
contribution.
The proposed methodology utilizes a network of distributed location beacons as
its reference infrastructure; hence the system is more robust since it does not
have any single point-of-failure. Each location beacon periodically broadcasts its
coordinate to announce its presence in the area, plus coefficients that model its
real-time RSS distribution around the transmitting antenna. These coefficients
are constantly self-calibrated by the location beacon using empirical RSS
measurements obtained from neighbouring location beacons in a collaborative
fashion, and fitting the values using path loss with log-normal shadowing model
as a function of inter-beacon distances while minimizing the error in a least-squared
sense. By self-modelling its RSS distribution in real-time, the location
beacon becomes aware of its dynamically fluctuating signal levels caused by
physical, environmental and temporal characteristics of the indoor
environment. The implementation of this self-modelling feature on commodity
Wi-Fi hardware is another original contribution of this thesis.
Location discovery is managed locally by the clients, which means the proposed
system can support unlimited number of client devices simultaneously while
also protect userâs privacy because no information is shared with external
parties. It starts by listening for beacon frames broadcasted by nearby location
beacons and measuring their RSS values to establish the RF fingerprint of the
unknown point. Next, it simulates the reference RF fingerprints of
predetermined points inside the target area, effectively calibrating the siteâs
radio map, by computing the RSS values of all detected location beacons using
their respective coordinates and path loss coefficients embedded inside the
received beacon frames. Note that the coefficients model the real-time RSS
distribution of each location beacon around its transmitting antenna; hence, the
radio map is able to adapt itself to the dynamic fluctuations of the radio signal to
maintain its signal-spatial correlations. The final step is to search the radio map
to find the reference RF fingerprint that most closely resembles the unknown
sample, where its coordinate is returned as the location result.
One positioning approach would be to first construct a full radio map by
computing the RSS of all detected location beacons at all predetermined
calibration points, then followed by an exhaustive search over all reference RF
fingerprints to find the best match. Generally, RF fingerprint algorithm performs
better with higher number of calibration points per unit area since more
locations can be classified, while extra RSS components can help to better
distinguish between nearby calibration points. However, to calibrate and search
many RF fingerprints will incur substantial computing costs, which is unsuitable
for power and resource limited client devices. To address this challenge, this
thesis introduces a novel algorithm suitable for client-centric positioning as
another contribution. Given an unknown RF fingerprint to solve for location, the
proposed algorithm first sorts the RSS in descending order. It then iterates over
this list, first selecting the location beacon with the strongest RSS because this
implies the unknown location is closest to the said location beacon. Next, it
computes the beaconâs RSS using its path loss coefficients and coordinate
information one calibration point at a time while simultaneously compares the
result with the measured value. If they are similar, the algorithm keeps this
location for subsequent processing; else it is removed because distant points
relative to the unknown location would exhibit vastly different RSS values due
to the different site-specific obstructions encountered by the radio signal
propagation. The algorithm repeats the process by selecting the next strongest
location beacon, but this time it only computes its RSS for those points identified
in the previous iteration. After the last iteration completes, the average
coordinate of remaining calibration points is returned as the location result.
Matlab simulation shows the proposed algorithm only takes about half of the
time to produce a location estimate with similar positioning accuracy compared
to conventional algorithm that does a full radio map calibration and exhaustive
RF fingerprint search.
As part of the thesisâ contribution, a prototype of the proposed indoor
positioning system is developed using only commodity Wi-Fi hardware and
open-source software to evaluate its usability in real-world settings and to
demonstrate possible implementation on existing Wi-Fi installations.
Experimental results verify the proposed system yields consistent positioning
accuracy, even in highly dynamic indoor environments and changing location
beacon topologies
The always best positioned paradigm for mobile indoor applications
In this dissertation, methods for personal positioning in outdoor and indoor environments are investigated. The Always Best Positioned paradigm, which has the goal of providing a preferably consistent self-positioning, will be defined. Furthermore, the localization toolkit LOCATO will be presented, which allows to easily realize positioning systems that follow the paradigm. New algorithms were developed, which particularly address the robustness of positioning systems with respect to the Always Best Positioned paradigm. With the help of this toolkit, three example positioning-systems were implemented, each designed for different applications and requirements: a low-cost system, which can be used in conjunction with user-adaptive public displays, a so-called opportunistic system, which enables positioning with room-level accuracy in any building that provides a WiFi infrastructure, and a high-accuracy system for instrumented environments, which works with active RFID tags and infrared beacons. Furthermore, a new and unique evaluation-method for positioning systems is presented, which uses step-accurate natural walking-traces as ground truth. Finally, six location based services will be presented, which were realized either with the tools provided by LOCATO or with one of the example positioning-systems.In dieser Doktorarbeit werden Methoden zur Personenpositionierung im Innen- und AuĂenbereich von GebĂ€uden untersucht. Es wird das ,,Always Best Positionedâ Paradigma definiert, welches eine möglichst lĂŒckenlose Selbstpositionierung zum Ziel hat. Weiterhin wird die Lokalisierungsplattform LOCATO vorgestellt, welche eine einfache Umsetzung von Positionierungssystemen ermöglicht. Hierzu wurden neue Algorithmen entwickelt, welche gezielt die Robustheit von Positionierungssystemen unter BerĂŒcksichtigung des ,,Always Best Positionedâ Paradigmas angehen. Mit Hilfe dieser Plattform wurden drei Beispiel Positionierungssysteme entwickelt, welche unterschiedliche Einsatzgebiete berĂŒcksichtigen: Ein kostengĂŒnstiges System, das im Zusammenhang mit benutzeradaptiven öffentlichen Bildschirmen benutzt werden kann; ein sogenanntes opportunistisches Positionierungssystem, welches eine raumgenaue Positionierung in allen GebĂ€uden mit WLAN-Infrastruktur ermöglicht, sowie ein metergenaues Positionierungssystem, welches mit Hilfe einer Instrumentierung aus aktiven RFID-Tags und Infrarot-Baken arbeitet. Weiterhin wird erstmalig eine Positionierungsevaluation vorgestellt, welche schrittgenaue, natĂŒrliche Bewegungspfade als Referenzsystem einsetzt. Im Abschluss werden 6 lokationsbasierte Dienste vorgestellt, welche entweder mit Hilfe von LOCATO oder mit Hilfe einer der drei Beispiel-Positionierungssysteme entwickelt wurden
Advanced Location-Based Technologies and Services
Since the publication of the first edition in 2004, advances in mobile devices, positioning sensors, WiFi fingerprinting, and wireless communications, among others, have paved the way for developing new and advanced location-based services (LBSs). This second edition provides up-to-date information on LBSs, including WiFi fingerprinting, mobile computing, geospatial clouds, geospatial data mining, location privacy, and location-based social networking. It also includes new chapters on application areas such as LBSs for public health, indoor navigation, and advertising. In addition, the chapter on remote sensing has been revised to address advancements
Semantic discovery and reuse of business process patterns
Patterns currently play an important role in modern information systems (IS) development and their use has mainly been restricted to the design and implementation phases of the development lifecycle. Given the increasing significance of business modelling in IS development, patterns have the potential of providing a viable solution for promoting reusability of recurrent generalized models in the very early stages of development. As a statement of research-in-progress this paper focuses on business process patterns and proposes an initial methodological framework for the discovery and reuse of business process patterns within the IS development lifecycle. The framework borrows ideas from the domain engineering literature and proposes the use of semantics to drive both the discovery of patterns as well as their reuse
Advanced Trends in Wireless Communications
Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics
Proceedings, MSVSCC 2012
Proceedings of the 6th Annual Modeling, Simulation & Visualization Student Capstone Conference held on April 19, 2012 at VMASC in Suffolk, Virginia
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