Because of its potential applications, mobile localization in wireless networks has attracted much attention recently. It is essential that a mobile user should be able to know its location anytime and anywhere. In practice, however, it is not always possible to obtain an accurate location of the mobile user; the presence of non-line-of-sight (NLOS) radio signal propagation and malicious beacons could cause considerable errors in localization. Therefore, NLOS identification and the detection of malicious beacons are important issues in localization. Existing NLOS identification methods usually assume that localization involving the use of NLOS radio signals cannot be performed in a consistent manner. However, the validity of the foregoing assumption has not been properly investigated. As a result, it is questionable whether these methods can be used to identify NLOS effectively. Existing malicious beacon identification methods require the cooperation of several detecting nodes for the verification of a location claim from a target node. They all suffer from one or both of the drawbacks: (i) not able to cope with a sparse network situation, and (ii) their design being based on a particular distance measurement technique. Moreover, even if NLOS propagation and malicious beacons can be identified, the following problem could arise: if the localization systems do not use the beacons involving NLOS propagation and the malicious beacons, they may not be able to locate a mobile user because of not having enough beacons. / In the first part of this thesis, we present a theoretical analysis of localization using NLOS radio signals, and show that the above-mentioned assumption would no longer be valid when the mobile user is located outside the convex hull of the underlying beacons. As a result, existing NLOS identification methods, as well as many localization approaches, could perform poorly. Extensive experiments on different wireless networks demonstrate that NLOS in localization and the localization error caused by NLOS have been greatly underestimated in previous studies. In the second part, we propose a general location verification scheme to identify malicious beacons. It employs a node-to-node approach for location estimation, and could use different measurement techniques; moreover, it supports secure location verification in sparse networks. The proposed verification scheme has been shown able to achieve satisfactory performance via extensive real world GPS-based wireless sensor network experiments. In the third part, we present a mobility enhanced localization (MEL) scheme. By introducing the user's mobility information into the localization process, the proposed MEL can work in the area where current mobile localization systems cannot locate a mobile user for not having enough beacons. Extensive real world GPS experimental results demonstrate the superiority of the proposed MEL scheme. With the proposed solutions to the above problems, we could obtain improved mobile localization. / Liu, Dawei. / Adviser: Moon-Chuen Lee. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 90-97). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Student Number : 9301997W - MSc thesis - School of Electrical and Information Engineering - Faculty of Engineering and the Built Environment / Emergency services are vital for the minimization of damage, injury and loss of life. These services are, by definition, a combination of telecommunications and information services, and are by nature, distributed. However, most current emergency services do not take advantage of emerging technology, and hence, are restricted in the functionality they offer. This project proposes the design a full information structure for an emergency call centre service, which can be offered as a service or application on any core network. As emergency services are distributed, and combine both telecommunications and information services, an appropriate design tool which caters for these issues, is the Reference Model for Open Distributed Processing (RM-ODP), which will be used in the design of the emergency service. In addition, OSA/Parlay Application Programming Interfaces (APIs) will be used for the application to access telecommunication network functionality. The enterprise viewpoint examines the design requirements and considerations for an emergency system, which is the first step in designing a service based on the RMODP guidelines. Secondly, the information viewpoint is defined, which identifies the information flows between the objects and classes defined in the enterprise viewpoint with the aid of robustness diagrams and high level message sequence charts. Next, the computational viewpoint of the emergency service describes the components that the service consists of and the interfaces through which they communicate, enabling distribution of the system to be visualized. In addition, the engineering and technology viewpoints are briefly touched upon. The RM-ODP proves to be a useful tool the design of this application. In addition, the use of OSA/Parlay APIs have also proved beneficial, enabling the application to run on any platform, irrespective of the level of functionality it already provides. The benefits that this design offers over conventional emergency services are allowing callers and emergency response personnel full access to the functionality of the service, despite any limitations on their telecommunications network, finding the location of a caller from a fixed or mobile phone, ease and speed of obtaining relevant emergency information, and the ease and speed of sending relevant information to emergency response personnel. Finally we recommend improvements in the reliability and accuracy of finding the location of mobile phones, as well as creating ways of identifying the location of VoIP users.

This dissertation investigates three topics related to movement and events associated with geospatial barriers. This research makes a unique contribution to geographic information science (GIScience), by examining how boundaries influence the interactions of other geographic features and to location-based services by bringing a GIScience perspective to geofence services. Chapters 2, 3, and 4 can be considered independently as journal articles. Each of these chapters builds on the previous. Chapter 2 serves as the base by examining geospatial barriers and impedance events associated with these barriers. The relationships between barriers, the features they protect and the features that they hinder are formalized in an ontology design pattern (ODP) that also includes events associated with these features. Algorithms are written to demonstrate the ODP can be used to answer queries about the presence or absence of barrier events. Chapter 3 transitions from physical boundaries to digital boundaries by examining geofences, a location-based notification service. Interaction between users and multiple geofences are investigated when the configuration of geofences differs (i.e. disconnected, partially overlapping, and completely overlapping) and when geofences are independent or dependent (a rule states that the activation of geofence Y depends on users having visited geofence X). A geofence system is prototyped in an iOS environment and used to further evaluate user-geofence interactions. Chapter 4 expands on the topic of location- based notification regions by investigating what is required for a geofence system to handle events. How changes in conditions (e.g. the spreading of a flood or movement of a fire) interact with geofences and users and what new categories of interactions are required to handle these changes are discussed. The proposed system is applied to a scenario of flooding on multiple rivers interrupting the transportation network.

Indoor localization systems have a variety of applications such as tracking of assets, indoor robot navigation, and monitoring of people (e.g. patients) in hospitals or at home. Global positioning system (GPS) offers location accuracy of several meters and is mainly used for outdoor location-based applications as its accuracy degrades significantly in indoor scenarios. Wireless local area networks (WLAN) have also been used for indoor localization, but the accuracy is too low and power consumption of WLAN terminals is too high for most applications. Ultra-wideband (UWB) localization is superior in terms of accuracy and power consumption compared with GPS and WLAN localization, and is thus more suitable for most indoor location-based applications [1-4]. The accuracy and precision requirements of localization systems depend on the specific characteristics of the applications. For example, centimeter or even millimeter localization accuracy is required for dynamic part tracking, while decimeter accuracy might be sufficient for tracking patients in hospitals or at home. Note that accuracy is not the only aspect of the overall performance of the system. Factors such as cost, range, and complexity should also be considered in system design. In the first part of this dissertation, a centimeter-accurate UWB localization system is developed. The technical challenges to achieve centimeter localization accuracy are investigated. Since all the receivers are synchronized through wire connection in this system, a wireless localization system with centimeter accuracy is introduced in order to make the system easier for deployment. A two-step synchronization algorithm with picosecond accuracy is presented, and the system is tested in a laboratory environment. The second part of this dissertation focuses on reducing the complexity of UWB localization systems when the localization accuracy requirement is relaxed. An UWB three-dimensional localization scheme with a single cluster of receivers is proposed. This scheme employs the time-of-arrival (TOA) technique and requires no wireless synchronization among the receivers. A hardware and software prototype that works in the 3.1-5.1 GHz range is constructed and tested in a laboratory environment. An average position estimation error of less than 3 decimeter is achieved by the experimental system. This TOA scheme with receivers in a single unit requires synchronization between the transmitter and the receiver unit. In order to further reduce system complexity, a new time-difference-of-arrival localization scheme is proposed. This scheme requires multiple units, each operating on its own clock. It avoids synchronization between the transmitter and receivers, and thus makes the development of the transmitter extremely simple. The performance of this system is simulated and analyzed analytically, and turns out to be satisfactory for most indoor localization applications. / Graduation date: 2013

Technology used for real-time locating is being used to identify and track the movements of individuals in real time. With the increased use of mobile technology by individuals, we are now able to explore more potential interactions between people and their living environment using real-time tracking and communication technologies. One of the potentials that has hardly been taken advantage of is to use cell phone tracking information for activity-based transportation study. Using GPS-embedded smart phones, it is convenient to continuously record our trajectories in a day with little information loss. As smart phones get cheaper and hence attract more users, the potential information source for self-tracking data is pervasive. This study provides a cell phone plus web method that collects volunteer cell phone tracking data and uses an algorithm to identify the allocation of activities and traveling in space and time. It also provides a step that incorporates user-participated prompted recall attribute identification (travel modes and activity types) which supplements the data preparation for activity-based travel demand modeling. Besides volunteered geospatial information collection, cell phone users’ real-time locations are often collected by service providers such as Apple, AT&T and many other third-party companies. This location data has been used in turn to boost new location-based services. However, few applications have been seen to address dynamic human interactions and spatio-temporal constraints of activities. This study sets up a framework for a new kind of location-based service that finds joint-activity opportunities for multiple individuals, and demonstrates its feasibility using a spatio-temporal GIS approach.

Informationssökningar av olika slag sker dagligen världen över och sökresultatet kan många gånger vara så stort att användarna har svårt att veta vilka sökresultat som är relevanta. I denna uppsats har syftet varit att undersöka hur sökresultat kan filtreras och sorteras med hjälp av platsbaserad sökning för att det ska bli mer relevant för användaren. Genom litteraturstudie och intervjuer har det blivit möjligt att ta reda på hur ett sökresultat skulle kunna filtreras och sorteras för att möta användarnas förväntningar. De teorier och slutsatser som framkom tillämpades vid utvecklingen av en prototyp. Prototypen testades och utvärderades sedan genom ett användartest där resultatet visar att filtreringen och sorteringen som används i studien kan göra sökresultatet mer relevant för användaren. / Information searches of various kinds take place daily around the world and search results can often be so large that users have difficulty knowing which results are relevant. In this paper the aim has been to examine how search results can be filtered and sorted by using location-based search to make the results more relevant to the user. Through a literature review and interviews it was possible to investigate how a search result can be filtered and sorted to meet user expectations. The theories and conclusions that emerged were applied in the development of a prototype. Usability tests were performed on the prototype and the results show that the filtering used in the study can provide a more relevant search result.

For many applications of location-based services, such as friend finding, buddy tracking,information sharing and cooperative caching in ad hoc networks, it is often important to be able to identify whether the positions of a given set of moving objects are within close proximity. To compute these kinds of proximity relations among large populations of moving objects, continuously available location position information of these objects must be correlated against each other to identify whether a given set of objects are in the specified proximity relation. In this dissertation, we state this problem, referring to it as the location constraint matching problem, both in the Euclidean space and the road network space. In the Euclidean space, we present an adaptive solution to this problem for various environments. We also study the position uncertainty associated with the constraint matching. For the road network space, where the object can only move along the edges of the road network, we propose an efficient algorithm based on graph partitioning, which dramatically restricts the search space and enhances performance. Our approaches reduce the constraint processing time by 80% for Euclidean space and by 90% for road network space respectively. The logical combination of individual constraints with conjunction, disjunction and negation results in more expressive constraint expressions than are possible based on single constraints. We model constraint expressions with Binary Decision Diagrams (BDD). Furthermore, we exploit the shared execution of constraint combinations based on the BDD modeling. All the algorithms for various aspects of the constraint processing are integrated in the research prototype L-ToPSS (Location-based Toronto Publish/Subscribe System). Through experimental study and the development of an analytical model, we show that the proposed solution scales to large numbers of constraints and large numbers of moving objects.

For many applications of location-based services, such as friend finding, buddy tracking,information sharing and cooperative caching in ad hoc networks, it is often important to be able to identify whether the positions of a given set of moving objects are within close proximity. To compute these kinds of proximity relations among large populations of moving objects, continuously available location position information of these objects must be correlated against each other to identify whether a given set of objects are in the specified proximity relation. In this dissertation, we state this problem, referring to it as the location constraint matching problem, both in the Euclidean space and the road network space. In the Euclidean space, we present an adaptive solution to this problem for various environments. We also study the position uncertainty associated with the constraint matching. For the road network space, where the object can only move along the edges of the road network, we propose an efficient algorithm based on graph partitioning, which dramatically restricts the search space and enhances performance. Our approaches reduce the constraint processing time by 80% for Euclidean space and by 90% for road network space respectively. The logical combination of individual constraints with conjunction, disjunction and negation results in more expressive constraint expressions than are possible based on single constraints. We model constraint expressions with Binary Decision Diagrams (BDD). Furthermore, we exploit the shared execution of constraint combinations based on the BDD modeling. All the algorithms for various aspects of the constraint processing are integrated in the research prototype L-ToPSS (Location-based Toronto Publish/Subscribe System). Through experimental study and the development of an analytical model, we show that the proposed solution scales to large numbers of constraints and large numbers of moving objects.

There have been a number of methods proposed for increasing the precision of mobile positioning systems. One of the latest methods is Assisted GPS, A-GPS, on the Secure User Plane for Location, SUPL, platform, which seems to be a very interesting alternative from TeliaSoneras perspective, thanks to minimal infrastructural investment costs. According to theory and lab testing A-GPS has the potential of providing a very good customer value in relation to the investment needed. There is, however, a great need to see the performance when used in real user environments and with real user equipment. This is the basis for the choice of field testing as the method used in this thesis. The result from the field tests conducted in this thesis shows that the performance of A-GPS is very good in outdoor environments, but when used in indoor environments, poor signal strength in combination with multipath and fading becomes a problem with low accuracy and long response times as a result. Using a hosted mapping service, in combination with A-GPS, provides the possibilities of launching location based services even outside the home network. TeliaSonera had already found such a hosted mapping service that matched their compatibility, and reliability, requirements. This thesis investigates this hosted mapping service further and finds that the quality of the cartographic presentation of the map information is very poor. The conclusion is that A-GPS performance, today, is limited by the hardware and algorithms used. If these are further adapted to indoor conditions, A-GPS has the potential of providing the customer value promised by the theoretical performance. For a successful launch of A-GPS services there is a great need of better cartographic presentation of map information, than what is currently is provided by the investigated hosted mapping service.

Spatial subscriptions have been used to specify locations of interest in Distributed Event-based Systems (DEBSs). However, current DEBSs representations to support spatial subscriptions are not expressive enough to describe some forms of subscriptions in mobile settings. For instance, users are not allowed to specify a spatial subscription that refers to other more well-known locations, in case they are not familiar with the names of their current locations. In addition, the middleware in existing DEBSs does not support changes at runtime, and modification to these middleware systems to support spatial subscriptions are highly coupled with specific DEBS infrastructures. In this thesis, I argue that by enhancing the expressiveness of spatial subscriptions, a new model of mobile spatial subscriptions for location-aware services can be defined and a reusable plug-in implementation approach that supports existing DEBSs can be developed. This thesis first summarizes the essential abstractions to specify mobile spatial subscriptions, and analyze the expressiveness of existing DEBSs to support these abstractions. Second, it proposes a three-level mobile spatial subscription model, which supports the essential abstractions used to specify spatial subscriptions. The first level of the model handles subscriptions consisting of geometric coordinates; the second level supports subscriptions with location labels; the third level interprets subscriptions which specify locations by stating their dynamic properties. Next, a plug-in implementation approach is introduced, and hence, the three-level model can be integrated with different DEBSs with minimal modification to the middleware. The subscription model is implemented as a subscriber/publisher component, instead of directly modifying the existing DEBS. Finally, I develop a prototype system, Dynamic Mobile Subscription System (DMSS), and illustrate the usefulness and applicability of the three-level model and the plug-in implementation approach.