Fundamental limits of wideband localization

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 107-112).Location-awareness is essential for many wireless network applications. However, determining nodes' positions precisely is a challenging task, especially in harsh multipath propagation environments. To address this problem, wide bandwidth signals are envisioned to be used in future localization systems, since such signals can provide accurate range measurements. In this paper, we investigate the localization performance of wideband networks and proposed a performance measure called the squared position error bound (SPEB) to characterize the localization accuracy. We derive the SPEB succinctly by applying the notion of equivalent Fisher information (EFI). The EFI provides insights into the essence of localization problem by unifying the localization information from individual anchors and that from a priori knowledge of the agent's position in a canonical form. We also investigate the use of wideband antenna arrays and the effect of clock asynchronism on the localization accuracy. Our analysis begins with the received waveforms themselves rather than utilizing only signal metrics, such as time-of-arrival and received signal strength, extracted from the waveforms. Our framework exploits all the information inherent in the received waveforms, and therefore the SPEB serves as a fundamental limit of localization accuracy.by Yuan Shen.S.M

Resource-aware plan recognition in instrumented environments

This thesis addresses the problem of plan recognition in instrumented environments, which is to infer an agent';s plans by observing its behavior. In instrumented environments such observations are made by physical sensors. This introduces specific challenges, of which the following two are considered in this thesis: - Physical sensors often observe state information instead of actions. As classical plan recognition approaches usually can only deal with action observations, this requires a cumbersome and error-prone inference of executed actions from observed states. - Due to limited physical resources of the environment it is often not possible to run all sensors at the same time, thus sensor selection techniques have to be applied. Current plan recognition approaches are not able to support the environment in selecting relevant subsets of sensors. This thesis proposes a two-stage approach to solve the problems described above. Firstly, a DBN-based plan recognition approach is presented which allows for the explicit representation and consideration of state knowledge. Secondly, a POMDP-based utility model for observation sources is presented which can be used with generic utility-based sensor selection algorithms. Further contributions include the presentation of a software toolkit that realizes plan recognition and sensor selection in instrumented environments, and an empirical evaluation of the validity and performance of the proposed models.Diese Arbeit behandelt das Problem der Planerkennung in instrumentierten Umgebungen. Ziel ist dabei das Erschließen der Pläne des Nutzers anhand der Beobachtung seiner Handlungen. In instrumentierten Umgebungen erfolgt diese Beobachtung über physische Sensoren. Dies wirft spezifische Probleme auf, von denen zwei in dieser Arbeit näher betrachtet werden: - Physische Sensoren beobachten in der Regel Zustände anstelle direkter Nutzeraktionen. Klassische Planerkennungsverfahren basieren jedoch auf der Beobachtung von Aktionen, was bisher eine aufwendige und fehlerträchtige Ableitung von Aktionen aus Zustandsbeobachtungen notwendig macht. - Aufgrund beschränkter Resourcen der Umgebung ist es oft nicht möglich alle Sensoren gleichzeitig zu aktivieren. Aktuelle Planerkennungsverfahren bieten keine Möglichkeit, die Umgebung bei der Auswahl einer relevanten Teilmenge von Sensoren zu unterstützen. Diese Arbeit beschreibt einen zweistufigen Ansatz zur Lösung der genannten Probleme. Zunächst wird ein DBN-basiertes Planerkennungsverfahren vorgestellt, das Zustandswissen explizit repräsentiert und in Schlussfolgerungen berücksichtigt. Dieses Verfahren bildet die Basis für ein POMDP-basiertes Nutzenmodell für Beobachtungsquellen, das für den Zweck der Sensorauswahl genutzt werden kann. Des Weiteren wird ein Toolkit zur Realisierung von Planerkennungs- und Sensorauswahlfunktionen vorgestellt sowie die Gültigkeit und Performanz der vorgestellten Modelle in einer empirischen Studie evaluiert

Empirical modelling as a new paradigm for educational technology

Educational technology has yet to deliver the benefits or successes that were expected in educational practice, especially in relation to issues other than the communication and delivery of teaching materials. Evidence suggests that these difficulties stem from the mismatch between formalised virtual learning environments and everyday sensemaking and between the rich potential for enhanced learning afforded by new technology and the constraints of old-style educational practice. In addressing this mismatch, some commentators suggest that the primary need is for a new culture of educational practice-and even that such a culture is already emerging, and others identify the need for a new paradigm for educational technology. The aim of this thesis is to explore the potential for a new paradigm for educational technology based on the principles and tools of Empirical Modelling (see http://dcs.warwick.ac.uk/modelling). The thesis builds upon previous research on Empirical Modelling as a constructionist approach to learning, and in particular Roe's doctoral thesis 'Computers for learning: an Empirical Modelling perspective'. Roe's treatment of Empirical Modelling can be viewed as generalising the use of spreadsheets for learning through applying 'programming by dependency' within the framework of existing educational practice. In contrast, this thesis is concerned at a more fundamental level with the contribution that Empirical Modelling can make to technology enhanced learning that may lead to new educational practices. In particular, it identifies eight significant characteristics of learning that are well-matched to Empirical Modelling activity, and associates these with experimental, flexible and meaningful strands in learning. The credentials of Empirical Modelling as a potential new foundation for educational technology are enhanced by demonstrating that Empirical Modelling is radically different from traditional software development and use. It provides a methodology for modelling with dependency that is more closely related to the use of spreadsheets for learning. The thesis elaborates on the relationship between Empirical Modelling and learning in a variety of different contexts, ways and applications. Three examples drawn from computer science higher education are explored to emphasise the experimental, flexible and meaningful characteristics of Empirical Modelling. This discussion of Empirical Modelling in a specific educational context is complemented by an investigation of its relevance to learning in a wider context, with reference to a broad range of subjects, to specific issues in language learning, and to the topics of lifelong learning and collaborative learning. Although the application of Empirical Modelling for learning is as yet too immature for large scale empirical studies, its potential is evaluated using informal empirical evidence arising from Empirical Modelling practice at Warwick. The sources for this evaluation are well-established teaching activities relating to Empirical Modelling in Computer Science at the University of 'Warwick, comprising an introductory module and a number of final year undergraduate projects. The thesis concludes by considering the extent to which Empirical Modelling can go beyond the support for constructionism envisaged by Roe, to address the broader agenda of supporting constructivist learning using computers. To this end, a close relationship between Empirical Modelling and a vision of constructivism recently set out by Bruno Latour in his paper 'The Promises of Constructivism' is demonstrated

Proceedings of the 1993 Conference on Intelligent Computer-Aided Training and Virtual Environment Technology, Volume 1

These proceedings are organized in the same manner as the conference's contributed sessions, with the papers grouped by topic area. These areas are as follows: VE (virtual environment) training for Space Flight, Virtual Environment Hardware, Knowledge Aquisition for ICAT (Intelligent Computer-Aided Training) & VE, Multimedia in ICAT Systems, VE in Training & Education (1 & 2), Virtual Environment Software (1 & 2), Models in ICAT systems, ICAT Commercial Applications, ICAT Architectures & Authoring Systems, ICAT Education & Medical Applications, Assessing VE for Training, VE & Human Systems (1 & 2), ICAT Theory & Natural Language, ICAT Applications in the Military, VE Applications in Engineering, Knowledge Acquisition for ICAT, and ICAT Applications in Aerospace

Empirical modelling as a new paradigm for educational technology

Educational technology has yet to deliver the benefits or successes that were expected in educational practice, especially in relation to issues other than the communication and delivery of teaching materials. Evidence suggests that these difficulties stem from the mismatch between formalised virtual learning environments and everyday sensemaking and between the rich potential for enhanced learning afforded by new technology and the constraints of old-style educational practice. In addressing this mismatch, some commentators suggest that the primary need is for a new culture of educational practice-and even that such a culture is already emerging, and others identify the need for a new paradigm for educational technology. The aim of this thesis is to explore the potential for a new paradigm for educational technology based on the principles and tools of Empirical Modelling (see http://dcs.warwick.ac.uk/modelling). The thesis builds upon previous research on Empirical Modelling as a constructionist approach to learning, and in particular Roe's doctoral thesis 'Computers for learning: an Empirical Modelling perspective'. Roe's treatment of Empirical Modelling can be viewed as generalising the use of spreadsheets for learning through applying 'programming by dependency' within the framework of existing educational practice. In contrast, this thesis is concerned at a more fundamental level with the contribution that Empirical Modelling can make to technology enhanced learning that may lead to new educational practices. In particular, it identifies eight significant characteristics of learning that are well-matched to Empirical Modelling activity, and associates these with experimental, flexible and meaningful strands in learning. The credentials of Empirical Modelling as a potential new foundation for educational technology are enhanced by demonstrating that Empirical Modelling is radically different from traditional software development and use. It provides a methodology for modelling with dependency that is more closely related to the use of spreadsheets for learning. The thesis elaborates on the relationship between Empirical Modelling and learning in a variety of different contexts, ways and applications. Three examples drawn from computer science higher education are explored to emphasise the experimental, flexible and meaningful characteristics of Empirical Modelling. This discussion of Empirical Modelling in a specific educational context is complemented by an investigation of its relevance to learning in a wider context, with reference to a broad range of subjects, to specific issues in language learning, and to the topics of lifelong learning and collaborative learning. Although the application of Empirical Modelling for learning is as yet too immature for large scale empirical studies, its potential is evaluated using informal empirical evidence arising from Empirical Modelling practice at Warwick. The sources for this evaluation are well-established teaching activities relating to Empirical Modelling in Computer Science at the University of 'Warwick, comprising an introductory module and a number of final year undergraduate projects. The thesis concludes by considering the extent to which Empirical Modelling can go beyond the support for constructionism envisaged by Roe, to address the broader agenda of supporting constructivist learning using computers. To this end, a close relationship between Empirical Modelling and a vision of constructivism recently set out by Bruno Latour in his paper 'The Promises of Constructivism' is demonstrated.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Seventh Annual Workshop on Space Operations Applications and Research (SOAR 1993), volume 1

This document contains papers presented at the Space Operations, Applications and Research Symposium (SOAR) Symposium hosted by NASA/Johnson Space Center (JSC) on August 3-5, 1993, and held at JSC Gilruth Recreation Center. SOAR included NASA and USAF programmatic overview, plenary session, panel discussions, panel sessions, and exhibits. It invited technical papers in support of U.S. Army, U.S. Navy, Department of Energy, NASA, and USAF programs in the following areas: robotics and telepresence, automation and intelligent systems, human factors, life support, and space maintenance and servicing. SOAR was concerned with Government-sponsored research and development relevant to aerospace operations. More than 100 technical papers, 17 exhibits, a plenary session, several panel discussions, and several keynote speeches were included in SOAR '93