1,680 research outputs found

    Personalised trails and learner profiling within e-learning environments

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    This deliverable focuses on personalisation and personalised trails. We begin by introducing and defining the concepts of personalisation and personalised trails. Personalisation requires that a user profile be stored, and so we assess currently available standard profile schemas and discuss the requirements for a profile to support personalised learning. We then review techniques for providing personalisation and some systems that implement these techniques, and discuss some of the issues around evaluating personalisation systems. We look especially at the use of learning and cognitive styles to support personalised learning, and also consider personalisation in the field of mobile learning, which has a slightly different take on the subject, and in commercially available systems, where personalisation support is found to currently be only at quite a low level. We conclude with a summary of the lessons to be learned from our review of personalisation and personalised trails

    Content-Aware Multimedia Communications

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    The demands for fast, economic and reliable dissemination of multimedia information are steadily growing within our society. While people and economy increasingly rely on communication technologies, engineers still struggle with their growing complexity. Complexity in multimedia communication originates from several sources. The most prominent is the unreliability of packet networks like the Internet. Recent advances in scheduling and error control mechanisms for streaming protocols have shown that the quality and robustness of multimedia delivery can be improved significantly when protocols are aware of the content they deliver. However, the proposed mechanisms require close cooperation between transport systems and application layers which increases the overall system complexity. Current approaches also require expensive metrics and focus on special encoding formats only. A general and efficient model is missing so far. This thesis presents efficient and format-independent solutions to support cross-layer coordination in system architectures. In particular, the first contribution of this work is a generic dependency model that enables transport layers to access content-specific properties of media streams, such as dependencies between data units and their importance. The second contribution is the design of a programming model for streaming communication and its implementation as a middleware architecture. The programming model hides the complexity of protocol stacks behind simple programming abstractions, but exposes cross-layer control and monitoring options to application programmers. For example, our interfaces allow programmers to choose appropriate failure semantics at design time while they can refine error protection and visibility of low-level errors at run-time. Based on some examples we show how our middleware simplifies the integration of stream-based communication into large-scale application architectures. An important result of this work is that despite cross-layer cooperation, neither application nor transport protocol designers experience an increase in complexity. Application programmers can even reuse existing streaming protocols which effectively increases system robustness.Der Bedarf unsere Gesellschaft nach kostengĂŒnstiger und zuverlĂ€ssiger Kommunikation wĂ€chst stetig. WĂ€hrend wir uns selbst immer mehr von modernen Kommunikationstechnologien abhĂ€ngig machen, mĂŒssen die Ingenieure dieser Technologien sowohl den Bedarf nach schneller EinfĂŒhrung neuer Produkte befriedigen als auch die wachsende KomplexitĂ€t der Systeme beherrschen. Gerade die Übertragung multimedialer Inhalte wie Video und Audiodaten ist nicht trivial. Einer der prominentesten GrĂŒnde dafĂŒr ist die UnzuverlĂ€ssigkeit heutiger Netzwerke, wie z.B.~dem Internet. Paketverluste und schwankende Laufzeiten können die DarstellungsqualitĂ€t massiv beeintrĂ€chtigen. Wie jĂŒngste Entwicklungen im Bereich der Streaming-Protokolle zeigen, sind jedoch QualitĂ€t und Robustheit der Übertragung effizient kontrollierbar, wenn Streamingprotokolle Informationen ĂŒber den Inhalt der transportierten Daten ausnutzen. Existierende AnsĂ€tze, die den Inhalt von Multimediadatenströmen beschreiben, sind allerdings meist auf einzelne Kompressionsverfahren spezialisiert und verwenden berechnungsintensive Metriken. Das reduziert ihren praktischen Nutzen deutlich. Außerdem erfordert der Informationsaustausch eine enge Kooperation zwischen Applikationen und Transportschichten. Da allerdings die Schnittstellen aktueller Systemarchitekturen nicht darauf vorbereitet sind, mĂŒssen entweder die Schnittstellen erweitert oder alternative Architekturkonzepte geschaffen werden. Die Gefahr beider Varianten ist jedoch, dass sich die KomplexitĂ€t eines Systems dadurch weiter erhöhen kann. Das zentrale Ziel dieser Dissertation ist es deshalb, schichtenĂŒbergreifende Koordination bei gleichzeitiger Reduzierung der KomplexitĂ€t zu erreichen. Hier leistet die Arbeit zwei BetrĂ€ge zum aktuellen Stand der Forschung. Erstens definiert sie ein universelles Modell zur Beschreibung von Inhaltsattributen, wie Wichtigkeiten und AbhĂ€ngigkeitsbeziehungen innerhalb eines Datenstroms. Transportschichten können dieses Wissen zur effizienten Fehlerkontrolle verwenden. Zweitens beschreibt die Arbeit das Noja Programmiermodell fĂŒr multimediale Middleware. Noja definiert Abstraktionen zur Übertragung und Kontrolle multimedialer Ströme, die die Koordination von Streamingprotokollen mit Applikationen ermöglichen. Zum Beispiel können Programmierer geeignete Fehlersemantiken und Kommunikationstopologien auswĂ€hlen und den konkreten Fehlerschutz dann zur Laufzeit verfeinern und kontrolliere

    Network-based IP flow mobility support in 3GPPs evolved packet core

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    Includes bibliographical references.Mobile data traffic in cellular networks has increased tremendously in the last few years. Due to the costs associated with licensed spectrum, Mobile Network Operators (MNOs) are battling to manage these increased traffic growths. Offloading mobile data traffic to alternative low cost access networks like Wi-Fi has been proposed as a candidate solution to enable MNOs to alleviate congestion from the cellular networks. This dissertation investigates an offloading technique called IP flow mobility within the 3rd Generation Partnership Project (3GPP) all-IP mobile core network, the Evolved Packet Core (EPC). IP flow mobility would enable offloading a subset of the mobile user‟s traffic to an alternative access network while allowing the rest of the end-user‟s traffic to be kept in the cellular access; this way, traffic with stringent quality of service requirements like Voice over Internet Protocol (VoIP) would not experience service disruption or interruption when offloaded. This technique is different from previous offloading techniques where all the end-user‟s traffic is offloaded. IP flow mobility functionality can be realised with either host- or network-based mobility protocols. The recommended IP flow mobility standard of 3GPP is based on the host-based mobility solution, Dual-Stack Mobile IPv6. However, host-based mobility solutions have drawbacks like long handover latencies and produce signaling overhead in the radio access networks, which could be less appealing to MNOs. Network-based mobility solutions, compared to the host-based mobility solutions, have reduced handover latencies with no signaling overhead occurring in the radio access network. Proxy Mobile IPv6 is a networkbased mobility protocol adapted by 3GPP for mobility in the EPC. However, the standardisation of the Proxy Mobile IPv6-based IP flow mobility functionality is still ongoing within 3GPP. A review of related literature and standardisation efforts reveals shortcomings with the Proxy Mobile IPv6 mobility protocol in supporting IP flow mobility. Proxy Mobile IPv6 does not have a mechanism that would ensure session continuity during IP flow handoffs or a mechanism enabling controlling of the forwarding path of a particular IP flow i.e., specifying the access network for the IP flow. The latter mechanism is referred to as IP flow information management and flow-based routing. These mechanisms represent the basis for enabling the IP flow mobility functionality. To address the shortcomings of Proxy Mobile IPv6, this dissertation proposes vi enhancements to the protocol procedures to enable the two mechanisms for IP flow mobility functionality. The proposed enhancements for the session continuity mechanism draw on work in related literature and the proposed enhancements for the IP flow information management and flow-based routing mechanism are based on the concepts used in the Dual- Stack Mobile IPv6 IP flow mobility functionality. Together the two mechanisms allow the end-user to issue requests on what access network a particular IP flow should be routed, and ensure that the IP flows are moved to the particular access network without session discontinuity

    Quality of Service for Information Access

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    Information is available in many forms from different sources, in distributed locations; access to information is supported by networks of varying performance; the cost of accessing and transporting the information varies for both the source and the transport route. Users who vary in their preferences, background knowledge required to interpret the information and motivation for accessing it, gather information to perform many different tasks. This position paper outlines some of these variations in information provision and access, and explores the impact these variations have on the user’s task performance, and the possibilities they make available to adapt the user interface for the presentation of information

    Systematic development of courseware systems

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    Various difficulties have been reported in relation to the development of courseware systems. A central problem is to address the needs of not only the learner, but also instructor, developer, and other stakeholders, and to integrate these different needs. Another problem area is courseware architectures, to which much work has been dedicated recently. We present a systematic approach to courseware development – a methodology for courseware engineering – that addresses these problems. This methodology is rooted in the educational domain and is based on methods for software development in this context. We illustrate how this methodology can improve the quality of courseware systems and the development process
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