Network-Integrated Multimedia Middleware, Services, and Applications

Today, there is a strong trend towards networked multimedia devices. However, common multimedia software architectures are restricted to perform all processing on a single system. Available software infrastructures for distributed computing — commonly referred to as middleware — only partly provide the facilities needed for supporting multimedia in distributed and dynamic environments. Approaches from the research community only focus on specific aspects and do not achieve the coverage needed for a full-featured multimedia middleware solution. The Network-Integrated Multimedia Middleware (NMM) presented in this thesis considers the network as an integral part. Despite the inherent heterogeneity of present networking and device technologies, the architecture allows to extend control and cooperation to the network and enables the development of distributed multimedia applications that transparently use local and remote components in combination. The base architecture of this middleware is augmented by several middleware services that especially aim at providing additional support for developing complex applications that involve mobile users and devices. To this end, previously not available services and corresponding abstractions are proposed, realized, and evaluated. The performance and applicability of the developed middleware and its additional services are demonstrated by describing different realized application scenarios.Eine wachsende Anzahl von Multimedia-Geraeten verfuegt heute bereits ueber Netzwerkschnittstellen. Verfueugbare Multimedia Software-Architekturen beschraeanken jedoch die gesamte Datenverarbeitung auf ein einzelnes System. Verbreitete Software-Infrastrukturen fuer Verteilte Systeme — ueblicherweise Middleware genannt — bieten nur teilweise die Eigenschaften, die fuer die Multimedia-Datenverarbeitung in vernetzten und dynamischen Umgebungen benoetigt werden. Ansaetze aus der Forschung behandeln nur spezielle Teilaspekte und erreichen deshalb nicht den Funktionsumfang einer vollwertigen Middleware fuer Multimedia. Die in dieser Arbeit beschriebene Netzwerk-Integrierte Multimedia Middleware (NMM) betrachtet das Netzwerk als integralen Bestandteil. Die Architektur erlaubt trotz der inhaerenten Heterogenitaet der vorhandenen Netzwerk- und Geraetetechnologie die Kontrolle und das Zusammenspiel von Systemen auf das Netzwerk auszuweiten. Dies ermoeglicht die Entwicklung verteilter Multimedia-Anwendungen, die transparent lokale und entfernte Komponenten zusammen einsetzen. Die Kernarchitektur dieser Middleware wird durch verschiedene Dienste erweitert, die speziell die Realisierung komplexer Anwendungsszenarien mitmobilen Geraeten und Benutzern unterstuetzt. Insbesondere werden neue, bisher nicht vorhandene Middleware-Dienste und zugehoerige Abstraktionen vorgeschlagen, realisiert und evaluiert. Anhand verschiedener Anwendungsszenarien wird die Leistungfaehigkeit, die Effizienz und die praktische Relevanz der entwickelten Middleware und der ergaenzenden Dienste demonstriert

Estudio del rendimiento de arquitecturas basadas en grupos para WAHSN

[ES] Existen muchos trabajos relacionados con las redes ad hoc y las redes de sensores donde se presentan nuevos protocolos que encaminamiento que aportan mejores características, otros trabajos donde se comparan para ver cual posee un mejor rendimiento ó incluso presentan nuevas aplicaciones basadas en este tipo de redes, pero este trabajo aporta otro punto de vista. ¿Por que no ver la red como un conjunto que se divide en grupos para aportar un mejor rendimiento a la red independientemente del protocolo de encaminamiento utilizado?. Para ello, en este trabajo, vamos a demostrar a través de simulaciones, que la agrupación de nodos en redes WAHSN (Wireless Ad Hoc & Sensor Networks) aporta mejoras a la red en general, disminuyendo el tráfico de encaminamiento, el retardo, el throughput, etc. Este estudio se ha realizado evaluando los protocolos estándar más utilizados (DSR [1], AODV [2] y OLSR [3]), así podemos observar cual de ellos aporta un mejor rendimiento. Finalmente, se propone una arquitectura de red basada en grupos optimizada para las redes WAHSN[EN] There are many works related with ad hoc networks and sensor networks where the authors present new routing protocols with better or enhanced features, others just compare the performance of them or present an application environment, but this work tries to give another point of view. Why don¿t we see the network as a whole and split it intro groups to give better performance to the network regardless of the used routing protocol?. First, we will demonstrate, through simulations, that grouping nodes in WAHSN (Wireless Ad Hoc & Sensor Networks) improves the whole network by diminishing the routing traffic, the delay, the throughput, etc. This study was conducted to assess the most used standard protocols (DSR [1], AODV [2] and OLSR [3]) that gives better performance to the whole network when there are groups of nodes. Finally, a group-based network architecture optimized for WAHSN is proposedGarcía Pineda, M. (2008). Estudio del rendimiento de arquitecturas basadas en grupos para WAHSN. http://hdl.handle.net/10251/13472Archivo delegad

Handling Emergent Conflicts in Adaptable Rule-based Sensor Networks

This thesis presents a study into conflicts that emerge amongst sensor device rules when such devices are formed into networks. It describes conflicting patterns of communication and computation that can disturb the monitoring of subjects, and lower the quality of service. Such conflicts can negatively affect the lifetimes of the devices and cause incorrect information to be reported. A novel approach to detecting and resolving conflicts is presented. The approach is considered within the context of home-based psychiatric Ambulatory Assessment (AA). Rules are considered that can be used to control the behaviours of devices in a sensor network for AA. The research provides examples of rule conflict that can be found for AA sensor networks. Sensor networks and AA are active areas of research and many questions remain open regarding collaboration amongst collections of heterogeneous devices to collect data, process information in-network, and report personalised findings. This thesis presents an investigation into reliable rule-based service provisioning for a variety of stakeholders, including care providers, patients and technicians. It contributes a collection of rules for controlling AA sensor networks. This research makes a number of contributions to the field of rule-based sensor networks, including areas of knowledge representation, heterogeneous device support, system personalisation, and in particular, system reliability. This thesis provides evidence to support the conclusion that conflicts can be detected and resolved in adaptable rule-based sensor networks

Brave New Wireless World: Mapping the Rise of Ubiquitous Connectivity from Myth to Market

This dissertation offers a critical and historical analysis of the myth of ubiquitous connectivity—a myth widely associated with the technological capabilities offered by “always on” Internet-enabled mobile devices like smartphones and tablets. This myth proclaims that work and social life are optimized, made more flexible, manageable, and productive, through the use of these devices and their related services. The prevalence of this myth—whether articulated as commercial strategy, organizational goal, or mode of social mediation—offers repeated claims that the experience and organization of daily life has passed a technological threshold. Its proponents champion the virtues of the invisible “last mile” tethering individuals (through their devices) primarily to commercial networks. The purpose of this dissertation is to uncover the interaction between the proliferation of media artifacts and the political economic forces and relations occluded by this myth. To do this, herein the development of the BlackBerry, as a specific brand of devices and services, is shown to be intimately interrelated with the myth of ubiquitous connectivity. It demonstrates that the BlackBerry is a technical artifact whose history sheds light on key characteristics of our media environment and the political economic dynamics shaping the development of other technologies, workforce composition and management, and more general consumption proclivities. By pointing to the analytic significance of the BlackBerry, this work does not intend to simply praise its creators for their technical and commercial achievements. Instead, it aims to show how these achievements express a synthesis that represents the motivations of economic actors and prevailing modes of thought most particularly as they are drawn together in and through the myth of ubiquitous connectivity. The narrative arc of this dissertation is anchored by moments of harmonization among political economic interests as these shape (and are shaped by) prevailing modes of producing and relating through ubiquitous connectivity

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

Atomic Transfer for Distributed Systems

Building applications and information systems increasingly means dealing with concurrency and faults stemming from distribution of system components. Atomic transactions are a well-known method for transferring the responsibility for handling concurrency and faults from developers to the software\u27s execution environment, but incur considerable execution overhead. This dissertation investigates methods that shift some of the burden of concurrency control into the network layer, to reduce response times and increase throughput. It anticipates future programmable network devices, enabling customized high-performance network protocols. We propose Atomic Transfer (AT), a distributed algorithm to prevent race conditions due to messages crossing on a path of network switches. Switches check request messages for conflicts with response messages traveling in the opposite direction. Conflicting requests are dropped, obviating the request\u27s receiving host from detecting and handling the conflict. AT is designed to perform well under high data contention, as concurrency control effort is balanced across a network instead of being handled by the contended endpoint hosts themselves. We use AT as the basis for a new optimistic transactional cache consistency algorithm, supporting execution of atomic applications caching shared data. We then present a scalable refinement, allowing hierarchical consistent caches with predictable performance despite high data update rates. We give detailed I/O Automata models of our algorithms along with correctness proofs. We begin with a simplified model, assuming static network paths and no message loss, and then refine it to support dynamic network paths and safe handling of message loss. We present a trie-based data structure for accelerating conflict-checking on switches, with benchmarks suggesting the feasibility of our approach from a performance stand-point

Creation of value with open source software in the telecommunications field

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

Zeitsynchronisation in drahtgebundenen Rechnernetzen

Ausgehend von einer Analyse des Standes der Technik werden neuartige Verfahren für die Zeitsynchronisation in drahtgebundenen Netzwerken vorgestellt. Unter anderem wird, zum ersten Mal im Bereich der Zeitsynchronisation, eine Kombination aus Linearer Optimierung und Broadcast-Nachrichten vorgestellt, was eine Verbindung der jeweiligen Genauigkeits- und Skalierbarkeitsvorteile ermöglicht. Weiterhin wird, ebenfalls zum ersten Mal im Bereich der Zeitsynchronisation, eine Kombination aus Linearer Optimierung und Temperaturkompensation vorgestellt.Based on an analysis of the state of the art, several new time synchronization methods for wired networks are proposed. Among others, for the first time in the synchronization domain, a combination of linear programming and broadcast messages is proposed, which allows combining the respective accuracy and scalability advantages. Moreover, this thesis proposes combining linear programming and temperature compensation, also for the first time in the field of time synchronization

Reuse of Digital Learning Resources in Collaborative Learning Environments

With background in the proliferation of Information- and Communication Technologies(ICTs) in educational institutions, there is a growing interest in deploying ICT that complies with specifications and standards for learning technologies in these institutions. A key to obtaining the benefits of cost-efficiency and quality that motivate this interest is reuse of digital learning resources. Despite the significant efforts being made in design and deployment of learning technology standards facilitating the reuse of learning resources, the phenomenon of reuse is understudied. Central standardization initiatives originate in the requirements for training in large corporations and the US military. My research is concerned with learning resource reuse in educational institutions, with a particular interest in pedagogical approaches emphasizing the social aspects of learning. The central aim of my research is to develop a conception of reuse that facilitates systematic analysis of learning resource reuse in ICT-mediated collaborative learning environments. This aim locates my research at the intersection between learning technology standardization and the research area of Computer Supported Collaborative Learning (CSCL). The theoretical basis for my research is sociocultural perspectives on human learning and development. This perspective contends that the process of learning is essentially a social process, situated in cultural and historical contexts. The sociocultural understanding of technological agency, that human actions are mediated by artifacts, has fundamentally shaped my understanding of learning resource reuse. I have used the more specific approach of Cultural-Historical Activity Theory as my analytical framework,which implies that I have studied the students, teachers, and technology designers’ engagement with learning resources as activity. The empirical basis for the research is formed by three interpretive case studies. Two of the case studies were carried out on an introductory course on object-oriented programming at the University of Aarhus in Denmark, during two consecutive semesters. The third case study was conducted on the development of a framework for technology-enhanced inquiry learning at the University of California, Berkeley, USA. The most important contribution of my research is that it brings the issue of how learning resources are reused in educational institutions into the foreground. The intermediate conv cept of reuse developed in this thesis informs the two research areas CSCL and learning technology standardization. It serves as a mechanism for discussing the issue of scalability of CSCL systems, and provides empirically informed perspectives on reuse to the learning technology standardization community. I argue that standardization will become more relevant for CSCL research as experimental CSCL systems are brought into educational institutions and help shape the everyday practice in these institutions. Learning technology standards represent an opportunity for the CSCL research community to reify findings on productive collaborative interactions, and to implement sustainable CSCL systems in educational institutions. The conception of reuse can be used in deliberations on standards deployment in educational institutions. It can help guide decisions on which learning resources to design according to standards, and the findings on how the specifications SCORM and IMS Learning Design accommodate collaborative learning approaches can assist decision-makers in choosing appropriate mechanisms for facilitating reuse of learning resources. For the design of learning technology standards, the conception of reuse offers an opportunity to think about how well the standards reflect reuse practice. The findings on how learning resources are reused can also be used for redesigning standards with respect to reducing complexity. In addition to the findings on reuse, my empirical research on social interactions in distributed CSCL settings has yielded new insights on the communicative conditions constituted by CSCL environments in the problem domain of university-level introductory objectoriented programming. My research pays particular attention to how the mediating ICTs shape these interactions, as well as taking other aspects of the learning situations into account