Consistency Algorithms and Protocols for Distributed Interactive Applications

The Internet has a major impact not only on how people retrieve information but also on how they communicate. Distributed interactive applications support the communication and collaboration of people through the sharing and manipulation of rich multimedia content via the Internet. Aside from shared text editors, meeting support systems, and distributed virtual environments, shared whiteboards are a prominent example of distributed interactive applications. They allow the presentation and joint editing of documents in video conferencing scenarios. The design of such a shared whiteboard application, the multimedia lecture board (mlb), is a main contribution of this thesis. Like many other distributed interactive applications, the mlb has a replicated architecture where each user runs an instance of the application. This has the distinct advantage that the application can be deployed in a lightweight fashion, without relying on a supporting server infrastructure. But at the same time, this peer-to-peer architecture raises a number of challenging problems: First, application data needs to be distributed among all instances. For this purpose, we present the network protocol RTP/I for the standardized communication of distributed interactive applications, and a novel application-level multicast protocol that realizes efficient group communication while taking application-level knowledge into account. Second, consistency control mechanisms are required to keep the replicated application data synchronized. We present the consistency control algorithms “local lag”, “Timewarp”, and “state request”, show how they can be combined, and discuss how to provide visual feedback so that the session members are able to handle conflicting actions. Finally, late-joining participants need to be initialized with the current application state before they are able to participate in a collaborative session. We propose a novel late-join algorithm, which is both flexible and scalable. All algorithms and protocols presented in this dissertation solve the aforementioned problems in a generic way. We demonstrate how they can be employed for the mlb as well as for other distributed interactive applications

Freeform User Interfaces for Graphical Computing

報告番号: 甲15222 ; 学位授与年月日: 2000-03-29 ; 学位の種別: 課程博士 ; 学位の種類: 博士(工学) ; 学位記番号: 博工第4717号 ; 研究科・専攻: 工学系研究科情報工学専

On Consistency and Network Latency in Distributed Interactive Applications: A Survey—Part I

This paper is the first part of a two-part paper that documents a detailed survey of the research carried out on consistency and latency in distributed interactive applications (DIAs) in recent decades. Part I reviews the terminology associated with DIAs and offers definitions for consistency and latency. Related issues such as jitter and fidelity are also discussed. Furthermore, the various consistency maintenance mechanisms that researchers have used to improve consistency and reduce latency effects are considered. These mechanisms are grouped into one of three categories, namely time management, Information management and system architectural management. This paper presents the techniques associated with the time management category. Examples of such mechanisms include time warp, lock step synchronisation and predictive time management. The remaining two categories are presented in part two of the survey

Multimedia Synchronization Protocol Dedicated for Virtual Classrooms over Narrowband networks

This paper is presenting design and implementation of web based e-learning synchronization protocol. The protocol is HTTP/TCP based and specifically designed to increase the cognitive productivity of learning session conducted over the internet in analogous scheme to real classroom interaction. The presenting protocol is holding an innovative technique to enhance the performance of broadcasting whiteboards and classrooms to distributed students over narrowband networks. In narrowband networks race condition is raised between multimedia streams  in gaining network bandwidth. Throughout presented protocol; multimedia streams are packetized and synchronized in a compatible model for the cognitive natural learning mechanisms for the human being where actions drag attention and continuous interaction maintain the focus. Keywords: virtual class, WebSocket, HTML5, Servlet, HTTP, JSpeex, Whiteboard CODEC, e-learning, synchronous and Asynchronous learning

Using digital technologies to teach mathematics by English secondary school teachers: the barriers, constraints, teaching and learning opportunities and training provided

This thesis aims to explore ‘How English secondary school mathematics teachers could be better supported to integrate digital technologies into their teaching’ by answering four sub-questions: How were computers introduced into schools? Responses here present the history behind the present state of affairs. Using the voices of those involved when computers were first introduced, the origins of much that is “taken for granted” are explicated. What barriers and constraints do teachers face teachers when using ICT? The usefulness and reliability of the hardware and software are key here alongside the ease of access to ICT. More subtle influences uncovered are the influence of a “top-down” approach which results in teachers’ lacking autonomy and causes negative teacher beliefs about the merits of using digital technologies. How do teachers use ICT in the teaching and learning of mathematics? The merits, or otherwise, of using digital technologies for teaching are explored, uncovering a lack of awareness of the benefits of using ICT or the wide variety of resources and applications available to benefit pupil learning. Only a limited number of resources are used and often inefficiently. How could mathematics teachers training in the use of ICT for teaching be more effective? Teachers seem to “not know what there is to know” due in part to a lack of effective professional development. Findings here support ways teachers can be informed and supported outside the traditional professional development course. Ideas were explored from the perspective of the teachers who might potentially benefit from using educational technology as a tool to increase learning. Research has explored the use and benefits of specific software and hardware but here the teachers themselves are given a voice on what influences them to choose to use digital technologies in their teaching or not

Decoding learning: the proof, promise and potential of digital education

With hundreds of millions of pounds spent on digital technology for education every year – from interactive whiteboards to the rise of one–to–one tablet computers – every new technology seems to offer unlimited promise to learning. many sectors have benefitted immensely from harnessing innovative uses of technology. cloud computing, mobile communications and internet applications have changed the way manufacturing, finance, business services, the media and retailers operate. But key questions remain in education: has the range of technologies helped improve learners’ experiences and the standards they achieve? or is this investment just languishing as kit in the cupboard? and what more can decision makers, schools, teachers, parents and the technology industry do to ensure the full potential of innovative technology is exploited? There is no doubt that digital technologies have had a profound impact upon the management of learning. institutions can now recruit, register, monitor, and report on students with a new economy, efficiency, and (sometimes) creativity. yet, evidence of digital technologies producing real transformation in learning and teaching remains elusive. The education sector has invested heavily in digital technology; but this investment has not yet resulted in the radical improvements to learning experiences and educational attainment. in 2011, the Review of Education Capital found that maintained schools spent £487 million on icT equipment and services in 2009-2010. 1 since then, the education system has entered a state of flux with changes to the curriculum, shifts in funding, and increasing school autonomy. While ring-fenced funding for icT equipment and services has since ceased, a survey of 1,317 schools in July 2012 by the british educational suppliers association found they were assigning an increasing amount of their budget to technology. With greater freedom and enthusiasm towards technology in education, schools and teachers have become more discerning and are beginning to demand more evidence to justify their spending and strategies. This is both a challenge and an opportunity as it puts schools in greater charge of their spending and use of technolog

TechNews digests: Jan - Nov 2009

TechNews is a technology, news and analysis service aimed at anyone in the education sector keen to stay informed about technology developments, trends and issues. TechNews focuses on emerging technologies and other technology news. TechNews service : digests september 2004 till May 2010 Analysis pieces and News combined publish every 2 to 3 month

Multicast Services for Multimedia Collaborative Applications

This work aims at providing multicast services for multimedia collaborative applications over large inter-networks such as the Internet. Multimedia collaborative applications are typically of small group size, slow group membership dynamics, and awareness of participants\u27 identities and locations. Moreover, they usually consist of several components such as audio, video, shared whiteboard, and single user application sharing engines that collectively help make the collaboration session successful. Each of these components has its demands from the communication layer that may differ from one component to another. This dissertation identifies the overall characteristics of multimedia collaborative applications and their individual components. It also determines the service requirements of the various components from the communication layer. Based on the analysis done in the thesis, new techniques of multicast services that are more suitable for multimedia collaborative applications are introduced. In particular, the focus will be on multicast address management and connection control, routing, congestion and flow control, and error control. First, we investigate multicast address management and connection control and provide a new technique for address management based on address space partitioning. Second, we study the problem of multicast routing and introduce a new approach that fits the real time nature of multimedia applications. Third, we explore the problem of congestion and flow control and introduce a new mechanism that takes into consideration the heterogeneity within the network and within the processing capabilities of the end systems. Last, we exploit the problem of error control and present a solution that supports various levels of error control to the different components within the collaboration session. We present analytic as well as simulation studies to evaluate our work, which show that our techniques outperform previous ones