As the number of Web users and the diversity of Web applications continues to explode, Web Quality of Service (QoS) is an increasingly critical issue in the domain of e-Commerce [re]. This paper presents experiments designed to estimate users' tolerance of QoS in the context of e-commerce. In addition to objective measures we discuss contextual factors that influence these thresholds and show how users' conceptual models of Web tasks affect their expectations. We then show how user thresholds of tolerance can be taken into account when designing web servers. This integration of user requirements for QoS into systems design is ultimately of benefit to all stakeholders in the design of Internet services.

The number of heterogeneous networked applications is constantly increasing. It is likely that network resources will have to be partitioned according to the different Quality of Service (QoS) demands made by the users of these applications. One way of implementing a partitioned network -- favored in technical literature - is in terms of quality-based pricing (e.g.[1],[2],[3]). Most published proposals for partitioned networks assume users' assessments of the quality they receive mirrors the objective quality delivered at the network level (measurable through characteristics such as packet loss and delay). It is also assumed that users are prepared to pay more for higher levels of objective QoS when they need it. In this paper, we demonstrate that these assumptions may not be correct. We report an experiment in which users' QoS requirements for interactive audio were investigated. During the experiment the QoS received was linked to an expendable resource. We also established participa...

This paper presents an experiment comparing the relative impact of different types of degradation on subjective quality ratings of interactive speech transmitted over packet-switched networks. The experiment was inspired by observations made during a largescale, long-term field trial of multicast conferencing. We observed that user reports of unsatisfactory speech quality were rarely due to network effects such as packet loss and jitter. A subsequent analysis of conference recordings found that in most cases, the impairment was caused by end-system hardware, equipment setup or user behavior. The results from the experiment confirm that the effects of volume differences, echo and bad microphones are rated worse than the level of packet loss most users are likely to experience on the Internet today, provided that a simple repair mechanism is used. Consequently, anyone designing or deploying network speech applications and services ought to consider the addition of diagnostics and tutorials to ensure acceptable speech quality. Keywords Internet audio, speech, media quality assessment, subjective assessment, multicast conferencing. 1.

The introduction of multimedia on pervasive and mobile communication devices raises a number of perceptual quality issues, however, limited work has been done examining the 3-way interaction between use of equipment, quality of perception and quality of service. Our work measures levels of informational transfer (objective) and user satisfaction (subjective) when users are presented with multimedia video clips at three different frame rates, using four different display devices, simulating variation in participant mobility. Our results will show that variation in frame-rate does not impact a user’s level of information assimilation, however, does impact a users ’ perception of multimedia video ‘quality’. Additionally, increased visual immersion can be used to increase transfer of video information, but can negatively affect the users ’ perception of ‘quality’. Finally, we illustrate the significant affect of clip-content on the transfer of video, audio and textual information, placing into doubt the use of purely objective quality definitions when considering multimedia presentations.

In our study, we explore the human side of the multimedia experience. The authors propose a model that assesses quality variation from three distinct levels: the network-, the media- and the content-levels; and from two views: the technical- and the user-perspective. By facilitating parameter variation at each of the quality levels and from each of the perspectives, we were able to examine their impact on user quality perception. Results show that: a significant reduction in frame rate does not proportionally reduce the user's understanding of the presentation, independent of technical parameters; the type of video clip significantly impacts user information assimilation, user level of enjoyment and user perception of quality; the display type impacts user information assimilation and user perception of quality. Finally, to ensure transfer of informational content, network parameter variation should be adapted; to maintain user enjoyment, video content variation should be adapted.

communication for enhanced medical e-collaboration in back pain treatment

Over recent years, middleware is becoming an increasingly important tool for distributed application development. Furthermore, coupled with object-oriented development techniques, middleware is becoming the de facto approach to distributed application programming. Already, standardised distributed object platforms have emerged, including the Object Management Group’s CORBA and Microsoft’s DCOM. In their maturity, the services that such platforms offer are becoming progressively richer, as new horizontal application requirements are addressed. Examples of these ‘value added’ services include support for transactions, asynchronous messaging, persistence, migration and concurrency. These are now all considered basic services and are consequently integrated in the off-the-shelf middleware packages. Nevertheless, one of the most significant challenges in addressing horizontal requirements is that of support for continuous media, and as a superset, multimedia applications. Continuous media requires new interaction paradigms and consequently new modelling abstractions beyond conventional client/server communications.