Modeling QoE in Dependable Tele-Immersive Applications: A Case Study of World Opera

Abstract

With the advent of recent technological advances, more demanding tele-immersive applications have started to emerge. In the World Opera application, artists from different opera houses across the globe can participate in a single united performance, and interact almost as if they were co-located.One of the main design challenges in this application domain is to assess to what extent the inevitable failures of some of the numerous and complex hardware, software, and network components affect the quality of experience for the user. This challenge cannot be addressed by traditional system-centric methods for dependability evaluation, which do not take personalized user perspective into account when considering meaningful and acceptable degradation of services.In this paper, we propose a novel method to assess the quality of experience in presence of failures, based on a new metric called perceived reliability. The method takes the human perspective into account and allows considering factors such as human perception of video and audio, characteristics of the audience, as well as performance elements and artistic content. This method can help system designers and engineers compare architectural variants and determine the dependability budget.We show the feasibility of our method by applying it to a World Opera performance. To this end, we construct a SANbased model and run simulations in the Möbius framework. The obtained results provide useful guidelines for system engineers towards improving the quality of experience of World Opera performances despite the presence of failures.

A Template-Based Methodology for the Specification and Automated Composition of Performability Models

“…Often, submodels include parameters and structural variability, to improve their reuse. Examples of works that apply such approach are [11] and [21]- [28].…”

“…In this section, we demonstrate the application of our approach to a concrete case study from the literature. The case study is based on the work in [11], in which a large-scale distributed application was analyzed, focusing on how different configuration and arrangement of system components would reflect on performability metrics.…”

“…The model in [11] considers components and streams as the basic elements of a WO performance, both having different possible working states (e.g., working/failed for components, good/missing/delayed for streams). The state of a stream in a certain point of the architecture depends on the state of all the components that have processed it so far (including components that captured it).…”

“…In [11], a template-based approach was "empirically" used, that is, without formally defining such templates, variability aspects, or composition rules. Four atomic templates were identified: Component, StreamAcquiring, StreamProcessing, and StreamMixing.…”

“…3) Such model-transformation algorithm is defined and implemented only once, since composition patterns become part of reusable model libraries. In the application of the approach, we focus on the stochastic activity networks (SANs) formalism [9], [10], for two practical reasons: first, the use case we use as a reference [11] was modeled with SANs (see Section VI), and second, we can use the discreteevent simulator provided by Möbius [12] to actually analyze the composed models that are generated. The paper is organized as follows.…”