QoE Metrics for Interactivity in Video Conferencing Applications: Definition and Evaluation Methodology

Video conferencing applications (VCAs) have become an indispensable tool for business, educational, and personal communications. There is, therefore, considerable interest in understanding and measuring the Quality of Experience (QoE) delivered by VCAs to their users. Video quality, one QoE measure, has received considerable attention in the literature. In this paper, we are concerned with another important aspect of VCA QoE, namely interactivity. We define this informally as the ability of a VCA to facilitate satisfying interaction among its users. Interactivity is primarily impacted by the media transmission latency among users which is, in turn, a function of network and application processing delays. Our goal in this work is to address two challenges in investigating interactivity-related QoE in VCAs. First, we propose a suite of meaningful quantifiable interactivity metrics, such as the proportion of silence time and rate of overlapping speech, that correlate well with conversational impairments and, hence, QoE perceptions. Second, we investigate scalable approaches for measuring these metrics. We develop a validated model for user behavior that enables realistic simulation of interactivity in VCA sessions. We also briefly consider an approach to measure interactivity metrics from packet traces. Through a set of experimental results, we demonstrate how our evaluation methodology provides a way for researchers, VCA service providers and network operators to perform large-scale investigations of how latency can interfere with user interactivity and impact VCA QoE.