QoE Beyond the MOS: An In-Depth Look at QoE via Better Metrics and their Relation to MOS

Abstract

While Quality of Experience (QoE) has advanced very significantly as a field in recent years, the methods used for analyzing it have not always kept pace. When QoE is studied, measured or estimated, practically all the literature deals with the so-called Mean Opinion Score (MOS). The MOS provides a simple scalar value for QoE, but it has several limitations, some of which are made clear in its name: for many applications, just having a mean value is not sufficient. For service and content providers in particular, it is more interesting to have an idea of how the scores are distributed, so as to ensure that a certain portion of the user population is experiencing satisfactory levels of quality, thus reducing churn. In this article we put forward the limitations of MOS, present other statistical tools that provide a much more comprehensive view of how quality is perceived by the users, and illustrate it all by analyzing the results of several subjective studies with these tools.