Generalizing MOS to assess technical quality for end-to-end Telecom session

This paper introduces research that addresses the subjective measure of the customer experience regarding the technical quality of an end-to-end Telecom service session. We begin by explaining why the quality of customer experience is a crucial consideration for Telecom operators that necessitates a Service Quality Experience process for tracking customer experience. The customer experience is determined by the entire life cycle of a service session, so the assessment of quality must now consider three service components: Accessibility, Retainability, and Integrity. The traditional Mean Opinion Score (MOS) is concerned with the "integrity" or degree of impairment in signal quality. We propose to extend the concept of MOS to that of a session MOS (sMOS) that encompasses Integrity impairments as well as failures in accessibility and retainability. We consider how to incorporate traditional MOS assessments into sMOS, and we discuss the choice of rating scales for sMOS evaluation. We also consider how to use sMOS to track the acceptability of a service to customers. Finally we present a case study assessing sMOS experimentally for Over-the Top (OTT) progressive video streaming. We conclude by sketching a possible path for incorporating our findings into future ITU standards.