The effectiveness of distributed multimedia applications as well as mobile computing services – which are becoming dominant in the modern telecommunications era – is primarily based on the networking protocols and communication systems that deliver content to the end-user. Research and development in these protocols and delivery systems is currently being driven from a technical perspective for the end-user's benefit. However, it is a fact that the effectiveness of any service presentation is ultimately measured by the end-user's experience in terms of aesthetic quality, accuracy of information, system responsiveness, and many other impacting factors.

Quality of Experience (QoE) can be defined as the overall acceptability of an application or service strictly from the end-user's point of view. It is a subjective measure of end-to-end service performance from the user's perspective, and it is an indication of how well any system and network components meet the user's needs. Encompassing many different aspects, QoE rivets on the true feelings of end-users when they watch streaming video and podcasts, listen to digitized music, and browse the Internet through a plethora of methods and devices.

The problem of understanding and enhancing QoE in complex, distributed, and diverse environments has been and is continuing to be the subject of intense research investigation. Considerable effort has been devoted to assessing QoE via objective or subjective means for new and emerging multimedia services over modern fixed/mobile devices (e.g., IPTV/HDTV/3DTV, tablet video calls, 3D smartphones). Many researchers have looked at this as a usability problem, while others have studied the correlation between specific technological settings and user-perceived QoE. However, as of today, we do not know how to manage and control QoE in a diverse heterogeneous environment. The variables that affect QoE are just too many and span several interdisciplinary areas, including multiple technologies, but also psychological and sociological factors. Despite the effort devoted to QoE study, managing and controlling user QoE is still an open issue. Currently, services and applications offer QoE as a by-product of QoS management. Most commonly, QoE is achieved by over-provisioning and over-committing network and computational resources. Therefore, QoE is still a best-effort service, which is not a viable option when applications become multimodal (a complex combination of voice, video, and data). In these cases, resources have to be managed and controlled more accurately and proactively for a successful, QoE-assured, service delivery.