reaming due to higher bitrates in the access net- works, then the same user will increase the expectations of such a service (i.e. TV or video streaming). Figure 1.4 illustrates how the QoS depends on the end-to-end technical aspects, which include network performance and terminal performance, and non-technical aspects (those that are not directly related to the equipment), which include customer care and point of sale. 1.3 Introduction to QoS, QoE, and Network Performance Personal Environment Advertising Trends Tariffs, costs (home, office) Customer expectations of QoS Customer satisfaction and quality of experience (QoE) QoS (technical) QoS (non-technical) Network Terminal Customer Point of sale performance performance Figure 1.4 Technical and non-technical points of view for quality of service. 1.3.2 Quality of Experience (QoE) Initially QoE was defined as the overall acceptability of an application or service, as per- ceived subjectively by the end-user (according to ITU-T Recommendation P.10/G.100, [11]). ITU-T has replaced the QoE definition developed in 2007 with a new definition adopted in 2016, which is currently the actual QoE definition given as follows [11]: Quality of experience (QoE) is the degree of delight or annoyance of the user of an appli- cation or service. However, one should note that there is continuous research on the QoE topic, SO the definition is expected to evolve further. Regarding the QoE there are two topics that need to be addressed together with the definition: QoE influencing factors. They include the type and characteristics of the application or service, context of use, the user's expectations with respect to the application or service and their fulfillment, the user's cultural background, socio-economic issues, psychological profiles, emotional state of the user, and other similar factors. QoE assessment. This is the process of measuring or estimating the QoE for a given number of end-users of a given application or a service. The assessment is typically based on an establish