s, and costs, which are interrelated with the customer expectation of the QoS. So, on one side, QoE is influenced by technical QoS (that is, all network equipment and all customer equipment on the path end-to-end) and non-technical QoS (including points of sale, customer care, etc.). On the other side, QoE is also influenced by cus- tomers' expectations of QoS, which include current trends (at a given time), advertising (it has also an influence on customers), tariffs, and costs for enjoying the given service. The influences on QoS (technical and non-technical) and customer expectation of QoS are shown in Figure 1.9. QoE can take into account additional parameters, such as customer experience (more experienced users may have better experience of service use), user context (mood, envi- ronment, etc.), and potential discrepancy between the offered service and individual user feelings about the quality of the service delivery and its features. 1.5.1 QoE and QoS Comparison If one compares QoE and QoS, it appears that QoE is wider and bigger. But let's discuss QoE versus QoS further. On one side, QoS can be seen as an objective measure at pre- defined measurements points, such as network interfaces in hosts and network nodes. On the other side, there is a need for subjective merit for the quality of the given service perceived by the end-users, and that is where QoE comes onto the scene. Quality of experience (QoE) Customer Customer Customer experience expectation perception of QoS of QoS Service provision QoS planning QoS delivery by the service by the service provider provider Technical Non-technical performance performance Figure 1.9 Customer experience dependence on QoS and customer expectation of QoS. 1.5 QoE Concepts and Standards If one considers the four viewpoints in the ITU-T QoS framework, QoE can be consid- ered as a viewpoint of QoS from the customer's perspective. However, QoE also includes the customer's decision on retaining the service or withdrawing from that service. So, QoE can be considered as bei