esides KPIs based on service utilization there are KPIs derived from the set of generic QoS parameters (e.g. as given in Table 7.2). End-users require and expect the QoS, and they experience it during the utilization of the given service. Therefore, the telecom operators design the networks to meet the QoS requirements for given services used by given number of end-users. However, the planned QoS by the service providers will not always or everywhere match the delivered level of QoS. For example, the QoS delivered can be lower than predicted (or contracted in the user agreements) in certain parts of the fixed networks or in certain cells or cover- age areas of the mobile networks due to various causes (bad network design, increase of traffic load without needed increase of the network capacity, network reconfiguration, etc.). So, in certain cases the QoS level experienced by the end-users may be lower than expected. Then, from the end-users' point of view, achieving satisfactory QoS depends on the appropriate combinations of the following elements: Network performance. Capacity of network links in the access, core and transit net- works, as well as capabilities of the networks nodes (processing capabilities, available QoS mechanisms and policies, etc.). Terminal performance. Different terminals may have different capabilities and that has influence on the QoS metrics and on the QoE. Typical example are smartphones, which develop with fast pace in each mobile generation. So, different smartphones (i.e. mobile devices) in the same network may support different network interfaces (e.g. some smartphones may support 3G/3.5G only, while others may have support for 3G, 4G, and 5G). Also, different mobile devices may have different processing power, memory capacity as well as support for different modulation and coding schemes and different number of antennas (e.g. for MIMO communication over the radio access network). In such case, mobile terminals with better capabilities will experi- ence better QoS (higher bitrate, l