ower delay including network delay and application delay aspects, etc.) and hence provide higher QoE to mobile users with high end mobile equipment than the QoE experienced by mobile users with older or less capa- ble mobile devices in the same mobile network. Hence, mobile operators need to organize provision of lower cost mobile devices with necessary capabilities in order to offer a high quality experience. Of course, the price of services matters, SO higher prices may provide better QoS (e.g. higher bitrates in the same access network) than the same service obtained for a lower price. Retail channels. There are different channels to sell services to end-users, which may span from service providers' selling points to digital retail channels (e.g. buying or upgrading/downgrading a service online or via the end-user equipment). Customer care. This is the part of the service providers which is typically combina- tion of human support for service management and configuration/reconfiguration 7.4 KPIs for Real-Time Services and automatic voice machines (or Web-based service assistants which are becoming more common with the development of the Artificial Intelligence use in the ICTs). 7.4.1 KPIs for Voice Over LTE Services The legacy telecommunication/ICT service which has transferred to VoIP (with the NGN deployments by telecom operators, as replacement of PSTN/ISDN) is the main and most known real-time service that includes human users on both sides of the connection. Operator grade (i.e. carrier grade) VoIP is provided with QoS guarantees end-to-end in both fixed and mobile IP access networks. Typically, the end-users are not aware of transition of the digital telephony to VoIP with QoS support, as they were not aware of transition of analogue to digital telephony in the last decades of the twentieth century. The VoIP provided in mobile environments is more prone to QoS degradations than VoIP provided by telecom operators via fixed access networks (e.g. optical access such as FTTH), due to lower predictability of 