connectivity, mobility, etc.) via certain application interfaces. However, to have a common core for different radio access technologies, the QoS mechanisms in the core should be able to work indepen- dently from the QoS mechanisms in the access parts, of course with a given mapping of the QoS parameters between them. The end-to-end QoS control in IMT-2020 requires QoS mapping between the QCIs and 5QIs (in the access part, standardized by 3GPP), and DSCP on the network layer (standardized by the IETF). Furthermore, for certain services, IMT-2020 mobile systems require finer granularity regarding QoS, such as end-to-end QoS provisioning on a per flow basis. Also, IMT-2020 is required to pro- vide the possibility for user specified QoS parameters, such as minimum or guaranteed bitrate for a given service (smart home, gaming, etc.). So, IMT-2020 is intended to satisfy unified QoS control mechanisms which are independent of the access technology, end-to-end QoS mechanism (because applica- tion/service QoS is always end-to-end), implicit and explicit QoS policy enforcement mechanisms, user-initiated QoS control mechanisms, as well as interworking with legacy IMT networks (e.g. 3G) and NGNs [13]. The IMT-2020 networks will coexist with existing UMTS, LTE, and/or WiFi; however, they provide new technologies that are designed to provide low latency, high reliability, or massive types of communications (considering the three main scenarios listed in this subsection). Such new capabilities of IMT-2020 mobile networks require bigger expen- diture and operational expenditures (CAPEX (capital expenditure) and OPEX (operat- ing expenses)), SO mobile operators require different ways of optimization of networks and equipment, which lead further to network virtualization. Similar to the transition from separate networks for separate services to a single (IP) network for all services, the following step is further flexibility in allocation and control of network resources by means of network virtualization and softwarization for t