ultimedia priority service users, public safety users, enterprise customers, and mobile virtual network operators). A network slice can provide the functionality of a complete network including radio access and core network functions. Each physical network can support one or more network slices [21]. It must be possible to verify if the UE is allowed to access a specific network slice. The management of life cycle of network slice and network function instances is also a key aspect in the overall framework for network slicing in 3GPP. Energy efficiency is a critical issue in 5G systems. The potential to deploy systems in areas without a reliable energy source requires new methods of managing energy con- sumption not only in the UEs but also through the entire 5G network. The 5G access network is required to support an energy-saving mode which can be activated/deacti- vated either manually or automatically and the service can be restricted to a group of users (e.g., public safety user, emergency callers). When in energy-saving mode, the inactive UEs transmit power may be reduced or turned off or their latency and jitter constraints may be relaxed with no impact on active users or applications in the net- work. Small form factor UEs also typically have a small battery, and this not only imposes restrictions on power optimization but also on how the energy is consumed. The unambiguous definition of the functional split between the next-generation core and the access network(s) is an important consideration for the support of heterogeneous access types where new interfaces between the next-generation core and the new 3GPP RAN need to be specified. 8. Mobility management is a key feature of 5G to support UEs with different mobility conditions which include stationary UEs during their entire usable life (e.g., sensors embedded in an infrastructure), stationary UEs during active periods, but nomadic between activations (e.g., fixed access), limited mobility within a constrained area (e.g., robots in a factory), and full