g components or analog radio components. The sharing may be done in a dynamic or static manner depending on the configuration rules of the network slice. In the case of dynamic sharing, each slice obtains resources based on its demand and priority using either scheduling (that is, the slice requests resources from a cen- tralized scheduler, which allocates resources based on the overall traffic load or the priority of the slice) or contention. In the case of static sharing, a slice is pre-configured to operate with a dedicated resource throughout its operation time. Static sharing enables guaranteed resource allocation to the slice, whereas dynamic resource sharing allows overall resource usage optimization. Slice-specific configuration rules for the control-plane functions adapt the RAN control-plane functions for each slice. This is because slices may not require all control-plane functions. There is also a need for network slice-specific admission control, SO that the system can meet the initial access requirements of various network slices. 3 Key Performance Indicators, Architectural, System, and Service Requirements Unlike previous generations of 3GPP systems that attempted to provide a general-purpose framework, the 5G systems are expected to provide customized and optimized support for a variety of different services, traffic patterns, and end-user demographics. Several industry- led 5G white papers and in particular the one from Next-generation Mobile Network10 Alliance [14,25,32,35] described a multi-purpose 5G system capable of simultaneously Next-Generation Mobile Network Alliance, http://www.ngmn.org/. Introduction and Background xlix supporting various combinations of requirements such as reliability, latency, throughput, positioning, and availability to enable different use cases and deployment scenarios. Such revolutionary systems would be achievable with introduction of new technologies, both in access network and the core network, with configurable, flexible, and scalable assignment of network re