ration of the concept. A slice is composed of a collection of logical network functions that support the communication service requirements of particular use case(s). Some slices will be very rich in functionality, while other slices will be very minimalist, but the network slices are not arranged in any form of hierarchy. A given network slice will simply contain the functions required for a given application or class of service(s). Devices can be directed to the appropriate network slice in a way that fulfills operator and user needs, for example, based on subscription or device type. The network slicing primarily targets a partition of the core network, but it is not excluded that the RAN may need specific functionality to support multiple slices or even partitioning of resources for different network slices. Migration toward network slicing for 5G services necessitates careful consideration of the security requirements, isolation between slices, and the specific individual needs of each operator, whether it is the hosting platform provider or network slice tenant, in ensuring the integrity of the data processing and data stored in the network slices [45]. The presence of a very large number of IoT devices on the cellular network may require radically new technology and solutions that the current 4G networks may not be able to pro- vide. A fundamental feature needed in order to support massive IoT deployments is scalabil- ity on the device and the infrastructure sides. Current LTE networks are designed in a manner that makes such scalability technically and financially prohibitive. 5G systems are designed to provide connectivity to an extremely large number of low-cost, low-power, low-complexity devices under mMTC usage scenario. In general, IoT devices require to xxxvi Introduction and Background operate in low-power mode during communication while maintaining a high level of reli- ability and coverage. Mobility-on-demand provides a selection of options, which may be dynamically assigned to a device or applic