 as partitioning the physical resources of the network into a set of logically segregated virtual networks [165]. Accordingly, the slice can be considered as a set of virtualized or non-virtualized NFs that contains the session management, application, user plane functions, and SO on [166, 167]. Moreover, network slicing should be capable to provide resources for the various UCs of URLLC, eMBB, and mMTC. Several benefits can be gained by adopting network slicing concept within the 5G networks as follows [168]: M. Alfaqawi et al. 1. Multi-tenancy: The same physical infrastructure is shared between several operators. 2. Service differentiation: Each slice fulfills the desired QoS for a network service such as delay, data rate, and packet loss. 3. On-demand by facilitating the creation, modification, or removal of a slice in real time. 4. Resource optimization, reducing the CAPEX/OPEX, and energy savings. This section highlights recent research works on network slicing architecture and presents the conceptual architecture of network slicing. Meanwhile, several challenging issues and recent research works on network slicing are addressed in Sect. 1.4.4 and Table 1.8. 1.4.3.1 Network Slicing Architecture Network slicing within 5G technology has been discussed in several standards and research works. Table 1.7 presents standards and research works that discussed network slicing architectural framework and the modifications on RAN and the core network (CN). Unlike network slicing for LTE that supports only MBB services, network slicing in 5G networks provides services for vertical industries including the UCs of eMBB, URLLC, and mMTC. 3GPP in [164] defined the fundamental regulations to enable network slicing within the NG-RAN, including RAN aware- ness of slices, resource management and isolation between slices, selection of CN entity, and SO on. Meanwhile, ITU-T in [179] specified the framework for the non- radio aspects of 4G LTE and 5G technologies including network slicing. The architectural framework proposed by I