### Introduction to 5G Network Slicing  
The architecture of 5G mobile networks enables the creation and existence of multiple independent logical networks known as network slices (NSs) on the shared 5G networks' physical infrastructure. Each independent 5G network segment (NS) has its own resource requirements, with the aim of meeting the quality of service (QoS) requirements of each application, user, or specific market. Within the concept of network slicing, each distinct NS, constituting a virtual network, is a self-contained assembly of network resources and functions. These NSs operate autonomously, spanning from initiation to completion, and possess diverse requirements that include energy consumption considerations. Additionally, they feature independent management and control mechanisms that are customized to align with the precise requirements of an operator, application, service, user, or a specific vertical market [4].  
In Figure 1, a standalone (SA) 5G network is shown. This implies that in practical network realization, there are also non-standalone 5G mobile network deployments that rely on the integration of the established fourth-generation (4G) long-term evolution (LTE) network alongside a 5G radio access network (RAN). In contrast, SA 5G networks operate independently by utilizing both a 5G RAN and a native cloud 5G core. This is the main reason why non-standalone 5G networks do not have network slicing capabilities and they are beyond the scope of this paper.  
From Figure 1, it can be seen that the 5G network is composed of a user plane consisting of the user equipment (UE), RAN, transport network (TN), and user plane function (UPF) of the core network (CN). Thus, the user plane encompasses data flow, data encapsulation, and particularities related to data transmission. On the other hand, the control plane comprises the transfer of control and management information and takes into account all functionalities unrelated to the actual communication of user content. The control plane manages session administration, verifies access rights for services or NSs, distributes and enforces service rules, and stores user data. Network slicing can be applied to some of these components, establishing distinct entities for each NS, or it can allow for a single entity to be shared across multiple NSs. Typically, in practical realizations of 5G network slicing, the access and mobility function (AMF) is shared among several NSs, whereas the session management function (SMF) and UPF are generally allocated to each NS separately. The rationale behind distributing the AMF among slices is to minimize signaling from the UEs when the utilized services span across various NSs. Alongside the AMF, the unified data management (UDM) and network slicing selection function (NSSF) are shared among multiple NSs, encompassing all NSs to simplify NS management complexity.  
Although TN is typically owned by the MNO, in practice, different allocations of TN infrastructure elements in 5G network slicing can be seen. According to Figure 2, network slicing can be applied separately to each architecture element of the 5G mobile network or it can be realized as a combination of some parts or all elements of the 5G standalone network. If an NS encompasses the CN part, the TN part, and the RAN part of the mobile network (as presented for slice 7 in Figure 2), it is referred to as end-to-end (E2E) network slicing.  
Figure 1: 5G standalone network [5].  
Figure 2: Network slicing in 5G.