###### Abstract
SDN has many benefits, such as the acceleration of innovation and rapid adaptation to the demands and customization of network resources. It also promises to improve the programmability and flexibility of networks. NFV aims to make a network more flexible and simpler by minimizing dependence on hardware constraints. NFV mainly decouples network functions from proprietary devices, such as firewalls, routers, and traffic controls, and runs their functions as software in virtual machines. This virtualization scenario will consolidate the many specialized types of network equipment used in the industry, reduce the cost of network changes and upgrades, and increase network efficiency and flexibility [2; 3; 4]. The 5G network slicing is a promising technology enabled by SDN and NFV for providing network service convergence and on-demand services tailored to users' specific QoS requirements with limited network resources. It also reduces capital expenditures and operational expenses [5; 8]. A slicing network can enhance the efficiency of the entire network and provide miscellaneous 5G services by utilizing a virtual network. Network slicing can divide the 5G physical network into many logical networks to support on-demand services for all expected requests and applications. It should be noted that the logical networks are in the same physical network and point to network slices [2; 3; 4; 5; 8; 9]. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Case**} & **Ultra-Reliable and Low-Latency** & **Enhanced Mobile** & **Massive Machine-Type** \\  & **Communications (uRLLC)** & **Broadband (eMBB)** & **Communications (mMTC)** \\ \hline Priority & 1 & 2 & 3 \\ Min. bandwidth & 25 Mbps “Low” & 100 Mbps “High” & 100 Kbps “Low” \\ Latency & Low & Medium & High \\ End-to-end latency & 1 ms & 10 ms & s to h \\ \hline \hline \end{tabular}
\end{table} 
Table 1: 5G use cases and their priorities. The C-RAN is defined as one of the main components of the new architecture of 5G networks. Generally, the main radio resources located at the 5G base station (BS) include the radio antennas, the remote radio heads (RRHs), and the baseband units (BBUs). In order to improve the 5G architecture, the Next Generation Mobile Networks project transferred the BBUs from the BS to the 5G C-RAN. Therefore, all the BBUs of the RRHs connected by the same C-RAN are transferred and grouped into a virtualized BBU pool located in the C-RAN. In this new architecture, the BS is connected to the C-RAN using a high speed fronthaul connection and has only the RRHs and the radio [11; 12; 13]. With this new 5G C-RAN, the processing of the resource allocation is centralized at the C-RAN and can serve hundreds of distributed RRHs [3]. The BBUs are responsible for allocating the C-RAN resources to RRHs based on the defined network needs. CRAN has three main components, which are BBU, RRU, and front-haul. This architecture is used in 5G, where it can serve as a transport network for 5G and improve network performance. It also has the ability to pool resources, simplify network management and operation, reduce energy consumption, and co-execute RAN functionalities along with other network functions in a data center. Distributed RAN is a classical setup where remote radio units and BBUs are collocated at every cell site, and it is not appropriate for enhancing network performance. C-RAN combines both network virtualization and centralization of processing units (BBUs) in order to increase resource utilization and reduce the cost of deploying dense mobile networks. Using the network slicing concept, the C-RAN BBU pool can be virtually sliced into different slices, where each slice is allocated for different types of 5G use cases. These centralized and sliced resources are in critical need of efficient and flexible radio resource management [3]. Based on the 5G use cases, the BBU pool can be sliced into three slices, as shown in Figure 1. These 5G slices have different QoS requirements and different priority levels.