###### Abstract  
The 5G network is designed to serve three main use cases: enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable and low-latency communications (uRLLC). There are many new technological enablers, including the cloud radio access network (C-RAN) and network slicing, that can support 5G and meet its requirements. The C-RAN combines both network virtualization and based band unit (BBU) centralization. Using the network slicing concept, the C-RAN BBU pool can be virtually sliced into three different slices. 5G slices require a number of Quality of service (QoS) metrics, such as average response time and resource utilization. In order to enhance the C-RAN BBUs utilization while protecting the minimum QoS of the coexisting three slices, a priority-based resource allocation with queuing model is proposed. The uRLLC is given the highest priority, while eMBB has a higher priority than mMTC services. The proposed model allows the eMBB and mMTC to be queued and the interrupted mMTC to be restored in its queue to increase its chance to reattempt the service later. The proposed model's performance measures are defined and derived using a continuous-time Markov chain (CTMC) model and evaluated and compared using different methodologies. Based on the results, the proposed scheme can increase C-RAN resource utilization without degrading the QoS of the highest-priority uRLLC slice. Additionally, it can reduce the forced termination priority of the interrupted mMTC slice by allowing it to re-join its queue. Therefore, the comparison of the results shows that the proposed scheme outperforms the other states of the art in terms of improving the C-RAN utilization and enhancing the QoS of eMBB and mMTC slices without degrading the QoS of the highest priority use case. c 2023235111 2023235111 2023235111 20232351111 2023235111  
communications (mMTC), and ultra-reliable and low-latency communications (uRLLC) [5]. The main features of these categories (use cases) are as follows:  
eMBB features human-dependent use cases that cover high broadband communication, enhancing access to multimedia such as ultra-high-definition (3D/UHD) video and augmented reality, transmitting very high-performance data, and handling the data rate explosion [4; 5]. The mMTC is explicitly for the connection requests created by a huge number of small connected devices, such as the Internet of Things (IoT). These devices send and receive a low amount of non-delay-sensitive data and are required to have very low power consumption, low data rates, and reliability [6; 7]. uRLLC is a use case that handles an ultra-responsive connection with ultra-low latency. This use case is well suited for handling sensitive applications, such as smart vehicles, remote medical surgery, safety, and mission-critical applications [8; 9]. Table 1 shows the QoS requirements for each 5G use case and their priorities. In the table, priority (1) is the highest and priority (3) is the lowest. The table also presents the latency data rate. At the low end, mMTC has the lowest priority and has long latency, e.g., in a smart city [10]. In order for 5G networks to meet the QoS requirements for all of their use cases, many new technological features and enablers must be developed to support them. Agility and flexibility are the main defining features of 5G networks that enable them to meet the required ITU objectives. In order to meet the end-to-end flexibility requirements for 5G networks, network softwarization is defined as the main technology enabler for 5G networks. Network softwarization is a set of new technologies that separate the functions of the 5G core network hardware and software. This enabler technology of the 5G network includes software-defined networking (SDN), network function virtualization (NFV), cloud radio access network (C-RAN), and 5G network slicing. SDN is a networking technology in which the control plane, logically centralized in a software-based controller network brain, is decoupled from the forwarding plane.