 posing several challenges for network slicing in terms of mobility-aware slicing, anticipation of user mobility, pre-booking resources, and SO on. Furthermore, analytical studies and economic models on the service-level agreement are required in order to maximize the revenue of MNOs and third parties. 6. MEC: It faces several challenging issues in terms of the management of third- party applications, bringing the security and privacy drawbacks of the cloud into the MEC servers, and high maintenance cost in case of MEC failure. Therefore, efficient optimization and security solutions are mandated to enhance the performance of MEC. In addition, in case of mobility, a universal framework for offloading the tasks or applications and coexistence between different MEC is required. References 1. A. Toskala, H. Holma, T. Nakamura, 5G Technology: 3GPP New Radio (John Wiley and Sons, Hoboken, 2020) 2. O-RAN Alliance, O-RAN use cases and deployment scenarios (2021). https://static1. squarespace.com/static/5ad774cce74940d7115044b0/t/5e95a0a306c6ab2d1cbca4d3 e1586864301196/O-RAN+Use+Cases+and+Deployment+Scenarios+Whitepaper+February+ 2020.pdf. Accessed Jan 2021 3. M.A. Habibi, M. Nasimi, B. Han, H.D. Schotten, A comprehensive survey of RAN architec- tures toward 5G mobile communication system. IEEE Access 7, 70371-70421 (2019) 4. M.F. Hossain, A.U. Mahin, T. Debnath, F.B. Mosharrof, K.Z. Islam, Recent research in cloud radio access network (C-RAN) for 5G cellular systems - a survey. J. Netw. Comput. Appl. 139, 31-48 (2019) 5. W. Ejaz, S.K. Sharma, S. Saadat, M. Naeem, A. Anpalagan, N.A. Chughtai, A comprehensive survey on resource allocation for CRAN in 5G and beyond networks. J. Netw. Comput. Appl. (2020). https://doi.org/10.1016/j.jnca.2020.102638 6. F. Tian, P. Zhang, Z. Yan, A survey on C-RAN security. IEEE Access 5, 13372-13386 (2017) 7. M. Agiwal, A. Roy, N. Saxena, Next generation 5G wireless networks: a comprehensive survey. IEEE Commun. Surv. Tutorials 18(3), 1617-1655 (2016) 8. S.K. Sharma, X. Wang, Toward massive 