# Resource Management in Cloud Radio Access Network: Conventional and New Approaches
### Review of Existing Surveys
In [22], a comprehensive assessment was carried out to compare the existing radio resource management schemes proposed for LTE/LTE-A femtocell and relay networks, in terms of interference mitigation, radio resource utilization, fairness, complexity, and QoS. The authors also identified future challenges and potential research directions for RRM development and HetNet enhancement. The authors in [12] reviewed the works on designing base station switching-off strategies from different design perspectives such as random; distance-aware; load-aware; auction-based; and joint design with user association, resource allocation, and physical-layer interference cancellation strategies. Many research works have been proposed considering the 5G mobile communication systems. Furthermore, a few surveys have been conducted discussing the works on 5G networks, such as [8; 19; 23; 24]. The authors in [6] presented a comprehensive survey on radio interference and resource management schemes for 5G RAN. They classified the schemes into radio interference, energy-efficient, spectrum efficient, and hybrid resource management. They further made a few recommendations on the continuing research issues of 5G RAN systems that were deduced from the schemes reviewed. Meanwhile, a survey [17] was conducted recently on the research studies on C-RAN focusing on throughput enhancement, interference management, energy efficiency, latency, security, and system cost reduction for 5G cellular systems. The authors in [21] presented a comprehensive review of the revolution of RAN architectures, wherein they mentioned the architectures of C-RAN, H-CRAN, virtualized C-RAN, and F-RAN. Moreover, a comparative analysis based on the energy consumption, security, CAPEX/OPEX, performance, spectrum, mobility, resource allocation, and system architectures for fulfilling user requirements, was presented. In [24], a review of state-of-the-art technologies for energy efficiency in 5G was presented. The authors addressed areas such as energy efficiency at the BS level, with 5G NR; caching; and using SDN, energy-efficient NOMA, energy-efficient resource sharing, and interference-aware energy efficiency. A few reviews considered energy-efficient resource management in cellular networks and other communication systems, such as [9; 10; 11; 25]. In [8], the state-of-the-art techniques for energy-efficient wireless networks are introduced, including EE metric, network deployment strategies, resource management, relay, cooperative communication, and multi-input multi-output (MIMO) and OFDM technologies. Meanwhile, in [7], the authors reviewed sleep mode techniques to reduce power and energy consumption in base stations, with the objective of developing a green cellular network. Thereby, the authors highlighted the importance of green mobile networks. In [11], the authors presented a survey on the research activities on radio resource management in machine-to-machine (M2M) communications for LTE/LTE-A cellular networks. Here, they considered access control, radio resource allocation, and power management. They also reviewed radio resource management for M2M communications in heterogeneous networks in conjunction with recent standard activities and continuing research issues. Furthermore, the authors in [25] presented a survey of the state-of-the-art caching techniques developed in different types of cellular networks, such as macro-cellular networks, heterogeneous networks, device-to-device networks, C-RAN, and F-RAN, by comparing different algorithms in terms of performance metrics including throughput, backhaul cost, power consumption, and network delay. Although substantial efforts have been undertaken to review the resource management in different wireless network environments and clouds, none of these specifically cover the resource management approaches proposed for C-RAN in recent years. A few articles presented a description