# Resource Management in Cloud Radio Access Network: Conventional and New Approaches
###### Abstract  
Cloud radio access network (C-RAN) is a promising mobile wireless sensor network architecture to address the challenges of ever-increasing mobile data traffic and network costs. C-RAN is a practical solution to the strict energy-constrained wireless sensor nodes, often found in Internet of Things (IoT) applications. Although this architecture can provide energy efficiency and reduce cost, it is a challenging task in C-RAN to utilize the resources efficiently, considering the dynamic real-time environment. Several research works have proposed different methodologies for effective resource management in C-RAN. This study performs a comprehensive survey on the state-of-the-art resource management techniques that have been proposed recently for this architecture. The resource management techniques are categorized into computational resource management (CRM) and radio resource management (RRM) techniques. Then both of the techniques are further classified and analyzed based on the strategies used in the studies. Remote radio head (RRH) clustering schemes used in CRM techniques are discussed extensively. In this research work, the investigated performance metrics and their validation techniques are critically analyzed. Moreover, other important challenges and open research issues for efficient resource management in C-RAN are highlighted to provide future research direction. cloud radio access network; resource management; RRM; CRM; RRH clustering 20  
One of the novel network architectures that can potentially address the above-mentioned challenges is C-RAN architecture [4; 5]. The key concept of C-RAN is to break down the base station functionalities by decoupling the base station into Base band unit (BBU) and Remote radio head (RRH), and then centralizing the BBUs from multiple sites into a single geographical point such as a cloud data center, using cloud computing and virtualization techniques. BBUs are responsible for baseband signal processing, whereas RRHs take responsibility for signal amplification and modulation. RRHs are deployed with an antenna at the cell site and are connected to the BBU pool with a fronthaul link. As the baseband processing is centralized in a virtualized BBU pool, it can adapt to non-uniform traffic and utilize the resources effectively. Many operators can share the same BBU pool by renting it as a cloud service. Moreover, the network performance is improved by reducing the delay caused by handover. The operational cost can be reduced because the BBUs are centralized at a single site. Furthermore, the addition and upgrade of a new BBU is more convenient compared to a traditional RAN. MNOs only need to install an RRH to increase the network capacity. It also reduces the power and energy consumption, which eventually decreases the network costs. Although C-RAN appears to be a promising architecture for ensuring low cost and energy efficiency, a few challenges need to be resolved for maximizing its advantages. The co-location of many BBUs in a BBU pool connected to RRHs requires a reliable link with a high bandwidth capacity. The BBU-RRH association needs to be done in a way so that the BBU resources are utilized effectively, and user demands are also fulfilled. Effective strategies for base station mode switching must be adopted considering the real-time environment. The efficient management of the resources in C-RAN to satisfy user demand is a significant challenge due to the user mobility and dynamic environment. The resource in wireless communication mainly refers to the radio frequency (RF) spectrum, which is very limited. For optimal resource management, the RF resource must be utilized effectively by maximizing the number of users getting service. The objective of resource management is to utilize the limited radio frequency spectrum resources and radio network infrastructure with maximum efficiency. Different resource allocation mechanisms have been proposed for efficient resource management in C-RAN.