A Survey on Cloud Radio Access Network Algorithms for Energy-Efficient Networks

Cloud Radio Access Network (C-RAN) is considered as a catalyst in increasing energy efficiency in 5G networks by centralizing baseband units that are interconnected to remote radio heads (RRHs). This technology allows to split functions among baseband and radio to significantly optimize performance across the network (lower latency, function offload). However, the C-RAN framework offers several split options, each of which carries specific advantages and disadvantages, when it comes to energy efficiency considerations. In this work, we investigate C-RAN systems in 5G and beyond networks (B5G), with a particular focus on energy efficiency specifications. At first, the study examines the measurable energy-related benefits offered by C-RAN to confirm its importance through operational results. Then, we explore the available C-RAN models in detail, while critically analyzing them, to assess their energy efficiency. The study goes on to discuss the challenges and strategies of choosing the right C-RAN model. Finally, our study concludes that there is no one-size-fits-all approach, when it comes to C-RAN strategies, as their effectiveness depends on variables such as network load, RRH level, energy cost, etc. However, in regard to energy efficiency in B5G, we underline the promising potential of C-RAN to significantly improve the energy efficiency.