Toward Energy Efficiency in Radio Access Networks for 5G and Beyond: A Review of the State of the Art, Comparison of Power Consumption for Popular Open 5G RANs, and Techno-Economic Cost Impact

The increased energy demand in the fifth generation (5G) cellular networks and beyond has led to energy efficiency (EE) becoming a key research focus, particularly within the radio access network (RAN). This article presents a review of state-of-the-art techniques that address EE within the 5G RAN. These techniques are classified into six categories: hardware advancements, Multiple-Input Multiple-Output (MIMO) and antenna design, network architecture, sleep modes, optimisation techniques, and green energy sources. The article goes on to introduce a cost-effective power measurement setup designed for mobile network testbeds and demonstrates its use to compare the power consumption profile of different open-source RAN configurations deployed in the testbed. The proposed platform can be used not only to monitor and evaluate power consumption for different configurations of mobile network testbeds, but also to evaluate the implementation of different EE techniques. Further, we link the considered EE technologies with the capital and operational expenditures (Capex, Opex), total cost of ownership (TCO), and break-even points (BEP) across urban/rural deployments and open/proprietary deployment scenarios. Finally, by highlighting the least-explored areas and open research challenges, this work provides guidance for future research in this field.