# Adaptive Energy Management in 5G Network Slicing: Requirements, Architecture, and Strategies
## 1 Introduction
### Background and Motivation
To guarantee energy sustainability and efficiency for mobile communications, there are different solutions that fall into two major groups: (i) increasing the use of renewable energy sources; and (ii) optimizing energy consumption (e.g., using energy saving mechanisms) [12]. The use of renewable energy sources (e.g., solar and wind), also known as green energy, to power Information and Communication Technology (ICT) systems such as 5G networks, is a promising \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Slice/Service Type** & **SST Value** & **Characteristics** & **Examples of Services** \\ \hline \multirow{3}{*}{eMBB} & \multirow{3}{*}{1} & Slice suitable for the handling of 5G enhanced Mobile Broadband & 4K/8K UHD, hologram, augmented/virtual reality \\ \cline{3-4}  & & Slice suitable for the handling of ultra reliable low latency (e.g., 1 ms) communications & High-accuracy positioning systems, motion control, autonomous driving, automated factory, smart-grid service, augmented/virtual reality \\ \hline \multirow{3}{*}{MIoT} & \multirow{3}{*}{3} & Slice suitable for the handling of massive IoT logistics, cite, home, etc.) \\ \cline{3-4}  & & Slice suitable for the handling of V2X services & Vehicular communications systems (e.g., vehicle-to-vehicle, vehicle-to-infrastructure, etc.) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Standardized SST values and examples [1]. alternative that can reduce energy bills for the MNO and customers, the exclusive dependence on power grids, and is an opportunity to deliver a cleaner and more sustainable mobile communications ecosystem [10]. For instance, green energy can allow the deployment of base stations in remote areas where power grids are not available (e.g., photovoltaic installations), and it may be a choice to compensate the lack of energy capacity from the supplier. In addition, the adoption of renewable energy sources allows changing the traditional centralized energy supply scheme to distributed power grid architectures in which the energy harvesting processes can be used to improve energy distribution, as it has been demonstrated for mobile access networks [13]. For all these reasons, the use of green energy emerges as a feasible solution to deal with the ever-rising energy demand and sustainability requirements in 5G networks [12]. There are multiple benefits of using energy from renewable sources, but their intermittent nature may affect the continuity of services and the reliability of mobile networks. In addition, the use of green energy alone is not enough to make mobile networks more sustainable; they need to consume better and less. Consequently, there is a need to incorporate new methods for adaptive energy management consumption (i.e., mechanisms to adapt consumption to availability) [1]. In this regard, different strategies have been analyzed such as activation of network infrastructures on demand, the total or partial deactivation of services or devices (e.g., deactivation of sectors in base stations), periodical activation or deactivation of consumption (e.g., by using sleep or idle modes), degradation in the quality of service (e.g., decrease in transmitting power), or scale the energy consumption to the traffic dynamics [14; 15]. These strategies can be applied to specific segments (e.g., to access networks) or to the whole system, and they can be performed through the ICT infrastructures of mobile networks [14]. In 5G, for example, the enabling technologies NFV and SDN can be used to deploy an energy management framework [16; 17], which offers high computing capabilities (data centers or cloud computing infrastructures), flexibility, and agility for executing management strategies (NFV benefits) [5], as well as the separation of control and data planes (SDN benefits) [18], and they can be applied for energy managing for different customers and scenarios transparently.