# AI-Assisted Multi-Operator RAN Sharing for Energy-Efficient Networks
## 1 Introduction
### Multitenant Energy Management by TowerCo  
Traditionally, TowerCos were set up as entities that generated and provided electricity to their MNO tenants at telecom tower sites. Apart from energy services, other standard functions such as site security, the monitoring of active equipment, and the upgradation of passive infrastructure, etc., are provided. For a TowerCo providing these services, energy generation and provisioning can constitute up to 60 percent of all annual operating expenses. As a result, they are incentivized to continuously seek long-term opportunities for energy-efficiency initiatives to reduce costs and improve cost predictability. However, historically, this has not been the case as most contracts between the TowerCos and MNOs were structured in a way that provided little or no commercial or business incentives for TowerCos to prioritize energy cost reductions and energy efficiency. Nowadays, with network operators looking to reduce their carbon footprint, we could expect to see a shift in this trend as more operators look towards adopting green renewable energy solutions that would benefit both parties by reducing costs and helping meet sustainability goals. Figure 5: Illustration of the actors in a RANaaS and RAN services. Enabling Energy-Saving Features  
Energy-saving features are RAN-specific. Some of these features are autonomous once activated (e.g., symbol power saving), while others are activated on demand and could be controlled by AI functionalities. Currently, AI is typically used to identify thresholds suitable for features such as cell sleep, carrier sleep, and RF channel sleep. These thresholds are then used to activate or deactivate radio resources on a rather slow time scale (a few times per 24 h). As mentioned earlier, in the RANaaS RAN-sharing scenario, the operators have control of the activation and deactivation of energy-saving features involving various radio resources. Tenant differentiation also implies that the energy-saving features should be independently upgradeable. To reduce the data shared with the TowerCo, the RAN energy-saving features could be implemented as a part of the logical RAN, i.e., the RAN service layer of ClusterRAN (see Figure 4) and not belong to the shared service infrastructure layer (which the TowerCo is responsible for). With the RANaaS sharing scenario, the total energy consumption reduction becomes a joint effort by the MNOs and the TowerCo. The TowerCo is responsible for distributing the total energy cost that includes active RAN components, cooling, and other energy-consuming equipment amongst the operators. As the energy-saving differentiation between operators could be a complex task, the TowerCo actor needs to have certain functionalities to distribute energy costs among the operators. As the TowerCo controls the activation-deactivation of the physically shared infrastructure resources, a resource can be deactivated only when all the sharing MNOs have decided to deactivate it. Overall, one can easily conclude that the TowerCo RANaaS architecture must support special coordination requirements for the energy management of shared hardware units such as remote radio units (RRUs)/active antenna units (AAUs). Preferably, this support is achieved by separating the TowerCo's energy management of the multiple logical RANs and the MNO energy-saving functionality within each logical RAN, as suggested in Figure 6.  
As shown in Figure 6, there is a logically individual AI functionality for each logical RAN serving different energy-saving features. If the TowerCo's energy management requires using AI, then there is a logically separated AI service for the TowerCo. The RAN services offering the AI functionality of the RAN are still logically individual from other RANs and that of the TowerCo's energy management. However, the TowerCo selects the AI services to use as it controls the logical RAN. The coordination functionality managed by the TowerCo shall be as independent as possible of the different RANs provided to the tenants.