# AI-Assisted Multi-Operator RAN Sharing for Energy-Efficient Networks
## 4 System Model
### Energy Cost Distribution  
The energy cost distribution involves distributing the TowerCo energy consumption amongst all the operators. The TowerCo power model is similar to the description in Section 4.2 except that the total power consumption as given in Equation (13) is now a contribution of all the participating MNOs. Measured during the observation window, the TowerCo's energy consumption consists of two parts, _(i)_ the active-mode and _(ii)_ the idle-mode energy consumption. The active-mode energy consumption further comprises the static (or no-load) and dynamic (or variable) energy consumption as seen in Figure 12. As for the dynamic energy consumption, it is the load-dependent power consumption inEquation (13) that plays a crucial role. Unlike the single-RAN scenario where the power amplifiers experience similar load, in a TowerCo scenario, the load experienced by the power amplifiers could vary depending on the configuration and the power amplifiers used by the active MNOs. This variation leads to their differing energy consumption measured during the observation window. The power amplifiers can be divided into two types:  
* Shared power amplifiers --the power amplifiers used by two or more MNOs.
* Independent power amplifiers--the power amplifiers used by only one of the MNOs.  
In the RANaaS scenario, the TowerCo divides that energy consumption of the shared power amplifiers amongst the operators based on their usage as outlined in Algorithm 1. On the other hand, the load-independent (or no-load) power consumption depends only on the highest configuration of all the active operators at a given site.  
```
1:Initialize the energy consumption share of each operator
2:for each sitedo
3:for each banddo
4: Identify the MNOs that are active and their activity factors
5: Determine the sleep level activated based on the maximum activity factor
6:if (_active period > 0_and number of active MNOs > 1_)then
7: Obtain the configurations and bandwidth utilized by the active MNOs
8: Compute the dynamic power consumption of each configuration based on: - The activity factor - The total bandwidth utilized - The configuration overlap information
9: Split the power consumption amongst the configuration overlapping MNOs
10: Calculate the energy consumed by the variably loaded power amplifiers and add the no-load or static energy consumption of the maximum configuration for the observation window
11: Split the energy consumption amongst the active MNOs based on - The load contributed - The configuration overlap information
12: Save the energy consumption per MNO
13:elseif (_active period > 0_)then
14: Obtain the configurations and bandwidth utilized by the active MNO
15: Compute the dynamic power consumption based on: - The activity factor - The total bandwidth utilized
16: Calculate the energy consumption during the observation window
17: Add the no-load/static energy consumption
18: Save the energy consumption for the MNO
19:else
20: Calculate the energy consumption based on the deepest sleep level activated during the observation window
21:endif
22:endfor
23:endfor
```  
**Algorithm 1** TowerCo's energy cost distribution algorithm