# Design of an Energy Efficient Future Base Station with Large-Scale Antenna System
## 3 Energy-Efficient BS Structure and Related Operation
The BS can get even higher energy savings by skipping the real calculation of operation points for some interval. The system parameters for the operation of an energy-efficient BS is summarized in Table 3.  
Note that the performance of the proposed power control scheme critically depends on the threshold of the data rate and power consumption. The threshold is a bandwidth-limited regime and a power-limited regime in Shannon's channel capacity. Increasing power guarantees increasing the data rate significantly up to the power-limited regime in channel capacity. However, if the system goes to the bandwidth-limited regime in channel capacity, the data rate is no longer increased significantly, even if we increase it with large amounts of the power. There are various ways to adjust the TP or data rate and EE using the power control, as shown in Table 4. There is a trade-off between the EE and TP. However, if we appropriately allocate power for each component, it could be possible to increase both EE and TP, such as when using big data/machine learning-based RSD-PS. To show the systematic operation of the proposed BS, we provide one example using a flow chart, as shown in Figure 6.  
After gathering important parameters from the BS TX parts and user terminals, the proposed BS can derive the EE based on the power consumption estimation and data rate estimation. We set the number of iterations for the parameter adjustment between the data rate and the power consumption to obtain the expected performance, as well as to reduce the complexity. If the pre-defined number \begin{table}
\begin{tabular}{c l} \hline \hline
**Operation Metrics** & **Parameters** \\ \hline \multirow{4}{*}{**Data Rate**} & Channel Information (from Terminal) \\  & System Bandwidth (from BS) \\  & Radiation power (from BS) \\  & Number of Operating TXantenna (from BS) \\  & Number of Co-Scheduled User Terminals (from BS) \\ \hline \multirow{4}{*}{**Power Consumption**} & PA power consumption (from BS) \\  & RF power consumption (from BS) \\ \cline{1-1}  & BB power consumption (from BS) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The system parameters for the operation of energy-efficient BS. PA: power amplifier. of iterations is smaller than the current number of iterations, then the iteration stops, and the BS finds the operation point based on the information of the current parameters and the RSD-PS. If not, the proposed BS estimates whether the current power consumption is larger than the threshold for the power consumption. If the current power consumption is larger than the threshold, the proposed BS reduces the power consumption in appropriate ways by using the RSD-PS. Then, the proposed BS checks the TP. If the TP is within the satisfactory range, with the help of RSD-PS, the proposed BS determines the operating point. If the TP is not in a satisfactory range, the proposed BS goes to the loop and increases the power consumption to obtain a better TP, and so on. A proper power control algorithm should be included to reduce inter-cell interference. After achieving an operating point, the BS could operate with the operating point for a while. After that, the process could be performed again because the optimum point can change anytime in a dynamic wireless environment. Note that the operating procedure can be determined in various ways based on the proposed BS structure. \begin{table}
\begin{tabular}{l l} \hline (1) & Method to increase TP while decreasing EE \\ \hline (2) & Method to increase EE while decreasing TP \\ \hline (3) & Method to maintain EE while increasing TP \\ \hline (4) & Method to maintain TP while decreasing EE \\ \hline (5) & Method to increase both TP and EE and increase TP further \\ \hline (6) & Method to decrease both TP and EE and decrease EE further \\ \hline \end{tabular}
\end{table} 
Table 4: Examples of BS operation. TP: throughput; EE: energy efficiency. Figure 6: Example of the systematic operation of the proposed BS.