# A Power Control and Intervention Algorithm for Co-Existing IMT Base Stations and Satellite Services
## 3 Optimisation Algorithm
### Average Power Allocation Algorithm Based on Partitioning Strategy
Considering the long distance between the satellite and the ground, the deployment positions of the ground base stations are relatively small compared to the satellite-ground distance, thus the elevation angles of the base stations within the same partition to the satellite can be approximately the same. The base stations within a partition are equivalent to a virtual large base station with a transmit power equal to the sum of all base stations within that partition, and the interference caused by this equivalent large base station to the satellite is measured. The figure shows the interference values from 1000 virtual large base stations to the satellite, and based on experience, an interference threshold of \(-34\) dB is set for each. The blue line in the figure represents the partitions that meet the interference threshold, meaning no power control is required, while the red line represents the partitions that require interference control. Figure 4: The empirical cumulative distribution function (CDF) of the aggregate interference-to-noise ratio (I/N) caused by ground networks on satellites. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Maximum transmit power of the base station & 46 dBm/100 MHz \\ Bandwidths & 100 MHz \\ Antenna front-to-back ratio & 30 dB \\ Bypass Level Limit & 30 dB \\ Antenna array element gain & 5.5 dBi \\
3 dB pitch angle & 65\({}^{\circ}\) \\
3 dB direction angle & 65\({}^{\circ}\) \\ Mechanical downward angle & 10\({}^{\circ}\) \\ Antenna Horizontal Spacing & 0.5 wavelength \\ Antenna vertical spacing & 0.5 wavelength \\ Pitch/Direction & Input parameters \\ Base station coverage diameter & 300 m \\ Array of antennas & 8H16V \\ \hline \hline \end{tabular}
\end{table} 
Table 5: _Cont._Figure 6 shows the transmission power values of base stations in each partition after power control when the number of partitions is K = 1000. In the figure above, an average power scheme is adopted for the base stations within each partition, so the transmission power of the base stations within the same partition is the same. The figure only shows the transmission power of base stations in different partitions. As can be seen, the transmission power of most base stations is greater than 25 dBm/100 MHz. Meanwhile, due to the average distribution of power among base stations, there are no sleeping base stations. Correspondingly, Figure 7 presents the CDF curve of the base station transmission power. From the figure, we can conclude that 60% of the base stations have a transmission power less than 46 dBm, which means 40% of the base stations in the network can transmit signals at their maximum transmission power. Figure 5: \(I/N\) (dB) of each region to the satellite when the number of partitions is \(K=1000\), where the blue line indicates the partitions that do not require power control. (Threshold = \(-34\) dB, empirical value). Figure 6: Transmission Power Values of Base Stations in Each Region after Power Control When the Number of Partitions is K = 1000. ### Performance of the Channel Gain-Based Power Allocation Algorithm Based on Partitioning Strategy

As observed in Figure 8, under this power allocation scheme, a small portion of base stations receive the majority of power due to their favorable channel conditions, resulting in significant rates for their served users. However, the remaining base stations transmit information with extremely low power, leading to lower user rates. According to statistics, under a 100-MHz bandwidth, the coverage rate for 50 Mbps is only 34.95%. For ease of observation, Figure 9 takes a single partition as an example and shows the CDF curves of user rates within a partition and for all users. Table 6 compares the performance of three different power control methods. The results in the table show that without power control, the maximum terrestrial network sum rate can be achieved, approximately 9.2447 kbps/Hz.