## 5 Conclusions  
In this study, a new angular isolation method was proposed to enable the coexistence of the FSS ESs and BSs. This method solves the influence of the ES antenna elevation angle on the protection method. Further, the methods of determining the area and power control scheme within the restricted area were verified. The numerical results reveal that, when combining distance protection and angular protection, both the exclusion and restriction zones can be decreased at the expense of the beam sweep angle of the BSs using angular protection. In addition, a higher beam shut-off range (i.e., sacrificing more beam sweep angles) leads to smaller exclusion and restriction zones. A tradeoff exists between the coexistence of beam sweep angles of BSs. As the number of antenna elements increases, the angular protection becomes more efficient. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Region Type**} & \multirow{2}{*}{\begin{tabular}{c} **Beam** \\ **Shut-Off** \\ **Range** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **No. of** \\ **Deployable** \\ **Base Stations** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Restriction** \\ **Interference** \\ **Threshold** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **No. of** \\ **Rateriction** \\ **Ratetions** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **\% of Deployed** \\ **Base Stations** \\ **Requiring Tx** \\ **Power Control** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Mean Tx Power** \\ **Reduction in** \\ **Restriction Zone** \\ \end{tabular} } \\ \hline \multirow{4}{*}{\begin{tabular}{c} **RMa** \\ (100 km \(\times\) 100 km) \\ \end{tabular} } & No Protection & 3194 & \(-\)47.24 dB & 886 & 27.74\% & 17.51 dB \\  & 45\({}^{\circ}\) & 3331 & \(-\)47.43 dB & 676 & 20.29\% & 14.49 dB \\  & 90\({}^{\circ}\) & 3345 & \(-\)47.44 dB & 493 & 14.74\% & 13.09 dB \\  & 180\({}^{\circ}\) & 3352 & \(-\)47.45 dB & 351 & 10.47\% & 12.26 dB \\  & 270\({}^{\circ}\) & 3358 & \(-\)47.46 dB & 259 & 7.71\% & 10.15 dB \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} **UMa** \\ (30 km \(\times\) 30 km) \\ \end{tabular} } & No Protection & 3300 & \(-\)47.39 dB & 1749 & 53.00\% & 21.07 dB \\  & 45\({}^{\circ}\) & 3622 & \(-\)47.79 dB & 1623 & 44.81\% & 19.29 dB \\  & 90\({}^{\circ}\) & 3666 & \(-\)47.84 dB & 1159 & 31.61\% & 18.41 dB \\  & 180\({}^{\circ}\) & 3688 & \(-\)47.87 dB & 809 & 21.94\% & 18.39 dB \\  & 270\({}^{\circ}\) & 3697 & \(-\)47.88 dB & 623 & 16.85\% & 14.92 dB \\ \hline \multirow{4}{*}{
\begin{tabular}{c} **UMi** \\ (30 km \(\times\) 30 km) \\ \end{tabular} } & No Protection & 20.855 & \(-\)55.39 dB & 13,010 & 62.38\% & 28.35 dB \\  & 45\({}^{\circ}\) & 22,492 & \(-\)55.72 dB & 12,201 & 54.24\% & 25.55 dB \\ \cline{1-1}  & 90\({}^{\circ}\) & 22,646 & \(-\)55.75 dB & 9683 & 42.76\% & 24.08 dB \\ \cline{1-1}  & 180\({}^{\circ}\) & 22,692 & \(-\)55.76 dB & 6223 & 27.42\% & 23.89 dB \\ \cline{1-1}  & 270\({}^{\circ}\) & 22,746 & \(-\)55.77 dB & 4886 & 21.48\% & 21.50 dB \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Mean transmission (Tx) power reduction in the restriction zone for RMa, UMa, and UMi using a 16 \(\times\) 16 antenna array. Moreover, the advantage of beamforming the antenna arrays is more significant in UMa and UMi than in RMa. In UMa and UMi, only minor improvements of the exclusion zone can be achieved when using 90\({}^{\circ}\), 180\({}^{\circ}\) and 270\({}^{\circ}\) beam shut-off ranges compared with using a 45\({}^{\circ}\) beam shut-off range. In contrast to the exclusion zone, the size of the restriction zone significantly decreases as the beam shut-off range increases to 90\({}^{\circ}\), 180\({}^{\circ}\) and 270\({}^{\circ}\). As for UMa and UMi, angular protection is primarily efficient in terms of the number of deployable BSs and the power control efficiency when using an antenna array with a high number of elements.