# Optimization for an Indoor 6G Simultaneous Wireless Information and Power Transfer System
## 4 Numerical Results
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & _BER_ & \
\begin{tabular}{c} **Harvesting** \\ **Power Ratio** \\ \end{tabular} &
\begin{tabular}{c} **Harvesting Power Ratio** \\ **Improvement** \\ \end{tabular} & \(\alpha\) \\ \hline Rx1 & O & \(5.00\times 10^{-8}\) & & 0.5 \\ \hline Rx2 & & \(4.88\times 10^{-7}\) & & \\ \hline Rx1 (\(\alpha\)) & O & \(5.00\times 10^{-8}\) & 2.6\% & 0.53 \\ \hline Rx2 (\(\alpha\)) & & \(5.02\times 10^{-7}\) & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Harvesting power ratios for Rx1 (7, 2, 1) and Rx2 (3, 6, 1). Figure 6: Harvesting power of the WPT node with and without power\(-\)splitting adjustment (Scenario 1). Simulations showed that the harvesting power was convergent at about 250 iterations. The harvesting power for the SWIPT node was increased by adjusting the power-splitting ratio. Table 3 shows the harvesting power ratio for the first group Rx1 (5, 8, 1) and Rx2 (2, 2, 1). It can be seen that the harvesting power ratio was increased about 7.87% due to \(\alpha\) adjustment. As long as the minimum power harvesting requirement for Rx2 is met, the harvesting power can be efficiently allocated to Rx1 through \(\alpha\) adjustment. Consequently, the total power for Rx1 plus Rx2 can be obtained. Table 4 shows the harvesting power for the second group of Rx1 (6, 6, 1 m) and Rx2 (2, 5, 1 m). In this case, the harvesting power ratio for Rx1 was increased due to the large power-splitting factor (\(\alpha\) = 0.95). Again, the harvesting power ratio for Rx2 without (0.5\(\alpha\)) and with (0.95\(\alpha\)) power-splitting adjustment was the same. Eventually, the total harvesting power for Rx1 plus Rx2 increased by 86.7% compared with that of \(\alpha\) = 0.5. Figure 9 shows the radiation pattern from the transmitter to Rx1 (6, 6, 1 m) and Rx2 (2, 5, 1 m). The diagrams illustrate that both beams point correctly towards Rx1 (6, 6, 1 m) and Rx2 (2, 5, 1 m). However, the gain for the case with power-splitting adjustment is slightly greater than that without power-splitting adjustment. Figure 8: Harvesting power of the WPT node with and without power—splitting adjustment (Scenario 2). Figure 7: Harvesting power of the SWIPT node with and without power—splitting adjustment (Scenario 2). In the third scenario, the distance of Rx1 and Rx2 from Tx was less than 1 m. Figures 10 and 11 show the SWIPT and WPT harvesting power, respectively, with and without \(\alpha\) adjustment, where \(\alpha\) = 0.5 (the power allocation ratio) is preset for the case without optimization adjustment. Convergence was reached after 350 iterations. Table 5 shows the harvesting power ratio for the first group Rx1 (9, 8, 1 m) and Rx2 (3, 1, 1 m). It can seen that the harvesting power ratio was increased by about 0.13% due to \(\alpha\) adjustment. As long as the minimum power harvesting requirement for Rx2 is achieved, the excess power can \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & _BER_ & \
\begin{tabular}{c} **Harvesting** \\ **Power Ratio** \\ \end{tabular} &
\begin{tabular}{c} **Harvesting Power Ratio** \\ **Improvement** \\ \end{tabular} & \(\alpha\) \\ \hline Rx1 & O & \(8.53\times 10^{-8}\) & & 0.5 \\ \hline Rx2 & & \(1.59\times 10^{-7}\) & & \\ \hline Rx1 (\(\alpha\)) & O & \(1.13\times 10^{-7}\) & & 0.59 \\ \hline Rx2 (\(\alpha\)) & & \(1.50\times 10^{-7}\) & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Harvesting power ratios for Rx1 (5, 8, 1) and Rx2 (2, 2, 1). Figure 9: Radiation patterns for the transmitter to Rx1 (6, 6, 1 m) and Rx2 (2, 5, 1 m) (**a**) without power\(-\)splitting adjustment and (**b**) with power-splitting adjustment. Table 6 shows the harvesting power ratio for the second group, Rx1 (7, 8, 1 m) and Rx2 (2, 7, 1 m). It can be seen that the harvesting power ratio was increased by about 0.52% via \(\alpha\) adjustment. Note that the power collected by Rx1 before (\(\alpha\) = 0.5) and after (\(\alpha\) = 0.55) the adjustment was similar.