# AoI Analysis of Satellite-UAV Synergy Real-Time Remote Sensing System
## 4 Numerical Results  
This section analyzes and compares the AAoIPW-related performance in the SAGIN remote sensing system. The system consists of a low earth orbit (LEO) satellite and a UAV as information sources and ground users (GUs) as information receivers. These GUs continuously receive status information from both sources and perform multiscale information fusion. Considering the limited spectrum resources in real SAGIN, the FFR strategy is  
Figure 6: The average AoI under three queuing disciplines. employed in the system. Under the FFR strategy, GUs adopt successive interference cancellation (SIC) to first decode the information from the UAV and then decode the information from the satellite. Since satellite and UAV nodes are sensitive to the transmission energy consumption and system bandwidth resources in the SAGIN remote sensing system, here, we mainly focus on the impact of transmission power and bandwidth. The main simulation parameters of SAT are presented in Table 4. According to the technical reports of the 3 rd Generation Partnership Project (3 GPP) [45], for SAT, set orbital height \(H_{s}\) = 600 km, 3 dB beamwidth \(\theta_{s,3\,\mathrm{dB}}\) = 8.83\({}^{\circ}\), beam diameter \(r_{u}\) = 45 km, and maximum gain \(G_{s,\mathrm{max}}\) = 24 dBi. For UAV, set altitude \(H_{u}\) = 5 km, and half beamwidth \(\phi_{u}\) = 80\({}^{\circ}\). The downlink carrier frequency in system \(f_{c}=2\) GHz. Moreover, the receiver noise temperature for the GUs is set as 24 dBK [46]. Without loss of generality, the bandwidths allocated to SAT and UAV are equal under FDMA. Additionally, \(\overline{M_{1}}=\overline{M_{2}}=2*10^{6}\). A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FF}}\) and A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FD}}\), respectively, denote the A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}\) under FFR and FDMA. Unless stated otherwise, in the simulation environment, the magnitudes of the variables are set to standard units. Figure 7 shows the performance of A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FD}}\) and A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FF}}\) versus \(p_{u}\), for \(p_{s}\in\{40,43,45\}\), \(\mathrm{d}\)bm, \(p_{u}\in\{0,2,4,\ldots,28,30\}\)\(\mathrm{d}\)bm, and \(B\) = 2 MHz. From the red line in the figure, the A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FF}}\) initially experiences a decline followed by an incline as \(p_{u}\) increases. The inclining trend is due to the augmented interference with the SAT-GU link resulting from the increased \(p_{u}\) of the UAV at a lower altitude. Consequently, the SAT's status information update rate \(\lambda_{1}\) decreases, leading to a deterioration in A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FF}}\). It can be further noted that increasing \(p_{s}\) decreases minimum A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FF}}\) and the \(p_{u}\) value corresponding to minimum A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FF}}\) increases. This is owing to the fact that increasing \(p_{s}\) improves the update rate \(\lambda_{1}\) and mitigates interference from UAV. Nevertheless, due to stringent power constraints for individual beams of the satellite, enhancing A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FF}}\) performance through increasing \(p_{s}\) is a cost-ineffective approach. Moreover, under the FDMA strategy, the UAV signals do not interfere with the SAT signals, resulting in a limited impact of \(p_{u}\) on A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FD}}\). Furthermore, as \(p_{u}\) increases, the relative performance advantage of A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FF}}\) over A\(\mathrm{A}\)o\(\mathrm{I}_{\mathrm{PW}}^{\mathrm{FD}}\) diminishes progressively. The above analysis can provide a reference for the design of power control algorithms that dynamically adjust the transmit power of satellites and UAVs in SAGIN based on real-time channel conditions to optimize AoI.