# Satellite-Assisted Disrupted Communications: IoT Case Study
## 3 Methodology  
The section provides an overview of our experimental methodology, including a generic description of the investigated scenarios. We have conducted two sets of experiments to assess the impact of various experimentation parameters, including the number of satellites and the presence of inter-satellite links within LEO constellations, on the mean and range of the RTT as well as the ping loss. These experiments investigated different constellations and topologies in the IoT/smart-city scenarios where sensors transmit pings to various ground stations around the globe. The position of each ground station was specifically defined by their exact geographical longitude and latitude. We highlighted the potential relevance of the aforementioned parameters in the context of networking communications, especially when confronted with disruptive network conditions. In the first scenario, a topology where sensors communicate with ground stations located in the EU and the U.S. was examined. Subsequently, we explored an IoT Case Study (scenario 2) where the data from real sensors located in the Smart Santander testbed [47] and obtained \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Research Area** & **Papers** & **Focus** & **OMNeT++** \\ \hline \multirow{3}{*}{Smart Cities} & [11; 12; 13; 14; 15; 16; 17] & Implementations for VANET, V2X & \\  & [11; 12; 13; 14; 15; 16; 17] & communications \& Integration with other & Yes \\  & & frameworks e.g., SUMO, VEINS & & \\ \hline \multirow{2}{*}{IoT relays} & [18; 19; 20; 21; 22; 23] & UAV/Drone frameworks for WSNs, security, energy consumption & Yes \\ \hline \multirow{3}{*}{Space related} & [24; 25; 26; 27; 28; 29; 30] & Examine protocols and standards impact & \\  & [24; 25; 26; 27; 28; 29; 30] & In the context of satellite communications & Yes \\  & & e.g., routing, CSMA/CA etc. & \\ \hline \multirow{3}{*}{Space related} & [4; 5; 31; 32; 33; 34; 35; 36; 37; 38; 39] & Impact and optimization of space design & \\  & [4; 5; 31; 32; 33; 34; 35; 36; 37; 38; 39] & parameters on throughput, end-to-end & No \\  & & latency etc. & & \\ \hline \multirow{2}{*}{DTN related} & [3; 7; 32; 40; 41; 42; 43; 44; 45; 46] & DTN communication protocols and & \\  & & solutions in dense environments & No \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of literature works. within the Rewire project [48] were imported into OMNeT++. This experiment extended over 24 h, during which different testbeds in the EU and the U.S. received pings, according to the real sensors' timestamps derived from.csv files. The coverage area or footprint of a satellite is illustrated as a circular area on the surface of Earth, indicating the zone within which satellites can communicate with ground stations. The primary variables affecting the footprint are: (i) the elevation angle (\(\epsilon_{0}\)), (ii) the nadir angle (\(\alpha_{0}\)), (iii) the central angle (\(\beta_{0}\)), (iv) the slant range (d)-i.e., the distance from a satellite to a ground station, and (v) the satellite altitude above the surface of the Earth (H), while \(Re=6378\times 10^{3}\) m is the constant distance from a ground station to the Earth's center. In Table 2, the coverage area at different satellite altitudes and elevation angles is calculated by applying the related equations below (where \(\mathrm{r}=\mathrm{H}+R_{e}\)) and utilizing trigonometry as featured in Figure 1:  
\[\epsilon_{0}+\alpha_{0}+\beta_{0}=90^{\circ} \tag{1}\]  
\[d*\mathrm{cos}\epsilon_{0}=r*\mathrm{sin}\beta_{0} \tag{2}\]  
\[d*\mathrm{cos}\alpha_{0}=R_{e}*\mathrm{sin}\beta_{0} \tag{3}\]  
Applying the cosines law, on the largest triangle we obtain:  
\[r^{2}=R_{e}^{2}+d^{2}-2*R_{e}*d*\mathrm{cos}(90+\epsilon_{0}) \tag{4}\]  
Observing the large sub-triangle, we calculate the \(sin\alpha_{0}\) which depends on the elevation angle according to Equation (5). Consequently, the maximum coverage can be achieved for elevation angle \(\epsilon_{0}=0\rightarrow\mathrm{cos}\epsilon_{0}=1\).