## 2 Materials and Methods
### Performance Evaluation by Simulation of the UAV Network
#### 2.3.2 Simulation of the UAV Network  
When a pandemic (for instance, due to the new COVID-19) occurs, a zone is very likely to be rapidly allocated away from the cities in an isolated area, where ill people are moved. This area, being away from civilization, it is very likely not to have access to any communication systems. In this area, buildings are located with a safe distance between them. In this scenario, each building can be a house where patients are isolated, a warehouse with food or drugs, a laboratory where medical tests are performed for patients, a location where doctors are working (isolated from patients), etc. Data packages (medical images, tests, results, prescriptions from doctors, etc.) must be sent between these buildings. The communication between these buildings can be assured by UAVs organized in a triangular-shaped network. The drone network is kept active until the quarantined area is no longer needed. Of course, when/if direct communication becomes available, the drones could be stopped. The network could be adapted for other purposes such as parcel delivery. To validate the proposed method, simulations were performed using the UAV network maps as collections of hexagons. Most of the simulations were performed using the Java-based simulator ONE [54; 55]. The routing protocols used for the simulation within the ONE simulator are Epidemic, Spray and Wait, PRoPHET, MaxProp, and MaxDelivery. Based on the characteristics in Table 2, the performance of each of the six considered algorithms was influenced more or less by the parameters in Table 4. For instance, it is clear that the number of fixed transfer points had a greater effect on the algorithms with a limited number of hops, or the average cruise speed and data transmission speed had a greater effect on the algorithms with a short TTL (time to leave for files). \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Triangular-Shaped Flight Mission** \\ \hline Number of UAVs for cruising & 48 \\ Number of fixed transfer points & 65 \\ Number of charging/changing battery points & 24 \\ Average cruise speed of a UAV & 47.37 km/h (13.16 m/s) \\ Flight height of UAVs & 30 m \\ Operating time of the UAV in one day & 11 h \\ Data transmission speed & 2 Mbps \\ UAV’s buffer space & 2 Gb \\ Message size & 500 kb–1 Mb \\ Message time to live & 10 h \\ Source and destination of messages & any UAV \\ No. of route simulations & 1000 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Simulation parameters. Figure 11: (**a**) DJI Mavic 2 Pro quadcopter with a communication drone-station module; (**b**) 3D model of the communication module case within the 3D printer software simulation. All the simulations were performed on an ASUS ROG GL752 VW-T4015D laptop with an Intel(r) Core(tm) i7-6700 HQ 2.60 GHz processor and 8 GB of RAM. The main steps within the ONE simulator were as follows:  
* Defining the map (Figure 12) in wkt file format, in which the coordinates of all the points that establish the route of each UAV on the map have been defined. * Implementing the algorithms that define the mobility of UAVs:
* establishing the initial positions of UAVs and the recharge/swapping points;
* associating each UAV with a recharger/swapping point;
* establishing stationary points for data transfer;
* defining the route of each UAV;
* Establishing the simulation parameters as shown in Table 4. The time parameters (the travel autonomy time, the hovering time for the transfer points, and the parking time) in the charging points or swapping points were established based on the experimental flight tests of the DJI Mavic 2 Pro UAV. The proposed Dijkstra time-dependent variant was implemented in Visual C++ 2017 programming language. The application has about 1100 lines of C++ source code. The C++ application was executed for each of the two considered situations: triangles with battery charging, and triangles with battery changing. For each case, the same 1000 route simulations from ONE were executed.