## 3 Materials and Methods
### Design and Development of the LoRa Evaluation Experiments
#### 3.3.2 Variable Distance Experiments  
In Experiment 4, only one LoRa device was used, and the distance between the gateway and the device ranged between 255 and 1245 m. The device was located in a vehicle, and 1100 m were driven  
Figure 4: Location of the gateway and long-range (LoRa) devices from Experiment 3. Figure 3: Distances and device locations in the three initial experiments (with fixed distances). on a road at an approximate speed of 20 km/h (not exceeding 25 km/h to avoid issues due to Doppler effect [25]). This experiment used the same 44 LoRa settings from Experiment 3. The route followed by the vehicle in Experiment 4 is presented in Figure 5 (red line). The figure also shows the distances between the gateway and the starting and ending points of the route (yellow lines). For each run of this experiment, the vehicle was located at the starting point and began its route to the arrival point at a maximum speed of 20 km/h; the drive took approximately 3 min and 30 s. One packet was sent every 10 s. Once the vehicle finished the route, packet sending was stopped and new parameters were configured for the next run. Experiment 5 used the same route as Experiment 4. Three vehicles were used, and only 17 settings (the ones yielding the best performance in Experiment 4 in terms of successfully received packets and range) were used. One packet was sent every 10 s. Each vehicle started from the starting point every 15 s, so all three devices were transmitting 30 s into the experiment run. All vehicles were driven at a maximum speed of 20 km/h. Once all vehicles finished the route, packet sending was stopped, and the devices and vehicles were configured for the next run. In the experiments it was considered important to have an environment as controlled as possible, so that the results obtained are affected as little as possible by external factors. For this reason, vehicle speed was limited to 20 km/h, to minimize Doppler effect impact. In addition, worth considering is the context of the service, since the transit service in intermediate cities of developing countries shares the road with other types of vehicles, which restricts vehicle speed to a range of 10 to 30 km/h for the most part of the route. In a few sections of the route, and depending upon traffic conditions, vehicles may reach 60 km/h, the city speed limit in Colombia. The packet rate for Experiments 4 and 5 was determined considering the average and maximum vehicle speed. The distance traveled by a vehicle at the average speed (25 km/h) in 10 s is about 70 m, and the distance traveled at the speed limit (60 km/h) in 10 s is about 166 m. A maximum vehicle location error between 70 and 166 m was considered adequate, because the accuracy in this type of service is not critical for the user. In selecting the appropriate packet rate, it was determined that packets should be sent every three or more seconds, since the microcontroller card (ESP32 LoRa Heltec) requires this much time to read the data from the Global Positioning System (GPS)module and prepare  
Figure 5: Vehicle route in Experiment 4 and distances to the gateway. the data packet. In addition, for settings with a high SF the propagation time is higher, and packet collisions may occur at the gateway if the packet rate is too high. Experiment 6 was designed to verify the impact on communications that may occur when vehicles travel at speeds between 20 and 60 km/h. The route followed by the vehicle in Experiment 6 is presented in Figure 6 (red arrows). The figure also shows the distances between the gateway and the starting and ending points of the route (yellow lines). Three vehicles were used, and 17 settings (the ones used in Experiment 5) were used. One packet was sent every 7 s (the frequency of sending packets was increased, considering that the speed of the vehicle was higher). Vehicles departed from the starting point every 15 s. All vehicles were driven at a maximum speed of 60 km/h.