# Tracking and Monitoring System Based on LoRa Technology for Lightweight Boats
## 6 Results  
In this section, the outcomes obtained in our validation tests are presented. As stated above, we have tracked a series of Optimist Class training sessions by placing a sensing and communication module on-board a number of sailboats (see Figure 5). Thus, firstly, a coverage study within the port area was made in order to analyze the impact of big buildings and other heavy machinery, e.g., cranes. Figures 10 and 11 present the RSSI level (received in the base station), obtained in different monitored training sessions with the two adopted LoRa configurations. Concretely, Figure 10 corresponds to the results attained with the following LoRa configuration: SF = 12, CR = 4/5, and BW = 125 kHz, while Figure 11 shows the measured RSSI level corresponding to this configuration: SF = 7, CR = 4/5, and BW = 125 kHz. Observe that both configurations permit covering the whole port area with good levels of coverage. However, a non-coverage zone was detected in both experiments (marked in red). This small area was surrounded by tall buildings that blocked the transmissions from the sailboats to the base station (small dots in the figures). Comparing both LoRa configurations, observe that, by using SF7, a greater data transmission frequency can be obtained (more sampling points in Figure 10 in comparison with Figure 11). This behavior is due to the data-rate attained with SF7 is greater than that of SF12, which permitted transmitting more tracking packets during the experiment. Regarding the robustness of the transmission links, Table 2 presents the PDR attained in both tests. In the studied area, we did not notice any packet loss with the exception of the non-coverage area mentioned above. Observe that we have considered both areas for calculating the PDR. The PDR level attained with SF7 is lower than that of SF12 because, due to the greater data-rate of SF7, in the non-coverage area more packets were sent (and not received) with this configuration. However, although not presented here, the PDR attained without considering the non-coverage area was almost 100% in both scenarios. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**SF (Spreading Factor)/DR (Data-Rate)** & **Employed Payload (B)** & **Data-Date (bps)** & **ToA (ms)** \\ \hline
**12/0** & **52** & **146.1** & **2465.7** \\
11/1 & 52 & 261.4 & 1314.8 \\
10/2 & 52 & 584.2 & 616.4 \\
9/3 & 52 & 1359.2 & 328.7 \\
8/4 & 52 & 2738.1 & 184.8 \\
7/**5** & **52** & **4844.7** & **102.6** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: LoRa (Long Range) transmissions’ data-rate and ToA (Time-on-air) for the employed payload and BW (Bandwidth) of 125 kHz. In order to validate the afore-discussed results, a regular Optimist training session was tracked. In this case, five sailboats (Figure 5) were simultaneously tracked during a period of 1 h in order to obtain their gathered data which were visualized by means of the monitoring dashboard (Figure 8). Thereby, Figure 12 presents the sampling points and the corresponding RSSI measured by the base station. Please note that, due to the good results attained in the previous experiment, a LoRa's SF7 was employed in this test and the sailboats sent their monitoring data every 5 min. With this experiment, we aim to show the validity of the proposed infrastructure for tracking activities inside the port by means of the LoRa technology. During a real race, the sampling period would be shorter as that employed in the previous experiment. Regarding the most proper LoRa configuration, as explained in previous sections, SF12 provides a superior robustness than SF7. For that reason, one could decide to always make use of the most reliable configuration (SF = 12). However, there is an important trade-off that should be taken into account; \begin{table}
\begin{tabular}{c c c} \hline \hline  & **SF7** & **SF12** \\ \hline Packets Received & 2900 & 275 \\ Packets Transmitted & 4046 & 283 \\ PDR & 71.67\% & 97.17\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Packet Delivery Ratio (PDR) in the port area.