# Unveiling LoRa's Oceanic Reach: Assessing the Coverage of the Azores LoRaWAN Network from an Island
## 4 Results and Discussion
Subsets were created considering the range of distances to the gateway and the density of points within a 3 km radius, i.e., for different distances (from close to far), the locations with the most samples were chosen to form a subset. The application of the criteria mentioned above gave rise to the subsets that can be seen in Figure 10.  
The subsets are described in Table 2.  
Figure 10: Data subsets. Figure 6.0 SNR as a function of RSSI. Figure 11 plots the average RSSI value of each subset against its average distance to the gateway. At first glance, there are unusual RSSI values from the 0 to 40 Km distances, specifically regarding the orange, pink, and yellow subsets. However, these subsets contain a mix of high and low values. Also, there are subsets within the areas in question with normal/expected RSSI values. An analysis of the line-of-sight (LOS) between the sender and the receiver reveals the possible cause for the disparity of values within subsets. Figures 12-14 illustrate the LOS analysis conducted for the orange, pink, and yellow subsets, respectively. The occurrence of LOS obstruction by the terrain is verified for the orange and pink subsets. Besides the losses associated with free space path loss, which are expected, events such as LOS obstruction cause attenuations due to terrain shielding. In a simulated environment, the attenuations are 32 dB for the orange subset and 11 dB for the pink subset. The obstruction of the LOS explains the unexpected RSSI values for these two subsets. Still referring to the LOS analysis, although the terrain does not block the LOS, the yellow subgroup invades the Fresnel zone. The Fresnel zone is an imaginary zone with a relative radius between the distance from the transmitter to the receiver and the transmitting frequency. The Fresnel zone assumes an elliptical shape along the LOS \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Subset** & **Point Count** & \begin{tabular}{c} **Center Coordinates** \\ **(Latitude, Longitude)** \\ \end{tabular} & \begin{tabular}{c} **Mean Distance to** \\ **Gw (km)** \\ \end{tabular} & \
\begin{tabular}{c} **Mean RSSI (dBm)** \\ \end{tabular} &
\begin{tabular}{c} **Mean SNR (dB)** \\ \end{tabular} \\ \hline Red & 101 & 39.620395, \(-\)26.90367 & 106.290 & \(-\)120.06 & \(-\)7.37 \\ \hline Green & 715 & 38.204023, \(-\)27.701205 & 67.26 & \(-\)120.06 & 0.21 \\ \hline Blue & 1654 & 38.834382, \(-\)27.907589 & 52.08 & \(-\)113.34 & 5.25 \\ \hline Yellow & 206 & 39.044477, \(-\)27.548558 & 41.82 & \(-\)117.99 & \(-\)1.63 \\ \hline Orange & 657 & 38.800204, \(-\)27.459609 & 14.99 & \(-\)115.88 & 1.190 \\ \hline Purple & 475 & 38.458097, \(-\)27.347993 & 30.21 & \(-\)115.42 & 1.62 \\ \hline Pink & 307 & 38.910218, \(-\)27.337965 & 20.39 & \(-\)118.37 & \(-\)1.05 \\ \hline Brown & 433 & 38.633978, \(-\)27.274188 & 10.63 & \(-\)108.56 & 6.17 \\ \hline Gray & 10 & 38.165462, \(-\)28.571266 & 125.62 & \(-\)120.60 & \(-\)14.16 \\ \hline Black & 208 & 38.782374, \(-\)28.430655 & 95.75 & \(-\)119.71 & \(-\)4.780 \\ \hline White & 10 & 39.257761, \(-\)28.666294 & 130.69 & \(-\)121.40 & \(-\)13.40 \\ \hline Cyan & 8 & 38.788358, \(-\)28.796452 & 128.28 & \(-\)120.63 & \(-\)12.80 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Information about the subsets. Figure 11: Average RSSI value of the subsets as a function of distance from the GW. between the transmitter and receiver. As a rule, this zone should always be unobstructed; however, this is not always the case, so it is said that after 40% blockage of the site, there will be significant losses in the signal. In the case of subset yellow, there is a blockage greater than 40%, which, in a simulated environment, manifests itself in a signal attenuation of an order of 4 dB. For the remaining Red, Green, Blue, Purple, Brown, Gray, Black, White, and Cyan subsets, all present LOS and Fresnel zones without obstacles. The RSSI values of these subsets are considered adequate relative to their distance from the GW.