# Overcoming Limitations of LoRa Physical Layer in Image Transmission
## 5 Results
### Packet Loss in LoRa Transmission  
Table 3 shows a series of characteristics that define the success of image transmission over the LoRa physical layer. With this set of experiments, the \(SF\) was varied from 7 to 12, and communication ranges between 1 and 7 km were tested. In this table, we record the number of hexadecimal packets received, the packet loss ratio, and the time elapsed for data transfer (calculated using additional code in the receiver node) for each \(SF\) and distance setting.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} \(SF\) \\ **Setting** \\ \end{tabular} } & **Distance** & **Received** & \begin{tabular}{c} **Number of** \\ **(km)** \\ \end{tabular} & \begin{tabular}{c} **Number of** \\ **Transmitted** \\ **Packets** \\ \end{tabular} & \
\begin{tabular}{c} **Packet Loss** \\ **Ratio** \\ \end{tabular} &
\begin{tabular}{c} **Elapsed Time** \\ **(Average)** \\ \end{tabular} \\ \hline
7 & 1 & Y & 314 & 314 & 0 P (0\%) & 1 min + 7 s \\
7 & 2 & Y & 315 & 315 & 0 P (0\%) & 1 min + 7 s \\
7 &  
Remarkably, we observed no packet loss between 1 and 4 km, when \(SF\) = 7 (see Table 3 above) where time elapsed during data transfer was less than 2 min. We also observed that 4.82% of the packets were lost when the image was transferred over a 5 km range. All packets were lost when transferring at ranges of 6 km and above. Similarly, no packet loss was observed at distances shorter than 4 km when \(SF\) = 8, 9 and 10. The communication range without packet loss increased to 5 km when \(SF\) = 11 and 6 km when \(SF\) = 12. With the latter \(SF\), a packet loss of 2.82% was observed (see Table 3 above). Most important notice that an \(SF\) of 7 reduces the time elapsed during transfer, and \(SF\) 12 is preferable for long distance transmission. At the end 12 images out of 21 were received successfully (see Table 4) and most remarkable results that SF7, SF8, and SF9 were very close, although the measurements were in different distances and this is clearly shown in Figure 10.  
Visual inspection of the images before and after transfer over the LoRa network (see Table 5) indicate the success of the new image encryption scheme, although some of the received images were affected by noise. By splitting this 'high bit rate data' into packets, we are able to overcome the LoRa bandwidth limitation.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Total** & **Y** & **N** \\ \hline
21 & 12 & 9 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Summary of the numbers of successfully and unsuccessfully received images.  
Figure 10: Correlation between \(SF\) and packet loss ratio.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Original** & **Received** & **Original** & **Received** \\ \hline
**D = 1 km, \(SF\) = 7** & **D = 2 km, \(SF\) = 7** & **D = 4 km, \(SF\) = 7** \\ \hline
**D = 4 km, \(SF\) = 8** & **D = 4 km, \(SF\) = 9** \\ \hline \hline \end{tabular}
\end{table}
Table 5: Visual comparison between original and transferred images for each \(SF\) setting used in testing.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Original** & **Received** & **Original** & **Received** \\ \hline
**D = 4 km, \(SF=10\) & D = 4 km, \(SF=11\) & D = 5 km, \(SF=11\) \\ \hline
**D = 5 km, \(SF=12\)** & D = 6 km, \(SF=12\) & D = 6 km, \(SF=12\) \\ \hline \hline \end{tabular}
\end{table}
Table 5: _Cont._