# Underwater Communications for Video Surveillance Systems at 2.4 GHz
## 4 Results of Maximum Distances
### Measurements for OFDM at Different Temperatures  
Due to the large number of parameters to be represented, the OFDM results are grouped by temperature. Figure 11 shows the results of the maximum distances between antennae for all data transfer rates referred in OFDM modulation at 16 \({}^{\circ}\)C. As we can see, the maximum distance (22 cm) are registered for 2427 MHz and 2432 MHz for all data transfer rates. The lowest distances are registered at 2452 MHz. Figure 12 shows the results of the maximum distances between antennae, for all data transfer rates in OFDM modulation at 18 \({}^{\circ}\)C. In this case, the maximum distance is registered for 12 Mbps and 18 Mbps at 2437 MHz. Again, the worst results (16-17 cm) are registered for highest frequency at all data transfer rates. Figure 13 shows the results of the maximum distance registered between both antennae depending on the working frequency for all data transfer rates considered in OFDM modulation at 20 \({}^{\circ}\)C. As Figure 12 shows the best results (25 cm) are registered for the lowest frequency (2412 MHz)  
Figure 11: Maximum distances for OFDM at 16 \({}^{\circ}\)C.  
Figure 12: Maximum distances for OFDM at 18 \({}^{\circ}\)C.  
for all data transfer rates and 12 MHz at 2427 MHz (26 cm). From 2437 MHz the maximum distance achieved is 19 cm. Figure 14 shows the results of the maximum distance registered between both antennae depending on the as a function of working frequency for all data transfer rates considered in OFDM modulation at 22 \({}^{\circ}\)C. In this case, the maximum distance is registered for the lowest frequency (2412 MHz). In addition, it is important to highlight that the minimum distance for this temperature is 22 cm. However, we cannot use OFDM for temperatures higher than 22 \({}^{\circ}\)C.  
Finally, Tables 11-19 show the calculation of residuals, for OFDM modulation at all data transfer rates that the IEEE 802.11 standard specifies. We can observe that all values match with the hypothesis H1 where all residuals differ from 0, so we are sure that these parameters cause some effect over maximum distance. Figure 14: Maximum distances for OFDM at 22 \({}^{\circ}\)C.  
Figure 13: Maximum distances for OFDM at 20 \({}^{\circ}\)C. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Data Transfer** & **2412** & **2417** & **2422** & **2427** & **2432** & **2437** & **2442** & **2447** & **2452** & **2457** & **2462** \\
**Rates** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** \\ \hline
6 Mbps at 16 \({}^{\circ}\)C & 2.875 & 2.625 & 1 & 0.01 & 1.5 & 0.625 & 1.875 & 1.625 & 1.25 & - & - \\
6 Mbps at 18 \({}^{\circ}\)C & 2.375 & 1.125 & 1.5 & 2 & 0.5 & 0.375 & 0.125 & 0.125 & 1.25 & - & - \\
6 Mbps at 20 \({}^{\circ}\)C & 2.125 & 0.875 & 2 & 2 & 2.5 & 3.125 & 1.375 & 1.625 & 0.25 & 0.03 & 0.22 \\
6 Mbps at 22 \({}^{\circ}\)C & 3.125 & 2.875 & 0.5 & 0.02 & 1.5 & 3.375 & 3.125 & 3.375 & 2.75 & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Calculation of residuals for OFDM at 6 Mbps. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Data Transfer** & **2412** & **2417** & **2422** & **2427** & **2432** & **2437** & **2442** & **2447** & **2452** & **2457** & **2462** \\
**Rates** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** & **MHz** \\ \hline
22 Mbps at 16 \({}^{\circ}\)C & 3 & 2 & 1 & 0.09 & 0.5 & 2 & 1.5 & 1.25 & 1.5 & - & - \\
22 Mbps at 20 \({}^{\circ}\)C & 2 & 0.5 & 1.5 & 2 & 1.5 & 0.05 & 0.04 & 0.25 & 2.5 & & \\
24 Mbps at 20 \({}^{\circ}\)C & 2 & 1 & 2 & 2 & 0.5 & 2 & 1.5 & 1.75 & 0.5 & 0.1 & 0.2 \\
24 Mbps at 22 \({}^{\circ}\)C & 3 & 1.5 & 0.5 & 0.1 & 0.5 & 4 & 3 & 3.25 & 4.5 & - & \\ \hline \hline \end{tabular}
\end{table} 
Table 16: Calculation of residuals for OFDM at 24 Mbps.