# Underwater Communications for Video Surveillance Systems at 2.4 GHz
## 4 Results of Maximum Distances
### Measurements for CCK at Different Temperatures  
Figure 10 shows the values of maximum distance for the CCK coding scheme which has two values of data transfer rate (\(5.5\) Mbps and \(11\) Mbps) at \(16\), \(18\), \(20\), \(22\) and \(26\ ^{\circ}\)C. The first point to note is that the largest distances are obtained in all cases for the temperatures of \(20\ ^{\circ}\)C and \(22\ ^{\circ}\)C. The best results are obtained at a frequency of \(2412\) MHz and \(22\ ^{\circ}\)C. Both data transfer rates achieve the same distance. Other values that can be considered good enough at \(20\ ^{\circ}\)C are \(5.5\) Mbps for \(2427\) MHz  
\begin{table}
\begin{tabular}{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
2 Mbps at \(16\ ^{\circ}\)C & 1.7 & 1.7 & 0.7 & 0.8 & 2.2 & 0.5 & 1.3 & 1.2 & 1.375 & - & - \\
2 Mbps at \(18\ ^{\circ}\)C & 1.2 & 0.2 & 0.8 & 1.2 & 0.2 & 0.5 & 0.7 & 0.8 & 1.375 & - & - \\
2 Mbps at \(20\ ^{\circ}\)C & 3.3 & 2.3 & 2.7 & 3.8 & 1.8 & 2 & 0.8 & 1.2 & 0.375 & 0.1 & 0.15 \\
2 Mbps at \(22\ ^{\circ}\)C & 4.3 & 3.8 & 1.2 & 0.8 & 2.2 & 4.5 & 3.7 & 3.8 & 3.125 & - & - \\
2 Mbps at \(26\ ^{\circ}\)C & 4.7 & 4.2 & 3.8 & 4.2 & 2.8 & 3.5 & 2.3 & 2.2 & - & - & - \\ \hline \hline \end{tabular}
\end{table}
Table 6: Calculation of residuals for QPSK.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Origin of** & **Sum of** & **Degree of** & **Average** & **F** & **Probability** & **Critical Value for F** \\ \hline Temperatures & 403.3 & 4 & 100.825 & 6.71606994 & 0.00031136 & 2.60597495 \\ Frequency & 2384.72727 & 10 & 238.472727 & 15.8849444 & 5.3453 \(\times 10^{-11}\) & 2.07724805 \\ Error & 600.5 & 40 & 15.0125 & & & & \\ Total & 3388.52727 & 54 & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 7: ANOVA for QPSK.  
Figure 9: Maximum distances for QPSK.  
and 5.5 Mbps and 11 Mbps at 22 \({}^{\circ}\)C for 2437 MHz. The remaining results show lower distances between antennae.  
Tables 8 and 9 show the calculation of residuals, for CCK modulation at 5.5 Mbps and 11 Mbps. We can observe that all values match with the hypothesis H1 where all residuals are different to 0. So, we are sure that these parameters cause some effect over maximum distance.  
take the alternative hypothesis. This means that the maximum distance for each frequency depends on the temperature.  
On the other hand, for columns, the value of the probability (6.1007 \(\times\) 10\({}^{-24}\)) is lower than defined for \(\alpha\). Therefore, the variation of the results is also significant. Moreover, the value of F (28.8675745) is higher than the critical value of F (1.93756679). We can discard the null hypotheses for taking the alternative which means that the maximum distance between antennae using CCK modulation depends on the working frequency.  
These results show that there are significant differences between groups which are due to the increase in the working frequency and temperature and not due to a random effect. With this, we have checked that the maximum distance for CCK modulation are statistically different and they depend significantly on the working frequency and temperature. Finally, we have checked that the maximum distance is not affected by changes in data transfer rates.