# Underwater Communications for Video Surveillance Systems at 2.4 GHz
## 3 Scenario and Test Bench
### Test Bench and Measurement Process  
To perform the test bench and monitor the network activity, both computers run a MS-DOS shell. This tool offers us several network commands which allow us to see the network activity. In this case, we have used the ping command that provides the RTT for each packet. These tests analyze the values of RTT between both devices depending on several parameters. The parameters under study are the distance, modulation, working frequency and temperature. In addition, the ping command and the RTT will indicate us if the connection between devices is possible.  
The average values of RTT are calculated considering only the packets that were successfully received. If a packet was not received or it was wrongly received, the value of RTT assigned is 3000 ms. This value was not taken into account in the RTT average calculation. It is very common the use of this value to define wrong/not received packets [32].  
Tests were performed in the frequency range between 2412 MHz and 2462 MHz (specified by the IEEE 802.11b/g standard). Because of the effect of water and temperature, each temperature allows limited frequencies to perform our tests. Taking into account this fact, the tests for 16 \({}^{\circ}\)C were performed for the frequencies between 2412 MHz and 2452 MHz. At higher frequency values were not possible to establish an underwater wireless link. At 18 \({}^{\circ}\)C, we could take measurements for frequencies between 2412 MHz and 2452 MHz. We were also able to establish an underwater link for frequencies between 2457 MHz and 2462 MHz at 20 \({}^{\circ}\)C. At 22 \({}^{\circ}\)C, the highest frequency that allows establishing an underwater wireless link was 2452 MHz. Finally, Orthogonal Frequency-Division Multiple Access (OFDM) was measured for all temperatures, in exception of 26 \({}^{\circ}\)C because it did not work. At 26 \({}^{\circ}\)C, the frequency range analyzed was 2412 MHz to 2442 MHz. Table 2 summarizes the parameters analyzed in the performed tests.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Modulation** & **Parameter** & **Value** \\ \hline \multirow{4}{*}{BPSK} & Temperatures & 16 \({}^{\circ}\)C, 18 \({}^{\circ}\)C, 20 \({}^{\circ}\)C, 22 \({}^{\circ}\)C, 26 \({}^{\circ}\)C \\ \cline{2-3}  & Data transfer Rates & 1 Mbps \\ \cline{2-3}  & Frequencies tested & 2412 MHz, 2417 MHz, 2422 MHz, 2427 MHz, 2432 MHz, 2437 MHz, \\  & 2442 MHz, 2447 MHz, 2452 MHz, 2457 MHz, 2462 MHz \\ \hline \multirow{4}{*}{QPSK} & Temperatures & 16 \({}^{\circ}\)C, 18 \({}^{\circ}\)C, 20 \({}^{\circ}\)C, 22 \({}^{\circ}\)C, 26 \({}^{\circ}\)C \\ \cline{2-3}  & Data transfer Rates & 2 Mbps \\ \cline{2-3}  & Frequencies tested & 2412 MHz, 2417 MHz, 2422 MHz, 2427 MHz, 2432 MHz, 2437 MHz, \\  & 2442 MHz, 2447 MHz, 2452 MHz, 2457 MHz, 2462 MHz \\ \hline \multirow{4}{*}{CCK (Complementary Code Keying)} & Temperatures & 16 \({}^{\circ}\)C, 18 \({}^{\circ}\)C, 20 \({}^{\circ}\)C, 22 \({}^{\circ}\)C, 26 \({}^{\circ}\)C \\ \cline{2-3}  & Data transfer Rates & 5.5 Mbps, 11 Mbps \\ \cline{2-3}  & Frequencies tested & 2412 MHz, 2417 MHz, 2422 MHz, 2427 MHz, 2432 MHz, 2437 MHz, \\  & 2442 MHz, 2447 MHz, 2452 MHz, 2457 MHz, 2462 MHz \\ \hline \multirow{4}{*}{OFDM} & Temperatures & 16 \({}^{\circ}\)C, 18 \({}^{\circ}\)C, 20 \({}^{\circ}\)C, 22 \({}^{\circ}\)C \\ \cline{2-3}  & Data transfer Rates & 6 Mbps, 9 Mbps, 12 Mbps, 18 Mbps, 22 Mbps, 24 Mbps, 36 Mbps, \\ \cline{1-1} \cline{2-3}  & Frequencies tested & 418 MHz, 54 Mbps \\ \cline{1-1} \cline{2-3}  & Frequencies tested & 2412 MHz, 2417 MHz, 2422 MHz, 2427 MHz, 2432 MHz, 2437 MHz, \\ \cline{1-1} \cline{2-3}  & Frequencies tested & 2442 MHz, 2447 MHz, 2452 MHz, 2457 MHz, 2462 MHz \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parameters analyzed in the tests performed.