# Underwater Communications for Video Surveillance Systems at 2.4 GHz
## 7 Conclusions  
Underwater networks presents several application fields such as monitoring applications, as oceanographic data collection, video surveillance, pollution monitoring/detection, and off-shore oil/gas field monitoring. They can also be used for exploration applications such as submarine detection, loss treasure discovery, and hurricane disaster recovery [31]. The paper has presented the behavior of EM signals working at 2.4 GHz in fresh water underwater environments in order to evaluate if it is possible to send video through this medium. Measurements has been performed at 16, 18, 20, 22 and 26 \({}^{\circ}\)C and taking into account the dependence on the working frequency. On the one hand, we have seen that it is possible to record video (with a standard resolution of 800 \(\times\) 600 pixels and 30 fps) from fish farms and transmit them without errors if we have a bandwidth around 2.5 Mbps. Should one want to transmit videos with bigger resolution, we would need to increase this bandwidth. On the other hand, we have seen in practical tests about acoustic waves that the bandwidth and the data transfer rates provided by this technology are not big enough. In addition, several previous works have claimed that EM wave propagation in fresh water has no relation with the working frequency, but our results have shown that there is an evident relationship between the maximum distance and the working frequency, type of modulation used and the water temperature. In addition, we have added a comparison of the BPSK, QPSK, CCK and OFDM schemes for several temperatures. This type of analysis has not been performed in previous studies. We have compared our results with theoretical estimations and we have checked that these values were more optimistic than those obtained on the real environment. In addition, the measurement results have shown that the water temperature affects the maximum distance we can achieve between devices. For this reason, we have modeled the value of maximum distance between underwater nodes as a parametric function that depends on the water temperature and the working frequency through which the systems transmit. Our proposal suggests a technique for short range communications. There are several interesting applications where short range communication is suitable. Precision monitoring of ecosystems contaminated by invasive plants or hazardous waste (e.g., in swamps, the quality of the water is different depending on the season because of the water evaporation and possible uncontrolled spills  
Figure 23: Estimated maximum distances for CCK transmission scheme. that can contain harmful substances that may affect the environment and the changes of parameters such as the pH value or salinity concentration. In these situations the water is not suitable for human consumption. However, this water to supply water cooling systems for industrial uses. The neutrino telescope [35] is an underwater structure located at the bottom of the Mediterranean Sea. There is some part that needs to be wirelessly connected, such as the hydrophone and the structure. Currently, researchers use cables and penetrators to connect the different parts, but these materials are very expensive. Using our system, we could reduce the cost of this infrastructure and would avoid the critical connections that can propagate a fault (or leak) through the system. There are other applications such as military applications, marine monitoring and even industrial applications such as marine fish farms [36] where the deployment of a UWSN would reduce the deposition of organic waste on the seabed and to enhance the marine fish farms sustainability. The measurements presented provide several benefits. The first one is that the use of IEEE 802.11 standard is cheaper than designing and implementing a modulator and demodulator for this frequency (IEEE 802.11 devices are very cheap because of the large commercial demand).