Abstract
Underwater Wireless Sensor Network (UWSN) communication at high frequencies is extremely challenging. The intricacies presented by the underwater environment are far more compared to the terrestrial environment. The prime reason for such intricacies are the physical characteristics of the underwater environment that have a big impact on electromagnetic (EM) signals. Acoustics signals are by far the most preferred choice for underwater wireless communication. Because high frequency signals have the luxury of large bandwidth (BW) at shorter distances, high frequency EM signals cannot penetrate and propagate deep in underwater environments. The EM properties of water tend to resist their propagation and cause severe attenuation. Accordingly, there are two questions that need to be addressed for underwater environment, first what happens when high frequency EM signals operating at 2.4 GHz are used for communication, and second which factors affect the most to high frequency EM signals. To answer these questions, we present real-time experiments conducted at 2.4 GHz in terrestrial and underwater (fresh water) environments. The obtained results helped in studying the physical characteristics (i.e., EM properties, propagation and absorption loss) of underwater environments. It is observed that high frequency EM signals can propagate in fresh water at a shallow depth only and can be considered for a specific class of applications such as water sports. Furthermore, path loss, velocity of propagation, absorption loss and the rate of signal loss in different underwater environments are also calculated and presented in order to understand why EM signals cannot propagate in sea water and oceanic water environments. An optimal solk6ution for underwater communication in terms of coverage distance, bandwidth and nature of communication is presented, along with possible underwater applications of UWSNs at 2.4 GHz.
Highlights
Underwater Wireless Sensor Networks (UWSNs) are comprised of a sensor or a group of sensors that are deployed inside water to sense and explore the deep underwater environments [1].These sensors communicate wirelessly, with each other and with the central base station where information of different sensors is collected for underwater applications [2]
The path loss exponent is estimated for the two environments, and a detailed analysis is presented by comparing the overall path loss in the two environments
It is concluded that path loss inside fresh water at 2.4 GHz is 1.6 times greater than the path loss in the terrestrial indoor environment using the same frequency
Summary
Underwater Wireless Sensor Networks (UWSNs) are comprised of a sensor or a group of sensors that are deployed inside water to sense and explore the deep underwater environments [1] These sensors communicate wirelessly, with each other and with the central base station where information of different sensors is collected for underwater applications [2]. Underwater Optical Communication Systems (UW-OCSs) use optical frequencies for information transmission [9] These are typically very high frequencies of the order of THz. UW-OCSs can be used for shallow water applications at less distances (few meters) as light is attenuated highly at greater distances inside water [9].
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