A joint research efforts on Under Water Communications between the Centre for Telecommunications Research at SLTC and Research Laboratory of Telecommunications, Instrumentation and Marine Geology at Tomsk Polytechnic University, Russia has published a paper in a prestigious Springer journal of Archives of Computational Methods in engineering which has impact factor of 7.424. The project was led by Prof. Dushantha Nalin K. Jayakody.
Underwater wireless communication (UWC) is the most challenging and comprehensive technology for wired and wireless communications. UWC networks are necessarily important approaches of accessing data in an unguided water medium of deep oceans. It has been an essential field for researchers and among academicians in recent years. The deployable technologies are advantageous to use in oceanographic data analysis, observing water pollution, environmental monitoring, and early warning of natural disasters such as floods and Tsunamis. They are also used to get to know the phenomena of rising water levels in the oceans. Thus, in the UWC, we use the three customized existing approaches available for underwater wireless signal transmission. The first technology is Electromagnetic waves (in the form of Radio frequencies) that enable a feature of high data rate over short ranges. Secondly, the Optical signal transmission (OPT) technique in underwater to achieve high bandwidth, which needs a line attenuating position during signal propagation over moderate distances. The third and the most employable technology is Acoustic waves, which are widely used for the long range of communication.”
Acoustic waves, as shown in Fig. 1, are the most popular method to achieve targeted signals in underwater over long distances with low latency and high spreading delay as compared with underwater optical communication. Acoustic waves propagate longitudinally with channel particles through adiabatic compression and expansion. However, propagation towards the direction of induced vibration in water medium travels horizontally. In underwater, acoustic waves propagate faster than in air with fewer energy losses. The acoustic waves propagate generally at 1400 m/s to 1600 m/s in the ocean, but travels at the speed of 340 m/s in the air.
Fixed and anchored nodes in Fig. 01, play an ample role of communication for detection and collection data from the unseen segment of river, lakes and sea. Acoustic wave propagation totally depends on the physical channel properties such as pressure, temperature, and salinity. However, during propagation, a huge power loss occurs due to absorption and scattering, which could have an effect on the speed.
Due to limited bandwidth and low data rates of acoustic and EM waves, an alternative approach is an optical communication that provides high-bandwidth, low latency and minimum spreading delay in an aquatic medium. Optical signals have many distinct properties during propagation at different frequencies over different ranges.
Although optical signal in the underwater environment faces several extreme challenges and this affected by scattering, absorption, dispersion and fluctuations of temperature also by physio-chemical properties of the channel. The number growth of human activities, as shown in Fig 2, through Underwater Wireless Sensor Network as depicted in Fig 3, and Autonomous Underwater Vehicles (AUV) are exponentially increasing to explore of the underwater environment. Thus, the necessity of reliable and relatively mature visible light communication (VLC) required. Underwater VLC (UVLC) specially uses to military and industrial purposes. Therefore, VLC is considered as a high speed communication network candidate in the future. Swimmers and divers in deep underwater use to hand signals and writing-boards to communicate where the light signal required. The VLC can be used for signaling and data transfer through a light emitting diode (LEDs).
In this work, we summarized, all available technologies of UWC and future research directions in UWC to improve the QoE. Finally, 5G wireless techniques are proposed to support RF, acoustic and optical signal carrier for improving communication probabilities in UWC.