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This paper exhibits the performance of visual light communication in the underwater environment at different salt concentrations. The output is measured in terms of the signal received power at different link budgets. A series of experiments were conducted to verify the results and concluded that light attenuation increases with an increase in water salinity. Furthermore, we analyzed that salinity also affects data rate and link budget. It is found that water salinity cannot block the communication completely as the maximum possible saturation is 40% which can degrade the system by upto 20% only. Along salinity, we also tested the system performance against turbidity and found that it has a much more significant effect. A slight increase in turbidity may block a more considerable portion of the communication channel. The study can help researchers when developing an underwater communication system using visible light for freshwater or salty water (seawater). As per our observation, visual light communication is feasible for both of these environments as even in the saltiest water, it will work because the maximum concentration of salt and percentage of turbidity will not degrade the system beyond a specific limit.

Решению вопросов, связанных с телекоммуникационным оборудованием, функционирующем в водной среде, в настоящее время уделяется особое внимание. На смену традиционным подводным системам обмена информацией в гидроакустических полях приходят открытые системы её оптической передачи и приёма, базирующиеся на лазерных технологиях. Это вызвано необходимостью трансляции с высокой разрешающей способностью видеоданных, среди которых, например, может быть либо визуальное отображение подводных систем в динамике, либо результаты мониторинга объектов подводной инфраструктуры в реальном масштабе времени, либо что-то другое с учётом требований Заказчика. Канал передачи такого большого объёма информации при условии ее считывания с задаваемым качеством должен иметь пропускную способность более 1 Мбит/с. Такую высокую скорость передачи невозможно реализовать в подводных гидроакустических системах, граница технических возможностей которых на превышает 10...50 кбит/с. В аналогичной ситуации при заданных параметрах канала связи частоты несущих оптического диапазона имеют порядок 1014 Гц, что обеспечивает динамический диапазон полосы пропускания в районе 1012…1013 Гц. С учётом условия квазимонохроматичности применение гидроакустических средств для передачи видеоданных становится проблематичным, так как техническая реализация такой задачи потребует слишком большого времени. С учётом сказанного, преимуществом подводных беспроводных оптических систем связи является их высокая широкополосность, которая обеспечит высокую скорость передачи данных. В статье обосновывается целесообразность использования открытых оптических системы связи для создания высокоскоростных подводных инфотелекоммуникаций, среди которых наиболее предпочтительными являются лазерные системы. Special attention is currently paid to the solution of issues related to telecommunication equipment operating in the aquatic environment. The traditional underwater systems for the exchange of information in hydroacoustic fields are being replaced by open systems for its optical transmission and reception, based on laser technologies.This is due to the need to broadcast high-resolution video data, among which, for example, there can be either a visual display of underwater systems in dynamics, or the results of monitoring objects of underwater infrastructure in real time, or something else, taking into account the requirements of the Customer. The transmission channel of such a large amount of information, provided it is read with a specified quality, must have a bandwidth of more than 1 Mbit / s. Such a high transmission rate cannot be realized in underwater sonar systems, the technical capabilities limit of which does not exceed 10 ... 50 kbit/s. In a similar situation, given the parameters of the communication channel, the carrier frequencies of the optical range are 1014 Hz, which provides a dynamic bandwidth range about 1012…1013Hz. Taking into account the condition of quasimonochromaticity, the use of hydroacoustic means for transmitting video data becomes problematic, since the technical implementation of such a task will take too long. In view of the above, the advantage of underwater wireless optical communication systems is their high broadband, which will provide a high data transfer rate. The article substantiates the expediency of using open optical communication systems for creating high-speed underwater information telecommunications, among which the most preferable are laser systems.

The visible light communication (VLC) technique using a rolling-shutter sensor-based commercial camera has an advantage in that the LED and camera mounted on an underwater device (e.g., drone, sensor) can be effectively used as a transmitter (Tx) and a receiver (Rx), respectively, under water. On the other hand, a suitable modulation technique has not been well considered to realize a VLC system using a rolling-shutter sensor in an underwater channel that includes high ambient light conditions. In this paper, we design VLC systems using phase-shift keying (PSK), non-return-to-zero on- off keying (NRZ-OOK), and orthogonal frequency division multiplexing (OFDM), and evaluate them through simulations and experiments. The results suggested that the VLC system using PSK or OFDM is more resilient than that using NRZ-OOK in an underwater channel with low-frequency ambient light, and that a VLC system using PSK or NRZ-OOK is more tolerant than that using OFDM in environments with high ambient light, resulting in pixel saturation. In conclusion, the present study has demonstrated that PSK is the most suitable modulation technique for a VLC system using a rolling-shutter sensor in an underwater channel that includes high ambient light conditions.

Underwater wireless communication is a rapidly growing field, especially with the recent emergence of technologies such as autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs). To support the high-bandwidth applications using these technologies, underwater optics has attracted significant attention, alongside its complementary technology – underwater acoustics. In this paper, we propose a hybrid opto-acoustic underwater wireless communication model that reduces network power consumption and supports high-data rate underwater applications by selecting appropriate communication links in response to varying traffic loads and dynamic weather conditions. Underwater optics offers high data rates and consumes less power. However, due to the severe absorption of light in the medium, the communication range is short in underwater optics. Conversely, acoustics suffers from low data rate and high power consumption, but provides longer communication ranges. Since most underwater equipment relies on battery power, energy-efficient communication is critical for reliable underwater communications. In this work, we derive analytical models for both underwater acoustics and optics, and calculate the required transmit power for reliable communications in various underwater communication environments. We then formulate an optimization problem that minimizes the network power consumption for carrying data from underwater nodes to surface sinks under varying traffic loads and weather conditions. The proposed optimization model can be solved offline periodically, hence the additional computational complexity to find the optimum solution for larger networks is not a limiting factor for practical applications. Our results indicate that the proposed technique yields up to 35% power savings compared to existing opto-acoustic solutions.

Internet of underwater things (IoUT) will empower underwater humanitarian applications. IoUT will have the ability to sense locations in the underwater environment, process the data locally, and transmit it via underwater wireless communication. In this article, we discuss how IoUT can benefit humanitarian needs, such as mitigating disasters, relieving in global warming, and providing access to scientific data. We also describe the main approaches and challenges for water sensing and communications, and outline the challenges for IoUT-based humanitarian applications. Finally, we envision future research directions.

Since many years, the life and environment in underwater especially the oceans are being explored, yet there are many parts of oceans remained unexplored due to the particularities of underwater environment. The increasing interest in underwater exploration has paved way to the development of different technologies for underwater communication. Underwater wireless communication plays a vital role in the study of marine life, water pollution, monitoring of natural calamities, coastal surveillance, and to monitor various phenomena in underwater environment. Hence, the underwater wireless communication has become a key area of research for exploring underwater environment for a variety of applications. The primary underwater wireless technology uses acoustic waves, electromagnetic waves in RF band, and optical waves as communication carriers to transmit data in an underwater environment. This paper provides a survey of these communication technologies discussing their physical characteristics, compatibility and technical issues, thus enabling to understand use of these technologies for underwater communications.

Underwater wireless communication in seawater is becoming more interesting and challenging in recent years. The development of antenna for underwater wireless communication in seawater at 900 MHz UHF range frequency is implemented by using patch antenna. In this paper, the antennas were designed using FEKO, an electromagnetic simulation software, and a suitable size for rectangular patch antenna for seawater application was developed to study the relevance between λ0 with W and L in seawater. The major difference between the patches in free space and seawater was the feedpoint distance for antenna. For L size, which was slightly bigger, about 0.9 mm than free space size can consider almost same. But the gain for patch antenna in seawater was found at -2.51 dBi, lower than patch antenna in free space, which was 5.76 dBi due to the path loss in seawater. This shows that attenuation happened, and a better antenna will be design. The one that has better gain, which is around above 2dBi in seawater, in order to get better performance antenna in seawater environment.

Underwater wireless communication is an advanced research area need to be explored extensively. This topic is highly significant for various purposes, starting from aquatic pollution control, marine life monitoring, and quality of the water and moreover signal transmission. Different sensors can be used under water for the above said applications. For signal transmission under water, sound waves and optical signals were used extensively in back. The drawback is low data rate, attenuation and backscattering due to suspended particles which are the major challenges. To meet the above challenges here, a prototype of underwater RF wireless network is developed. It not only establishes the wireless network but also tracks the underwater devices and updates the location in the IOT cloud. It also measures temperature, vibration and quality of the water using underwater sensors and update in www.thingspeak.com website. The established underwater wireless network provides coverage upto 1.2 km in diameter and 50 m in depth which is highly considerable. Further optimization can be done to enhance the range.

Wireless communication in the ocean might be a challenging venture due to the natural outcomes and hard backgrounds of saltwater. The characteristics of land region communication are totally different than underwater circumstances. The facts could even be modulated through single-channel mode which can be resulting from outside factors of underwater. Thus, conversation channel formation and separation are rigid due to the risky factors of underwater circumstance. The Stochastically evolved mathematical derivations used to model the single-channel conversation and also used to evolve the delay facts between the nodes with uni-mode communications. This work is to simulate the single-channel conversation of facts generator and facts observer in underwater condition and derive the mathematical effects based on the SNC. The SNC is used to derive mathematical models to understand the abnormality from the simulation effects as compared to numerical effects.

The feasibility of 200Mbps UWOC system based on DPSK modulation scheme has been experimentally demonstrated for the first time. The measured system BER values below the FEC limit of 3.8 × 10−3 have been achieved with received powers greater than about -25.2 dBm.

Underwater communication (UWC) with multi-hop techniques utilizes sensors to convey information to the sink/sonobuoy, which is situated on the top surface of the sea. The down to earth motivation to arrive at the sea surface is, it has higher proliferation speed. The electromagnetic and optical correspondence has high recurrence in submerged condition, along these lines it makes higher constriction coefficient with its particular separation. To conquer this confinement, the acoustic correspondence is joined in submerged condition. Acoustic correspondence has insignificant weakening and vitality utilization in submerged condition. Versatility of sensor hubs is expected to sea flows, which innately causes correspondence void. Because of this, sensor hubs can't speak with other sensor hubs. The correspondence void because of versatility issue prompts finding a legitimate recuperation hub. In this paper the studied of OFDM-MIMO system using visible light LEDs technology is presented. Receiver power, channel gain, output signal and signal to noise ratio is measure with variation of the surface of the light.

Driven by the huge demand to explore oceans, underwater wireless communications have been rapidly developed in the past few decades. Due to the complex physical characteristics of water, acoustic wave is the only media available for underwater wireless communication at any distance. As a result, underwater acoustic communication (UAC) is the major research field in underwater wireless communication. In this paper, characteristics of underwater acoustic channels are first introduced and compared with terrestrial communication to demonstrate the difficulties in UAC research. To give a general impression of the UAC, current important research areas are mentioned. Furthermore, different principal modulation-based schemes for short- and medium-range communications with high data rates are investigated and summarized. To evaluate the performance of UAC systems in general, three criteria are presented based on the research publications and our years of experience in high-rate short- to medium-range communications. These three criteria provide useful tools to generally guide the design and evaluate the performance of underwater acoustic communication systems.

This paper has evaluated and analyzed the influence of utilization of different number of mobile sinks in water. The velocity of mobile sinks is precisely determined which supports the aggregation of data from static sensors without the degradation of synchronization and scheduling. The mobility of sink is an approbation to improve the throughput, reduce delay, jitter, and also extend the lifetime of the network. The utilization of mobile sinks has mitigated the energy-hole problem. The performance metrics are compared and analyzed. The purpose of this research work is to find the precise number of mobile sinks and its exact velocity at which average delay is minimized, and the lifetime is prolonged along with gaining the assistance of researchers in this field.

We present a new method for underwater wireless communication with high bandwidth and over long distance. A swarm of Autonomous Underwater Vehicles (AUVs) is used to relay an optical signal between two points at any distance. Each vehicle is equipped with multiple attitude stabilization systems to reach the required pointing and tracking accuracy for optical communication. This technology would enable fast and efficient underwater exploration which is highly needed as only 5% of the world’s oceans have been explored so far. We carried out an experimental proof of concept to show that it is possible to relay an optical signal underwater between two points using a swarm of AUVs. The experiment took place in a 2m deep water tank. We modified and controlled two submarine models to reflect the laser beam stemming from a laser pointer at the bottom of the tank to the desired location. To know their positions, we developed an image processing technique which required the setup of a RF communication link at 315Mhz between the computers processing the camera’s videos and the units.

High-bandwidth underwater wireless communication can be achieved over long-distance using a swarm of Autonomous Underwater Vehicles (AUVs) relaying an optical signal. The swarm behavior is of critical importance as it will determine the robustness and the autonomy of the communication link. Each vehicle must remain at a distance lower than the optical communication system range from each other while fighting against environmental disturbances such as ocean current. This technology could be a game changer in the deployment and supervision of future oil wells and of deep sea mining which will be deeper and deeper in the oceans. We developed an optimization program to maximize the communication link autonomy while assuring its robustness. The nonlinear optimization problem is transformed to a Second-Order Cone Problem (SOCP), a special case of convex problems that can be efficiently solved with Yalmip on Matlab. We show on two case studies that the autonomy of the swarm and thus the lifetime of the communication link is increased by more than 10% compared to a direct approach where the reference position of the vehicles is fixed.

Underwater wireless communication has gained a great deal of attention in the last couple of decades because of its applications in the military, industrial, and monitoring sectors. Despite the extreme physical and MAC layer difficulties, acoustics are used for various applications among the various modes of underwater communication technologies used. While significant research efforts have been made to address these issues, the bottleneck remains in achieving high bandwidth, high throughputs, and data rate. Researchers have begun to look into full duplex (FD) implementation to improve bandwidth efficiency and increase data rate and throughput. Users can send and receive data simultaneously over the FD links, maximizing bandwidth utilization and increasing throughput. As a result, we thoroughly reviewed various FD physical layered UWAC systems and MAC layered protocols for underwater communication. The various problems that the aforementioned systems and protocols have faced, as well as the solutions suggested in previous works to solve each problem, are also highlighted. Various metrics are used to compare the performance of various physical layered FD systems and FD MAC protocols. We also explore some of the open research questions in these FD-physical layered and MAC layered protocols, as well as future research directions. Based on ample information, we suggest a cross-layered architecture based on various IBFD-SI cancellations, DA-CSMA, and FD-MAC protocols. This review provides a broad view of the current FD physical and MAC layered protocols based on acoustic communication, as well as recommendations.

The most difficult medium for data communication is the underwater medium. It is due to its characteristics. The various existing mode of the communication in water medium are electromagnetic waves, acoustic waves and optical signal. But all these have its own drawbacks. The loss will be huge for Electro-Magnetic (EM) waves, so it is limited to the short range communication, optical waves has line of sight issues. To overcome these, in this paper, a Li-Fi technique is used for data transmission in water medium. It uses Light Emitting Diode (LED) sources for transmission of data. This will ensure the maximum transmission rate and it is more efficient and cheaper than the other existing methods. In this paper, automation via Bluetooth, IoT and it has GPS tracking capabilities are also incorporated.

In this research article, we present the broad classification and exhaustive review of the various routing protocols available for underwater wireless communication. In this work, we addressed the ...

The increasing exploitation of natural resources under water, particularly in the sea, has ignited the development of many technological advances in the domains of environmental monitoring, oil and gas exploration, warfare, among others. In all these domains, underwater wireless communications play an important role, where the technologies available rely on radio-frequency, optical, and acoustic transmissions. This paper surveys key features inherent to these communication technologies, putting into perspective their technical aspects, current research challenges, and to-be-explored potential. In the end we list several technical challenges that are addressed with the aid of signal processing tools.

Hydrophone is a type of microphone that are used in underwater for recording and also for listening to the underwater sound. Generally, Hydrophones are based upon the transducer named Piezo electric that can convert the sound signals into an electrical signals. Here the frequencies associated with the underwater acoustic communications are 10Hz-IMHz. Frequencies above 1 MHz is rarely used but they can be easily absorbed in underwater. In Underwater wireless communication the information is transmitted through the channel named as UAC channel. This paper deals with the gain brought by using the underwater MIMO channel techniques.

In an underwater environment it is difficult to implement solutions for wireless communications. The existing technologies using electromagnetic waves or lasers are not very efficient due to the large attenuation in the aquatic environment. Ultrasound reveals a lower attenuation, and thus has been used in underwater long-distance communications. The much slower speed of acoustic propagation in water (about 1500 m/s) compared with that of electromagnetic and optical waves, is another limiting factor for efficient communication and networking. For high data-rates and real-time applications it is necessary to use frequencies in the MHz range, allowing communication distances of hundreds of meters with a delay of milliseconds. To achieve this goal, it is necessary to develop ultrasound transducers able to work at high frequencies and wideband, with suitable responses to digital modulations. This work shows how the acoustic impedance influences the performance of an ultrasonic emitter transducer when digital modulations are used and operating at frequencies between 100 kHz and 1 MHz. The study includes a Finite Element Method (FEM) and a MATLAB/Simulink simulation with an experimental validation to evaluate two types of piezoelectric materials: one based on ceramics (high acoustic impedance) with a resonance design and the other based in polymer (low acoustic impedance) designed to optimize the performance when digital modulations are used. The transducers performance for Binary Amplitude Shift Keying (BASK), On-Off Keying (OOK), Binary Phase Shift Keying (BPSK) and Binary Frequency Shift Keying (BFSK) modulations with a 1 MHz carrier at 125 kbps baud rate are compared., This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI607/2011 and project PTDC/CTM-NAN/112574/2009. M. S. Martins thanks the FCT for the grant SFRH/BD/60713/2009.

A wide variety of underwater applications, such as warning systems and deep water positioning systems used to track autonomous underwater vehicles etc, warrant underwater wireless communication in ...

In underwater acoustic sensor networks (UWASNs), several transmitters using the same power send data to the sink. Then, the sink will collect more interference because of the slow-fading of signal, due to this, a higher outage probability and high energy consumption occurs. Underwater wireless communication is quite difficult because of the factors like propagation delay, small available bandwidth, strong signal attenuation, and interference from natural and man-made acoustic interferences. In underwater wireless acoustic communication all these factors depend on the frequency and distance. Higher frequency defines the worst case in terms of power consumption, and in terms of battery lifetime of the network. So in this work, we consider optimal distance between transmit nodes and receiver node to enhance the performance. The optimal power control schemes has been proposed in underwater wireless networks, of which the principle thought is to utilize distinctive power levels for enhancing the performance. By using this scheme, we get reduction of outage probability and enhancement of transmission capacity. Simulation results confirm the effectiveness of the optimal power allocation schemes compared to the frequency domain allocation scheme.

Underwater wireless communication using acoustic signals is a difficult problem and progress in finding robust solutions has been disappointing. Methods employed successfully in terrestrial wireless communications have not always transitioned successfully to underwater scenarios. An engineer’s intuition developed in solving the terrestrial problem may actually become a hindrance to solving the underwater problem. In the present work, several seemingly counterintuitive experimental results are examined: communications performance can be better when the range is longer rather than shorter, when the sea surface is rough rather than calm, when the bathymetry is undulating rather than flat. Physics-based explanations for the observed results are developed. A physicist’s intuition, however, also may fail when trying to develop useful models. A seemingly counterintuitive fact is that acoustic paths that undergo incoherent reflection from a rough sea surface can be shown experimentally to be useful for coherent communications. The requirements for a proper physics-based model are sketched.