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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.

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.

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.

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.

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.

OptoCOMM aims at demonstrating the potential, at physical level, of a communication facility for the SUNRISE platform constituted by an Optical Underwater Wireless Communication (OUWC) module with target performance of 10 Mb/s transmission rate at 10 meters range in shallow medium/high turbidity harbour waters. The module, which is based on blue Light Emitting Diode (LED) units and common photodiodes, is an evolution of the proof-of-principle prototype already proven in laboratory (pool). It will constitute an additional node integrated in the Littoral Ocean Observatory Network (LOON) test-bed of the SUNRISE infrastructures, providing a high speed and short-range communication node, which will complete the capability of acoustic modems already present in the test-bed. Three modules (nodes) will be developed and experimentally demonstrated: one for direct integration with the LOON infrastructures, one, battery powered, to be potentially installed on buoys, Remotely Operated Vehicles (ROVs), etc., and one to be installed on the eFolaga Autonomous Underwater Vehicle (AUV) of the proponents. The paper describes in detail the development of the modems as well as the first lab experiments, where the core technology has been successfully tested.

Underwater communication has a wide range of applications like environmental monitoring to predict the natural disasters, underwater ex-ploration and military applications. The need for effective underwater communication is the high demand in the present scenario. The im-plementation of precise modulation technique is also important because the underwater channel environment is time variant due to various noises present in the underwater like natural and vehicle noise (mechanical noises). The bandwidth is also highly limited in underwater communication. The existing method is adaptive modulation based OFDM system. This method has low spectral efficiency, however, each symbol is modulated with different carriers. The proposed method is Adaptive Modulation Level MC-CDMA (Multi carrier Code Division Multiple Access). The CDMA techniques share the same carrier frequency to multiple number of users. It adapts the modulation scheme according to the present channel conditions in the underwater. The performance of the proposed system improves the Data Throughput and Bit Error Rate.

[EN] Wireless technology for underwater communication possesses a wide range of potential application, but it is still a relatively unexplored area in many aspects concerning modems physical design. A step towards future deployment of underwater networks is the reduction of power consumption. Therefore, asynchronous wakeup systems need to be integrated within the physical layer design while avoiding the use of additional transducers. This paper offers a practical and generic solution to adapt data reception and transmission together with asynchronous wakeup sub-systems in acoustic underwater modem architectures using a low power and low cost solution. The proposal has been implemented in a real prototype with success., The translation of this paper was funded by the Universitat Politècnica de València, Spain.The authors gratefully acknowledge financial support from the CICYT. ANDREA: Automated Inspection and Remote Performance of Marine Fish Farms (CTM2011-29691-C02-01) and RIDeWAN: Research on Improvement of the Dependability of WSN-based Applications by Developing a Hybrid Monitoring Platform. (TIN2011-28435-C03-01).