Group items tagged

Ocean observation system that involves multiple underwater vehicles and seafloor nodes plays an important role in better learning the ocean, where underwater wireless communication is mandatory for massive data interaction. Optical communication that has wide bandwidth and comprehensive working distance is the preferred method compared to acoustic and other methods. However, the presence of directionality makes the optical method difficult to use especially when the transceiver is equipped on a motive vehicle. In this study, an underwater free-space optical communication method of transmitting information is proposed. Characteristics of underwater optical transmission, as well as the photoelectric signal processing and modulation and demodulation algorithms, are studied and modeled. New approach for realizing underwater free-space optical communication is proposed and simulated. A prototype including a free-space optical transmitter and a receiver is developed; tests in different scenarios were carried out, and the results were observed: (1) by using the minimum number of LEDs, the effect of uniform lighting in space is achieved, and the transmitter coverage reaches 160°. (2) When the power of the transmitter is 10 W and the communication rate is 1 Mbps, the maximum communication distance reaches 13 m.

This paper presents a geometric stochastic channel model designed for analyzing maritime communication and navigation services between moving ships using the C-band or sub-6 GHz spectrum, which aligns with the focus of emerging 5G networks on land. The channel model is validated through channel measurements conducted both on the sea and land. A software tool has been developed to integrate and analyze these measurements, which is included with this publication. The main challenge in developing the channel model for maritime services lies in the dynamic nature of the sea surface, leading to constantly changing reflection conditions due to varying reflectors and scatterers on the water. Additionally, the motion conditions of the transmitter and receiver on ships change in all three dimensions, depending on the sea state. To address these complexities, data from several measurement campaigns in diverse areas were collected. The analysis involved examining the propagation conditions over the sea with variations in sea surface roughness, antenna heights, and used bandwidths. Moreover, additional propagation conditions over nearby land were also taken into account. The study demonstrates that the changing antenna height on the ship, influenced by sea conditions, significantly affects the reflection and scattering conditions. The research aims to develop reliable, high-data rate, and broadband marine communication systems. Therefore, a measurement bandwidth of 120MHz was employed to derive the propagation model. This model not only offers absolute timing information but can also be used for time-based ranging or positioning systems. The proposed geometric stochastic channel model provides valuable insights into the complex maritime communication and navigation environment. By accounting for the continuously evolving sea surface and its impact on antenna height, the model offers a robust framework for studying and optimizing marine communication systems. The availability of

China has deployed a network of sensors and communications capabilities between Hainan Island and the Paracel Islands in the northern South China Sea. These capabilities are part of a "Blue Ocean Information Network" (蓝海信息网络) developed by China Electronics Technology Group Corporation (CETC), a state-owned company, to aid in the exploration and control of the maritime environment using information technology. The network constructed in the northern South China Sea between early 2016 and 2019 is referred to as a demonstration system. However, future plans for the Blue Ocean Information Network involve expanding the sensor and communications network to the rest of the South China Sea, the East China Sea, and other ocean areas far from Chinese territory. While the Blue Ocean Information Network is largely cast as an environmental monitoring and communications system, the military utility of its sensing and communications functions makes its development important to monitor.

At present, contact watertight connectors are commonly utilized for the connection between underwater electromechanical equipment and the seabed observation network. Such traditional watertight connectors are easy to be irreversibly worn when plugging and unplugging, however, they have complicated sealing structures and limited service life. This paper designs a Non-contact Wet Mateable connector for Optical Communication and Power Transmission (OCPT-NWMC), which is based on technology of Contactless Power Transmission (CLPT) and optical communication. Docking structure of the sockets and plugs are designed, facilitating Remotely Operated Vehicle (ROV) to operate. A prototype of the OCPT-NWMC was established. The experimental results show that the connector designed can achieve 200W power transmission, with a maximum power transmission efficiency of 94%. The communication bandwidth reaches 18MHz. The OCPT-NWMC can assist the rapid and safe deployment and operation of seabed observation network.

The in-band full-duplex underwater acoustic communication (IBFD-UWAC) mode has twice the information throughput of the traditional half-duplex communication mode, significantly increasing the communication efficiency. Extracting the weak desired signal from the high-power self-interference signal without distortion remains a challenging problem in implementing IBFD-UWAC systems. This paper proposes a spatial-digital joint self-interference cancellation (SDSIC) method for IBFD-UWAC. We first perform spatial self-interference cancellation (SSIC) and propose an improved wideband constant-beamwidth beamformer to overcome the problem of direction- and array-dependent interference in IBFD-UWAC systems. Convex optimization is used to maintain a constant beam response in the main flap and cancel the self-interference signal from a fixed direction, thus increasing the signal-to-interference ratio of the desired signal. Subsequently, we perform digital self-interference cancellation (DSIC) on the residual self-interference signal, and propose a variable-step-size least-mean-squares algorithm based on the spatial noise threshold. This algorithm modifies the least-mean-squares step-size adjustment criterion according to the noise level after SSIC and the desired signal, resulting in better DSIC. A series of simulations are implemented in a hardware-in-the-loop platform to verify the practicality and real-time performance of the proposed SDSIC method. The results show that the self-interference signal power can be reduced by 41.5 dB using the proposed method, an improvement of 13.5 dB over the conventional SIC method.

Maritime high-speed over-the-horizon wireless communication is realizable through evaporation ducts. Detailed measurement, analysis, and modeling of duct channels are essential for application of this communication technique. In this paper, X-band electromagnetic (EM) wave propagation systems were developed and deployed for a 133-km over-the-horizon microwave link in coastal areas of the Yellow Sea. The propagation length was 7.7 times the line-of-sight length. Measurement results including the path loss (PL) and meteorological data were obtained during a 54-day period in autumn 2021. The long-term channel results were analyzed on the basis of statistical analysis and model simulations. Results showed that our measurement system, with a maximum measurable power loss of 200 dB, had connected with a probability of 56.2% during the measurement period. Model simulation showed that evaporation duct environments are not ideal in autumn, with an average evaporation duct height (EDH) of 10.6 m. The land breeze in autumn introduced dry and cold air to the link, which could promote evaporation of seawater and reduce PL by approximately 40 dB. Annual spatiotemporal characteristics of EDH showed that evaporation ducts are most suitable for over-the-horizon communication in spring, especially May.

Shipping is a large industry responsible for atmospheric emissions of hazardous substances including SOX, NOX, and particulate matter. Many ships have installed exhaust gas cleaning systems (scrubbers) to remove primarily SOX from the exhaust, but the hazardous substances are instead transferred to the water used in the scrubbing process. Ships with closed-loop scrubbers recirculate the water but can still discharge around 126-150 m3 directly to the surrounding marine environment every day. The discharged water contains metals and organic substances, such as polycyclic aromatic hydrocarbons, that are known to be toxic to marine zooplankton. Here we show that closed-loop scrubber washwater is toxic to communities of marine mesozooplankton at our lowest tested dilution, 1.5% (v/v), and affects survival, reproduction, diversity, and ability to predate on microzooplankton. The cumulative toxic unit of the undiluted closed-loop scrubber washwater was estimated to 17, which indicates that the water could be toxic at levels below what was tested in this study. Among all detected substances, vanadium, copper, benzo[ghi]perylene, nickel, and zinc were identified as toxicity-driving substances in the order listed. Closed-loop scrubber washwater has been shown to affect development and survival in single species of copepods, but here we find evidence of toxicity at the community level, irrespective of seasonal community structure, and that the exposure has potential to disrupt the interactions between trophic levels in the pelagic food web. We show that the closed-loop scrubber washwater cause both lethal and sublethal effects in marine zooplankton, due to contaminants, some of which are persistent in the marine environment.

The noise and presence of boats can harm humpback whales' ability to communicate and socialise, in some cases reducing their communication range by a factor of four.

With increasing demand for exploration and utilization of marine resources, achieving direct and efficient communication between water and air has been an urgent need. Sound waves, as the only propagation way with low attenuation in both water and air, has been considered the most practical way to achieve water-air communication.

China to enhance communication ability in Northeast Passage of Arctic.

The propagation of electromagnetic waves on land and sea is significantly different. Although the Los scenario is significant in marine wireless communication, the marine wireless channel exists an obvious two-ray phenomenon due to the strong reflection path reflected through the sea surface. By modeling the measured data of marine wireless channels, this paper calculates the radio propagation characteristics of the Pearl River estuary. In addition, the wave fluctuations and high humidity environment will also impact the properties of the marine wireless channel. Therefore, sea surface morphology models under multiple wind speeds are built. To estimate the path loss in the same area under different conditions, the Monte Carlo method is employed to quantify the results. The simulation results show that the electric wave propagation gradually degenerated from the round earth loss (REL) model to the free space model with increasing wind speed. Moreover, the distribution of the shadow fading varies with distance. The findings provide references for the network planning of marine communication

The importance of shipping in supporting and sustaining today's global society makes it indispensable to the world and to meeting the challenges of the sustainable development agenda, top UN officials declared today, as the international community marked World Maritime Day.

The importance of shipping in supporting and sustaining today's global society makes it indispensable to the world and to meeting the challenges of the sustainable development agenda, top UN officials declared today, as the international community marked World Maritime Day.

Elizabeth DEL CARMEN and Juan Felipe CARDENAS, residents on the Pacific coast of Nicaragua, describe their fears of what will happen to their community as building begins on the interoceanic canal. They worry that promises of relocation and compensation will not be sufficient and that their families will be badly affected

Elizabeth DEL CARMEN and Juan Felipe CARDENAS, residents on the Pacific coast of Nicaragua, describe their fears of what will happen to their community as building begins on the interoceanic canal. They worry that promises of relocation and compensation will not be sufficient and that their families will be badly affected

Saudi Arabia urges int'l community to securing Bab Al-Mandab strait.

Canada: sea ice prevents crucial supply deliveries to isolated communities.

Study finds way to pack more data in single acoustic beam for underwater communications.

NOAA scientists studying sounds made by Atlantic cod and haddock at spawning sites in the Gulf of Maine have found that vessel traffic noise is reducing the distance over which these animals can communicate with each other. As a result, daily behavior, feeding, mating, and socializing during critical biological periods for these commercially and ecologically important fish may be altered, according to a study published in Nature Scientific Reports.

Introduction: The Scotia Sea and Antarctic Peninsula are warming rapidly and changes in species distribution are expected. In predicting habitat shifts and considering appropriate management strategies for marine predators, a community-level understanding of how these predators are distributed is desirable. Acquiring such data, particularly in remote areas, is often problematic given the cost associated with the operation of research vessels. Here we use cruise vessels as sampling platforms to explore seabird distribution relative to habitat characteristics.

Key Points ◆ An autonomous underwater vehicle automatically retrieved data from equipment mounted on seabed for observation. ◆ For the first time, an autonomous underwater vehicle automatically retrieved data using optical wireless communication. ◆ Autonomous underwater vehicles can retrieve data from several seabed observation equipment (instruments) by patrolling (harvesting), which can be applied to various seabed observation applications, such as efficient seismic observation.

Building a "Maritime Community with a Shared Future" (MCSF) is a maritime development concept with Chinese characteristics proposed by Chinese President Xi Jinping in 2019. It is based on the rich cultural tradition and unique historical value of China's maritime civilization. It aims to solve real ocean problems and has outlined the future direction of human ocean development from the perspective of China. The essence of the MCSF is an issue of both ocean cultural and development concepts. It is a conceptual issue that transcends specific national boundaries and regions and is based on how all of humankind, with common interests and common values, can develop in harmony with the oceans. It is not a covert discourse strategy adopted by China in order to realize its "maritime power" ambition, as occasionally described by some Western countries. Starting with an analysis of the essential nature and implications of maritime culture by Chinese researchers, this article clarifies and summarizes the interaction, exchange, and integration of Chinese maritime culture in East Asia from a historical perspective, and extracts the unique characteristics and values of Chinese maritime culture. From the perspective of human-sea interactions, the three historical stages, as well as the existing problems of transforming and upgrading human-ocean culture, are analyzed. The article also contrasts Chinese and Western maritime cultures and proposes to absorb the outstanding achievements of both Chinese and Western maritime civilizations into a common framework in order to fundamentally reverse the antagonistic human-sea relationship that has existed historically. Finally, we propose giving full play to the fundamental role of marine cultural exchange and integration and, through international cooperation on specific issues in the field of global ocean international relations, propose specific and feasible practical pathways to promoting the realization of the MCSF.