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"underwater acoustic"
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Sounds in the sea : from ocean acoustics to acoustical oceanography
\"Sounds in the Sea is a comprehensive and accessible textbook on ocean acoustics and acoustical oceanography. 'Ocean acoustics' describes the traditional direction in which our knowledge of ocean temperature and salinity allows us to use sound to find fish, submarines, icebergs, and the depth of the ocean. 'Acoustical oceanography' interprets the distinctive details of time-varying sound amplitudes and phases over acoustical paths to deduce the physical and biological parameters of the specific ocean through which the sound has travelled.\" \"Sounds in the Sea is an invaluable textbook for any course in ocean acoustics in the physical and biological ocean sciences, engineering, and physics. It will also serve as a reference for researchers and professionals in ocean acoustics, and an excellent introduction to the topic for scientists from related fields.\"--BOOK JACKET.
Book
An Acoustic Underwater Glider for the Real-Time Transmission of Observation Data via an Underwater Acoustic Communication Modem
This paper introduces the development of an acoustic underwater glider integrated with an underwater acoustic modem designed to enable the real-time transmission of ocean observation data. The glider features three sequentially connected, independent compartments and is capable of operating at depths exceeding 1000 m. To ensure stable communication, two acoustic transducers are mounted at the rear of the glider and optimized to maintain a consistent energy radiation angle despite variations in the glider’s attitude. The acoustic modem, housed within one of the compartments, operates with a standby power consumption as low as 5 mW, significantly enhancing the overall energy efficiency of the system. To address the glider’s motion dynamics and the unique characteristics of the underwater acoustic channel, a multi-carrier frequency shift keying-based underwater acoustic communication scheme combined with a Stop-and-Wait Automatic Repeat Request protocol was designed and implemented. The system’s performance and reliability were validated through sea trials conducted in the South China Sea. The results demonstrated that the glider achieved reliable underwater acoustic communication over distances of up to 5 km. This research highlights the potential of the acoustic underwater glider for applications such as underwater acoustic measurements and distributed networking collaboration. The system holds significant promise for advancing underwater acoustic communication and ocean observation technologies.
Journal Article
Channel Prediction for Underwater Acoustic Communication: A Review and Performance Evaluation of Algorithms
Underwater acoustic (UWA) channel prediction technology, as an important topic in UWA communication, has played an important role in UWA adaptive communication network and underwater target perception. Although many significant advancements have been achieved in underwater acoustic channel prediction over the years, a comprehensive summary and introduction is still lacking. As the first comprehensive overview of UWA channel prediction, this paper introduces past works and algorithm implementation methods of channel prediction from the perspective of linear, kernel-based, and deep learning approaches. Importantly, based on available at-sea experiment datasets, this paper compares the performance of current primary UWA channel prediction algorithms under a unified system framework, providing researchers with a comprehensive and objective understanding of UWA channel prediction. Finally, it discusses the directions and challenges for future research. The survey finds that linear prediction algorithms are the most widely applied, and deep learning, as the most advanced type of algorithm, has moved this field into a new stage. The experimental results show that the linear algorithms have the lowest computational complexity, and when the training samples are sufficient, deep learning algorithms have the best prediction performance.
Journal Article
A Review of Subsea AUV Technology
The observation and detection of the subsea environment urgently require large-scale and long-term observation platforms. The design and development of subsea AUVs involve three key points: the subsea-adapted main body structure, agile motion performance that adapts to complex underwater environments, and underwater acoustic communication and positioning technology. This paper discusses the development and evolution of subsea AUVs before proposing solutions to underwater acoustic communication and positioning navigation schemes. It also studies key technologies for the agile motion of subsea AUVs and finally gives an example of a solution for implementing underwater AUVs, i.e., the disk-shaped autonomous underwater helicopter (AUH). This paper will provide guidance for the design of subsea AUVs and the development of corresponding observation and detection technologies.
Journal Article
Survey on Low-Cost Underwater Sensor Networks: From Niche Applications to Everyday Use
Traditionally, underwater acoustic modems and positioning systems were developed for military and Oil & Gas industries, that require deep water deployments and extremely reliable systems, focusing on high power expensive systems and leaving the use of low-cost devices only attractive for academic studies. Conversely, recent developments of low-cost unmanned vehicles, such as remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs), suitable for shallow water coastal missions, and the need of sensors network deployments for measuring water quality and studying the effect of climate change in coastal areas, called to the need of low-cost and low-power acoustic modems and positioning systems that are gaining more and more momentum to date. The use of these devices can enable a wide set of applications, often based on low-cost AUV swarm formations, where an acoustic link between the vehicles is required to coordinate the mission, perform the maneuvers, and maintain the formation along the time. Moreover, they can make environmental wireless sensor deployment cost effective by substituting wired systems. Underwater positioning systems, usually used in large-scale operations, can be finally applied to small-scale application thanks to the reduction in costs, at the price of a lower transmission and positioning range and precision. While in open-sea application this performance reduction is a huge limitation, in river, lagoon, port and lake deployments this is not an issue, given that the extremely shallow water and the presence of many obstacles would deteriorate the acoustic signal anyway, not allowing long range transmissions even with expensive and sophisticated acoustic devices. In this paper, we review the recent developments of low-cost and low-power acoustic communication and positioning systems, both analyzing University prototypes and new commercial devices available in the market, identifying advantages and limitations of these devices, and we describe potential new applications that can be enabled by these systems.
Journal Article
Underwater sensor networks: applications, advances and challenges
This paper examines the main approaches and challenges in the design and implementation of underwater wireless sensor networks. We summarize key applications and the main phenomena related to acoustic propagation, and discuss how they affect the design and operation of communication systems and networking protocols at various layers. We also provide an overview of communications hardware, testbeds and simulation tools available to the research community.
Journal Article
A Survey of Underwater Acoustic Target Recognition Methods Based on Machine Learning
Underwater acoustic target recognition (UATR) technology has been implemented widely in the fields of marine biodiversity detection, marine search and rescue, and seabed mapping, providing an essential basis for human marine economic and military activities. With the rapid development of machine-learning-based technology in the acoustics field, these methods receive wide attention and display a potential impact on UATR problems. This paper reviews current UATR methods based on machine learning. We focus mostly, but not solely, on the recognition of target-radiated noise from passive sonar. First, we provide an overview of the underwater acoustic acquisition and recognition process and briefly introduce the classical acoustic signal feature extraction methods. In this paper, recognition methods for UATR are classified based on the machine learning algorithms used as UATR technologies using statistical learning methods, UATR methods based on deep learning models, and transfer learning and data augmentation technologies for UATR. Finally, the challenges of UATR based on the machine learning method are summarized and directions for UATR development in the future are put forward.
Journal Article
Exact Analysis of SIR Performance for the Mobile OFDM Communication Systems Over the Underwater Acoustic Channel
Orthogonal frequency division multiplexing (OFDM) serves as a fundamental waveform in mobile high‐speed underwater acoustic (UWA) communication scenarios. However, the large sidelobe energy of its sub‐carriers leads to significant performance degradation when subjected to the large‐scale UWA non‐uniform Doppler effects caused by relative motion between transceivers. To quantitatively assess the impact of the UWA Doppler effects on the mobile OFDM UWA communication systems, we derive a closed‐form analytical expression for the signal‐to‐interference ratio performance by integrating the effects of distortion and non‐uniform Doppler shifts in the UWA channel. The simulation results corroborate the theoretical computations derived from the expression, exhibiting substantial predictive precision across various UWA Doppler shift scales.
Journal Article
State-of-the-Art Underwater Acoustic Communication Modems: Classifications, Analyses and Design Challenges
Acoustic modem is one of the key elements of an underwater wireless sensor network (UWSN). Compared to a terrestrial wireless sensor network (WSN), designing a UWSN is more time consuming and expensive due to harsh conditions of the aquatic environment. Commercial modems provide better characteristics, but they consume more energy and are more expensive, while research modems have exploited diverse alternatives with varying success. The main contribution of the article is a comparative analyses of commercial and research modems based on their characteristics and design constraints, in order to describe the current trends and more promising techniques. This paper is focused on the state-of-the-art underwater acoustic modems designed, developed and implemented in the last few years. Various parameters of the modems are considered and analyzed: operating range, data-rate, modulation schemes, center frequency, bandwidth, power consumption, bit error rates, etc. Finally, design challenges, which need to be addressed, are identified. This study is useful for the engineering community to comprehend the characteristics, trends and design challenges of state-of-the-art underwater acoustic communication modems.
Journal Article
Chirp Rate Estimation of LFM Signals Distorted by Underwater Acoustic Modal Dispersion
Low‐frequency sonar signals experience modal dispersion during long‐range propagation, leading to multipath effects and non‐linear phase distortion. This distortion causes the failure of traditional chirp rate estimation methods that rely on the linear frequency characteristics of linear frequency modulated (LFM) signals. This paper proposes a chirp rate estimation algorithm based on the fractional Fourier transform (FrFT) and modal dispersion compensation. The algorithm estimates the channel impulse response (CIR) by modifying the FrFT of the LFM signal, applies a de‐dispersion transform to eliminate modal dispersion in the CIR, and finally obtain the chirp rate estimate through a parameter search. Simulation and experimental results validate the effectiveness of the algorithm under dispersive conditions.
Journal Article