The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Characteristics of an underwater acoustic channel, which hydro-acoustic modems of the S2C technology can measure and provide to upper layer protocols, were used for evaluation of several important communication metrics and so for evaluation of the modem performance under the actual channel conditions. Particularly, these channel characteristics were used for assessment of the delivery success related...
The aim of the SONIC project is to develop tools to investigate and mitigate the effects of underwater noise generated by shipping. One way to study the contribution of shipping noise to the background noise in the seas is to produce shipping noise maps. The SONIC project delivers the required technical knowledge for noise mapping, based on a source definition of shipping traffic composed of various...
This paper deals with underwater acoustic communication, and especially details an innovative approach for off the shelves existing modems performances evaluation. The originality is to be able to predict the operational performances of existing acoustic modems in a real complex situation, without sea trials.
Underwater sensor networks have a wide range of applications, many of which do not tolerate long delays and time-consuming retransmissions. Moreover, as most sensors are battery powered, saving energy is fundamental to increase network lifetime. In this paper, we investigate the minimum energy consumption for transmitting one bit of information over an underwater acoustic channel. Considering the...
Orthogonal frequency division multiplexing (OFDM) implicitly assumes that the channel used for signal transmission is linear and time-invariant for the length of each OFDM symbol. This is necessary for the channel matrix to be diagonalizable via the DFT, under cyclic prefix. The underwater acoustic channel is highly time-variant due to platform motion and environmental fluctuations. As a result, the...
This paper presents a high-level overview of NEMO, an implementation of a communications research software workspace with special focus on application scenarios involving underwater (e.g. acoustic), and other maritime communications methods. The NEMO is an organic result of marine autonomy and communications experimentation, basically being composed of reconfigurable modules and services that interact...
Acoustic signal is one of the most important sensor data for autonomous navigation of underwater vehicles. Underwater vehicles can navigate autonomously by localizing underwater acoustic sources. This paper presents a method of source localization for multiple underwater acoustic sources. The proposed method extracts and identifies target acoustic signals using frequency bands of each source. Then,...
Communication and positioning protocols for underwater acoustic sensor networks are widely covered in the scientific papers during the last decade and partly implemented in a few proprietary and open-source networking frameworks. The different protocols to be combined in a stack running on an acoustic modems' hardware and thus to solve various tasks of practical interest. This paper presents a novel...
Underwater acoustic laboratory (UAL) at National Taiwan University (NTU) was dedicated to four major research directions: development of sound propagation models, for example underwater reverberation model, research on underwater acoustic communication, research on man-made noises in the habitat of marine mammal, and development of underwater research equipment. Underwater acoustic repeater system...
Underwater acoustic vector sensor (AVS) is a passive sensor which can provide bearing information of the acoustic sources at a single point in space. This is achieved by combining three dimensional acceleration or particle velocity with scalar pressure measurement. In this work, we study the problem of bearing tracking of two targets using the measurements of a single AVS. For this problem, we propose...
By exploiting the intrinsic sparse structure of the underwater acoustic channel, we adopt ℓl-ℓ2 optimization criterion, which incorporates least squares with the penalized ℓ1 minimization to reduce noise effects while inducing channel sparsity. However, the estimate of channel parameters might not be in the feasible region. Therefore, we then define convex sets and utilize convex projection as a supplement...
This study presents an innovative way for underwater acoustic signal analysis. It is based on multi-directional filters implementation on time-frequency representation, where each filter is designed to enhance a given direction on the time-frequency plane. To do so, the proposed technique processes the time-frequency plane by taking into account the actual atom and its neighborhood for each direction,...
Suppression of grating lobes caused by spatial aliasing should be considered in array design for underwater acoustic imaging. To address this problem, a different approach to beamform with nonsinusoidal signal for grating lobes suppression is proposed in this paper. The desirable nonsinusoidal signal can be obtained by exacting the envelopes of the received signals. The reception of the envelopes...
Vertical arrays provide the most convenient geometry for many underwater passive acoustic applications that require the identification and isolating of propagating normal modes. Unfortunately, practical deployments of vertical arrays face several practical issues, including the need to compensate for vertical array inclination, and incomplete coverage of the water column that makes the use of Sturm-Liouville...
As part of the EU FP7 project CADDY, an efficient and reliable acoustic communication network is required to connect a diver, autonomous underwater vehicle (AUV) and surface vehicle (ASV) working cooperatively. This paper describes the development of the modulation, receiver algorithms and miniature hardware platform for multi user communication and simultaneous positioning. Experiments using vehicles...
In this paper, a channel model used to develop a high-speed underwater acoustic MIMO communication link is described. A low-complexity stochastic model is controlled to fully characterize a doubly spread behaviour with extreme variations and over a long period interval. Key parameters of the stochastic channel model are extracted from seaport measurements taken in the Bedford Basin in Halifax. Using...
This paper proposes an algorithm for real-time clock synchronisation in underwater acoustic networks. The algorithm models modem clocks as linear functions and embeds the data necessary for the clock synchronisation procedure as time stamps that can be communicated in the payload of later messages and only when necessary, hence limiting the communication overhead. The proposed solution takes explicitly...
Instead of single sensor processing, information fusion uses several sensors' data to get more accuracy in signal processing. Underwater acoustic networks has played more and more important roles in underwater monitoring and surveillance, in which target detection is a significant aspect. The so-called networked target detection uses network as a kind of tool to find underwater objects, so information...
This paper presents a widely linear equalizer in single carrier systems with frequency-domain equalization (SC-FDE) for underwater acoustic communications. The usage of this equalizer instead of its common strictly linear counterpart allows the distance between transmitter and receiver for a given transmitted power to be increased while maintaining the same bit error performance in a variety of scenarios.
Marine renewable energy (MRE) is an emerging technology and at present there are an increasing number of MRE prototypes and full-scale devices deployed. The future commercialization in the near future may contribute to the mitigation of carbon emissions and diversify the renewable electricity generation portfolio. Because of the high costs of marine intervention, it is important to establish reliable,...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.