Thèses : « Underwater Acoustic Communicati »

1

Garin, Raphaël. « Communication et positionnement simultanés pour les drones sous-marins autonomes ». Electronic Thesis or Diss., Brest, 2023. http://www.theses.fr/2023BRES0097.

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Cette thèse porte sur la navigation des drones sous-marins autonomes (AUV) en l’absence de signaux GPS sous l’eau. Pour résoudre ce problème, elle propose une approche innovante qui combine la localisation de l’AUV avec la communication acoustique sous-marine avec une balise en surface. Cette méthode utilise l’estimation du décalage Doppler requis pour le décodage des signaux de communication afin d’estimer la vitesse relative de l’AUV. De plus, le temps de vol de la communication est utilisé pour mesurer la distance entre l’AUV et la balise. Le système final nécessite seulement des capteurs peu onéreux, tels qu’une centrale inertielle, un capteur de pression, un GPS pour l’initialisation, et un transpondeur acoustique pour le drone, combine avec un capteur de profilage de la vitesse du son. Une balise fixe communique avec le drone et est équipée d’un transpondeur acoustique. Cette approche offre une précision comparable à l’état de l’art, avec une faible empreinte spatiale et un cout réduit. Des simulations et des essais en bassin de 6 m3 ont été effectués avec succès, confirmant la faisabilité du système. De plus, des expérimentations en mer dans des conditions réelles ont montré une précision d’environ 3 mètres, démontrant l’efficacité de l’algorithme. En comparaison avec l’état de l’art, le système proposé est plus rapide à mettre en place, ne nécessite pas de calibration, est plus économique, et consomme moins d’énergie, bien qu’il soit légèrement moins précis
This thesis focuses on the navigation of autonomous underwater drones (AUVs) in the absence of underwater GPS signals. To address this issue, it proposes an innovative approach that combines AUV localization with underwater acoustic communication to a surface beacon. This method utilizes the Doppler shift estimation required for communication signal demodulation in order to estimate the relative velocity of the AUV. Additionally, the communication’s time of flight is used to measure the distance between the AUV and the beacon. The final system requires only affordable components, such as an inertial navigation system, a pressure sensor, a GPS for initialization, and an acoustic transponder for the drone, combined with a sound velocity profiling sensor. A fixed beacon communicates with the drone and is equipped with an acoustic transponder. This approach offers accuracy comparable to the state-of-the-art, with a small spatial footprint and reduced cost. Successful simulations and tests were conducted in a 6 m3 test tank, confirming the feasibility of the system. Furthermore, real-world sea trialsdemonstrated an accuracy of approximately 3 meters, showcasing the algorithm’s effectiveness.Compared to the state-of-the-art, the proposed system is quicker to set up, requires no calibration, is more cost-effective, and consumes less power, although it is slightly less accurate

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Keeser, Christopher Corson. « Shallow under water communication with passive phase conjugation and iterative demodulation and decoding ». Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/c_keeser_112408.pdf.

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Thesis (M.S. in electrical engineering)--Washington State University, December 2008.
Title from PDF title page (viewed on Jan. 21, 2009). "School of Electrical Engineering and Computer Science." Includes bibliographical references (p. 51-53)

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Tate, William R. « Full-duplex underwater networking ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03sep%5FTate.pdf.

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Thottappilly, Arjun. « OFDM for Underwater Acoustic Communication ». Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/34873.

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Communicating wirelessly underwater has been an area of interest for researchers, engineers, and practitioners alike. One of the main reasons for the slow rate of progress in this area is that the underwater acoustic channel is in general much more hostile â in terms of multipath, frequency selectivity, noise, and the Doppler effect â than the over-the-air radio frequency channel. In this work a time warp based technique which can be used to model time-varying wideband Doppler shifts (as seen in an UWA channel) in MATLAB is proposed. A corresponding procedure to estimate the parameters from observed data, required for inverting the effect of the time warp, is also proposed. Two different Doppler correction methods are compared; both can be used to undo the Doppler effect in measured data from an experiment subject to the wideband Doppler effect. The techniques presented correct for the wideband Doppler effect as if it changed the time scale of the received signal. The first resampling based technique corrects for the average expansion/contraction over a packet, inherently assuming the relative velocity to be constant over the duration of the packet. The second time warp based technique models time-varying Doppler shift. Sinusoids, added to the beginning and end of each packet, are used to estimate the parameters required to invert the effect of the warp. The time warp based methods are demonstrated using Orthogonal Frequency Division Multiplexing (OFDM) signals, but will in principle work for other kinds of wideband signals also. The presented results â using MATLAB based simulations, and over-the-air experiments performed in such a way as to introduce the Doppler effect in the received signals â emphasize the improvements that can be attained by using the time warp based Doppler modeling and correction method. The thesis concludes with suggestions for future work.
Master of Science

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Eggen, Trym H. 1963. « Underwater acoustic communication over Doppler spread channels ». Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42768.

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Nykvist, Kim. « Underwater probe for deep sea exploration : Long range acoustic underwater communication system ». Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80474.

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This was a thesis that was commissioned by Researcher Peter Sigray at the Royal Institute of Technology (KTH) in Stockholm and was based on an idea by Professor Thomas Rossby, University of Rhode Island (URI). The idea was to further develop the existing Expendable Bathythermograph (XBT), which has been in use since the 1960s. This by first and foremost replacing existing transfer technology, which involved using a thin copper wire when communicating with the recipient remaining on the ship. The new way in which communication is to take place, is by acoustic signals transmitted from the freely descending probe. The goal is to be able to measure down to greater depth compared to the previous type. The aim is to increase today's in-depth measuring capacity of about 900 meters, down to depth of at least 2000 meters, preferably even deeper. The thesis project was divided into several smaller parts, some of which went on in parallel, while others had to have the preceding portion completed, in order for them to take place, i.e., to begin. Initially – and in parallel during the rest of the thesis work – their were studies of two selected books and a set of documents. This to ensure the understanding of all the concepts to be used during the development of the probe. In parallel with the studies, simulations in the computer program COMSOL Multiphysics began. The model probe geometry and material parameters were programmed. An important task was to implement and verify that the so called Perfectly Matched Layer (PML) performed as expected. This was of crucial importance, as different implementations of the PML turned out to result in different outcomes of the simulations’ data. With the results from Perfectly Matched Layer tests verified, the actual simulations could be initiated. Two different pipes were evaluated; one made of stainless steel and the other made of aluminum alloy. Their proportions were slightly different regarding diameter and length. The simulations led to the makings of plots/diagrams over the Transmission Voltage Response (TVR) over a certain frequency range (3000-17000 Hz). Directivity polar plots were also created for both pipes in the program MATLAB and by using a MATLAB. The actual assessment of the probes began in the latter part of the simulation work. There were several different steps in the process of assembling the probes. Finally, the tests in the water tank at The Defense Research Institute (FOI) could take place. For three days all the simulated results were “put to test.” The results during the tests in the water tank at FOI were promising and the remaining challenges, before a complete probe is developed, are achievable. The hypothesis that initially was set got proven, and it can be argued that the thesis as a whole successfully demonstrated it to be true. The idea of the probe is definitely worth further development, in the making of the new version of the Expendable Bathythermograph.

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Haug, Ole Trygve. « Acoustic communication for use in underwater sensor networks ». Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9057.

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In this study an underwater acoustic communications system has been simulated. The simulations has been performed through use of a simulation program called EasyPLR that is based on the PlaneRay propagation model. In the simulations different pulse shapes have been tested for use in underwater communication. Different types of loss have also been studied for different carrier frequencies. Changing the carrier frequency from 20 kHz to 75 kHz gives a huge difference in both absorption loss and reflection loss. This means that there will be a tradeoff between having a high frequency for high data rate and reducing the carrier frequency to reduce the loss. The modulation technique used in this study is Quadrature phase shift keying and different sound speed profiles have been tested to see how this affects the performance. The transmission distance has been tested for several distances up to 3 km. The results show a significant difference in the performances at 1 km and 3 km for the same noise level. Direct sequence spread spectrum with Quadrature phase shift keying has also been simulated for different distances with good performance. The challenge is to get good time synchronization, and the performance is much better at 1 km than at 3 km.

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Pompili, Dario. « Efficient Communication Protocols for Underwater Acoustic Sensor Networks ». Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16301.

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Underwater sensor networks find applications in oceanographic data collection, pollution monitoring, offshore exploration, disaster prevention, assisted navigation, tactical surveillance, and mine reconnaissance. The enabling technology for these applications is acoustic wireless networking. UnderWater Acoustic Sensor Networks (UW-ASNs) consist of sensors and Autonomous Underwater Vehicles (AUVs) deployed to perform collaborative monitoring tasks. The objective of this research is to explore fundamental key aspects of underwater acoustic communications, propose communication architectures for UW-ASNs, and develop efficient sensor communication protocols tailored for the underwater environment. Specifically, different deployment strategies for UW-ASNs are studied, and statistical deployment analysis for different architectures is provided. Moreover, a model characterizing the underwater acoustic channel utilization efficiency is introduced. The model allows setting the optimal packet size for underwater communications. Two distributed routing algorithms are proposed for delay-insensitive and delay-sensitive applications. The proposed routing solutions allow each node to select its next hop, with the objective of minimizing the energy consumption taking the different application requirements into account. In addition, a resilient routing solution to guarantee survivability of the network to node and link failures in long-term monitoring missions is developed. Moreover, a distributed Medium Access Control (MAC) protocol for UW-ASNs is proposed. It is a transmitter-based code division multiple access scheme that incorporates a novel closed-loop distributed algorithm to set the optimal transmit power and code length. It aims at achieving high network throughput, low channel access delay, and low energy consumption. Finally, an efficient cross-layer communication solution tailored for multimedia traffic (i.e., video and audio streams, still images, and scalar sensor data) is introduced.

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Yellepeddi, Atulya. « Direct-form adaptive equalization for underwater acoustic communication ». Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1912/5281.

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Thesis (S.M.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and the Woods Hole Oceanographic Institution), 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 139-143).
Adaptive equalization is an important aspect of communication systems in various environments. It is particularly important in underwater acoustic communication systems, as the channel has a long delay spread and is subject to the effects of time- varying multipath fading and Doppler spreading. The design of the adaptation algorithm has a profound influence on the performance of the system. In this thesis, we explore this aspect of the system. The emphasis of the work presented is on applying concepts from inference and decision theory and information theory to provide an approach to deriving and analyzing adaptation algorithms. Limited work has been done so far on rigorously devising adaptation algorithms to suit a particular situation, and the aim of this thesis is to concretize such efforts and possibly to provide a mathematical basis for expanding it to other applications. We derive an algorithm for the adaptation of the coefficients of an equalizer when the receiver has limited or no information about the transmitted symbols, which we term the Soft-Decision Directed Recursive Least Squares algorithm. We will demonstrate connections between the Expectation-Maximization (EM) algorithm and the Recursive Least Squares algorithm, and show how to derive a computationally efficient, purely recursive algorithm from the optimal EM algorithm. Then, we use our understanding of Markov processes to analyze the performance of the RLS algorithm in hard-decision directed mode, as well as of the Soft-Decision Directed RLS algorithm. We demonstrate scenarios in which the adaptation procedures fail catastrophically, and discuss why this happens. The lessons from the analysis guide us on the choice of models for the adaptation procedure. We then demonstrate how to use the algorithm derived in a practical system for underwater communication using turbo equalization. As the algorithm naturally incorporates soft information into the adaptation process, it becomes easy to fit it into a turbo equalization framework. We thus provide an instance of how to use the information of a turbo equalizer in an adaptation procedure, which has not been very well explored in the past. Experimental data is used to prove the value of the algorithm in a practical context.
by Atulya Yellepeddi.
S.M.

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Kilfoyle, Daniel B. (Daniel Brian). « Spatial modulation in the underwater acoustic communication channel ». Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/29046.

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Thesis (Ph. D.)--Joint Program in Oceanography and Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and the Woods Hole Oceanographic Institution), 2000.
Vita.
Includes bibliographical references (leaves 180-181).
A modulation technique for increasing the reliable data rate achievable by an underwater acoustic communication system is presented and demonstrated. The technique, termed spatial modulation, seeks to control the spatial distribution of signal energy such that multiple parallel communication channels are supported by the single, physical ocean channel. Results from several experiments successfully demonstrate higher obtainable data rates and power throughput. Given a signal energy constraint, a communication architecture with access to parallel channels will have increased capacity and reliability as compared to one with access to a single channel. Assuming the use of multiple element spatial arrays at both the transmitter and receiver, an analytic framework is developed that allows a multiple input, multiple output physical channel to be transformed into a set of virtual parallel channels. The continuous time, vector singular value decomposition is the primary vehicle for this transformation. Given knowledge of the channel impulse responses and assuming additive, white Gaussian noise as the only interference, the advantages of using spatial modulation over a deterministic channel may be exactly computed. Improving performance over an ensemble of channels using spatial modulation is approached by defining and then optimizing various average performance metrics including average signal to noise ratio, average signal to noise plus interference ratio, and minimum square error. Several field experiments were conducted. Detailed channel impulse response measurements were made enabling application of the decomposition methodology. The number, strength, and stability of the available parallel channels were analyzed. The parallel channels were readily interpreted in terms of the underlying sound propagation field. Acoustic communication tests were conducted comparing conventional coherent modulation to spatial modulation. In one case, a reliable data rate of 24000 bits per second with a 4 kHz bandwidth signal was achieved with spatial modulation when conventional signaling could not achieve that rate. In another test, the benefits of spatial modulation for a horizontally distributed communication system, such as an underwater network with autonomous underwater vehicles, were validated.
by Daniel Brian Kilfoyle.
Ph.D.

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Newborough, Darryl. « Underwater position-fixing using digital acoustic communication techniques ». Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/36078.

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This thesis describes an intelligent underwater acoustic system that allows the positions of several divers or Remotely Operated Vehicles (ROV) to be tracked in three-dimensional space and to telemeter the co-ordinates to a remote receiver at the surface. The positions are fixed using three randomly deployed seabed transponders that may be described as intelligent. The transponders fix their own relative positions and the position of the surface receiver, usually a vessel, by an exchange of coded acoustic pulses. These positions can be related to a differential GPS system at the surface if absolute coordinates are required. An underwater acoustic positioning and communication system can provide a vital navigation aid for a diver and surface supervisor. Often underwater positioning systems only provide the surface supervisor with diver's positions, with the diver navigating from voiced instruction via an acoustic or wire link communication. In the system described the divers each know their own position from a wrist-worn computer with a backlit graphical/numerical display. As well as the current position, the display can show the track from the beginning of the dive, the location of the surface vessel and the instantaneous position of the other divers.

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Xia, Charlene. « A low-cost modular underwater acoustic communication system ». Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/130598.

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Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, September, 2020
Cataloged from the official PDF version of thesis.
Includes bibliographical references (pages 99-102).
This thesis describes the design of a novel modular acoustic communication device for underwater wireless communication. The ocean plays a vital role in the global climate system and biosphere, providing a wealth of biodiversity and resources. Human exploitation, pollutants, and contaminants have already impacted the deepest trenches of the ocean. Yet most of this impact remains invisible - the depth and breadth of the ocean, the opacity of water to light, and the lack of mass-deployable ocean instrumentation, mean that current observations are wildly under sampled in space and time. Even given suitable instruments, a major challenge remains: how to get the data home. Given the opacity of sea water to radio, and the complexity and expense of underwater cabling, audio communication is in may ways the low hanging fruit. Unfortunately, most commercial audio communication systems are both extremely expensive and more powerful than needed for many, if not most, monitoring requirements.
They are also proprietary, a frustrating barrier to development of novel devices. As a result, these off-the-shelf systems are ill-suited to the global multi-scale instrumentation challenges of the future. In what follows we document the design, development, and testing of a low-cost, high-efficiency, modular, and fully open-sourced acoustic communication system. This system is specifically intended for mass deployment, with particular emphasis on standardized hardware and software interfaces. Crucially, this design prioritizes cost and simplicity over performance - as such, this system does not aim to replace the current crop of commercially available systems, but rather to provide a new kind of tool specifically for scalable deployments of low-cost instruments.
Functionally, the system is composed of three core modules: a power management unit; a central processing unit; and a family of interchangeable acoustic transceiver units operating across a spectrum of transmission frequencies. The resulting design should be of valuable use to the scientific community, environmental agencies, citizen scientists, and anyone who needs to transport low-bandwidth data through the ocean at extremely low cost.
by Charlene Xia.
S.M.
S.M. Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences

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Amorim, Maria Clara Correia de Freitas Pessoa de. « Acoustic communication in triglids and other fishes ». Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=232579.

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Sound production is widespread among teleosts and is usually observed in social contexts. Many fish, such as triglids, produce sounds by contracting a pair of specialised striated muscles attached to both sides of the swimbladder wall, yielding low frequency sounds made up of repeated brief pulses. Temporal features of acoustic emissions can be controlled by the rate of muscle contraction, thus providing a rich means of conveying information. In this study the sound features of the grey (EutrigJa gurnardus), the streaked (Trigloporus lastoviza), the red (Aspitrigla cuculus) and the tub (Trigla Jucerna) gurnards were compared. The grey and the red gurnards emitted 3 different sound types, knocks, grunts and growls, whereas the streaked and the tub gurnards only emitted one sound type, growls and grunts respectively. Interspecific differences of calls were marked and based on the temporal patterning and on the grouping of the pulses. In the grey gurnard, ontogenetic changes in sound production were found. The sound production rate, the proportion of emitted sound type and the physical features of sounds varied with fish size. A study of diel and seasonal variations of sound production in the grey gurnard showed that more sounds were uttered during the day than at night and that grunts were more important and intense during the SpringSummer period. The sonic apparatus was examined in the species mentioned above and also in the large-scaled gurnard (Lepidotrigla cavillone) and the piper (Trigla lyra). The swimbladder and the sonic muscles grew throughout life in all species. Variations in the sonic apparatus with fish gender or time of the year were not detected. This suggests that the ability to vocalise is similar in both male and female gurnards, probably even during courtship. The shape of the swimbladder was species-specific. All species possessed a pair of intrinsic sonic muscles except for the piper whose sonic muscles were extrinsic. The pair of intrinsic sonic muscles of the grey gurnard contracted synchronously and each contraction generated a pulse of sound. The biological Significance of sound production was studied in the grey, the streaked and the tub gurnards. Few other studies have made a comparison of the behavioural context of sound production in different species of fish of the same family. Competitive feeding interactions were examined and compared between species. The different sound types emitted were also correlated with different behavioural categories. Typical sequences of behaviour were found in each species. Disputes over food items were settled by either reaching food first or by being aggressive, but never involved fighting escalation. The knocks of the grey gurnard and the growls of the streaked gurnard were associated with feeding and low levels of aggressive behaviour, and the grunts of grey and tub gurnards were associated with agonistic behaviour, such as approach, chase and frontal displays. The grey gurnard was the most vocal and aggressive species during competitive feeding. Smaller grey gurnards interacted more frequently than did larger fish, and a larger proportion of their interactions were accompanied by grunt calls. The metabolic costs of sound production in fish were calculated theoretically for different types of acoustic activity. If the assumptions made are valid then it seems that producing acoustic signals in fish is cheap. The biological implications of these low energetic costs were discussed. Finally, the acoustic repertoire of several non-triglid species of fish was examined. Sounds from 7 species were described for the first time. These species uttered sounds during territorial defence and courtship; contexts quite different from those studied for triglids.

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Boayue, Abraham. « Characterization of Underwater Acoustic Communication Channels : Statistical Characteristics of the Underwater Multipath Channnels ». Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for telematikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23108.

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Underwater communication and networking have become very essential both for commer-cial and military purposes. The number of research conducted in this field has increased over the past few decades. The need to communicate between sensor nodes in sensor network requires the characterization of underwater acoustic channel. This project focuses on the statistical characterization of an underwater communication channel using real data. This kind of approach of characterizing a channel makes it possible to access the performance of modern digital systems before they are built. The main idea behind this thesis report is to be able to perform simulations on real data using matlab to get reasonable results that can be compared to existing research papers.

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Sari, Hayri. « Underwater acoustic voice communications using digital techniques ». Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/13854.

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An underwater acoustic voice communications system can provide a vital communication link between divers and surface supervisors. There are numerous situations in which a communication system is essential. In the event of an emergency, a diver's life may depend on fast and effective action at the surface. The design and implementation of a digital underwater acoustic voice communication system using a digital signal processor (DSP) is described. The use of a DSP enables the adoption of computationally complex speech signal processing algorithms and the transmission and reception of digital data through an underwater acoustic channel. The system is capable of operating in both transmitting and receiving modes by using a mode selection scheme. During the transmission mode, by using linear predictive coding (LPC), the speech signal is compressed whilst transmitting the compressed data in digital pulse position modulation (DPPM) format at a transmission rate of 2400 bps. At the receiver, a maximum energy detection technique is employed to identify the pulse position, enabling correct data decoding which in turn allows the speech signal to be reconstructed. The advantage of the system is to introduce advances in digital technology to underwater acoustic voice communications and update the present analogue systems employing AM and SSB modulation. Since the DSP-based system is designed in modular sections, the hardware and software can be modified if the performance of the system is inadequate. The communication system was tested successfully in a large indoor tank to simulate the effect of a short and very shallow underwater channel with severe multipath reverberation. The other objective of this study was to improve the quality of the transmitted speech signal. When the system is used by SCUBA divers, the speech signal is produced in a mask with a high pressure air environment, and bubble and breathing noise affect the speech clarity. Breathing noise is cancelled by implementing a combination of zero crossing rate and energy detection. In order to cancel bubble noise spectral subtraction and adaptive noise cancelling algorithms were simulated; the latter was found to be superior and was adopted for the current system.

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He, Qing Ph D. Massachusetts Institute of Technology. « A super-nyquist architecture for rateless underwater acoustic communication ». Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/75455.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 135-136).
Oceans cover about 70 percent of Earth's surface. Despite the abundant resources they contain, much of them remain unexplored. Underwater communication plays a key role in the area of deep ocean exploration. It is also essential in the field of the oil and fishing industry, as well as for military use. Although research on communicating wirelessly in the underwater environment began decades ago, it remains a challenging problem due to the oceanic medium, in which dynamic movements of water and rich scattering are commonplace. In this thesis, we develop an architecture for reliably communicating over the underwater acoustic channel. A notable feature of this architecture is its rateless property: the receiver simply collects pieces of transmission until successful decoding is possible. With this, we aim to achieve capacity-approaching communication under a variety of a priori unknown channel conditions. This is done by using a super-Nyquist (SNQ) transmission scheme. Several other important technologies are also part of the design, among them dithered repetition coding, adaptive decision feedback equalization (DFE), and multiple-input multiple-output (MIMO) communication. We present a complete block diagram for the transmitter and receiver architecture for the SNQ scheme. We prove the sufficiency of the architecture for optimality, and we show through analysis and simulation that as the SNQ signaling rate increases, the SNQ scheme is indeed capacity-achieving. At the end, the performance of the proposed SNQ scheme and its transceiver design are tested in physical experiments, whose results show that the SNQ scheme achieves a significant gain in reliable communication rate over conventional (non-SNQ) schemes.
by Qing He.
S.M.

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Albin, Barklund, et Daniel Adolfsson. « Integrated Localization and Directed Communication for Acoustic Underwater Systems ». Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-32162.

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Sifferlen, James F. « Iterative equalization and decoding applied to underwater acoustic communication ». Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3331419.

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Thesis (Ph. D.)--University of California, San Diego, 2008.
Title from first page of PDF file (viewed Dec. 16, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 131-134).

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Liu, Chunshan. « Advanced signal processing techniques for underwater acoustic communication networks ». Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/2102/.

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In this thesis, we develop and investigate novel signal processing techniques for underwater acoustic communication networks. Underwater acoustic channels differ from radio communication channels in the lower speed of signal propagation, richer and often sparse multipath arrivals, and more severe Doppler effect. Therefore, many signal processing techniques developed for radio communications may not work equivalently well for underwater acoustic channels. To investigate signal processing techniques in underwater acoustics, efficient simulation of signal transmission is required. Specifically, there is requirement for accurate simulation of doubly-selective underwater channels for different acoustic environments. In this thesis, a low-complexity channel simulator has been developed for scenarios with moving transmitter/receiver. The simulator is based on efficient generation of time-varying channel impulse response obtained using interpolation over a set of waymark impulse responses for a relatively small number of sampling points on the transmitter/receiver trajectory. The waymark impulse responses are generated using an acoustic field computation method, which is the most computationally expensive part of the simulator. To reduce the trajectory sampling rate, and thus, to reduce the complexity of the field computation, an approach for adjusting the time-varying multipath delays has been developed. For setting the trajectory sampling interval, a simple rule has been proposed, based on the waveguide invariant theory. To further reduce the simulator complexity, local spline interpolation is exploited. The developed simulator has been verified by comparing the simulated data with data from real ocean experiments. In particular, applying simulated data to an OFDM modem shows similar performance with that obtained from the data of a deep water experiment. In communication networks, knowledge of positions of communication nodes is important for improving the system performance. A multi-source localization technique has been proposed based on the matched field (MF) processing. The technique locates the nodes by solving a set of basis pursuit de-noising (BPDN) problems corresponding to a set of source frequencies. An efficient technique combining the homotopy approach and coordinate descent search has been developed to solve the BPDN problem. Further reduction in the complexity has been achieved by applying a position grid refinement method. Verified using simulated data generated by the proposed simulator and data from real experiment, the proposed technique outperforms other MF techniques in resolving sources positioned closely to each other, tolerance to noise and capability of locating multiple sources. To provide reliable localization based on MF techniques, accurate knowledge of the underwater acoustic environment is essential. However, such knowledge is not always available. Estimating uncertain environmental parameters can be achieved using MF inversion techniques. This requires solving a global optimization problem. Several global optimization algorithms have been investigated and an algorithm combining the simulated annealing and downhill simplex method has been applied for estimating the sound speed profile in a deep water scenario. Accurate MF localization results have been demonstrated when using the estimated sound speed profile. A very important task of communication receivers is accurate channel estimation. The knowledge of node positions and the environment can be exploited for enhancing the channel estimation accuracy and reducing the estimation complexity. This knowledge can be used to define the structure of the channel impulse response, such as the multipath spread and the sparsity. A channel estimator exploiting the channel sparsity estimated from the node positions has been proposed and investigated. The sparse taps of the channel impulse response are identified by solving a BPDN problem. The estimator employs an iterative tap-by-tap processing and uses local splines to interpolate the time-varying tap coefficients. This allows reduction in the complexity and memory requirement, whereas providing a high estimation accuracy.

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Duke, Peter S. « Direct-sequence spread-spectrum modulation for utility packet transmission in underwater acoustic communication networks ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02sep%5FDuke.pdf.

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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 2002.
Thesis advisor(s): Roberto Cristi, Joseph Rice. Includes bibliographical references (p. 129-130). Also available online.

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Lewis, Matthew Robert S. M. Massachusetts Institute of Technology. « Evaluation of vector sensors for adaptive equalization in underwater acoustic communication ». Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93793.

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Thesis: S.M., Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 123-125).
Underwater acoustic communication is an extremely complex field that faces many challenges due to the time-varying nature of the ocean environment. Vector sensors are a proven technology that when utilizing their directional sensing capabilities allows us to minimize the effect of interfering noise sources. A traditional pressure sensor array has been the standard for years but suffers at degraded signal to noise ratios (SNR) and requires maneuvers or a lengthly array aperture to direction find. This thesis explores the effect of utilizing a vector sensor array to steer to the direction of signal arrival and the effect it has on equalization of the signal at degraded SNRs. It was demonstrated that utilizing a single vector sensor we were able steer to the direction of arrival and improve the ability of an equalizer to determine the transmitted signal. This improvement was most prominent when the SNR was degraded to levels of 0 and 10 dB where the performance of the vector sensor outperformed that of the pressure sensor in nearly 100% of cases. Finally, this performance improvement occurred with a savings in computational expense.
by Matthew Robert Lewis.
S.M.

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Roee, Diamant. « Spatial reuse scheduling and localization for underwater acoustic communication networks ». Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44893.

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Ocean exploration, through the development of ocean-observation systems, is a key step towards a fuller understanding of life on Earth. Underwater acoustic communication networks (UWANs) will help to fulfill the needs of these ocean-observation systems, whose applications include gathering of scientific data, early warning systems, ecosystem monitoring and military surveillance. The data derived from UWANs is typically interpreted with reference to the location of a data collecting node, e.g. when reporting an event occurrence, or the location of an object itself is of interest, e.g. when tracking a moving underwater vehicle or diver. In this dissertation, we develop methods for localization and efficient data exchange in UWANs. In the first part of this work, we focus on underwater localization (UWL). Since global positioning system signals do not propagate through water, UWL is often based on fusing information from acceleration-based sensors and ranging information to anchor nodes with known locations. We consider practical challenges of UWL. The propagation speed varies with depth and location, anchor and unlocalized nodes are not time-synchronized, nodes are moving due to ocean currents, propagation delay measurements for ranging of non-line-of-sight communication links are mistakenly identified as line-of-sight, and unpredictable changes in the ocean current makes it hard to determine motion models for tracking. Taking these features of UWL into account, we propose localization and tracking schemes that exploit the spatially correlated ocean current, nodes' constant motion, and the periodicity of ocean waves. In the second part of this thesis, we use location information to develop medium access control scheduling algorithms and channel coding schemes. We focus on adaptive scheduling in which each node transmits based on timely network information. Specifically, our scheduling algorithms utilize the long propagation delay in the channel and the sparsity of the network topology to improve throughput, reliability and robustness to topology changes. To evaluate performance, we have developed a simulator combining existing numerical models of ocean current and of power attenuation in the ocean. We have also verified simulation results in four sea experiments of different channel bathymetry structures, using both industry and self-developed underwater acoustic modems.

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Dhanoa, Jasdeep Singh. « Acoustic digital communication systems for a doubly spread underwater channel ». Thesis, Cranfield University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413403.

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Goodfellow, Geraint Mark. « Development of an acoustic communication link for micro underwater vehicles ». Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2361.

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In recent years there has been an increasing trend towards the use of Micro Remotely Operated Vehicles (μROVs), such as the Videoray and Seabotix LBV products, for a range of subsea applications, including environmental monitoring, harbour security, military surveillance and offshore inspection. A major operational limitation is the umbilical cable, which is traditionally used to supply power and communications to the vehicle. This tether has often been found to significantly restrict the agility of the vehicle or in extreme cases, result in entanglement with subsea structures. This thesis addresses the challenges associated with developing a reliable full-duplex wireless communications link aimed at tetherless operation of a μROV. Previous research has demonstrated the ability to support highly compressed video transmissions over several kilometres through shallow water channels with large range-depth ratios. However, the physical constraints of these platforms paired with the system cost requirements pose significant additional challenges. Firstly, the physical size/weight of transducers for the LF (8-16kHz) and MF (16-32kHz) bands would significantly affect the dynamics of the vehicle measuring less than 0.5m long. Therefore, this thesis explores the challenges associated with moving the operating frequency up to around 50kHz centre, along with the opportunities for increased data rate and tracking due to higher bandwidth. The typical operating radius of μROVs is less than 200m, in water < 100m deep, which gives rise to multipath channels characterised by long timespread and relatively sparse arrivals. Hence, the system must be optimised for performance in these conditions. The hardware costs of large multi-element receiver arrays are prohibitive when compared to the cost of the μROV platform. Additionally, the physical size of such arrays complicates deployment from small surface vessels. Although some recent developments in iterative equalisation and decoding structures have enhanced the performance of single element receivers, they are not found to be adequate in such channels. This work explores the optimum cost/performance trade-off in a combination of a micro beamforming array using a Bit Interleaved Coded Modulation with Iterative Decoding (BICM-ID) receiver structure. The highly dynamic nature of μROVs, with rapid acceleration/deceleration and complex thruster/wake effects, are also a significant challenge to reliable continuous communications. The thesis also explores how these effects can best be mitigated via advanced Doppler correction techniques, and adaptive coding and modulation via a simultaneous frequency multiplexed down link. In order to fully explore continuous adaptation of the transmitted signals, a real-time full-duplex communication system was constructed in hardware, utilising low cost components and a highly optimised PC based receiver structure. Rigorous testing, both in laboratory conditions and through extensive field trials, have enabled the author to explore the performance of the communication link on a vehicle carrying out typical operations and presenting a wide range of channel, noise, Doppler and transmission latency conditions. This has led to a comprehensive set of design recommendations for a reliable and cost effective link capable of continuous throughputs of >30 kbits/s.

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Pusey, Grant Mark. « Characterisation of long-range horizontal performance of underwater acoustic communication ». Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1655.

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Underwater acoustic communication is a rapidly progressing field of technology, largely due to recent advances in low cost and power efficient digital signal processors. Unfortunately, the unpredictable and time varying physical properties of the underwater acoustic channel reduce communication reliability over long ranges. This study sought to characterise the performance of horizontal underwater acoustic data communication in various scenarios with particular application to subsea monitoring and control systems.To fulfil the experimental needs, two custom-built high frequency ambient noise recorder and modem control units were developed to operate with commercial underwater acoustic modems. Additionally, an underwater acoustic communication simulator based on the Bellhop propagation model was developed for Matlab, capable of producing performance predictions in both spatial and temporal studies. A series of short-term trials were conducted to determine the limitations of modem performance over different ranges. These trials included shallow water studies off the coast of Perth, Western Australia (D < 30 m), and a French deep water trial (D ≤ 1000 m) which used stand-alone modems. Experimental findings were compared to predictions obtained using two-dimensional range-depth performance simulations.A long-term investigation of the environmental influences on modem reliability was carried out off the coast of Perth in approximately 100 m of water. This involved simultaneously collecting environmental and modem performance data for over 16 days. The signal to noise ratio remained high for the duration of the trial so modem performance fluctuations could be attributed to changes in channel propagation. Using multiple linear regression, the measured environmental parameters were correlated with the observed modem performance and their contributions to an overall fitting curve were calculated. It was determined that the sound speed profile, in addition to the sea surface roughness, contributed strongly to the fitting curve, with a weaker contribution from the measured signal to noise ratio. This result was confirmed by performing temporal simulations which incorporated more detailed time-dependant environmental parameters. By progressively adding more parameters to the simulator including ambient noise, wave height and the sound speed profile, simulations provided more accurate predictions of the observed performanceOverall, the horizontal performance of underwater acoustic communication was characterised in several scenarios from a series of experimental and numerical investigations. Additionally, the developed simulator was shown to be an effective and flexible tool for predicting the performance of an underwater acoustic communication system. The results and tools discussed in this thesis provide an extensive investigation into the factors influencing horizontal underwater acoustic communication. The analysis demonstrates that whilst underwater acoustic communication can be effective, it is not yet a viable alternative to cabled telemetry for long-range subsea monitoring and control applications, where reliability is crucial. Underwater acoustic communication would best be suited as a non-critical or backup method for continuous monitoring systems until channel prediction and equalisation techniques are further refined.

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Li, Weichang. « Estimation and tracking of rapidly time-varying broadband acoustic communication channels / ». Cambridge, Mass. : Woods Hole, Mass. : Massachusetts Institute of Technology ; Woods Hole Oceanographic Institution, 2006. http://hdl.handle.net/1912/1509.

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Originally issued as the author's thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2006.
"February 2006". "Doctoral dissertation." "Department of origin: Applied Ocean Physics and Engineering." "Joint Program in Oceanography/Applied Ocean Science and Engineering"--Cover. Bibliography: p. 197-206.

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Zidi, Chaima. « Energy efficient underwater acoustic sensor networks ». Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCB003/document.

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Les réseaux de capteurs acoustiques sous-marins (UW-ASN) sont les plus nouveaux achèvements technologiques en termes de communication. Les UW-ASN visent à observer et à explorer les lacs, les rivières, les mers et les océans. Récemment, ils ont été soumis à une attention particulière en raison de leur grand potentiel en termes d'applications prometteuses dans divers domaines (militaires, environnementaux, scientifiques ...) et aux nouvelles questions scientifiques qu'ils suscitent. Un problème majeur dans les UW-ASN est l'épuisement rapide de l'énergie, car une grande puissance est nécessaire pour la communication acoustique, tandis que le budget de la batterie des capteurs est limité. Par conséquent, les protocoles de communication énergétiques revêtent une importance primordiale pour faire usage judiciaire du budget énergétique disponible. Dans ce contexte, cette thèse vise à étudier les principales caractéristiques des capteurs acoustiques sous-marins difficiles afin de concevoir des protocoles de communication énergétiques, plus spécifiquement au niveau routage et MAC. Tout d'abord, nous abordons le problème des trous énergétiques dans UW-ASN. Le problème du « sink-hole » se produit lorsque les capteurs les plus proches du sink épuisent leur énergie plus rapidement en raison de leur charge plus lourde. En effet, ces capteurs, en particulier ceux qui sont à un seul saut du sinkstatique, agissent comme des relais pour tous les autres capteurs, ce qui leur épuise sévèrement l’énergie.A la couche de routage,en particulier, nous proposons de distribuer la charge transmise par chaque capteur parmi plusieurs voisins potentiels, en supposant que les capteurs peuvent ajuster leur gamme de communication entre deux niveaux lorsqu'ils envoient ou transmettent des données. Plus précisément, nous déterminons pour chaque capteur l'ensemble des prochains sauts avec les poids de charge associés qui entraînent un épuisement équitable d'énergie entre tous les capteurs du réseau. Ensuite, nous étendons notre stratégie de routage équilibrée en supposant que chaque capteur n'est pas seulement capable d'ajuster sa puissance d'émission à 2 niveaux mais aussi jusqu'à n niveaux où n> 2. Par conséquent, à la couche de routage, pour chaque valeur possible de n, nous déterminons pour chaque capteur l'ensemble des éventuels sauts avec les poids de charge associés qui mènent à une consommation d'énergie équitable chez tous les capteurs du réseau. En outre, nous obtenons le nombre optimal de puissances de transmission n qui équilibre la consommation d'énergie de tous les capteurs pour chaque configuration de réseau. En plus de cela, il convient de souligner que notre protocole de routage étendu utilise un modèle de canal à variation de temps plus réaliste qui tient compte de la plupart des caractéristiques fondamentales de la propagation acoustique sous-marine. Les résultats analytiques montrent que notre protocole de routage assure une réduction importante de la consommation d’énergie. Deuxièmement, pour atténuer les impacts de collision spectaculaires gaspillant l’énergie, nous concevons un protocole MAC multicanal (MC-UWMAC) évitant les collisions pour les UW-ASNs. MC-UWMAC fonctionne avec un canal de contrôle (décomposé en créneaux de temps) et un ensemble de canaux de données à bande passante égale. Les créneaux du canal de contrôle sont dédiés à l’échange RTS / CTS permettant à une paire de capteurs communicants de s'accorder sur l'heure de début de la communication sur un canal de données pré-alloué. Dans cette thèse, nous proposons deux nouvelles procédures associées d'allocation des créneaux du canal de contrôle et d'attribution des canaux de données sans nécessiter de frais de négociation supplémentaires. En conséquence, chaque capteur peut initier l'échange RTS / CTS uniquement à son créneau assigné, calculé à l'aide d'une procédure d'allocation basée sur une partition virtuelle de grille de la zone de déploiement. (...)
UnderWaterAcoustic Sensor Networks (UW-ASNs) are the newest technological achievement in terms of communication. Composed of a set of communicating underwater sensors, UW-ASNs are intended to observe and explore lakes, rivers, seas and oceans. Recently, they have been subject to a special attention due to their great potential in terms of promising applications in various domains (military, environmental, scientific...) and to the new scientific issues they raise. A great challenging issue in UW-ASNs is the fast energy depletion since high power is needed for acoustic communication while sensors battery budget is limited. Hence, energy-efficient networking protocols are of a paramount importance to make judicious use of the available energy budget while considering the distinguishing underwater environment characteristics. In this context, this thesis aims at studying the main challenging underwater acoustic sensors characteristics to design energy-efficient communication protocols specifically at the routing and MAC layers. First, we address the problem of energy holes in UW-ASNs. The sink-hole problem occurs when the closest nodes to sink drain their energy faster due to their heavier load. Indeed, those sensors especially the ones that are 1-hop away from the static sink act as relays to it on behalf of all other sensors, thus suffering from severe energy depletion. In particular, at the routing layer, we propose to distribute the transmission load at each sensor among several potential neighbors, assuming that sensors can adjust their communication range among two levels when they send or forward data. Specifically, we determine for each sensor the set of next hops with the associated load weights that lead to a fair energy depletion among all sensors in the network. Then, we extend our balanced routing strategy by assuming that each sensor node is not only able to adjust its transmission power to 2 levels but eventually up to n levels where n > 2. Consequently, at the routing layer, for each possible value of n, we determine for each sensor the set of possible next hops with the associated load weights that lead to a fair energy consumption among all sensors in the network. Moreover, we derive the optimal number of transmission powers n that balances the energy consumption among all sensors for each network configuration. In addition to that, it is worth pointing out that our extended routing protocol uses a more realistic time varying channel model that takes into account most of the fundamental characteristics of the underwater acoustic propagation. Analytical results show that further energy saving is achieved by our extended routing scheme. Second, to mitigate the dramatic collision impacts, we design a collision avoidance energy efficient multichannel MAC protocol (MC-UWMAC) for UW-ASNs. MC-UWMAC operates on single slotted control and a set of equal-bandwidth data channels. Control channel slots are dedicated to RTS/CTS handshaking allowing a communicating node pair to agree on the start time of communication on a pre-allocated data channel. In this thesis, we propose two novel coupled slot assignment and data channels allocation procedures without requiring any extra negotiation overhead. Accordingly, each node can initiate RTS/CTS exchange only at its assigned slot calculated using a slot allocation procedure based on a grid virtual partition of the deployment area. Moreover, for each communicating pair of nodes, one data channel is allocated using a channel allocation procedure based on our newly designed concept of singleton- intersecting quorum. Accordingly, each pair of communicating nodes will have at their disposal a unique 2-hop conflict free data channel. Compared with existing MAC protocol, MC-UWMAC reduces experienced collisions and improves network throughput while minimizing energy consumption

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Zidi, Chaima. « Energy efficient underwater acoustic sensor networks ». Electronic Thesis or Diss., Sorbonne Paris Cité, 2018. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=2295&f=12490.

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Les réseaux de capteurs acoustiques sous-marins (UW-ASN) sont les plus nouveaux achèvements technologiques en termes de communication. Les UW-ASN visent à observer et à explorer les lacs, les rivières, les mers et les océans. Récemment, ils ont été soumis à une attention particulière en raison de leur grand potentiel en termes d'applications prometteuses dans divers domaines (militaires, environnementaux, scientifiques ...) et aux nouvelles questions scientifiques qu'ils suscitent. Un problème majeur dans les UW-ASN est l'épuisement rapide de l'énergie, car une grande puissance est nécessaire pour la communication acoustique, tandis que le budget de la batterie des capteurs est limité. Par conséquent, les protocoles de communication énergétiques revêtent une importance primordiale pour faire usage judiciaire du budget énergétique disponible. Dans ce contexte, cette thèse vise à étudier les principales caractéristiques des capteurs acoustiques sous-marins difficiles afin de concevoir des protocoles de communication énergétiques, plus spécifiquement au niveau routage et MAC. Tout d'abord, nous abordons le problème des trous énergétiques dans UW-ASN. Le problème du « sink-hole » se produit lorsque les capteurs les plus proches du sink épuisent leur énergie plus rapidement en raison de leur charge plus lourde. En effet, ces capteurs, en particulier ceux qui sont à un seul saut du sinkstatique, agissent comme des relais pour tous les autres capteurs, ce qui leur épuise sévèrement l’énergie.A la couche de routage,en particulier, nous proposons de distribuer la charge transmise par chaque capteur parmi plusieurs voisins potentiels, en supposant que les capteurs peuvent ajuster leur gamme de communication entre deux niveaux lorsqu'ils envoient ou transmettent des données. Plus précisément, nous déterminons pour chaque capteur l'ensemble des prochains sauts avec les poids de charge associés qui entraînent un épuisement équitable d'énergie entre tous les capteurs du réseau. Ensuite, nous étendons notre stratégie de routage équilibrée en supposant que chaque capteur n'est pas seulement capable d'ajuster sa puissance d'émission à 2 niveaux mais aussi jusqu'à n niveaux où n> 2. Par conséquent, à la couche de routage, pour chaque valeur possible de n, nous déterminons pour chaque capteur l'ensemble des éventuels sauts avec les poids de charge associés qui mènent à une consommation d'énergie équitable chez tous les capteurs du réseau. En outre, nous obtenons le nombre optimal de puissances de transmission n qui équilibre la consommation d'énergie de tous les capteurs pour chaque configuration de réseau. En plus de cela, il convient de souligner que notre protocole de routage étendu utilise un modèle de canal à variation de temps plus réaliste qui tient compte de la plupart des caractéristiques fondamentales de la propagation acoustique sous-marine. Les résultats analytiques montrent que notre protocole de routage assure une réduction importante de la consommation d’énergie. Deuxièmement, pour atténuer les impacts de collision spectaculaires gaspillant l’énergie, nous concevons un protocole MAC multicanal (MC-UWMAC) évitant les collisions pour les UW-ASNs. MC-UWMAC fonctionne avec un canal de contrôle (décomposé en créneaux de temps) et un ensemble de canaux de données à bande passante égale. Les créneaux du canal de contrôle sont dédiés à l’échange RTS / CTS permettant à une paire de capteurs communicants de s'accorder sur l'heure de début de la communication sur un canal de données pré-alloué. Dans cette thèse, nous proposons deux nouvelles procédures associées d'allocation des créneaux du canal de contrôle et d'attribution des canaux de données sans nécessiter de frais de négociation supplémentaires. En conséquence, chaque capteur peut initier l'échange RTS / CTS uniquement à son créneau assigné, calculé à l'aide d'une procédure d'allocation basée sur une partition virtuelle de grille de la zone de déploiement. (...)
UnderWaterAcoustic Sensor Networks (UW-ASNs) are the newest technological achievement in terms of communication. Composed of a set of communicating underwater sensors, UW-ASNs are intended to observe and explore lakes, rivers, seas and oceans. Recently, they have been subject to a special attention due to their great potential in terms of promising applications in various domains (military, environmental, scientific...) and to the new scientific issues they raise. A great challenging issue in UW-ASNs is the fast energy depletion since high power is needed for acoustic communication while sensors battery budget is limited. Hence, energy-efficient networking protocols are of a paramount importance to make judicious use of the available energy budget while considering the distinguishing underwater environment characteristics. In this context, this thesis aims at studying the main challenging underwater acoustic sensors characteristics to design energy-efficient communication protocols specifically at the routing and MAC layers. First, we address the problem of energy holes in UW-ASNs. The sink-hole problem occurs when the closest nodes to sink drain their energy faster due to their heavier load. Indeed, those sensors especially the ones that are 1-hop away from the static sink act as relays to it on behalf of all other sensors, thus suffering from severe energy depletion. In particular, at the routing layer, we propose to distribute the transmission load at each sensor among several potential neighbors, assuming that sensors can adjust their communication range among two levels when they send or forward data. Specifically, we determine for each sensor the set of next hops with the associated load weights that lead to a fair energy depletion among all sensors in the network. Then, we extend our balanced routing strategy by assuming that each sensor node is not only able to adjust its transmission power to 2 levels but eventually up to n levels where n > 2. Consequently, at the routing layer, for each possible value of n, we determine for each sensor the set of possible next hops with the associated load weights that lead to a fair energy consumption among all sensors in the network. Moreover, we derive the optimal number of transmission powers n that balances the energy consumption among all sensors for each network configuration. In addition to that, it is worth pointing out that our extended routing protocol uses a more realistic time varying channel model that takes into account most of the fundamental characteristics of the underwater acoustic propagation. Analytical results show that further energy saving is achieved by our extended routing scheme. Second, to mitigate the dramatic collision impacts, we design a collision avoidance energy efficient multichannel MAC protocol (MC-UWMAC) for UW-ASNs. MC-UWMAC operates on single slotted control and a set of equal-bandwidth data channels. Control channel slots are dedicated to RTS/CTS handshaking allowing a communicating node pair to agree on the start time of communication on a pre-allocated data channel. In this thesis, we propose two novel coupled slot assignment and data channels allocation procedures without requiring any extra negotiation overhead. Accordingly, each node can initiate RTS/CTS exchange only at its assigned slot calculated using a slot allocation procedure based on a grid virtual partition of the deployment area. Moreover, for each communicating pair of nodes, one data channel is allocated using a channel allocation procedure based on our newly designed concept of singleton- intersecting quorum. Accordingly, each pair of communicating nodes will have at their disposal a unique 2-hop conflict free data channel. Compared with existing MAC protocol, MC-UWMAC reduces experienced collisions and improves network throughput while minimizing energy consumption

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Blair, Ballard J. S. (Ballard Justin Smith). « Analysis of and techniques for adaptive equalization for underwater acoustic communication ». Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68436.

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Résumé :

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and the Woods Hole Oceanographic Institution), 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 203-215).
Underwater wireless communication is quickly becoming a necessity for applications in ocean science, defense, and homeland security. Acoustics remains the only practical means of accomplishing long-range communication in the ocean. The acoustic communication channel is fraught with difficulties including limited available bandwidth, long delay-spread, time-variability, and Doppler spreading. These difficulties reduce the reliability of the communication system and make high data-rate communication challenging. Adaptive decision feedback equalization is a common method to compensate for distortions introduced by the underwater acoustic channel. Limited work has been done thus far to introduce the physics of the underwater channel into improving and better understanding the operation of a decision feedback equalizer. This thesis examines how to use physical models to improve the reliability and reduce the computational complexity of the decision feedback equalizer. The specific topics covered by this work are: how to handle channel estimation errors for the time varying channel, how to use angular constraints imposed by the environment into an array receiver, what happens when there is a mismatch between the true channel order and the estimated channel order, and why there is a performance difference between the direct adaptation and channel estimation based methods for computing the equalizer coefficients. For each of these topics, algorithms are provided that help create a more robust equalizer with lower computational complexity for the underwater channel.
by Ballard J. S. Blair.
Ph.D.

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Kanthan, Rupesh R. « The ICoN integrated communication and navigation protocol for underwater acoustic networks ». Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/36783.

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Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.
Includes bibliographical references (p. 81-82).
The deployment of autonomous underwater devices has increased dramatically in the last several years, presenting a strong and growing need for a network protocol to mediate acoustic communications between devices. This network protocol must also provide an infrastructure for acoustic navigation, while ensuring that provisions for communication and navigation do not interfere with each other. To approach this difficult problem, we begin with a discussion of the limitations of traditional networking protocols when subjected to the complexities introduced by the underwater acoustic environment. We then present ICoN, a proposed network protocol, designed to integrate acoustic communication and navigation and optimized to operate in the low-bandwidth, high-loss underwater environment. A working description of ICoN and a discussion of its features are followed by analysis of the protocol through simulation, indicating its potential for improved performance over traditional networking protocols. The simulation results are reinforced through real-world experimental validation of ICoN, which, though limited, appears to confirm the effectiveness of the new protocol. We conclude with possible future extensions to ICoN, discussing various methods that might increase its potency in dealing with more demanding underwater acoustic applications.
by Rupesh R. Kanthan.
M.Eng.and S.B.

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31

Allander, Martin. « Channel Equalization Using Machine Learning for Underwater Acoustic Communications ». Thesis, Linköpings universitet, Kommunikationssystem, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166643.

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Wireless underwater acoustic (UWA) communications is a developing field with various applications. The underwater acoustic communication channel is very special and its behavior is environment-dependent. The UWA channel is characterized by low available bandwidth, and severe motion-introduced Doppler effectcompared to wireless radio communication. Recent literature suggests that machine learning (ML)-based channel estimation and equalization offer benefits overtraditional techniques (a decision feedback equalizer), in UWA communications. ML can be advantageous due to the difficultly in designing algorithms for UWA communication, as finding general channel models have proven to be difficult. This study aims to explore if ML-based channel estimation and equalization as a part of a sophisticated physical layer structure can offer improved performance. In the study, supervised ML using a deep neural network and a recurrent neural network will be utilized to improve the bit error rate. A channel simulator with environment-specific input is used to study a wide range of channels. The simulations are utilized to study in which environments ML should be tested. It is shown that in highly time-varying channels, ML outperforms traditional techniques if trained with prior information of the channel. However, utilizing ML without prior information of the channel yielded no improvement of the performance.

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32

Kreamer, William Ryan 1976. « Supervisory control of an autonomous underwater vehicle using an acoustic communication link ». Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8969.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2000.
Includes bibliographical references (leaves 84-86).
In this thesis, I designed and tested a supervisory control scheme for the Odyssey II-class Autonomous Underwater Vehicles that relies on a very-low-data-rate acoustic communication link. A human supervisor communicates with the AUV over a combination radio/acoustic network. The supervisor radios commands from shore to data repeater nodes moored at strategic locations on the ocean surface. Utility Acoustic Modems mounted on the moorings rebroadcast the binary data into the sea in the 12-17 kHz frequency band. The moving AUV detects the transmission, decodes the message, and carries out the command contained within. The operator's commands are implemented in the context of a behavior-based layered control software architecture. The supervisory control scheme was tested and verified during the Synaptic Internal Tide Experiment, which took place in Monterey Bay during August and September, 1999.
by William Ryan Kreamer.
S.M.

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33

Sanderson, Josh. « Hierarchical Modulation Detection of Underwater Acoustic Communication Signals Through Maximum Likelihood Combining ». Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1410872323.

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34

Svensson, Elin. « Physical modelling of acoustic shallow-water communication channels ». Doctoral thesis, Stockholm : Farkost och flyg, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4572.

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35

Nassr, Husam, et Kurt Kosbar. « PERFORMANCE EVALUATION FOR DECISION-FEEDBACK EQUALIZER WITH PARAMETER SELECTION ON UNDERWATER ACOUSTIC COMMUNICATION ». International Foundation for Telemetering, 2017. http://hdl.handle.net/10150/626999.

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This paper investigates the effect of parameter selection for the decision feedback equalization (DFE) on communication performance through a dispersive underwater acoustic wireless channel (UAWC). A DFE based on minimum mean-square error (MMSE-DFE) criterion has been employed in the implementation for evaluation purposes. The output from the MMSE-DFE is input to the decoder to estimate the transmitted bit sequence. The main goal of this experimental simulation is to determine the best selection, such that the reduction in the computational overload is achieved without altering the performance of the system, where the computational complexity can be reduced by selecting an equalizer with a proper length. The system performance is tested for BPSK, QPSK, 8PSK and 16QAM modulation and a simulation for the system is carried out for Proakis channel A and real underwater wireless acoustic channel estimated during SPACE08 measurements to verify the selection.

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36

Abdelkareem, Ammar Ebdelmelik. « Doppler compensation algorithms for DSP-based implementation of OFDM underwater acoustic communication systems ». Thesis, University of Newcastle Upon Tyne, 2012. http://hdl.handle.net/10443/1443.

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In recent years, orthogonal frequency division multiplexing (OFDM) has gained considerable attention in the development of underwater communication (UWC) systems for civilian and military applications. However, the wideband nature of the communication links necessitate robust algorithms to combat the consequences of severe channel conditions such as frequency selectivity, ambient noise, severe multipath and Doppler Effect due to velocity change between the transmitter and receiver. This velocity perturbation comprises two scenarios; the first induces constant time scale expansion/compression or zero acceleration during the transmitted packet time, and the second is time varying Doppler-shift. The latter is an increasingly important area in autonomous underwater vehicle (AUV) applications. The aim of this thesis is to design a low complexity OFDM-based receiver structure for underwater communication that tackles the inherent Doppler effect and is applicable for developing real-time systems on a digital signal processor (DSP). The proposed structure presents a paradigm in modem design from previous generations of single carrier receivers employing computationally expensive equalizers. The thesis demonstrates the issues related to designing a practical OFDM system, such as channel coding and peak-to-average power ratio (PAPR). In channel coding, the proposed algorithms employ convolutional bit-interleaved coded modulation with iterative decoding (BICM-ID) to obtain a higher degree of protection against power fading caused by the channel. A novel receiver structure that combines an adaptive Doppler-shift correction and BICM-ID for multi-carrier systems is presented. In addition, the selective mapping (SLM) technique has been utilized for PAPR. Due to their time varying and frequency selective channel nature, the proposed systems are investigated via both laboratory simulations and experiments conducted in the North Sea off the UK’s North East coast. The results of the study show that the proposed systems outperform block-based Doppler-shift compensation and are capable of tracking the Doppler-shift at acceleration up to 1m /s2.

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37

au, turtle111@aapt net, et Jacqueline Giles. « The underwater acoustic repertoire of the long-necked, freshwater turtle Chelodina oblonga ». Murdoch University, 2005. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20061121.103729.

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The major question addressed by this project was to determine if the long-necked, freshwater turtle Chelodina oblonga, vocalise underwater and whether their vocal activity could be related to behavioural or ecological aspects of their lives. These turtles often live in wetlands where visibility is restricted due to habitat complexity or light limitation caused by factors such as tannin-staining, or turbidity. For many aquatic animals, sound is a useful means of communication over distances beyond their visual acuity. This thesis gives the first detailed account of the underwater vocal repertoire of C. oblonga. In total, over 230 days were spent in the field and more than 500 hours of tape recordings were made for this research. Initially, a number of recordings took place in three wetlands known to support turtle populations: Blue Gum Lake; Glen Brook Dam; and Lake Leschenaultia in Perth, Western Australia; in order to determine the nature of the freshwater sound field and place turtle vocalisations into the context in which they were vocalising. The wetlands differed in terms of degree of enrichment, substrate material, water depth and habitat complexity. Recordings were made over a four-week period in the last month of summer and the first week of autumn (Feb-Mar 2003). Invertebrate sweeps were also taken over a two-week period at each recording site to determine if invertebrate distributions were related to patterns of sonic activity. To determine the influence of wind on ambient noise; recordings were undertaken on winter mornings (June-August, 2003) at Blue Gum Lake and Glen Brook Dam at locations north, south, west and east for four different wind speeds Beaufort Wind Scale (BWS) 0,1,2 & 3. There were seven distinctive calls recognised in the recordings. The frequency bandwidth most utilised by organisms was between 3 kHz up to around 14 kHz, with the exception of the bird-like song; which extended from 500 Hz up to around 10 kHz. Blue Gum Lake contained a more diverse and abundant assemblage of invertebrates than Lake Leschenaultia and Glen Brook Dam. Correspondingly, a greater diversity of calls was recorded at Blue Gum Lake, as well as the presence of chorus activity, which was not heard at the two less-enriched sites. The periods of greatest diversity and abundance of macroinvertebrates was synonymous with the increased sonic activity at dusk and midnight with noise levels greatest at dusk in particular, and to a lesser extent at midnight. There was no difference in ambient noise at Blue Gum Lake or Glen Brook Dam at wind speeds of Beaufort Wind Scale 0, 1 and 2. Turtles from three populations were recorded in artificial environments: consisting of round, plastic, above-ground ponds (1.8m dia. x 0.65m depth), which were set up to recreate small wetlands. Recordings occurred from September to October, 2003 and from February to December, 2004 as well as January, 2005. Seven hatchling and five juvenile turtles (CL <10cm) were also recorded in order to ascertain whether very young turtles vocalised. Hatchlings were recorded in a glass aquarium (35.5cm length x 20cm width x 22.0cm depth) and juveniles were placed into a below-ground outdoor pond (1m length x 0.5m width x 0.4m depth). Recordings occurred from as early as 4.30am (dawn recordings) to as late as 1.30am (evening recordings). The recordings revealed that turtles utilise an underwater acoustic communication system (calling at the waters surface was also noted but these were not recorded or a part of this research) involving a repertoire of both complex and percussive sounds with short, medium and potentially long-range propagation characteristics. Complex structures included harmonically related elements (richly or sparsely) and different rates of frequency modulation. Frequency use extended beyond the in-air auditory sensitivity known for a single species of turtle studied from the family Chelidae; with calls ranging from around 100 Hz in some of the percussive displays, to as high as 3.5 kHz in some complex calls, with clicks extending beyond the 20 kHz upper limit of the recording system. However, most of C. oblongas vocalisations had dominant frequencies below 1 kHz. Turtles were intermittent callers with an extensive vocal repertoire of seventeen (17) vocal categories - highly suggestive of complex social organisation. Vocalisations included: a) clacks; b) clicks; c) squawks; d) hoots; e) short chirps; f) high short chirps; g) medium chirps; h) long chirps; i) high calls; j) cries or wails; k) cat whines; l) grunts; m) growls; n) blow bursts; o) staccatos; p) a wild howl; and q) drum rolling. Also, two sustained pulse-bouts were recorded during the breeding months, hypothesised to function as acoustic advertisement displays possibly calling songs. Hatchling turtles were not heard to vocalise within the audible range. Only a single complex vocalisation was heard produced by the juvenile turtles, with a number of percussive calls. Preliminary playback trials were conducted under free-field conditions and within an artificial environment, which consisted of a below ground rectangular tank (2.4m length x 0.8m width x 0.6m deep). A number of turtle calls recorded in the artificial ponds were selected for playback. A UW 30 speaker was used for broadcast of calls. The free-field playbacks occurred at Mabel Talbot Lake and Blue Gum Lake during the months of April and May, 2005. Playback using 14 seconds of an artificially constructed sequence from the sustained pulse-bout occurred in the artificial channels. This sequence consisted of some of the first phase pulses followed by a section of the vibrato. The preliminary free-field playback trials indicated that turtles had some interest in the calls being played by responding with an alert posture. Turtles were shown to remain in the alert posture for a significantly longer time than when no sound was played or when white noise was played. The extensive repertoire and initial responses to the free-field playbacks indicated that sound has some biological importance for C. oblonga, although results of playbacks under artificial conditions were inconclusive.

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38

Giles, Jacqueline. « The underwater acoustic repertoire of the long-necked, freshwater turtle Chelodina oblonga ». Thesis, Giles, Jacqueline (2005) The underwater acoustic repertoire of the long-necked, freshwater turtle Chelodina oblonga. PhD thesis, Murdoch University, 2005. https://researchrepository.murdoch.edu.au/id/eprint/39/.

Texte intégral

Résumé :

The major question addressed by this project was to determine if the long-necked, freshwater turtle Chelodina oblonga, vocalise underwater and whether their vocal activity could be related to behavioural or ecological aspects of their lives. These turtles often live in wetlands where visibility is restricted due to habitat complexity or light limitation caused by factors such as tannin-staining, or turbidity. For many aquatic animals, sound is a useful means of communication over distances beyond their visual acuity. This thesis gives the first detailed account of the underwater vocal repertoire of C. oblonga. In total, over 230 days were spent in the field and more than 500 hours of tape recordings were made for this research. Initially, a number of recordings took place in three wetlands known to support turtle populations: Blue Gum Lake; Glen Brook Dam; and Lake Leschenaultia in Perth, Western Australia; in order to determine the nature of the freshwater sound field and place turtle vocalisations into the context in which they were vocalising. The wetlands differed in terms of degree of enrichment, substrate material, water depth and habitat complexity. Recordings were made over a four-week period in the last month of summer and the first week of autumn (Feb-Mar 2003). Invertebrate sweeps were also taken over a two-week period at each recording site to determine if invertebrate distributions were related to patterns of sonic activity. To determine the influence of wind on ambient noise; recordings were undertaken on winter mornings (June-August, 2003) at Blue Gum Lake and Glen Brook Dam at locations north, south, west and east for four different wind speeds - Beaufort Wind Scale (BWS) 0,1,2 and 3. There were seven distinctive calls recognised in the recordings. The frequency bandwidth most utilised by organisms was between 3 kHz up to around 14 kHz, with the exception of the 'bird-like song'; which extended from 500 Hz up to around 10 kHz. Blue Gum Lake contained a more diverse and abundant assemblage of invertebrates than Lake Leschenaultia and Glen Brook Dam. Correspondingly, a greater diversity of calls was recorded at Blue Gum Lake, as well as the presence of chorus activity, which was not heard at the two less-enriched sites. The periods of greatest diversity and abundance of macroinvertebrates was synonymous with the increased sonic activity at dusk and midnight with noise levels greatest at dusk in particular, and to a lesser extent at midnight. There was no difference in ambient noise at Blue Gum Lake or Glen Brook Dam at wind speeds of Beaufort Wind Scale 0, 1 and 2. Turtles from three populations were recorded in artificial environments: consisting of round, plastic, above-ground ponds (1.8m dia. x 0.65m depth), which were set up to recreate small wetlands. Recordings occurred from September to October, 2003 and from February to December, 2004 as well as January, 2005. Seven hatchling and five juvenile turtles (CL < 10cm) were also recorded in order to ascertain whether very young turtles vocalised. Hatchlings were recorded in a glass aquarium (35.5cm length x 20cm width x 22.0cm depth) and juveniles were placed into a below-ground outdoor pond (1m length x 0.5m width x 0.4m depth). Recordings occurred from as early as 4.30am (dawn recordings) to as late as 1.30am (evening recordings). The recordings revealed that turtles utilise an underwater acoustic communication system (calling at the water's surface was also noted but these were not recorded or a part of this research) involving a repertoire of both complex and percussive sounds with short, medium and potentially long-range propagation characteristics. Complex structures included harmonically related elements (richly or sparsely) and different rates of frequency modulation. Frequency use extended beyond the in-air auditory sensitivity known for a single species of turtle studied from the family Chelidae; with calls ranging from around 100 Hz in some of the percussive displays, to as high as 3.5 kHz in some complex calls, with 'clicks' extending beyond the 20 kHz upper limit of the recording system. However, most of C. oblonga's vocalisations had dominant frequencies below 1 kHz. Turtles were intermittent callers with an extensive vocal repertoire of seventeen (17) vocal categories - highly suggestive of complex social organisation. Vocalisations included: a) clacks; b) clicks; c) squawks; d) hoots; e) short chirps; f) high short chirps; g) medium chirps; h) long chirps; i) high calls; j) cries or wails; k) cat whines; l) grunts; m) growls; n) blow bursts; o) staccatos; p) a wild howl; and q) drum rolling. Also, two sustained 'pulse-bouts' were recorded during the breeding months, hypothesised to function as acoustic advertisement displays - possibly 'calling songs'. Hatchling turtles were not heard to vocalise within the audible range. Only a single complex vocalisation was heard produced by the juvenile turtles, with a number of percussive calls. Preliminary playback trials were conducted under free-field conditions and within an artificial environment, which consisted of a below ground rectangular tank (2.4m length x 0.8m width x 0.6m deep). A number of turtle calls recorded in the artificial ponds were selected for playback. A UW 30 speaker was used for broadcast of calls. The free-field playbacks occurred at Mabel Talbot Lake and Blue Gum Lake during the months of April and May, 2005. Playback using 14 seconds of an artificially constructed sequence from the sustained 'pulse-bout' occurred in the artificial channels. This sequence consisted of some of the first phase pulses followed by a section of the 'vibrato'. The preliminary free-field playback trials indicated that turtles had some interest in the calls being played by responding with an 'alert posture'. Turtles were shown to remain in the alert posture for a significantly longer time than when no sound was played or when white noise was played. The extensive repertoire and initial responses to the free-field playbacks indicated that sound has some biological importance for C. oblonga, although results of playbacks under artificial conditions were inconclusive.

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39

Giles, Jacqueline. « The underwater acoustic repertoire of the long-necked, freshwater turtle Chelodina oblonga ». Giles, Jacqueline (2005) The underwater acoustic repertoire of the long-necked, freshwater turtle Chelodina oblonga. PhD thesis, Murdoch University, 2005. http://researchrepository.murdoch.edu.au/39/.

Texte intégral

Résumé :

The major question addressed by this project was to determine if the long-necked, freshwater turtle Chelodina oblonga, vocalise underwater and whether their vocal activity could be related to behavioural or ecological aspects of their lives. These turtles often live in wetlands where visibility is restricted due to habitat complexity or light limitation caused by factors such as tannin-staining, or turbidity. For many aquatic animals, sound is a useful means of communication over distances beyond their visual acuity. This thesis gives the first detailed account of the underwater vocal repertoire of C. oblonga. In total, over 230 days were spent in the field and more than 500 hours of tape recordings were made for this research. Initially, a number of recordings took place in three wetlands known to support turtle populations: Blue Gum Lake; Glen Brook Dam; and Lake Leschenaultia in Perth, Western Australia; in order to determine the nature of the freshwater sound field and place turtle vocalisations into the context in which they were vocalising. The wetlands differed in terms of degree of enrichment, substrate material, water depth and habitat complexity. Recordings were made over a four-week period in the last month of summer and the first week of autumn (Feb-Mar 2003). Invertebrate sweeps were also taken over a two-week period at each recording site to determine if invertebrate distributions were related to patterns of sonic activity. To determine the influence of wind on ambient noise; recordings were undertaken on winter mornings (June-August, 2003) at Blue Gum Lake and Glen Brook Dam at locations north, south, west and east for four different wind speeds - Beaufort Wind Scale (BWS) 0,1,2 and 3. There were seven distinctive calls recognised in the recordings. The frequency bandwidth most utilised by organisms was between 3 kHz up to around 14 kHz, with the exception of the 'bird-like song'; which extended from 500 Hz up to around 10 kHz. Blue Gum Lake contained a more diverse and abundant assemblage of invertebrates than Lake Leschenaultia and Glen Brook Dam. Correspondingly, a greater diversity of calls was recorded at Blue Gum Lake, as well as the presence of chorus activity, which was not heard at the two less-enriched sites. The periods of greatest diversity and abundance of macroinvertebrates was synonymous with the increased sonic activity at dusk and midnight with noise levels greatest at dusk in particular, and to a lesser extent at midnight. There was no difference in ambient noise at Blue Gum Lake or Glen Brook Dam at wind speeds of Beaufort Wind Scale 0, 1 and 2. Turtles from three populations were recorded in artificial environments: consisting of round, plastic, above-ground ponds (1.8m dia. x 0.65m depth), which were set up to recreate small wetlands. Recordings occurred from September to October, 2003 and from February to December, 2004 as well as January, 2005. Seven hatchling and five juvenile turtles (CL < 10cm) were also recorded in order to ascertain whether very young turtles vocalised. Hatchlings were recorded in a glass aquarium (35.5cm length x 20cm width x 22.0cm depth) and juveniles were placed into a below-ground outdoor pond (1m length x 0.5m width x 0.4m depth). Recordings occurred from as early as 4.30am (dawn recordings) to as late as 1.30am (evening recordings). The recordings revealed that turtles utilise an underwater acoustic communication system (calling at the water's surface was also noted but these were not recorded or a part of this research) involving a repertoire of both complex and percussive sounds with short, medium and potentially long-range propagation characteristics. Complex structures included harmonically related elements (richly or sparsely) and different rates of frequency modulation. Frequency use extended beyond the in-air auditory sensitivity known for a single species of turtle studied from the family Chelidae; with calls ranging from around 100 Hz in some of the percussive displays, to as high as 3.5 kHz in some complex calls, with 'clicks' extending beyond the 20 kHz upper limit of the recording system. However, most of C. oblonga's vocalisations had dominant frequencies below 1 kHz. Turtles were intermittent callers with an extensive vocal repertoire of seventeen (17) vocal categories - highly suggestive of complex social organisation. Vocalisations included: a) clacks; b) clicks; c) squawks; d) hoots; e) short chirps; f) high short chirps; g) medium chirps; h) long chirps; i) high calls; j) cries or wails; k) cat whines; l) grunts; m) growls; n) blow bursts; o) staccatos; p) a wild howl; and q) drum rolling. Also, two sustained 'pulse-bouts' were recorded during the breeding months, hypothesised to function as acoustic advertisement displays - possibly 'calling songs'. Hatchling turtles were not heard to vocalise within the audible range. Only a single complex vocalisation was heard produced by the juvenile turtles, with a number of percussive calls. Preliminary playback trials were conducted under free-field conditions and within an artificial environment, which consisted of a below ground rectangular tank (2.4m length x 0.8m width x 0.6m deep). A number of turtle calls recorded in the artificial ponds were selected for playback. A UW 30 speaker was used for broadcast of calls. The free-field playbacks occurred at Mabel Talbot Lake and Blue Gum Lake during the months of April and May, 2005. Playback using 14 seconds of an artificially constructed sequence from the sustained 'pulse-bout' occurred in the artificial channels. This sequence consisted of some of the first phase pulses followed by a section of the 'vibrato'. The preliminary free-field playback trials indicated that turtles had some interest in the calls being played by responding with an 'alert posture'. Turtles were shown to remain in the alert posture for a significantly longer time than when no sound was played or when white noise was played. The extensive repertoire and initial responses to the free-field playbacks indicated that sound has some biological importance for C. oblonga, although results of playbacks under artificial conditions were inconclusive.

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40

Dayal, Avik. « Nonlinear Doppler Warp Correction for Acoustic OFDM ». Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/78157.

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The Underwater Acoustic (UWA) channel has been an area of interest for many researchers and engineers, but also a very challenging area. Compared to the over-the-air radio frequency (RF) channel, the underwater acoustic channel causes multiple distortions – due to multipath, frequency selectivity, noise, and Doppler – some of which are more severe. The increased distortion causes many techniques and assumptions made for typical RF communication systems to break down. One of the assumptions that breaks down is that the Doppler effect that the signal undergoes can be modelled with a simple shift in frequency, since the signals used to communicate in a UWA channel are effectively wideband. In this work the Doppler Effect that a signal undergoes is modelled as a nonlinear time warp. A procedure is developed to estimate the parameters of the time warp from the observed signal. These time warp parameters are then used to reverse the effect of the time warp. Two different methods for estimating the time warp parameters and correcting the Doppler are compared. The first technique uses sinusoids placed at the beginning and end of the signal to estimate the parameters of the warp that the signal undergoes. The second technique uses sinusoids that are present during the signal to estimate and correct for the warp. The frequencies of the sinusoids are outside of the frequency range used for the transmitted data signal, so there is no interference with the information that is being sent. The transmitted data signal uses Orthogonal Frequency Division Multiplexing (OFDM) to encode the data symbols, but the Doppler Correction technique will in principle work for other kinds of wideband signals as well. The results, which include MATLAB based simulations and over-the-air experiments, show that performance improvements can be realized using the time warp correction model.
Master of Science

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41

Pittman, Gell Tiger Lee. « Simulation of an orthogonal frequency division multiplexing based underwater communication system using a physics based model for the underwater acoustic sound channel ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA397494.

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Thesis (M.S. in Engineeirng Science (Major in Electrical Engineering))--Naval Postgraduate School, Sept. 2001.
Thesis advisors, Cristi, Roberto ; Smith, Kevin B. "September 2001." Includes bibliographical references (p. 185-186). Also available in print.

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42

Murphy, Christopher Alden. « Progressively communicating rich telemetry from autonomous underwater vehicles via relays ». Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/75643.

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Résumé :

Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and the Woods Hole Oceanographic Institution), 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 118-131).
As analysis of imagery and environmental data plays a greater role in mission construction and execution, there is an increasing need for autonomous marine vehicles to transmit this data to the surface. Without access to the data acquired by a vehicle, surface operators cannot fully understand the state of the mission. Communicating imagery and high-resolution sensor readings to surface observers remains a significant challenge - as a result, current telemetry from free-roaming autonomous marine vehicles remains limited to 'heartbeat' status messages, with minimal scientific data available until after recovery. Increasing the challenge, long-distance communication may require relaying data across multiple acoustic hops between vehicles, yet fixed infrastructure is not always appropriate or possible. In this thesis I present an analysis of the unique considerations facing telemetry systems for free-roaming Autonomous Underwater Vehicles (AUVs) used in exploration. These considerations include high-cost vehicle nodes with persistent storage and significant computation capabilities, combined with human surface operators monitoring each node. I then propose mechanisms for interactive, progressive communication of data across multiple acoustic hops. These mechanisms include wavelet-based embedded coding methods, and a novel image compression scheme based on texture classification and synthesis. The specific characteristics of underwater communication channels, including high latency, intermittent communication, the lack of instantaneous end-to-end connectivity, and a broadcast medium, inform these proposals. Human feedback is incorporated by allowing operators to identify segments of data that warrant higher quality refinement, ensuring efficient use of limited throughput. I then analyze the performance of these mechanisms relative to current practices. Finally, I present CAPTURE, a telemetry architecture that builds on this analysis. CAPTURE draws on advances in compression and delay tolerant networking to enable progressive transmission of scientific data, including imagery, across multiple acoustic hops. In concert with a physical layer, CAPTURE provides an end-to- end networking solution for communicating science data from autonomous marine vehicles. Automatically selected imagery, sonar, and time-series sensor data are progressively transmitted across multiple hops to surface operators. Human operators can request arbitrarily high-quality refinement of any resource, up to an error-free reconstruction. The components of this system are then demonstrated through three field trials in diverse environments on SeaBED, OceanServer and Bluefin AUVs, each in different software architectures.
by Christopher Alden Murphy.
Ph.D.

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43

Papp, Joseph C. « Physically constrained maximum likelihood (PCML) mode filtering and its application as a pre-processing method for underwater acoustic communication ». Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54649.

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Résumé :

Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and the Woods Hole Oceanographic Institution), 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 85-87).
Mode filtering is most commonly implemented using the sampled mode shape or pseudoinverse algorithms. Buck et al [1] placed these techniques in the context of a broader maximum a posteriori (MAP) framework. However, the MAP algorithm requires that the signal and noise statistics be known a priori. Adaptive array processing algorithms are candidates for improving performance without the need for a priori signal and noise statistics. A variant of the physically constrained, maximum likelihood (PCML) algorithm [2] is developed for mode filtering that achieves the same performance as the MAP mode filter yet does not need a priori knowledge of the signal and noise statistics. The central innovation of this adaptive mode filter is that the received signal's sample covariance matrix, as estimated by the algorithm, is constrained to be that which can be physically realized given a modal propagation model and an appropriate noise model. The first simulation presented in this thesis models the acoustic pressure field as a complex Gaussian random vector and compares the performance of the pseudoinverse, reduced rank pseudoinverse, sampled mode shape, PCML minimum power distortionless response (MPDR), PCML-MAP, and MAP mode filters. The PCML-MAP filter performs as well as the MAP filter without the need for a priori data statistics. The PCML-MPDR filter performs nearly as well as the MAP filter as well, and avoids a sawtooth pattern that occurs with the reduced rank pseudoinverse filter. The second simulation presented models the underwater environment and broadband communication setup of the Shallow Water 2006 (SW06) experiment.
(cont.) Data processing results are presented from the Shallow Water 2006 experiment, showing the reduced sensitivity of the PCML-MPDR filter to white noise compared with the reduced rank pseudoinverse filter. Lastly, a linear, decision-directed, RLS equalizer is used to combine the response of several modes and its performance is compared with an equalizer applied directly to the data received on each hydrophone.
by Joseph C. Papp.
S.M.

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44

Partan, James Willard. « Analysis of acoustic communication channel characterization data in the surf zone ». Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86872.

Texte intégral

Résumé :

Thesis (S.M. in Electrical Engineering)--Joint Program in Oceanography and Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and the Woods Hole Oceanographic Institution), 2000.
Includes bibliographical references (leaves 64-65).
by James Willard Partan.
S.M.in Electrical Engineering

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45

Macfarlane, Nicholas Blair Wootton. « The choreography of belonging : toothed whale spatial cohesion and acoustic communication ». Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103336.

Texte intégral

Résumé :

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Biology; and the Woods Hole Oceanographic Institution), 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references.
To maintain the benefits of group membership, social animals need mechanisms to stay together and reunite if separated. This thesis explores the acoustic signals that dolphins use to overcome this challenge and mediate their complex relationships in a dynamic 3D environment. Bottlenose dolphins are the most extensively studied toothed whale, but research on acoustic behavior has been limited by an inability to identify the vocalizing individual or measure inter-animal distances in the wild. This thesis resolves these problems by simultaneously deploying acoustic tags on closely-associated pairs of known animals. These first reported deployments of acoustic tags on dolphins allowed me to characterize temporal patterns of vocal behavior on an individual level, uncovering large variation in vocal rates and inter-call waiting time between animals. Looking more specifically at signature whistles, a type of call often linked to cohesion, I found that when one animal produced its own signature whistle, its partner was more likely to respond with its own whistle. To better evaluate potential cohesion functions for signature whistles, I then modeled the probability of an animal producing a signature whistle at different times during a temporary separation and reunion from its partner. These data suggest that dolphins use signature whistles to signal a motivation to reunite and to confirm identity prior to rejoining their partner. To examine how cohesion is maintained during separations that do not include whistles, I then investigated whether dolphins could keep track of their partners by passively listening to conspecific echolocation clicks. Using a multi-pronged approach, I demonstrated that the passive detection range of echolocation clicks overlaps with the typical separation ranges of Sarasota mother-calf pairs and that the amount of time since an animal was last able to detect a click from its partner helped explain its probability of producing a signature whistle. Finally, this thesis developed a portable stereo camera system to study cohesion in situations where tagging is not possible. Integrating a GPS receiver, an attitude sensor and 3D stereo photogrammetry, the system rapidly positions multiple animals, grounding behavioral observations in quantitative metrics and characterizing fine-scale changes that might otherwise be missed.
by Nicholas Blair Wootton Macfarlane.
Ph. D.

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Li, Weichang 1972. « Estimation and tracking of rapidly time-varying broadband acoustic communication channels ». Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39205.

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Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2006.
Includes bibliographical references (p. 197-206).
This thesis develops methods for estimating wideband shallow-water acoustic communication channels. The very shallow water wideband channel has three distinct features: large dimension caused by extensive delay spread; limited number of degrees of freedom (DOF) due to resolvable paths and inter-path correlations; and rapid fluctuations induced by scattering from the moving sea surface. Traditional LS estimation techniques often fail to reconcile the rapid fluctuations with the large dimensionality. Subspace based approaches with DOF reduction are confronted with unstable subspace structure subject to significant changes over a short period of time. Based on state-space channel modeling, the first part of this thesis develops algorithms that jointly estimate the channel as well as its dynamics. Algorithms based on the Extended Kalman Filter (EKF) and the Expectation Maximization (EM) approach respectively are developed.
(cont.) Analysis shows conceptual parallels, including an identical second-order innovation form shared by the EKF modification and the suboptimal EM, and the shared issue of parameter identifiability due to channel structure, reflected as parameter unobservability in EKF and insufficient excitation in EM. Modifications of both algorithms, including a two-model based EKF and a subspace EM algorithm which selectively track dominant taps and reduce prediction error, are proposed to overcome the identifiability issue. The second part of the thesis develops algorithms that explicitly find the sparse estimate of the delay-Doppler spread function. The study contributes to a better understanding of the channel physical constraints on algorithm design and potential performance improvement. It may also be generalized to other applications where dimensionality and variability collide.
by Weichang Li.
Ph.D.

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Caley, Michael Stephen. « Development of a dynamic underwater acoustic communication channel simulator with configurable sea surface parameters to explore time-varying signal distortion ». Thesis, Curtin University, 2016. http://hdl.handle.net/20.500.11937/1105.

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A wide-band phase-coherent multi-path underwater acoustic channel simulation is developed using an approximate quantitative model of the acoustic wave response to a time-varying three-dimensional rough surface. It has been demonstrated over transmission ranges from 100 m to 8 km by experimental channel probing and comparable synthetic replication of the channel probing through the simulated channel, that the simulation is capable of reproducing fine-time-scale Doppler and delay distortions consistent with those generated in real shallow channels.

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Ahmed, Sadia. « Channel Analysis and Estimation and Compensation of Doppler Shift in Underwater Acoustic Communication and Mitigation of IFI, ISI in Ultra-wideband Radio ». Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5408.

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Water occupies three fourth of earth's surface. The remaining one fourth is land. Although human habitats reside on land, there is no denying of the vital connection between land and water. The future sustainability of human species on this planet depends on wise utilization of all available resources, including that provided by the vast water world. Therefore, it is imperative to explore, understand, and define this massive, varying, and in many areas, unexplored water domain. The water domain exploration and data collection can be conducted using manned or unmanned vehicles, as allowed by the water environment. This dissertation addresses three of the key difficulties that occur during underwater acoustic communication among manned and/or unmanned vehicles and proposes feasible solutions to resolve those difficulties. The focus and the contributions of this research involve the following perspectives: 1) Representation of Underwater Acoustic Communication (UAC) Channels: Providing a comprehensive classification and representation of the underwater acoustic communication channel based on the channel environment. 2) Estimation and Compensation of Doppler Shift: Providing compensation algorithm to mitigate varying Doppler shift effect over subcarriers in UAC Orthogonal Frequency Division Multiplexing (OFDM) systems. 3) Mitigation of Inter-symbol Interference (ISI): Providing feasible solution to long delay spread causing ISI in Ultra-wideband channels.

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Azad, Md Saiful. « Medium access control, error control and routing in underwater acoustic networks : a discussion on protocol design and implementation ». Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423364.

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The journey of underwater communication which began from Leonardo’s era took four and a half centuries to ﬁnd practical applications for military purposes during World War II. However, over the last three decades, underwater acoustic communications witnessed a massive development due to the advancements in the design of underwater communicating peripherals and their supporting protocols. Successively, doors are opened for a wide range of applications to employ in the underwater environment, such as oceanography, pollution monitoring, offshore exploration, disaster prevention, navigation assistance, monitoring, coastal patrol and surveillance. Different applications may have different characteristics and hence, may require different network architectures. For instance, routing protocols designed for unpartitioned multi-hop networks are not suitable for Delay-Tolerant Networks. Furthermore, single-hop networks do not need routing protocols at all. Therefore, before developing a protocol one must study the network architecture properly and design it accordingly. There are several other factors which should also be considered with the network architecture while designing an efﬁcient protocol for underwater networks, such as long propagation delay, limited bandwidth, limited battery power, high bit error rate of the channel and several other adverse properties of the channel, such as, multi-path, fading and refractive behaviors. Moreover, the environment also has an impact on the performance of the protocols designed for underwater networks. Even temperature changes in a single day have an impact on the performance of the protocols. A good protocol designed for any network should consider some or all of these characteristics to achieve better performance. In this thesis, we ﬁrst discuss the impact of the environment on the performance of MAC and routing protocols. From our investigation, we discover that even temperature changes within a day may affect the sound speed proﬁle and hence, the channel changes and the protocol performance vary. After that we discuss several protocols which are speciﬁcally designed for underwater acoustic networks to serve different purposes and for different network architectures. Underwater Selective Repeat (USR) is an error control protocol designed to assure reliable data transmission in the MAC layer. One may suspect that employing an error control technique over a channel which already suffers from long propagation delays is a burden. However, USR utilizes long propagation by transmitting multiple packets in a single RTT using an interlacing technique. After USR, a routing protocol for surveillance networks is discussed where some sensors are laid down at the bottom of the sea and some sinks are placed outside the area. If a sensor detects an asset within its detection range, it announces the presence of intruders by transmitting packets to the sinks. It may happen that the discovered asset is an enemy ship or an enemy submarine which creates noise to jam the network. Therefore, in surveillance networks, it is necessary that the protocols have jamming resistance capabilities. Moreover, since the network supports multiple sinks with similar anycast address, we propose a Jamming Resistance multi-path Multi-Sink Routing Protocol (MSRP) using a source routing technique. However, the problem of source routing is that it suffers from large overhead (every packet includes the whole path information) with respect to other routing techniques, and also suffers from the unidirectional link problem. Therefore, another routing protocol based on a distance vector technique, called Multi-path Routing with Limited Cross-Path Interference (L-CROP) protocol is proposed, which employs a neighbor-aware multi-path discovery algorithm to support low interference multiple paths between each source-destination pair. Following that, another routing protocol is discussed for next generation coastal patrol and surveillance network, called Underwater Delay-Tolerant Network (UDTN) routing where some AUVs carry out the patrolling work of a given area and report to a shore based control-center. Since the area to be patrolled is large, AUVs experience intermittent connectivity. In our proposed protocol, two nodes that understand to be in contact with each other calculate and divide their contact duration equally so that every node gets a fair share of the contact duration to exchange data. Moreover, a probabilistic spray technique is employed to restrict the number of packet transmissions and for error correction a modiﬁed version of USR is employed. In the appendix, we discuss a framework which was designed by our research group to realize underwater communication through simulation which is used in most of the simulations in this thesis, called DESERT Underwater (short for DEsign, Simulate, Emulate and Realize Test-beds for Underwater network protocols). It is an underwater extension of the NS-Miracle simulator to support the design and implementation of underwater network protocols. Its creation assists the researchers in to utilizing the same codes designed for the simulator to employ in actual hardware devices and test in the real underwater scenario.
Il viaggio delle comunicazioni acustiche sottomarine che cominciò nell’era di Leonardo, è durato quattro secoli e mezzo prima di vedere messe in pratica le prime applicazioni per la Seconda GuerraMondiale. Comunque, nelle ultime tre decadi le comunicazioni sottomarine sono state protagoniste di un massiccio avanzamento a causa dell’avanzamento della tecnologia costruttiva dei modem, delle periferiche e dei protocolli soprastanti. Inoltre, si sono aperte le porte a una grande varietà di applicazioni che possono utilizzare le comunicazioni sottomarine, come per esempio l’oceanograﬁa, il monitoraggio dell’inquinamento, sorveglianza delle coste, assistenza alla navigazione, esplorazione al largo e prevenzioni di disastri che possono provenire dal mare. Diverse applicazioni potrebbero avere differenti richieste e caratteristiche, quindi la struttura di rete richiesta potrebbe differire tra le varie applicazioni. Per esempio, i protocolli di routing per reti multi-hop non connesse non sono adatti a reti Delay-Tolerant. Inoltre, le reti single-hop non necessitano di un protocollo di routing. Per questi motivi, prima di progettare un protocollo, bisogna studiare l’architettura di rete e progettare i relativi protocolli concordemente. Ci sono numerosi altri fattori che dovrebbero essere presi in considerazione nell’architettura di rete nella progettazione di un protocollo di rete, come lunghi tempi di propagazione, banda limitata, durata limitata della batteria dei modem, alto Bit Error Rate nel canale e molte altre propriet´ a avverse del canale come multipath fading e un elevato grado di rifrazione. Inoltre, l’ambiente ha un impatto sulle performance dei protocolli progettati per le reti underwater. Per esempio, anche la variazione della temperatura in un singolo giorno ha un impatto sulle prestazioni dei protocolli. Un buon protocollo dovrebbe tenere conto di queste caratteristiche per raggiungere buone prestazioni. In questa tesi, innanzitutto discutiamo l’impatto dell’ambiente sulle prestazioni di pro tocolli MAC e routing. Dalle nostre sperimentazioni, abbiamo scoperto che anche i cambiamenti di temperatura in un giorno provocano la variazione dell’SSP, quindi il canale varia e anche le prestazioni dei protocolli. Successivamente, abbiamo discusso numerosi protocolli progettati per varie applicazioni di comunicazione sottomarina con varie architetture di rete. Underwater Selective Repeat (USR) è un protocollo per il controllo d’errore progettato per assicurare trasmissioni afﬁdabili di dati a livello MAC. Si potrebbe pensare che adottare un protocollo per il controllo d’errore su un canale già affetto da grandi ritardi di propagazione provochi un carico eccessivo di trafﬁco. Tuttavia, USR utilizza costruttivamente i grandi tempi di propagazione per trasmettere più pacchetti in un Round Trip Time utilizzando una tecnica ad interlacciamento, quindi, diminuendo il carico di dati. Dopo USR, un protocollo di routing per reti di sorveglianza dove alcuni nodi sono piazzati nel fondale e alcuni sono fuori dall’acqua è stato discusso. Se un sensore intercetta una attività a nel suo raggio di copertura, annuncia la presenza di un intruso attraverso un messaggio al SINK. Potrebbe succedere che l’intruso sia una nave nemica o un sottomarino nemico che creano disturbi alla rete acustica sottomarina. Quindi, nelle reti di sorveglianza è importante che i protocolli di rete abbiano una resistenza ai disturbi. Inoltre, siccome la rete supporta una modalità multisink con simile indirizzo anycast proponiamo un protocollo di routing multicast resistente al jamming, Multi-Sink Routing Protocol (MSRP), che utilizza tecniche di source-routing. Tuttavia, uno dei maggiori problemi delle tecniche di routing basate su source-routing, è un grande over-head di dati (ogni pacchetto include tutti i dati del percorso) e,inoltre,il problema dell’ ”unidirectional link”. Quindi, un altro protocollo basato sulla tecnica Distance-Vector chiamato L-CROP (Multi-path Routing with Limited Cross-Path Interference) è stato proposto, che impiega un algoritmo neighbour-aware per instaurare un percorso multi-path a bassa interferenza tra mittente e destinatario del messaggio. A seguire un altro protocollo di routing è stato discusso per le reti di sorveglianza e di pattugliamento costiero di prossima generazione, chiamato UDTN (Undertwater Delay-Tolerant Networks), dove alcuni AUV svolgono il lavoro di pattugliamento e riportano i dati a un centro di controllo sulla costa. Siccome l’area da pattugliare è vasta, l’ AUV avrà connessione intermittente con la base. Nel protocollo progettato, i nodi preposti a contattare la base calcolano e dividono la durata delle loro connessioni in maniera equa, cosicché ogni nodo abbia la stessa durata di connessione per scambiare dati. Inoltre viene impiegata, una tecnica ”probabilistic spray” per restringere il numero di trasmissioni. Per quanto riguarda la correzione d’errore, una versione modiﬁcata di USR è stata adottata. Nell’appendice, abbiamo presentato un simulatore che abbiamo progettato per realizzare la maggior parte delle simulazioni presenti in questa tesi, chiamato DESERT (DEsign, Simulate, Emulate and Realize Test-beds for Underwater Networks). E' una estensione del simulatore NS-Miracle progettato per supportare simulazioni di protocolli per reti acustiche sottomarine. Questo simulatore assite il ricercatore nell’utilizzo di hardware e nel test dei protocolli in uno scenario reale.

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Desjonquères, Camille. « Ecologie et diversité acoustique des milieux aquatiques : exploration en milieux tempérés ». Thesis, Paris, Muséum national d'histoire naturelle, 2016. http://www.theses.fr/2016MNHN0015/document.

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Une grande diversité d’animaux produit des sons pour communiquer, s'orienter, ou lors de la réalisation d'actes comportementaux comme la prise de nourriture. Ces sons ne se répartissent pas aléatoirement dans l'espace et le temps suggérant l'existence de règles d'assemblage sonore qui structurent les populations et communautés acoustiques. Les environnements d'eau douce, et en particulier les mares, sont considérés comme les réservoirs d'une importante diversité biologique, et donc potentiellement abritant un nombre significatif d'espèces produisant des sons. Cependant la diversité acoustique de ces milieux naturels n'a jamais été explorée.L'objectif principal de cette thèse est d'explorer pour la première fois la diversité acoustique présente dans les milieux d'eau douce en climat tempéré en étudiant les structures des populations et communautés acoustiques et en explorant les processus pouvant déterminer ces structures.Une revue bibliographique sur la production sonore par les organismes d'eau douce ainsi que des enregistrements d'espèces cibles effectués en laboratoire révèlent qu'une diversité acoustique particulière existe dans les environnements d'eau douce en milieux tempérés. Pour comprendre comment cette diversité est structurée, les communautés acoustiques de trois mares situées dans des environnements différents ont été enregistrées et suivies au cours du temps. Cette étude révèle que les trois mares sont caractérisées par des communautés acoustiques riches et distinctes ayant des dynamiques spatio-temporelles spécifiques. Les facteurs potentiels structurant les communautés acoustiques d’eau douce ont été recherchés en testant si la composition de communautés acoustiques dans six bras morts de la plaine d'inondation du Rhône était liée à des variables environnementales. Nos résultats montrent que les communautés acoustiques des bras morts sont significativement liées à une variable environnementale : le degré de connectivité entre les bras morts et le lit principal de la rivière. Ce résultat suggère un rôle clé de cette variable dans les règles d'assemblage des communautés. Enfin, pour comprendre les processus possibles liant la production de sons et l'environnement naturel, une population de l'insecte aquatique Micronecta scholtzi a été suivie par des enregistrements acoustiques dans une mare méditerranéenne. Le niveau d'activité acoustique de M. scholtzi a été estimé de façon continue à l'aide d'un réseau de 12 capteurs sonores synchronisés. L'activité acoustique était caractérisée par un rythme circadien, dont les propriétés étaient perturbées par la diffusion expérimentale d'un bruit d'origine anthropique. Cette expérience révèle que les effets de la pollution sonore peuvent être observés à l'échelle d'une population d'insectes aquatiques.Ce travail montre ainsi l'existence d'une diversité acoustique dans les milieux d'eau douce et identifie des relations entre production acoustique et facteurs environnementaux. Ce travail ouvre également des perspectives intéressantes d'utilisation de l'acoustique pour aborder des problématiques d'écologie fondamentale et appliquée en milieu d'eau douce
An important diversity of animal species produces sounds during communication, orientation, movement, or prey-predator acts. These sounds are not distributed randomly in space and time and are therefore thought to follow assembly rules forming either acoustic populations or acoustic communities. Freshwater environments and ponds in particular, are considered as primary resources for biological diversity and as such host a potentially significant number of soniferous species. However the acoustic diversity of these natural environments remains totally unexplored.The main aim of this PhD was to explore for the first time the acoustic diversity found in temperate freshwater by studying the patterns and structural processes of a selection of acoustic populations and communities recorded in several types of freshwater environments. A review of the literature on sound production by freshwater organisms along with laboratory recordings of target species revealed that a valuable acoustic diversity can be found in temperate freshwater environments. To understand how the acoustic diversity is structured, the acoustic communities of three temperate ponds were acoustically monitored. This study revealed that the three ponds were characterized by rich and distinct acoustic communities with specific spatio-temporal dynamics. To further understand the potential factors structuring freshwater acoustic communities, environmental variables were assessed along with the composition of acoustic communities found in six secondary channels of the Rhône riverine floodplain. Two environmental variables were investigated: the water temperature and the level of lateral connectivity of the secondary channels to the main river. Acoustic communities in the Rhône riverine floodplain were clearly structured by lateral connectivity suggesting a role of this key variable as an assembly rule. Finally to understand the possible processes linking animal acoustics and the natural environment, a population of aquatic insect, Micronecta scholtzi, was acoustically monitored in a Mediterranean pond. The level of M. scholtzi acoustic activity was assessed continuously using a network of twelve synchronised acoustic sensors. The acoustic activity of \textit{M. scholtzi} showed a regular daily pattern that was modified in amplitude and phase by the playback of an anthropogenic noise. This experiment revealed that the effects of noise pollution may emerge at an aquatic insect population level. This PhD unraveled the existence of a significant amount of unexplored acoustic diversity in freshwater environments and identified links between acoustics and the environment. This research opens interesting perspectives in the use of acoustic to tackle fundamental and applied ecological questions in freshwater environments

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