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Dissertations / Theses on the topic 'Underwater communication'
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1
Yip, Chun Keung. "Underwater Communication using Electromagnetic waves." Thesis, University of Liverpool, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485947.
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This project was to investigate the EM waves for transmission in seawater with a varied frequency from about 1 MHz up to 40 MHz. Trials were carried out in the laboratory tank, the Albert Dock and the Loch Linnhe. Standalone transmitter and receiver units were constructed for performing the experimental trials. A receiver is used to pick up the signal from the transmitter and the signal was analysed using ,a spectrum analyser. Frequency can be varied outside the transmitter from a lap top by using an optical fiber. Different types of antennae were built and tried in the experiments. In the Albert Dock, the results have shown that EM waves in the range of 1 to 5 MHz is possible to propagate about 100m using a 30W power amplifier. A new antenna design was developed and investigated in the laboratory tank. Results have shown that there is about 30dB gained by implementing the new antenna design. The signal strength can be further improved by 10 dB when the antenna and the signal generator were matched at 10MHz. In the near field, EM waves suffer from high attenuation in seawater but have a low attenuation in the far field. This is due to the generation of EM waves by dipole oscillations of the water molecules within the antenna field which can be used to explain results obtained from trials.
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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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Marco, Rider Jaime. "Optical communication with underwater snake robots : Design and implementation of an underwater wireless optical communication system." Thesis, Mittuniversitetet, Institutionen för elektronikkonstruktion, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-37803.
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Eelume AS is a norwegian company that develops autonomous underwater vehicles. Their flagship model is an underwater snake robot that performs inspection, maintenance and repair operations. For the time being, Eelume has been using acoustic communications between their AUV's and the docking station, but it has a big drawback: bandwidth. Eelume is interested in streaming live high-quality video from their AUV's to the docking station, which requires several megabits per second. As underwater radio frequency communications are not possible, wireless optical communications seem to be the best available alternative. The focus of this Thesis is to design an underwater wireless optical communications system that could be implemented on the Eelume AUV, although it is designed as a standalone embedded system that could be integrated into any other platform. Two prototypes were designed and tested through-air: a low-cost system featuring a PIN photodiode that can stream a 1.5 Mbps video signal over 0.5 meters and a high-sensitivity system featuring an avalanche photodiode that can stream a 2.5 Mbps video signal over 10.5 meters. Even if further underwater testing is needed and some inherent limitations in the design like the precise calibration or the ambient light noise effects could be mitigated. The results achieved by this high-sensitivity system demonstrates that a high-bandwidth mid-range underwater wireless optical communication system featuring a blue/green LED array as the light source and an avalanche photodiode as the photodetector is a viable solution for streaming live high-quality video over several meters even in very turbid seawaters.
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Dunbar, Robin M. "Short range electromagnetic wave communication underwater." Thesis, Heriot-Watt University, 1986. http://hdl.handle.net/10399/1957.
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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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Zeng, Zhaoquan. "A survey of underwater wireless optical communication." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55675.
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Underwater wireless communication refers to transmitting data in unguided water environment through the use of wireless carriers, i.e., radio-frequency wave, acoustic wave, and optical wave. We focus, in this thesis, on the underwater wireless optical communication (UWOC) that employs optical wave as the transmission carriers. In comparison to RF and acoustic counterparts, UWOC has a much higher transmission bandwidth, thus providing much higher data rate. Due to this high-speed transmission advantage, UWOC has attracted considerable attention in recent years. Many potential applications of UWOC systems have been proposed for environmental monitoring, offshore exploration, disaster precaution, and military operations. However, UWOC systems also suffer from severe absorption and scattering introduced by underwater channel. In order to overcome these technical challenges, several new system design approaches, which are different from the conventional terrestrial free-space optical communication, have been explored in recent years. In this thesis, we provide a comprehensive survey of the state-of-the-art of UWOC research in three aspects: channel characterization, channel modulation and coding techniques, and practical implementations of UWOC. Based on the comprehensive understanding of UWOC, we also investigate the outage performance for vertical buoy-based UWOC with pointing errors. Closed-form outage probability with zero boresight pointing errors and outage probability bounds with nonzero boresight pointing errors have been derived.Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate
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Koosha, Abdolrahim. "Ultrasonic transducers for air and underwater communication." Thesis, Kingston University, 1991. http://eprints.kingston.ac.uk/20553/.
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The performance of a novel radiator capable of producing ultrasonic waves in air and liquids has been investigated. For commercial transducers when operating in air or liquids, impedance matching is the necessary condition for maximum transfer of energy to the medium (thus no standing waves are involved). 'However, "for this radiator the formation of the mechanical standing waves on it is the key condition for directional radiation of energy into the surrounding environment. Under this condition the radiator exhibits a practical conversion of electrical energy into ultrasound. To further improve the performance of the radiator . the wavelength coincidence condition must be satisfied. This condition implies that the wavelength of the bending vibration developed on the blade to be the same as that in the medium to which it is coupled. Consequently, an end-fire radiation pattern is obtained. The theory of this when applied to water and also for a double blade configuration are presented. The main component of the radiator consists .of a cantilever blade on which a pair of piezoelectric (PZT) ceramic bars are fixed. These the so called excitation gauges, are fixed on both sides of a thin rectangular metal blade near the clamped end. When wavelength coincidence condition is fulfilled, the radiator transmits ultrasonic wave in a highly directional pattern. The direction of propagation of ultrasound is solely steered by frequency of the applied signal. System imperfections such as inter modal coupling when used underwater are considered. An analytical approach is developed to investigate the performance of the radiator for transmission of digital signals in air as well as in water. This method is used to evaluate the efficiency of the device as a suitable means for communication between divers or a diver and an underwater stationary station. Amplitude modulation of speech signals demonstrated the capabilities of a new underwater transmission. system whose narrow beam width is the condition to obtain power gain and performance. The possibility of the same system to be used as a passive sonar is also examined. Finally, simulations of the above system to be implemented in beam-forming in air and in water have been developed.
8
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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Ubellacker, Wyatt. "Underwater communication via compact mechanical sound generation." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83751.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (page 55).
Effective communication with underwater remotely operated vehicles (UROV) can be difficult to accomplish. In water, simple radio communication is quickly dissipated at higher frequencies and lower frequencies require a large antenna, which may not be practical in all applications. Light can also be used to communicate with the vehicles, but requires line of sight between the source and detector. Sound can also be used as a communication method, and has many advantages. It can propagate long distances underwater and does not require line of sight to work effectively. However, generating sound electronically underwater requires a large power speaker to produce tones loud enough to travel far distances. Generating sound mechanically can take advantage of physical resonance and produce high intensity tones in a compact device with a relatively low power input. This can allow for a compact, high intensity method to communicate with remotely operated underwater vehicles.
by Wyatt Ubellacker.
S.B.
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Brundage, Heather. "Designing a wireless underwater optical communication system." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57699.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 61-63).
Though acoustic modems have long been the default wireless communication method for underwater applications due to their long range, the need for high speed communication has prompted the exploration of non-acoustic methods that have previously been overlooked due to their distance limitations. One scenario that drives this need is the monitoring of deep sea oil wells by AUVs that could be stationed at the well and communicate surveillance data wirelessly to a base station. In this thesis, optical communication using LEDs is presented as an improvement over acoustic modems for scenarios where high speed, but only moderate distances, is required and lower power, less complex communication systems are desired. A super bright blue LED based transmitter system and a blue enhanced photodiode based receiver system were developed and tested with the goal of transmitting data at rates of 1 Mbps over distances of at least 10 meters. Test results in a fresh water tow tank showed the successful transmission of large data files over a distance of 13 meters and at transmission rates of at least 3 Mbps. With an improved test environment, even better performance may be possible.
by Heather Brundage.
S.M.
11
Yuen, Nicholas Y. "Communication on limited-mobility underwater sensor networks." Scholarly Commons, 2013. https://scholarlycommons.pacific.edu/uop_etds/232.
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More than 70% of Earth's surface is covered by water. Earth's underwater world holds many exciting forms of life and undiscovered possibilities. It is sometimes referred to as "The Unexplored Frontier." We still do not fully understand the entirety of what happens in this mysterious world. The field of underwater sensor networks is a means of monitoring these environments. However, underwater sensor networks are still fraught with challenges; one of the main challenges being communication. In this thesis we look to improve communication in underwater sensor networks. We expand a simulation environment that models node to node communication in an underwater sensor network that utilizes AquaNodes. We address issues with the first iteration of the environment, expand it to include packet-loss for acoustic communication, and make the addition of three dimensional topologies. We found that acoustic packet-loss had a larger impact on the energy consumption of the communication algorithms with more acoustic communication and three dimensional topologies do not affect the communication algorithms. In addition to expanding the simulation environment we also explore using UAVs as a means of extracting data out of underwater sensor network. We conduct field experiments to characterize radio communication, develop an energy model to understand the energy limitations of an UAV, and develop overall policies for using an UAV with an underwater sensor network that utilizes AquaNodes. We learned that node to node radio communication range on the surface of the water had shorter ranges than on land. We also learned that node to UAV communication range was dependant on the altitude of the UAV. Overall, we found that using an UAV as a data mule was a viable method of extracting data out of certain underwater sensor network configurations.
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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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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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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, 2020Cataloged 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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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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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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Galvin, Ross. "Underwater fading channel simulator for a parametric communication system." Thesis, University of Birmingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366764.
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Reed, Brooks Louis-Kiguchi. "Controller design for underwater vehicle systems with communication constraints." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97773.
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Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2015.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 (pages 181-201).
Real-time cooperation between autonomous vehicles can enable time-critical missions such as tracking and pursuit of a dynamic target or environmental feature, but relies on wireless communications. Underwater, communication over distances beyond about one hundred meters is almost exclusively accomplished through acoustics, which bring challenges such as propagation delays, low data rates, packet loss, and scheduling constraints due to interference and limited bandwidth. These limitations make underwater pursuit missions preeminent applications of networked control. Motivated by such applications, this thesis presents contributions towards multi-vehicle feedback control in the presence of severe communication constraints. The first major area of work considers the formulation and solution of new underwater multi-vehicle tracking and pursuit problems using closed-loop control. We begin with a centralized robust optimization approach for multicast routing and power control which is suitable for integration with vehicle control. Next, we describe field experiments in range-based target pursuit at high tracking bandwidths in a challenging shallow-water environment. Finally, we present a methodology for pursuit of dynamic ocean features such as fronts, which we validate using hindcast ocean model data. The primary innovation is a projection algorithm which carries out linearization of ocean model forecast dynamics and uncertainty directly in vehicle coordinates via a forward model technique. The resulting coupled linear stochastic system is suitable for networked control. The second area of work presents a unified formalism for multi-vehicle control and estimation with measurement, control, and acknowledgment packets all subject to scheduling, delays and packet loss. The modular framework we develop is built around a jump linear system description incorporating receding horizon optimization and buffering at actuators. Integration of these elements enables synthesis of a novel technique for estimation using delayed and lossy control acknowledgments-a desirable and practical capability of fielded systems that has not been considered to date. Simulations and field experiments demonstrate the effectiveness of our approach.
by Brooks Louis-Kiguchi Reed.
Ph.D.
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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, and 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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Hellman, Marcus. "Development and tests of SONAR array for underwater communication." Thesis, KTH, Marina system, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276480.
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Water covers about 70 % of Earth’s surface. Most of the water is located in the ocean’s, which have an average depth of almost 3700 meters. This implies that there is a multitude of phenomena to investigate and discover. But due to human limitations other methods and tools need to be considered in order to investigate the depths. With help of underwater robotics it can be possible to reach further and deeper. In Sweden a research center named SMaRC (Swedish Maritime Robotics Centre) was established. Mainly to maintain the knowledge Sweden posses in underwater technology. The goal is to develop the next generation robots which are smarter, offers longer reach and higher endurance. Currently one of the projects at SMaRC is dealing with underwater communication, where a five element SONAR array has been developed.This thesis deals with characterising the five element SONAR array developed in SMaRC. This is done using two different methods, one theoretical and one experimental. The theoretical method involves modelling the directivity and beam steering the SONAR array has, using theoretical formulas. While the experimental method involves a field test where the directivity and beam steering is measured and analyzed. These two methods are then compared with each other and the result is analyzed.Both the methods are showing similar results for the directivity, where the main lobe is located at 0°. Beam steering of 45° and 60° also gives similar results. For a steering of 45° the main lobe is closer to the input angle in the theoretical method than in the experimental method. In beam steering of 60° the locations of the main lobes are shifted and the experimental method lies closer to the input angle. The side lobes also differs slightly between these two methods and no explanation was found. The Source Level (SL) for different beam steering are recorded in the experimental method to: Phase of 0° gives a SL of 131 dB re. μPA/V at 1 m Phase of 45° gives a SL of 129 dB re. μPA/V at 1 m Phase of 60° gives a SL of 128 dB re. μPA/V at 1 mVatten täcker omkring 70 % av jordens yta. Den största delen av vattnet hittas i haven, vilkethar ett medeldjup på nästan 3700 meter. Detta innebär att det finns en mängd fenomen attundersöka och upptäcka. Men på grund av människans begränsning måste andra metoderoch verktyg övervägas för att undersöka dessa djup. Med hjälp av undervattensrobotik är detmöjligt att nå längre och djupare. Ett forskningscenter vid namn SMaRC (Swedish MaritimeRobotics Center) inrättades i Sverige. Främst för att upprätthålla den kunskap som Sverigebesitter inom undervattensteknik. Målet för SMaRC är att utveckla nästa generation av robotarsom är smartare, erbjuder längre räckvidd och längre uthållighet. För närvarande handlarett av projekten på SMaRC om undervattenskommunikation, där en SONAR array med femelement utvecklats.Denna avhandling handlar om att karakterisera en SONAR array bestående av fem elementsom utvecklats hos SMaRC. Detta är gjort genom att använda sig av två olika metoder,en teoretisk och en experimentell. Den teoretiska metoden involverar beräkningar avdirektiviteten och möjliga fasförskjutningar hos SONAR arryen genom teoretiska formler.Medan i den experimentella metoden involveras av ett fälttest där direktiviteten och möjligaphasförskjutningar är inspelade och analyserade. Dessa två metoder jämförs sedan medvarandra och resultatet analyseras.Båda metoderna visar liknade resultat för direktiviteten, där huvudloben är belägen vid 0°.Fasförskjutningen för 45° och 60° ger också liknande resultat. En fasförskjutning av 45° liggerhuvudloben för den teoretiska metoden närmare den givna vinkeln än för den experimenellametoden. En fasförskjutning av 60° är positionen för huvudloben flyttad och den experimenellametoden ligger nu närmare till den givna vinkel. Sidloberna skiljer sig också en aning mellanmetoderna och det är svårt att säga något om dem. Signalnivå (SL) för olika fasförskjutningarär detekterad i den experimetella metoden med följande resultat: En fasförskjutning på 0° ger en SL på 131 dB re. μPA/V , 1 m En fasförskjutning på 45° ger en SL på 129 dB re. μPA/V , 1 m En fasförskjutning på 60° ger en SL på 128 dB re. μPA/V , 1 m
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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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Andronis, Nicholas. "Reliable Long-Range and High Ambient Noise Underwater Communication." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/76485.
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Long-Range and high ambient noise underwater communication reliability improvement via sea trail performance validation of whole-of-system algorithm and engineering optimisations. The resulting 10 dB performance improvement can be used to increase the transmit source level by up to 10 dB, extend communication range by 50%, operate in environments with up to 10 dB louder ambient noise, reduce hydro-acoustic noise pollution or lowering battery power consumption with the potential of ocean powered networked communication.
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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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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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Simanjuntak, Lastri. "A Novel Chirp Slope Keying Modulation Scheme for Underwater Communication." ScholarWorks@UNO, 2004. http://scholarworks.uno.edu/td/201.
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A digital modulation method using Chirp-Slope Keying (CSK) is developed for coherent underwater acoustic communications. Effective signal detection is a critical stage in the implementation of any communications system; we will see that CSK solves some significant challenges to reliable detection. This thesis is primarily based on analyzing the effectiveness of CSK through simulations using Matlab's Simulink for underwater communications. The procedure begins with modulating a chirp's slope by random binary data with a linear-down-slope chirp representing a 0, and a linear-up-slope chirp representing a 1. Each received symbol is demodulated by multiplying it with the exact linear-up-slope chirp and then integrating over a whole period (i.e., integrate and dump). This slope-detection technique reduces the need for the extensive recognition of the magnitude and/or the frequencies of the signal. Simulations demonstrate that CSK offers sturdy performance in the modeled ocean environment, even at very low signal-to-noise ratio (SNR). CSK is first tested using the fundamental communication channel, Additive White Gaussian Noise (AWGN) channel. Simulation results show excellent BER vs. SNR performance, implying CSK is a promising method. Further extensive analysis and simulations are performed to evaluate the quality of CSK in more realistic channels including Rayleigh amplitude fading channel and multipath.
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Alexander, Joshua L. "A Microcontroller-based, Optically-centric Communication System for Underwater Applications." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504868704379707.
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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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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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Lumsdon, Parivash. "Development and simulation of signal processing algorithms for high resolution wide band direction finding and multipath cancellation." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294375.
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Hutchison, Caroline Anne. "An Image Compression Approach to Cooperative Processing for Swarming Autonomous Underwater Vehicles." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/34805.
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Current wireless underwater communication technologiesâ i.e. underwater acoustic modemsâ are extremely bandwidth limited as compared to land-based wireless technologies. Additionally, acoustic modem technologies are not advancing at the same high rate as computing technologies. Therefore, it is proposed that image compression techniques be applied to sonar maps. This will both reduce the amount of information that must be transferred by these modems which in turn reduces the amount of time required to send information across acoustic channels. After compression is performed on one platformâ s map, the information is transformed into the coordinate system of the uncompressed second, non-collocated platformâ s map and the two maps are additively compared. If returns are common in both maps, they will be show up with higher energy than the individual mapsâ returns. This thesis proves that application of image compression techniques on range-angle maps allow for target detection, down to a minimum target strength value of 0 dB, independent of target return strength.Master of Science
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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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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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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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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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Jasman, Faezah. "Modelling and characterisation of short range underwater optical wireless communication channels." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/82113/.
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This thesis studies the modelling and characterisation of underwater optical wireless communication links, particularly short-range diffuse links, by using numerical Monte Carlo (MC) simulation. MC simulation provides a flexible, intuitive and accurate modelling of the underwater channel, which is severely affected by absorption and scattering processes. In diffuse Underwater Optical Wireless Communication (UOWC) links, scattering is expected to have a larger impact on communication link performance due to the wider beam divergence compared to collimated beams. Thus, this thesis will investigate the characterisation of path loss, spatial, temporal and angular dispersions of diffuse links in various types of water. Firstly, a detailed investigation on the path loss performance of diffuse beam in three types of water is presented. This includes the study on the contribution of unscattered and scattered components of light to the total received power and how they are attenuated. From the percentage of unscattered light that contributed to the total power reception, the distance at which the unscattered component drops to zero can be estimated. This distance is used to predict the transition point from minimal scattering to multiple scattering regime for diffuse beams in coastal and turbid water. In addition to this, the spatial dispersion effect is also studied at off-axis locations. To further understand the behaviour of scattering in diffuse links, the scattering order probability is evaluated for various beam sizes in various types of water. Currently, this kind of information cannot be obtained either analytically or experimentally. The information on the scattering order is used as the parameter to classify the links into three scattering regimes, namely minimal, intermediate and multiple scattering regimes. Further investigations into the transition regimes are conducted by investigating the impulse response and frequency response performance for temporal dispersion effects. From the impulse response and frequency response analysis, the bandwidth that can be supported by the channel can be predicted, which provides some insight into the potential and limits of the links. In addition to temporal dispersion, the angular dispersion performance is also evaluated. It is shown through the angle of arrival (AOA) distribution that diffuse beams exhibit significant angular dispersions, implying that a large receiver field of view (FOV) is needed for optimum power performance. The information on the AOA distribution is then used to study the impact of receiver FOV on the bandwidth. Finally, the effect of aperture on the power received and scattering order histogram is evaluated. As a conclusion, the numerical results presented in this thesis will provide an improved understanding of the effect of scattering on path loss, spatial, temporal and angular dispersions along with their relationships with each other.
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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.
Full textAbstract:
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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Doniec, Marek Wojciech. "Autonomous underwater data muling using wireless optical communication and agile AUV control." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79211.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 187-197).
Underwater exploration and surveillance currently relies on subsea cables and tethers to relay data back to the user. The cause for this is that water heavily absorbs most electromagnetic signals, preventing effective radio communication over large distances, and that underwater communication with acoustic signals affords only bit rates on the the order of Kilobits per second. In this thesis we present a novel design and implementation for an underwater data muling system. This system allows for automatic collection of underwater datasets without the need to physically connect to or move the sensors by using mobile robots to travel to the sensors and download the data using wireless optical communication to bring it back to the base station. The system consists of two parts. The first part is a modular and adaptive robot for underwater locomotion in six degrees of freedom. We present a hardware design as well as control algorithms to allow for in-situ deployment without the need for manual configuration of the parameter space. To achieve this we designed a highly parameterizable controller and methods and algorithms for automatically estimating all parameters of this controller. The second part of the data mulling system is a novel high-bandwidth optical underwater communication device. This device allows for transfer of high-fidelity data, such as high-definition video and audio, images, and sensor logs. Finally we present algorithms to control the robots path in order to maximize data rates as it communicates with a sensor while using only the signal strength as a measurement. All components and algorithms of the system have been implemented and tested in the real world to demonstrate the validity of our claims.
by Marek Wojciech Doniec.
Ph.D.
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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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Alfitouri, Abdurrahman. "Design and analysis of gateway systems over wireless and underwater communication channels." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/design-and-analysis-of-gateway-systems-over-wireless-and-underwater-communication-channels(05ff0b83-a829-4451-99ae-b992b5674812).html.
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Gateways play a major role in communications over two-hop wireless or hybrid systems. For instance, indoor-outdoor communication networks, satellite communications, and hybrid underwater-wireless communications. It can extend the coverage of cellular systems, and connect the isolated users in rural areas. This thesis considers mainly four different themes. Firstly, the design and performance analysis of a single gateway equipped with a single antenna was investigated over different wireless channel models. The gateway uses random access protocol to connect a random number of independent non-collaborative users. New mathematical expressions were derived for the overall spectral efficiency. Afterwards, the results were extended to include collaborative users in a space division multiple access (SDMA) scenario, where the linear zero-forcing (ZF) beamformer was employed at the gateway. New analytical expressions were derived for the overall spectral efficiency (SE) in both collaborative and non-collaborative SDMA scenarios. In addition to that, different types of fading and shadowing models were considered. Thereafter, a new model for cooperative multiple gateways was introduced and analysed in details for two different scenarios, namely, single and multiple antenna gateway. In this aspect, it was assumed that the getaways are arbitrarily distributed within the service area. Finally, a comprehensive analytical framework for hybrid underwater-wireless communication where the gateway acts as a convert-and-forward relay was developed. New analytical results were derived for the spectral efficiency over different wireless/underwater channel models. The accuracy of the new mathematical results was confirmed by Monte Carlo simulation. The results in our thesis showed that the gateway can greatly enhance the communication systems performance. Moreover, enhancement in spectral efficiency and coverage area extension can be achieved by integrating linear precoder with gateway systems.
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Du, Toit Jan Abraham. "The design of a communications strategy for an underwater sensor network." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/2211.
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Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2008.There is currently a disparity in the amount of research done in underwater communication when compared to terrestrial communication. Therefore, it was the goal of this work to try and make an initial step towards bridging that gap. To start with, an introductory analysis was made of the ocean as a communications medium, focusing on any areas where the ocean characteristics could negatively affect communication. Furthermore, an overview was conducted of current communication schemes, to determine where ocean communication would differ from terrestrial communication, with the idea of determining the limiting parameters of such communication, specifically in terms of protocol design for swarms and sensor networks. Using this research, a n-ary tree-based routing algorithm was designed and incorporated into an overall protocol in line with current ISO convention. The strategy was simulated using the Erlang platform and it was found that underwater communication can be achieved with favourable results. It was however also found that using Erlang as a communications tool is currently not the best option and has various shortcomings, although with further work it could be more usable. The implemented strategy appears eminently feasible and should provide a basis for further research and practical implementation