Underwater wireless sensor networks (UWSNs) are the enabling technology for a new era of underwater monitoring and actuation applications. However, there still is a long road ahead until we reach a technological maturity capable of empowering high-density large deployment of UWSNs. To the date hereof, the scientific community is yet investigating the principles that will guide the design of networking protocols for UWSNs. This is because the principles that guide the design of protocols for terrestrial wireless sensor networks cannot be applied for an UWSN since it uses the acoustic channel instead of radio-frequency-based channel. This thesis provides a general discussion for high-fidelity and energy-efficient data collection in UWSNs. In the first part of this thesis, we propose and study the symbiotic design of topology control and opportunistic routing protocols for UWSNs. We propose the CTC and DTC topology control algorithms that rely on the depth adjustment of the underwater nodes to cope with the communication void region problem. In addition, we propose an analytical framework to study and evaluate our mobility-assisted approach in comparison to the classical bypassing and power control-based approaches. Moreover, we develop the GEDAR routing protocol for mobile UWSNs. GEDAR is the first OR protocol employing our innovative depth adjustment-based topology control methodology to re-actively cope with communication void regions. In the second part of this thesis, we study opportunistic routing (OR) underneath duty-cycling in UWSNs. We propose an analytical framework to investigate the joint design of opportunistic routing and duty cycle protocols for UWSNs. While duty-cycling conserves energy, it changes the effective UWSN density. Therefore, OR is proposed to guarantee a suitable one-hop density of awake neighbors to cope with the poor and time-varying link quality of the acoustic channel. In addition, we propose an analytical framework to study the impact of heterogeneous and on-the-fly sleep interval adjustment in OR underneath duty-cycling in UWSNs. The proposed model is aimed to provide insights for the future design of protocols towards a prolonged UWSN lifetime. The developed solutions have been extensively compared to related work either analytically or through simulations. The obtained results show the potentials of them in several scenarios of UWSNs. In turn, the devised analytical frameworks have been providing significant insights that will guide future developments of routing and duty-cycling protocols for several scenarios and setting of UWSNs.

abstract: This thesis presents a novel, thorough approach to the application of low frequency electromagnetic (EM) wave wireless communication in marine environment. This investigation is both theoretical and experimental, and is oriented towards marine sensor network applications. Different solutions within the underwater low frequency EM communication area are compared on the basis of their feasibility and practicality, especially in relation to scientific environmental monitoring applications. As a result, this thesis gathers a coordinated series of application oriented analyses of devices, such as antennas, transmitters, receivers, and of propagation issues, like signal attenuation and antenna positioning. The concluding step in this analysis is constituted by experimental field tests. As a final outcome, this works provides facts, guidelines and prototype designs related to the application of EM communication in shallow water environment, and demonstrates this communication technique is convenient for shallow water sensor networks implementation. The process followed in this analysis starts from practical considerations regarding the characteristics required by scientific equipment used in environmental monitoring. A case study is presented where a hybrid (partially wired) marine sensor network is deployed in Moreton Bay, Queensland. Strengths and weaknesses of this system are analysed, and, based on this experience, new requirements and constraints are set for a prospective improved fully wireless sensor network. In particular, the shallow water marine environment is recognized as the most likely target for scientific investigation because of its biological, economical and social importance. Firstly, various underwater communication techniques are analysed and compared. This is done on the basis of two factors: the first one is the final use of the sensor network, and the second one is the peculiar nature of the shallow water marine environment. From this analysis, it emerges that EM communication may be, in the shallow water environment, a viable and good alternative to acoustic- and optical-based techniques. From this point on, this work is aimed to prove this possibility. The next step undertaken is the theoretical analysis of EM propagation in the shallow water environment, which is modelled as a stratified lossy dielectric. The outcome of theoretical calculations is that, within a certain distance, and for a given transmitter power, low frequency EM waves are a communication channel exploitable by underwater wireless sensor networks. This is particularly true when the required data rate is low, as it is in the case of monitoring variables such as temperatures or concentrations of dissolved substances in the sea. Following this, the electric dipole and the loop antenna are studied and compared when immersed in a lossy medium such as seawater. In particular, the comparison is drawn in terms of antenna size, with absorbed power and radiated field level held equal. This, together with other practical considerations, allows the choice of the electric dipole – with some variations with respect to free space applications – as the preferred transmitting and receiving antenna. Theoretical results are verified and completed by simulations, and final prototype design guidelines are presented, together with best deployment practice suggestions. Finally, measurements are conducted in order to verify the previous calculations and considerations. In addition to them, a sensor network prototype that uses EM underwater communication is presented and tested. The field tests verify, in a real situation and at several frequencies, the maximum distance coverable with a 100 mW power source. Moreover, the same test is also conducted in fresh water, and results are compared. The instruments used for the measurements are thoroughly described, as it is the wireless sensor prototype presented. The main feature of this design is its simplicity, demonstrating that shallow water EM communication is easily achievable and that it meets the standards required by a local area marine sensor network. It can be concluded that this work offers a thorough theoretical analysis of EM propagation in shallow water environment: in parallel with this, a synthesis of practical issues that are encountered in the design of EM communication devices for underwater sensor networks is also presented. In particular, EM underwater propagation, antennas, transmitters and receiver circuits and deployment issues are thoroughly covered. Aspects such as the application of advanced signal modulations and communication protocols, however, are intentionally left open to further investigation. In fact, the range of research topics opened by this work is very wide, and they could not be all covered within this work: they span from energy harvesting to communication protocols, from antenna design to power management. All these areas are well covered by literature for terrestrial sensor networks, but they are not covered for underwater sensor networks that use EM communication: these latter are, in fact, a novelty by themselves. The problems related to this particular application have been, therefore, thoroughly exposed and opened to future research.

abstract: This thesis presents a novel, thorough approach to the application of low frequency electromagnetic (EM) wave wireless communication in marine environment. This investigation is both theoretical and experimental, and is oriented towards marine sensor network applications. Different solutions within the underwater low frequency EM communication area are compared on the basis of their feasibility and practicality, especially in relation to scientific environmental monitoring applications. As a result, this thesis gathers a coordinated series of application oriented analyses of devices, such as antennas, transmitters, receivers, and of propagation issues, like signal attenuation and antenna positioning. The concluding step in this analysis is constituted by experimental field tests. As a final outcome, this works provides facts, guidelines and prototype designs related to the application of EM communication in shallow water environment, and demonstrates this communication technique is convenient for shallow water sensor networks implementation. The process followed in this analysis starts from practical considerations regarding the characteristics required by scientific equipment used in environmental monitoring. A case study is presented where a hybrid (partially wired) marine sensor network is deployed in Moreton Bay, Queensland. Strengths and weaknesses of this system are analysed, and, based on this experience, new requirements and constraints are set for a prospective improved fully wireless sensor network. In particular, the shallow water marine environment is recognized as the most likely target for scientific investigation because of its biological, economical and social importance. Firstly, various underwater communication techniques are analysed and compared. This is done on the basis of two factors: the first one is the final use of the sensor network, and the second one is the peculiar nature of the shallow water marine environment. From this analysis, it emerges that EM communication may be, in the shallow water environment, a viable and good alternative to acoustic- and optical-based techniques. From this point on, this work is aimed to prove this possibility. The next step undertaken is the theoretical analysis of EM propagation in the shallow water environment, which is modelled as a stratified lossy dielectric. The outcome of theoretical calculations is that, within a certain distance, and for a given transmitter power, low frequency EM waves are a communication channel exploitable by underwater wireless sensor networks. This is particularly true when the required data rate is low, as it is in the case of monitoring variables such as temperatures or concentrations of dissolved substances in the sea. Following this, the electric dipole and the loop antenna are studied and compared when immersed in a lossy medium such as seawater. In particular, the comparison is drawn in terms of antenna size, with absorbed power and radiated field level held equal. This, together with other practical considerations, allows the choice of the electric dipole – with some variations with respect to free space applications – as the preferred transmitting and receiving antenna. Theoretical results are verified and completed by simulations, and final prototype design guidelines are presented, together with best deployment practice suggestions. Finally, measurements are conducted in order to verify the previous calculations and considerations. In addition to them, a sensor network prototype that uses EM underwater communication is presented and tested. The field tests verify, in a real situation and at several frequencies, the maximum distance coverable with a 100 mW power source. Moreover, the same test is also conducted in fresh water, and results are compared. The instruments used for the measurements are thoroughly described, as it is the wireless sensor prototype presented. The main feature of this design is its simplicity, demonstrating that shallow water EM communication is easily achievable and that it meets the standards required by a local area marine sensor network. It can be concluded that this work offers a thorough theoretical analysis of EM propagation in shallow water environment: in parallel with this, a synthesis of practical issues that are encountered in the design of EM communication devices for underwater sensor networks is also presented. In particular, EM underwater propagation, antennas, transmitters and receiver circuits and deployment issues are thoroughly covered. Aspects such as the application of advanced signal modulations and communication protocols, however, are intentionally left open to further investigation. In fact, the range of research topics opened by this work is very wide, and they could not be all covered within this work: they span from energy harvesting to communication protocols, from antenna design to power management. All these areas are well covered by literature for terrestrial sensor networks, but they are not covered for underwater sensor networks that use EM communication: these latter are, in fact, a novelty by themselves. The problems related to this particular application have been, therefore, thoroughly exposed and opened to future research.

The production of clean water, the generation of nuclear power and the development of chemicals, petro-chemicals and pharmaceuticals all rely on liquid-based processes. They are fundamental to modern society, however the real-time monitoring of such processes is an inherently difficult challenge which has not yet been satisfactorily solved.Current methods of monitoring include on- and off-line spot checks and industrial process tomography. Neither of these methods provides the spatial or temporal resolution required to properly characterise the processes. This research project proposes a new monitoring method for processes which can tolerate foreign objects; a mobile underwater sensor network (MUSN).An MUSN has the potential to increase both the spatial and temporal resolution of measurements and could be used in real-time. The network would be formed by a number of mobile sensor platforms, in the form of micro-autonomous underwater vehicles (uAUVs) which would communicate using acoustics. The demonstrator for the technology is for use in the monitoring of nuclear storage ponds.Current AUV technology is not suitable for use in enclosed environments such as storage ponds due to the size and maneuverability. This thesis presents the research conducted in the development of a new vehicle uAUV. The work presented covers the mechatronic aspects of the vehicle; the design of the hull, propulsion systems, corresponding control circuitry and basic motion control systems. One of the main factors influencing the design of the vehicle has been cost. If a large number of vehicles are used to form a network, the cost of an individual uAUV should be kept as low as possible. This has raised a number of technical challenges as low-cost components are often of low-tolerance. Imbalanced time-varying thrust, low manufacturing tolerances and noisy indirect sensor measurements for the control systems have all been overcome in the design of the vehicle. The outcome of the research is a fully functional prototype uAUV. The vehicle is spherical in shape with a diameter of approximately 15cm, with six thruster units mounted around the equator (increasing the horizontal clearance to 20cm) to provide thrust in four degrees of freedom (surge, sway, heave and yaw). The vehicle has a sensor suite which includes a pressure sensor, digital compass and a gyroscope which provide inputs to the motion control systems. The controllers have been developed and implemented on the vehicle's custom built embedded system. Experiments have been conducted showing that the uAUV is able to move in 3D with closed-loop control in heave and yaw. Motion in surge and sway is open-loop, via a dead-reckoning system.

El concepto de entorno inteligente concibe un mundo donde los diferentes tipos de dispositivos inteligentes colaboran para conseguir un objetivo común. En este concepto, inteligencia hace referencia a la habilidad de adquirir conocimiento y aplicarlo de forma autónoma para conseguir el objetivo común, mientras que entorno hace referencia al mundo físico que nos rodea. Por tanto, un entorno inteligente se puede definir como aquel que adquiere conocimiento de su entorno y aplicándolo permite mejorar la experiencia de sus habitantes. La computación ubicua o generalizada permitirá que este concepto de entorno inteligente se haga realidad. Normalmente, el término de computación ubicua hace referencia al uso de dispositivos distribuidos por el mundo físico, pequeños y de bajo precio, que pueden comunicarse entre ellos y resolver un problema de forma colaborativa. Cuando esta comunicación se lleva a cabo de forma inalámbrica, estos dispositivos forman una red de sensores inalámbrica o en inglés, Wireless Sensor Network (WSN). Estas redes están atrayendo cada vez más atención debido al amplio espectro de aplicaciones que tienen, des de soluciones para el ámbito militar hasta aplicaciones para el gran consumo. Esta tesis se centra en las redes de sensores inalámbricas y subacuáticas o en inglés, Underwater Wireless Sensor Networks (UWSN). Estas redes, a pesar de compartir los mismos principios que las WSN, tienen un medio de transmisión diferente que cambia su forma de comunicación de ondas de radio a ondas acústicas. Este cambio hace que ambas redes sean diferentes en muchos aspectos como el retardo de propagación, el ancho de banda disponible, el consumo de energía, etc. De hecho, las señales acústicas tienen una velocidad de propagación cinco órdenes de magnitud menor que las señales de radio. Por tanto, muchos algoritmos y protocolos necesitan adaptarse o incluso rediseñarse. Como el despliegue de este tipo de redes puede ser bastante complicado y caro, se debe planificar de forma precisa el hardware y los algoritmos que se necesitan. Con esta finalidad, las simulaciones pueden resultar una forma muy conveniente de probar todas las variables necesarias antes del despliegue de la aplicación. A pesar de eso, un nivel de precisión adecuado que permita extraer resultados y conclusiones confiables, solamente se puede conseguir utilizando modelos precisos y parámetros reales. Esta tesis propone un ecosistema para UWSN basado en herramientas libres y de código abierto. Este ecosistema se compone de un modelo de recolección de energía y unmodelo de unmódemde bajo coste y bajo consumo con un sistema de activación remota que, junto con otros modelos ya implementados en las herramientas, permite la realización de simulaciones precisas con datos ambientales del tiempo y de las condiciones marinas del lugar donde la aplicación objeto de estudio va a desplegarse. Seguidamente, este ecosistema se utiliza con éxito en el estudio y evaluación de diferentes protocolos de transmisión aplicados a una aplicación real de monitorización de una piscifactoría en la costa del mar Mediterráneo, que es parte de un proyecto de investigación español (CICYT CTM2011-2961-C02-01). Finalmente, utilizando el modelo de recolección de energía, esta plataforma de simulación se utiliza para medir los requisitos de energía de la aplicación y extraer las necesidades de hardware mínimas. / Climent Bayarri, JS. (2014). Contribution to Research on Underwater Sensor Networks Architectures by Means of Simulation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/35328 / TESIS

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.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2018-08-22T18:37:28Z No. of bitstreams: 1 lucassaarcerqueira.pdf: 1610432 bytes, checksum: a5ce4c7b10b86e4e43966b9b9268e608 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-09-03T16:34:40Z (GMT) No. of bitstreams: 1 lucassaarcerqueira.pdf: 1610432 bytes, checksum: a5ce4c7b10b86e4e43966b9b9268e608 (MD5) / Made available in DSpace on 2018-09-03T16:34:40Z (GMT). No. of bitstreams: 1 lucassaarcerqueira.pdf: 1610432 bytes, checksum: a5ce4c7b10b86e4e43966b9b9268e608 (MD5) Previous issue date: 2018-03-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O monitoramento de ambientes aquáticos ainda é uma tarefa difícil e dispendiosa. De fato, em ambientes aquáticos, ondas eletromagnéticas e ópticas sofrem alta atenuação e, mesmo a comunicação acústica apresenta baixa vazão e alta taxa de erro de bits. A maioria das abordagens existentes para melhorar o desempenho da comunicação subaquática se baseia no desenvolvimento de modems acústicos, acesso múltiplo ao canal de comunicação e roteamento de dados. Neste trabalho apresentamos PCRA: um Protocolo Cooperativo para Redes de Sensores Aquáticas. O PCRA funciona de forma síncrona/assíncrona sobre o método TDMA combinado com um esquema ARQ baseado em Selective Repeat. Cada nó que não possui dados para transmitir pode se tornar um cooperador e retransmitir mensagens para auxiliar os nós vizinhos. Ele usa os nós sensores ociosos como nós retransmissores, aumentando a diversidade do espaço de comunicação. Nossas simulações mostram que, quando comparado a um protocolo não cooperativo, o PCRA reduz a taxa de erro de pacotes em 65% e aumenta o goodput em 16% enquanto gasta menos de 1% a mais de energia. / Monitoring underwater environments is still a hard and costly task. Indeed, electromagnetic and optical waves suffer high attenuation, being absorbed in a few meters and even acoustic communication presents low throughput and high bit error rate. Most of the existing approaches to enhance underwater communication performance relies on developing acoustic modems, multiple access of the communication channel, and data routing. In this paper we present PCRA: a Cooperative Protocol for Underwater Sensor Networks. PCRA synchronously/asynchronously works on top of TDMA method combined with an ARQ scheme based on selective repeat technique. Each node that has no data to transmit can become a cooperator and retransmit messages to assist neighboring nodes. It uses idle sensor nodes as relay nodes, enhancing communication space diversity. Our simulations show that, when compared to a non-cooperative protocol, PCRA enhances overall network performance metrics. For instance, it reduces packet error rate by 65% and increases goodput by 16% while spending less than 1% more energy.

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