Biblioteca Digital

As Cidades Digitais, viabilizadas pelo grande desenvolvimento alcançado pelas Tecnologias da Informação e das Comunicações nos últimos 30 anos, surgem hoje como um novo paradigma nestas áreas. As Cidades Digitais promovem grandes benefícios para a população e para o governo, através de ambientes virtuais de oferecimento de serviços, por meio de redes de comunicações digitais. Nesse cenário, as redes de sensores, principalmente as redes sem fio, desempenham papel fundamental para permitir a coleta de dados em tempo real no âmbito municipal, produzindo grande quantidade de informações importantes para fins de análise, previsão e tomada de decisão. Esse cenário permite o monitoramento de uma grande variedade de dados e informações. Sendo assim, são utilizados diferentes tipos de redes de sensores em termos de hardware e software. Essa heterogeneidade de dispositivos e de tecnologia resulta em ilhas de sistemas, restritos à domínios específicos de aplicação, prejudicando o gerenciamento das redes e a interoperabilidade entre as aplicações. Diante desse cenário, esse trabalho propõe uma arquitetura para monitoramento e gerenciamento de redes sensoras em Cidades Digitais. A arquitetura proposta é baseada no conceito de orientação a serviços...

Tese de doutoramento em Informática; Assuming a world where we can be surrounded by hundreds or even thousands of inexpensive computing nodes densely deployed, each one with sensing and wireless communication capabilities, the problem of efficiently dealing with the enormous amount of information generated by those nodes emerges as a major challenge. The research in this dissertation addresses this challenge. This research work proves that it is possible to obtain aggregate quantities with a timecomplexity that is independent of the number of nodes, or grows very slowly as the number of nodes increases. This is achieved by co-designing the distributed algorithms for obtaining aggregate quantities and the underlying communication system. This work describes (i) the design and implementation of a prioritized medium access control (MAC) protocol which enforces strict priorities over wireless channels and (ii) the algorithms that allow exploiting this MAC protocol to obtain the minimum (MIN), maximum (MAX) and interpolation of sensor values with a time-complexity that is independent of the number of nodes deployed, whereas other state-of-the-art approaches have a time-complexity that is dependent on the number of nodes. These techniques also enable to efficiently obtain estimates of the number of nodes (COUNT) and the median of the sensor values (MEDIAN). The novel approach proposed to efficiently obtain aggregate quantities in large-scale...

The use of sensors to capture disparate types of information from the environment has been increasing and they cover a wide range of applications, such as climate monitoring (e.g., seismic activity and climate), water quality monitoring, area surveillance, intelligent buildings, energy management, automotive industry and scientific purposes. Additionally, the Information Age has provided rapid and ubiquitous access to information produced by heterogeneous sources. Thus, the development of sensor networks has emerged as a way to exploit the Information Age capabilities into sensor applications. A major outcome of this combination is the capability to remotely receive and process sensor data (covering large areas) in real-time therefore allowing the development of new studies and algorithms aiming at anticipating and predicting (with high- reliability) events, such as storms (already state-of-the-art) and earthquakes (not yet possible). The developments in the scientific and industry communities were proficient in creating a large number of sensor networks that, nonetheless, (i) were designed to fit specific needs, (ii) were usually deployed in closed networks (not accessible to external parties), and/or (iii) do not interoperate with each-other...

Thesis (Ph. D.)--University of Rochester. Dept. of Electrical and Computer Engineering, 2009.; Complex applications and increased sensor capabilities will help proliferate wireless sensor networks into everyday life. However, as sensor nodes are battery-operated, sensor networks will require protocols to spare every possible bit of energy. This can be accomplished through cross-layer protocol optimizations that specialize the protocols for specific application requirements. However, as researchers continue to contribute to the field of sensor networks, protocols will evolve, and more efficient work will replace older ideas. Therefore, flexibility and eased maintenance of the network will be required to make sensor networks feasible for new deployments and customers. Thus there are competing goals of energy-efficiency, achieved by specialization through cross-layer protocol design, and flexibility, achieved through modularity in a layered protocol design. My thesis shows that these competing goals can be balanced by the use of crosslayer information exchange that enables the protocols (and hence the network) to adapt to current application and network conditions. Adapting the protocols via cross-layer information exchange allows the network to make best use of the limited energy resources of the sensor nodes while maintaining required application quality of service and retaining a flexible protocol stack. In support of this thesis...

With the developments in computing and communication technologies, wireless sensor networks have become popular in wide range of application areas such as health, military, environment and habitant monitoring. Moreover, wireless acoustic sensor networks have been widely used for target tracking applications due to their passive nature, reliability and low cost. Traditionally, acoustic sensor arrays built in linear, circular or other regular shapes are used for tracking acoustic sources. The maintaining of relative geometry of the acoustic sensors in the array is vital for accurate target tracking, which greatly reduces the flexibility of the sensor network. To overcome this limitation, we propose using only a single acoustic sensor at each sensor node. This design greatly improves the flexibility of the sensor network and makes it possible to deploy the sensor network in remote or hostile regions through air-drop or other stealth approaches. Acoustic arrays are capable of performing the target localization or generating the bearing estimations on their own. However, with only a single acoustic sensor, the sensor nodes will not be able to generate such measurements. Thus, self-organization of sensor nodes into virtual arrays to perform the target localization is essential. We developed an energy-efficient and distributed self-organization algorithm for target tracking using wireless acoustic sensor networks. The major error sources of the localization process were studied...

The promise of Wireless Sensor Networks (WSNs) is the autonomous collaboration of a collection of sensors to accomplish some specific goals which a single sensor cannot offer. Basically, sensor networking serves a range of applications by providing the raw data as fundamentals for further analyses and actions. The imprecision of the collected data could tremendously mislead the decision-making process of sensor-based applications, resulting in an ineffectiveness or failure of the application objectives. Due to inherent WSN characteristics normally spoiling the raw sensor readings, many research efforts attempt to improve the accuracy of the corrupted or “dirty” sensor data. The dirty data need to be cleaned or corrected. However, the developed data cleaning solutions restrict themselves to the scope of static WSNs where deployed sensors would rarely move during the operation. Nowadays, many emerging applications relying on WSNs need the sensor mobility to enhance the application efficiency and usage flexibility. The location of deployed sensors needs to be dynamic. Also, each sensor would independently function and contribute its resources. Sensors equipped with vehicles for monitoring the traffic condition could be depicted as one of the prospective examples. The sensor mobility causes a transient in network topology and correlation among sensor streams. Based on static relationships among sensors...

Target tracking is one of the typical applications of wireless sensor networks: a large number of spatially deployed sensor nodes collaboratively sense, process and estimate the target state (e.g., position, velocity and heading). This thesis aimed to develop the collaborative information processing techniques that jointly address information processing and networking for the distributive estimation of target state in the highly dynamic and resources constrained wireless sensor networks. Taking into account the interplay between information processing and networking, this thesis proposed a collaborative information processing framework. The framework integrates the information processing which is responsible for the representation, fusion and processing of data and information with networking which caters for the formation of network, the delivery of information and the management of wireless channels. Within the proposed collaborative information processing framework, this thesis developed a suite of target tracking algorithms on the basis of the recursive Bayesian estimation method. For tracking a single target in wireless sensor networks, this thesis developed the sequential extended Kalman filter (S-EKF), the sequential unscented Kalman filter (S-UKF) and the Particle filter (PF). A novel extended Kalman filter and Particle filter hybrid algorithm...

Providing efficient data transport is one of the uppermost objectives in the design of wireless sensor networks (WSNs) since the primary role for each sensor is to report the sensed data to the data sink(s). This thesis focuses on designing efficient data transport schemes for WSNs in the dimensions of energy consumption and time respectively. The developed schemes can be directly applied in a number of applications such as intrusion detection, target tracking, environment monitoring, etc., and can be further extended to underwater acoustic sensor networks and unmanned aerial vehicles (UAVs) networks. With the development of WSN technologies, new challenging research problems such as real-time streaming data gathering and intelligent data communication are emerging. This thesis provides useful foundation for designing next-generation data transport schemes for WSNs. Energy is the most important resource in WSNs because sensor nodes are commonly powered by small batteries, and energy is directly related to the lifetime of nodes and the network. In this thesis, energy-efficient data transport schemes are designed for two major types of WSNs: event-driven sensor networks and time-driven sensor networks. A novel on-line routing scheme called EBGR (Energy-efficient Beaconless Geographic Routing) is designed for event-driven sensor networks characterized by dynamic network topology. The main advantage of EBGR is that it can provide energy-efficient sensor-to-sink routing without any prior neighborhood knowledge. Moreover...

In the last years, wireless sensor networks (WSNs) are acquiring more importance as a promising technology based on tiny devices called sensor nodes or motes able to monitor a wide range of physical phenomenon through sensors. Numerous branches of science are being benefited. The intrinsic ubiquity of sensor nodes and the absence of network infrastructure make possible their deployment in hostile or, up to now, unknown environments which have been typically unaccessible for humans such as volcanos or glaciers, providing precise and up-to-date data. As potential applications continue arising, both new technical and conceptual challenges appear. The severe hardware restrictions of sensor nodes in relation to computation, communication and specifically, energy, have posed new and exciting requirements. In particular, research is moving towards heterogeneous networks that will contain different devices running custom WSN operating systems. Operating systems specifically designed for sensor nodes are intended to efficiently manage the hardware resources and facilitate the programming. Nevertheless, they often lack the generality and the high-level abstractions expected at this abstraction layer. Consequently, they do not completely hide either the underlying platform or its execution model...

In this thesis, within the context of sensor networks, we are interested in the distributed detection problem under the Neyman-Pearson formulation and conditionally dependent sensor observations. In order to exploit all the detection potential of the network, the literature on this issue has faced optimal distributed detection problems, where optimality usually consists in properly designing the parameters of the network with the aim of minimizing some cost function related to the overall detection performance of the network. However, this problem of optimization has usually constraints regarding the possible physical and design parameters that we can choose when maximizing the detection performance of the network. In many applications, some physical and design parameters, for instance the network architecture or the local processing scheme of the sensor observations, are either strongly constrained to a set of possible design alternatives or either cannot be design variables in our problem of optimization. Despite the fact that those parameters can be related to the overall performance of the network, the previous constraints might be imposed by factors such as the environment where the network has to be deployed, the energy budget of the system or the processing capabilities of the available sensors. Consequently...

peer-reviewed; The future of our society, the connected world of tomorrow, will be one of better integration with, and more awareness of our surroundings. Wireless sensor networks will breathe life into objects and allow us to extend our sensory perception to every square of land and water. Before large amounts of information regarding our private lives and surroundings start being sent around the world,privacy issues have to be addressed. At the moment there is no transparent or holistic security solution for wireless sensor networks. Because sensor networks have a wide range of applications with very di erent requirements, and because they have constrained hardware, security solutions can't be static but need to be con gured, tailored, for every single applications, to make effi cient use of the available resources while providing the required security level. Furthermore, the control over the security con guration needs to be placed in the hands of the sensor network's user, because only the user knows the details of the application and can control its parameters. This thesis presents a framework for the security con guration of wireless sensor networks (WSNs), which provides complete and transparent communication security to any data stream...

Wireless sensor networks have been used in different applications due to the advancement of sensor technology. These uses also have raised different optimization issues. Most of the algorithms proposed as solutions to the various optimization problems are either centralized or distributed which are not ideal for these real life applications. Very few strictly local algorithms for wireless sensor networks exist in the literature. In this thesis, we consider some of these optimization problems of sensor networks, for example, sleep-wake scheduling, mobile dispersion, mobile object monitoring, and gathering problems. We also consider the depth adjustment problem of underwater sensor networks. We design cellular automaton based local algorithms for these problems. The cellular automaton is a bioinspired model used to model different physical systems including wireless sensor networks. One of the main advantages of using cellular automaton based algorithms is that they need very little local information to compute a solution. We perform different simulations and analysis and find that our algorithms are efficient in practice.; Thesis (Ph.D, Computing) -- Queen's University, 2012-11-25 13:37:36.854

For the past years wireless sensor networks (WSNs) have been coined as one of the most promising technologies for supporting a wide range of applications. However, outside the research community, few are the people who know what they are and what they can offer. Even fewer are the ones that have seen these networks used in real world applications. The main obstacle for the proliferation of these networks is energy, or the lack of it. Even though renewable energy sources are always present in the networks environment, designing devices that can efficiently scavenge that energy in order to sustain the operation of these networks is still an open challenge. Energy scavenging, along with energy efficiency and energy conservation, are the current available means to sustain the operation of these networks, and can all be framed within the broader concept of “Energetic Sustainability”. A comprehensive study of the several issues related to the energetic sustainability of WSNs is presented in this thesis, with a special focus in today’s applicable energy harvesting techniques and devices, and in the energy consumption of commercially available WSN hardware platforms. This work allows the understanding of the different energy concepts involving WSNs and the evaluation of the presented energy harvesting techniques for sustaining wireless sensor nodes. This survey is supported by a novel experimental analysis of the energy consumption of the most widespread commercially available WSN hardware platforms.; Há já alguns anos que as redes de sensores sem fios (do Inglês Wireless Sensor Networks - WSNs) têm sido apontadas como uma das mais promissoras tecnologias de suporte a uma vasta gama de aplicações. No entanto...

Biomedical wireless sensor networks enable the development of real-time patient monitoring systems, either to monitor chronically ill persons in their homes or to monitor patients in step-down hospital units. However, due to the critical nature of medical data, these networks have to meet demanding quality of service requirements, ensuring high levels of confidence to their users. These goals depend on several factors, such as the characteristics of the network deployment area or the network topology. In such context, this work proposes a method to find the best network physical topology in order to maximise the quality of service provided by the network. The proposed method makes use of “virtual sensor nodes” to estimate the impact of adding real sensor nodes to the network in a specific location. Thus, assessing different locations, it is possible to find the best location to place the new sensor node while maximising the quality of service provided by the network. In particular, this work studies the feasibility of using “virtual sensor nodes” to assess the impact of adding a new sensor node to a biomedical wireless sensor network and presents some results showing the viability of the proposed method.

Sensor network coverage refers to the quality of service provided by a sensor network surveilling a region of interest. So far, coverage problems have been formulated to address area coverage or to maintain line-of-sight visibility in the presence of obstacles (i.e., art-gallery problems). Although very useful in many sensor applications, none of the existing formulations address coverage as it pertains to target tracking by means of multiple sensors, nor do they provide a closed-form function that can be applied to the problem of allocating sensors for the surveilling objective of maximizing target detection while minimizing false alarms. This dissertation presents a new coverage formulation addressing the quality of service of sensor networks that cooperatively detect targets traversing a region of interest, and is readily applicable to the current sensor network coverage formulations. The problem of track coverage consists of finding the positions of n sensors such that the amount of tracks detected by at least k sensors is optimized. This dissertation studies the geometric properties of the network, addressing a deterministic track-coverage formulation and binary sensor models. It is shown that the tracks detected by a network of heterogeneous omnidirectional sensors are the geometric transversals of non-translates families of disks. A novel methodology based on cones and convex analysis is presented for representing and measuring sets of transversals as closed-form functions of the sensors positions and ranges. As a result...

The huge advances in communication technologies and Micro Electrical and Mechanical Systems (MEMS) have triggered a revolution in sensor networks. One major application of sensor networks is in the investigation of complex and uninhabited under water surfaces; such sensor networks are called the Underwater Wireless Sensor Networks (UWSN). UWSN comprises of a number of sensors which are submerged in water and one or several surface stations or a sinks at which the sensed data is collected. In some underwater sensor applications, autonomous underwater vehicles (AUVs) could be used. The underwater sensor nodes communicate with each other using acoustic signals. Applications for this type of networks include oceanographic data collection, pollution monitoring, offshore exploration and tactical surveillance applications. The novel networking paradigm of UWSN is facing a totally different operating environment than the ground based wireless sensor networks. This introduces new challenges such as huge propagation delays, and limited acoustic link capacity with high attenuation factors. These new challenges have their own impact on the design of most of the networking layers preventing researchers from using the same layers used for other networks. The most affected layers are the Physical...

In future smart environments, ad hoc sensor networks will play a key role in sensing, collecting, and disseminating information about environmental phenomena. As sensor networks come to be wide-spread deployment, security issues become a central concern. So far, the main research focus has been on making sensor networks feasible and useful, and less emphasis has been placed on security. This paper analyzes security challenges in wireless sensor networks and summarizes key issues that need be solved for achieving security in an ad hoc network. It gives an overview of the current state of solutions on such key issues as secure routing, prevention of denial-of-service, and key management service.

A wireless sensor network (WSN) is a network made of thousands of sensing elements called as nodes with wireless capabilities. Their application is varied and diverse ranging from military to domestic and household. As the world of self-organizing sensor networks tip to the edge of maximum utilization, their wider deployment is adding pressure on the security front. Powerful laptops and workstations make it more challenging for small sensors. In addition, there are many security challenges in WSN, e.g- confidentiality, authentication, freshness, integrity etc. Contributions of this work are as follows: “Symmetric” security implementation: This thesis work designs a symmetric-key based security in sensor hardware in the Link layer of sensor network protocols. Link Layer security can protect a wireless network by denying access to the network itself before a user is successfully authenticated. This prevents attacks against the network infrastructure and protects the network from devastating attacks. “Public key” implementation in sensor hardware: Asymmetric key techniques are attractive for authentication data or session keys. Traditional schemes like RSA require considerable amounts of resources which in the past has limited their use. This thesis has implemented Elliptic Curve Cryptography (ECC) in Mica2 hardware...

Recent advances in microelectronic technology have made it possible to construct compact and inexpensive wireless sensors. Sensor networks have received significant attention due to their potential applications from civil to military domains. Since sensors in sensor networks are equipped with energy-limited batteries, energy conservation in such networks is of paramount importance in order to prolong the network lifetime. Sensing coverage and sensor connectivity in sensor networks are two fundamental issues, which have been extensively addressed in the literature, and most existing work on sensing coverage has focused on the (connected) full coverage problem that aims to cover the entire monitored region using the minimum number of sensors. However, in some application scenarios, full coverage is either impossible or unnecessary and a partial coverage with a certain degree guarantee is acceptable. In this paper, we study the connected coverage problem with a given coverage guarantee. We first introduce the partial coverage concept and analyze its properties for the first time in order to prolong the network lifetime. Due to NP-hardness of the concerned problem, we then present a heuristic algorithm which takes into account the partial coverage and sensor connectivity simultaneously. We finally conduct extensive experiments by simulations to evaluate the performance of the proposed algorithm.