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Title: A progressive reliability framework for wireless sensor networks
Creator: Qaisar, Saad Bin
Date: 2009
Collection: Electronic Theses & Dissertations

Title: Advanced data analysis framework for damage identification in civil infrastructure based on self-powered sensing
Creator: Alavi, Amir Hossein
Date: 2016
Collection: Electronic Theses & Dissertations
Description: "This interdisciplinary research proposes an advanced data analysis framework for civil infrastructure/structural health monitoring (I/SHM) based on a pioneering self-powered sensing technology. The current work characterizes the performance of a fairly new class of self-powered sensors for specific application problems with complex behavior. The proposed health monitoring systems are established through the integration of statistical, artificial intelligence and finite element methods....
Show more"This interdisciplinary research proposes an advanced data analysis framework for civil infrastructure/structural health monitoring (I/SHM) based on a pioneering self-powered sensing technology. The current work characterizes the performance of a fairly new class of self-powered sensors for specific application problems with complex behavior. The proposed health monitoring systems are established through the integration of statistical, artificial intelligence and finite element methods. Different infrastructure systems with various damage types are analyzed. A new probabilistic artificial intelligence-based damage detection technique is developed that hybridizes genetic programming and logistic regression algorithms. The proposed multi-class classification system assigns probabilities to model scores to detect damage progression. A probabilistic neural network method based on Bayesian theory is further introduced to improve the damage detection accuracy. Data obtained from the finite element simulations and experimental study of hybrid sensor networks is used to calibrate the data interpretation algorithms. The network architecture comprises self-powered sensors that use the electrical energy directly harvested by piezoelectric ceramic Lead Zirconate Titanate (PZT) transducers. The beauty of this so-called self-powered monitoring system is that the operating power for the smart sensors directly comes from the signal being monitored. An advantage of using these sensors is that there is no need to directly measure the absolute value of strain in order to estimate damage. In fact, the proposed self-sustained sensing systems use the sensor output to relate the variation rate of strain distributions to the rate of damage. The proposed data analysis framework consists of multilevel strategies for structural/infrastructure damage identification through: (a) analysis of individual self-powered strain sensors, (b) data fusion in a network of self-powered strain sensors, and (c) data analysis in a hybrid network of self-powered accelerometer and strain sensors. For each of these levels, several damage indicator features are extracted upon the simulation of the compressed data stored in memory chips of the self-powered sensors. A new data fusion concept based on the effect of group of sensors, termed as "group effect", is proposed. The goal is to improve the damage detection performance through spatial measurements over structures. Moreover, combination of the data from a network of accelerometer and strain sensors results in developing an integrated global-local damage detection approach. The investigated cases are crack growth detection in steel plates under a uniaxial tension mode, distortion-induced fatigue cracking in steel bridge girders, continuous health monitoring of pavement systems, failure of simply supported beam under three-point bending, and failure of gusset plate of the I-35W highway bridge in Minneapolis, Minnesota. 3D dynamic finite element models are developed for each of the cases. The experimental studies are carried out on a steel plate subjected to an in-plane tension, a steel plate with bolted connections, and on asphalt concrete specimens in three-point bending mode. PZT-5A ceramic discs and PZT-5H bimorph accelerometers are placed on the surface of the plates to measure the delivered voltage in each damage phase. For the asphalt experiments, a new miniaturized spherical packaging system is designed and tested to protect the PZT ceramic discs embedded inside the specimen. Uncertainty analyses are performed through the contamination of the damage indicator features with different noise levels. The results indicate that the proposed I/SHM systems are efficiently capable of detecting different damage states in spite of high-level noise contamination."--Pages ii-iii.
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Title: Analytical and quantitative characterization of wireless sensor networks
Creator: Ilyas, Muhammad Usman
Date: 2009
Collection: Electronic Theses & Dissertations

Title: Assessment of ultrasonic guided wave inspection methods for structural health monitoring
Creator: Dib, Gerges
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Structural health monitoring (SHM) has the potential to significantly increase safety and reduce manufacturing and maintenance costs of industrial structures. The use of piezoelectric material such as Lead-Zirconate-Titanate (PZT) in exciting and sensing ultrasonic guidedwaves for damage detection has become popular since its allows the rapid inspection of large areas in a structure using non-intrusive sensors. Ultrasonic guided waves interact with discontinuities in the structure, giving...
Show moreStructural health monitoring (SHM) has the potential to significantly increase safety and reduce manufacturing and maintenance costs of industrial structures. The use of piezoelectric material such as Lead-Zirconate-Titanate (PZT) in exciting and sensing ultrasonic guidedwaves for damage detection has become popular since its allows the rapid inspection of large areas in a structure using non-intrusive sensors. Ultrasonic guided waves interact with discontinuities in the structure, giving information about the potential presence of a damage, its size and location.The main concerns about using such methods is that PZT sensors and guided waves are affected by environmental conditions. The performance of the PZT sensors, in terms of their ability to detect damage, degrades over time and varies depending on current environmental conditions and surrounding, resulting in inconsistent measurements. This work gives a novel formulation of a model-based probability of detection method, which is able to quantifythe performance of guided wave inspection in a stochastically varying environment. An analytically and experimentally verified finite element model is used to generate data that represent the effects of varying environmental conditions. Then the stochastic approachis used to evaluate the probability of detection of cracks in riveted aluminum plates and delaminations in composite plates. Also, the performance of guided wave imaging algorithms under degrading PZT conditions is examined.Another concern is the ability to transfer data from the PZT sensors, which are per-manently located on the structure, to a computer where the data could be processed in real-time or near real-time. Wireless sensor networks (WSN) use low footprint smart sensor nodes that are permanently mounted on the structure. The sensor nodes have their own power supply and wireless communication devices to communicate with other sensor nodes or a base station. Wireless sensor node for guided waves require an actuation interfacesand high frequency sampling of the guided wave measurements. A proof-of-concept wireless sensor node prototype is developed for the data acquisition and actuation using PZT sensorsand guided waves.
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Title: Cost-aware routing protocols for location-privacy and efficiency in wireless sensor networks
Creator: Lightfoot, Leron J.
Date: 2015
Collection: Electronic Theses & Dissertations
Description: Wireless sensor networks (WSNs) can provide the world with a technology for real-time event monitoring for both military and civilian applications. One of the primary concerns that hinders the successful deployment of wireless sensor networks is how to provide adequate source and destination nodes location privacy. The privacy of the location is vital and highly jeopardized by the usage of wireless communications. While message content privacy can be ensured through message encryption, it is...
Show moreWireless sensor networks (WSNs) can provide the world with a technology for real-time event monitoring for both military and civilian applications. One of the primary concerns that hinders the successful deployment of wireless sensor networks is how to provide adequate source and destination nodes location privacy. The privacy of the location is vital and highly jeopardized by the usage of wireless communications. While message content privacy can be ensured through message encryption, it is much more difficult to adequately address the location privacy issue. For WSNs, location privacy service is further complicated by the fact that sensors consist of low-cost and energy efficient radio devices. Therefore, using computationally intensive cryptographic algorithms (such as public-key cryptosystems) and large scale broadcasting-based protocols are not suitable for WSNs.Many protocols have been proposed to provide location privacy but most of them are based on public-key cryptosystems, while others are either energy inefficient or have certain security flaws. After analyzing the security weaknesses of the existing schemes, we propose several creative and secure energy-aware routing protocols that can address the location privacy issue in WSNs. For source-location privacy, we propose 3 schemes. The first scheme routes each message to a randomly selected intermediate node (RSIN) before it is transmitted to the SINK node. However, this scheme can only provide local source-location privacy. In the second scheme, a network mixing ring (NMR) is proposed to provide network-level source-location privacy. The third scheme achieves network-level source-location privacy through a technique we call the Sink Toroidal Region (STaR) routing. For destination-location privacy, we propose the Bubble routing protocol and a series of R-STaR routing protocols. For each of these routing schemes, both security analysis using quantitative measurements and simulation results show that the proposed protocols are secure and energy-efficient.While providing location privacy is vital, prolonging the lifetime of the network can be a very essential component as well. In this dissertation, we propose a cluster-based energy-aware routing scheme, called Quad-Region Cluster-Head Selection (Q-ReCHS), which will prolong the network lifetime by evenly distributing the energy load among all the nodes. Our extensive simulation results on cluster-based routing demonstrates that our proposed Q-ReCHS scheme can out perform many of the existing schemes.
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Title: Cost-aware secure protocol design and analysis
Creator: Tang, Di
Date: 2015
Collection: Electronic Theses & Dissertations
Description: The recent technological progresses make sensor networks feasible to be widely used in both military and civilian applications. The nature of such networks makes energy consumption, communication delay and security the most essential issues for wireless sensor networks. However, these issues may be conflicting with each other. The existing works generally try to optimize one of these key issues without providing sufficient diversity and flexibility of various other requirements in protocol...
Show moreThe recent technological progresses make sensor networks feasible to be widely used in both military and civilian applications. The nature of such networks makes energy consumption, communication delay and security the most essential issues for wireless sensor networks. However, these issues may be conflicting with each other. The existing works generally try to optimize one of these key issues without providing sufficient diversity and flexibility of various other requirements in protocol design. In this dissertation, we investigate the relationship and design trade-offs among these conflicting issues.To deal with the lifetime optimization and security issues, we propose a novel secure and efficient Cost-Aware SEcure Routing (CASER) protocol to address them through two adjustable parameters: energy balance control (EBC) and security level to enforce energy balance and increase lifetime and determine the probabilistic distribution of random walking that provides routing security. We derive a tight numerical formula to quantitatively estimate the routing efficiency through the number of routing hops for a given routing security level. We also prove that CASER scheme can provide provable security under the quantitative security measurement criteria. Simulation results also show that the proposed CASER scheme can provide an excellent balance between routing efficiency and security while extending the network lifetime.We then discover that the energy consumption is severely disproportional to the uniform energy deployment for the given network topology. To solve this problem, we propose an efficient non-uniform energy deployment strategy to optimize the network lifetime and increase the message delivery ratio under the same energy resource and security requirements. Our theoretical analysis and OPNET simulation results demonstrate that the updated CASER protocol can provide an excellent trade-off between routing efficiency and energy consumption, while significantly extending the lifetime of the sensor networks in all scenarios. For the non-uniform energy deployment, our analysis shows that we can increase the lifetime and the total number of messages that can be delivered by more than four times under the same energy deployment, while achieving a high message delivery ratio and preventing routing traceback attacks.In WSNs, congestion introduces not only buffer overflow, but also communication delay for forwarding messages from the source node to the sink. We propose a novel congestion-aware routing (CAR) scheme to reduce the end-to-end communication delay while increasing network throughput. CAR employs two routing strategies, shortest path routing strategy and congestion-aware strategy, to achieve a trade-off between energy efficiency and communication delay. The OPNET simulation results demonstrate that the proposed routing scheme can reduce the end-to-end communication delay by 50% while increasing the network throughput by more than two times in our settings.People-centric urban sensing is envisioned as a novel urban sensing paradigm. Security, communication delay and delivery ratio are essential design issues in people-centric urban sensing networks. To address these three issues concurrently, we propose a novel delay-aware privacy preserving (DAPP) transmission scheme based on a combination of two-phase forwarding and secret sharing. The two-phase forwarding method detaches connection between the application data server and the source nodes, which renders it infeasible for the application data server to estimate source node identities. The underlying secret sharing scheme and dynamic pseudonym ensure confidentiality of the collected data and anonymity of participating users. DAPP provides a framework to achieve a design trade-off among security, communication delay and delivery ratio. The security analysis demonstrates that DAPP can preserve location privacy while defending against side information attacks. Theoretical analysis and simulation results show that our proposed algorithms can provide a flexible and diverse security design option for routing and data forwarding algorithm design.
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Title: Damage progression quantification and data robustness evaluation in self-powered sensors networks
Creator: Hasni, Hassene
Date: 2018
Collection: Electronic Theses & Dissertations
Description: "This research proposes novel damage progression quantification and data robustness evaluation approaches, for structural health monitoring (SHM), using a new class of self-powered piezo-floating-gate (PFG) sensors. This system relies on harvesting the mechanical energy from structures through the direct effect of piezoelectricity. The operating power of the smart sensor and the data used for damage identification is harvested directly from the sensing signal induced by a piezoelectric...
Show more"This research proposes novel damage progression quantification and data robustness evaluation approaches, for structural health monitoring (SHM), using a new class of self-powered piezo-floating-gate (PFG) sensors. This system relies on harvesting the mechanical energy from structures through the direct effect of piezoelectricity. The operating power of the smart sensor and the data used for damage identification is harvested directly from the sensing signal induced by a piezoelectric transducer under dynamic loading. The developed models integrate structural simulations using finite element method (FEM) techniques, experimental studies, and statistical and artificial intelligence (AI) methods. In this work, the performance of the sensing system in identifying damage is investigated for various damage scenarios based on numerical and experimental studies. Both steel and pavement structures are studied. A new surface sensing approach for detecting bottom-up cracks in asphalt concrete (AC) pavement is proposed. Two types of self-powered wireless sensors are investigated in this research. Different data interpretation techniques are developed for each type of sensor. The data are obtained from finite element simulations, or experimental measurement, and are fitted to probability distributions to define initial damage indicators. Sensor fusion models are developed based on the concept of group-effect of sensors, in order to increase the damage detection resolution of individual sensors. Probabilistic neural network (PNN) and support vector machine (SVM) methods are used to improve the accuracy of the proposed damage identification methods for the case of multi-class damage progression. The proposed work is divided into four main parts: (i) Damage identification in steel structures using data from a uniform PFG sensor, (ii) Damage detection in steel and pavement structures using a non-uniform PFG sensor, (iii) Damage detection and localization in steel frame structures using hybrid network of self-powered strain and vibration sensors, and, (iv) a field demonstration of the new technology on the Mackinac Bridge in Michigan. The cases of the U10W gusset plate of the I-35W bridge in Minneapolis, MN, a steel girder, a steel plate under compaction tension mode, and an AC beam under three-point bending configuration are investigated. A surface sensing approach to detect bottom-up cracking in AC pavement under dynamic moving load is also proposed. This approach is based on interpreting the data of a surface-mounted network of sensors. Moreover, a hybrid network of strain and vibration-based sensors is used to detect damage in bolted steel frames. The objective is to establish a local-to-global strategy for damage identification in frames. Data fusion models combined with AI classifiers are developed. Uncertainty analysis is performed to verify the performance of the sensors under different noise levels."--Pages ii-iii.
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Title: Design and deployment of low-cost wireless sensor networks for real-time event detection and monitoring
Creator: Phillips, Dennis Edward
Date: 2018
Collection: Electronic Theses & Dissertations
Description: As sensor network technologies become more mature, they are increasingly being applied to a wide variety of environmental monitoring applications, ranging from agricultural sensing to habitat monitoring, oceanic and volcanic monitoring. In this dissertation two wireless sensor networks (WSNs) are presented. One for monitoring residential power usage and another for producing an image of a volcano's internal structure.The two WSNs presented address several common challenges facing modern...
Show moreAs sensor network technologies become more mature, they are increasingly being applied to a wide variety of environmental monitoring applications, ranging from agricultural sensing to habitat monitoring, oceanic and volcanic monitoring. In this dissertation two wireless sensor networks (WSNs) are presented. One for monitoring residential power usage and another for producing an image of a volcano's internal structure.The two WSNs presented address several common challenges facing modern sensor networks. The first is in-network processing and assigning the processing tasks across a heterogeneous network architecture. By efficiently utilizing in-network processing power consumption can be reduced and operational lifetime of the network can be extended. As nodes are embedded into various environments sensing accuracy is intrinsically affected by physical noise. The second challenge relates to how to deal with this noise in a way which increases sensing accuracy. The third challenge is ease of deployment. As WSNs become more common place they will be installed by non-experts.As a key technology of home area networks in smart grids, fine-grained power usage monitoring may help conserve electricity. Smart homes outfitted with network connected appliances will provide this capability in the future. Until smart appliances have wide adaption there is a serious gap in capabilities. To fill this gap an easy to deploy monitoring system is needed. Several existing systems achieve the goal of fine-grained power monitoring by exploiting appliances' power usage signatures utilizing labor-intensive in situ training processes. Recent work shows that autonomous power usage monitoring can be achieved by supplementing a smart meter with distributed sensors that detect the working states of appliances. However, sensors must be carefully installed for each appliance, resulting in high installation cost. Supero is the first ad hoc sensor system that can monitor appliance power usage without supervised training. By exploiting multi-sensor fusion and unsupervised machine learning algorithms, Supero can classify the appliance events of interest and autonomously associate measured power usage with the respective appliances. Extensive evaluation in five real homes shows that Supero can estimate the energy consumption with errors less than 7.5%. Moreover, non-professional users can quickly deploy Supero with considerable flexibility.There are a number of active volcanos around the world with large population areas located nearby. An eruption poses a significant threat to the adjacent population. During times of increased activity being able to obtain a real-time images of the interior would allow seismologists to better understand volcanic dynamics. Volcano tomography can provide this valuable information concerning the internal structure of a volcano. The second sensor network presented in this dissertation is a seismic monitoring sensor network featuring in-network processing of the seismic signals with the capability to perform volcano tomography in real-time. The design challenges, analysis of processing/network processing times in the information processing pipeline, the system designed to meet these challenges and the results from deploying a prototype network on two volcanoes in Ecuador and Chile are presented. The study shows that it is possible to achieve in-network seismic event detection and real-time tomography using a sensor network that is 2 orders of magnitude less expensive than traditional seismic equipment.
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Title: Design and implementation of integrated self-powered sensors, circuits and systems
Creator: Huang, Chenling
Date: 2011
Collection: Electronic Theses & Dissertations
Description: Wireless sensor systems have been widely used for both industrial and civil applications. With the development of circuit design and fabrication technique, sensor nodes now can be implemented with small scale at low cost, which is promising for ubiquitous sensing. However, with more functions integrated, the conflict between power consumption and expected lifetime became critical. Sensor nodes powered with batteries are generally compromised by extra physical size and periodic battery...
Show moreWireless sensor systems have been widely used for both industrial and civil applications. With the development of circuit design and fabrication technique, sensor nodes now can be implemented with small scale at low cost, which is promising for ubiquitous sensing. However, with more functions integrated, the conflict between power consumption and expected lifetime became critical. Sensor nodes powered with batteries are generally compromised by extra physical size and periodic battery replacement. Therefore, energy harvesting techniques are intensively involved in sensor design where environmental signal acts as auxiliary energy source.A typical energy harvesting sensor consists of four parts: energy harvester, energy storage, power management and sensor subsystem. Energy harvester scavenges power from environmental signal which is then transferred into energy storage. Since the output power is usually not in appropriate form, power management is used to provide a usable supply voltage/current for sensor subsystem. The limitation of energy harvesting sensor is determined by the power consumption of sensor subsystem, the efficiency of energy conversion and the available energy level from environment.In this dissertation, a novel solution referred as "self-powered sensor" is proposed to extend the limitation of energy harvesting sensor. The proposed sensor can directly harvest energy from input signal being sensed. Therefore the usage of energy storage and power management is eliminated, which achieves higher energy efficiency.To demonstrate proposed solution, the system and circuit design of a self-powered sensor are presented for long-term ambient vibration monitoring. Constrained by its application, the sensor can only scavenge energy from input strain signal itself, in which scenario all existing energy harvesting techniques fail. The greatest design challenge is to achieve both ultra-low power computation and non-volatile storage. In this dissertation, a novel technique based on floating-gate transistor is presented. By exploiting controllable hot electron injection procedure, specific computation can be performed according to the characteristic of input signal. In addition, floating-gates can also retain computation results with no power consumption.For autonomous sensing, a hybrid energy harvesting topology is proposed on system level. The sensor is designed with two different operation modes. In self-powered sensing mode, it can perform continuous monitoring, computation and data storage which is powered by input strain signal. In data interrogating mode, additional functions such as data sampling and wireless communication can be enabled once a certain reading device is provided.The dissertation is organized as follows. In chapter 1, the history of wireless sensor system is reviewed. The motivation of self-powered sensor and the contributions of this dissertation are presented. Existing energy harvesting techniques are evaluated in chapter 2. In chapter 3, the case of long-term ambient vibration monitoring is studied and the hybrid energy harvesting topology is proposed for self-powered sensor system. In chapter 4, the principle of ultra-low power computation and non-volatile storage is explored based on controllable injection procedure on floating-gate transistor. To verified proposed solution, a sensor prototype was fabricated in 0.5-um standard CMOS process. The details of circuit design and evaluation are presented in chapter 5, including analog signal processor, analog-to-digital converter, radio frequency front-end, digital baseband, etc. Chapter 6 shows an extension of ultrasonic powering and communication system based on preliminary work and chapter 7 draws final remarks.
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Title: Development of small biomimetic robotic fish with onboard fine-grained localization
Creator: Shatara, Stephan W.
Date: 2008
Collection: Electronic Theses & Dissertations

Title: Environmental acoustics as an ecological variable to understand the dynamics of ecosystems
Creator: Joo, Wooyeong
Date: 2009
Collection: Electronic Theses & Dissertations

Title: Exploiting node mobility for energy optimization in wireless sensor networks
Creator: El-Moukaddem, Fatme Mohammad
Date: 2012
Collection: Electronic Theses & Dissertations
Description: Wireless Sensor Networks (WSNs) have become increasingly available for data-intensive applications such as micro-climate monitoring, precision agriculture, and audio/video surveillance. A key challenge faced by data-intensive WSNs is to transmit the sheer amount of data generated within an application's lifetime to the base station despite the fact that sensor nodes have limited power supplies such as batteries or small solar panels. The availability of numerous low-cost robotic units (e.g....
Show moreWireless Sensor Networks (WSNs) have become increasingly available for data-intensive applications such as micro-climate monitoring, precision agriculture, and audio/video surveillance. A key challenge faced by data-intensive WSNs is to transmit the sheer amount of data generated within an application's lifetime to the base station despite the fact that sensor nodes have limited power supplies such as batteries or small solar panels. The availability of numerous low-cost robotic units (e.g. Robomote and Khepera) has made it possible to construct sensor networks consisting of mobile sensor nodes. It has been shown that the controlled mobility offered by mobile sensors can be exploited to improve the energy efficiency of a network.In this thesis, we propose schemes that use mobile sensor nodes to reduce the energy consumption of data-intensive WSNs. Our approaches differ from previous work in two main aspects. First, our approaches do not require complex motion planning of mobile nodes, and hence can be implemented on a number of low-cost mobile sensor platforms. Second, we integrate the energy consumption due to both mobility and wireless communications into a holistic optimization framework.We consider three problems arising from the limited energy in the sensor nodes. In the first problem, the network consists of mostly static nodes and contains only a few mobile nodes. In the second and third problems, we assume essentially that all nodes in the WSN are mobile. We first study a new problem called max-data mobile relay configuration (MMRC) that finds the positions of a set of mobile sensors, referred to as relays, that maximize the total amount of data gathered by the network during its lifetime. We show that the MMRC problem is surprisingly complex even for a trivial network topology due to the joint consideration of the energy consumption of both wireless communication and mechanical locomotion. We present optimal MMRC algorithms and practical distributed implementations for several important network topologies and applications. Second, we consider the problem of minimizing the total energy consumption of a network. We design an iterative algorithm that improves a given configuration by relocating nodes to new positions. We show that this algorithm converges to the optimal configuration for the given transmission routes. Moreover, we propose an efficient distributed implementation that does not require explicit synchronization. Finally, we consider the problem of maximizing the lifetime of the network. We propose an approach that exploits the mobility of the nodes to balance the energy consumption throughout the network. We develop efficient algorithms for single and multiple round approaches. For all three problems, we evaluate the efficiency of our algorithms through simulations. Our simulation results based on realistic energy models obtained from existing mobile and static sensor platforms show that our approaches significantly improve the network's performance and outperform existing approaches.
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Title: Gliding robotic fish : design, collaborative estimation, and application to underwater sensing
Creator: Ennasr, Osama Nasr
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Autonomous underwater robots have received significant attention over the past two decades due to the increasing demand for environmental sustainability. Recently, gliding robotic fish has emerged as a promising mobile sensing platform in versatile aquatic environments. Such robots, inspired by underwater gliders and robotic fish, combine buoyancy-driven gliding and fin-actuated swimming to realize both energy-efficient locomotion and high maneuverability. In this dissertation, we first...
Show moreAutonomous underwater robots have received significant attention over the past two decades due to the increasing demand for environmental sustainability. Recently, gliding robotic fish has emerged as a promising mobile sensing platform in versatile aquatic environments. Such robots, inspired by underwater gliders and robotic fish, combine buoyancy-driven gliding and fin-actuated swimming to realize both energy-efficient locomotion and high maneuverability. In this dissertation, we first discuss the design improvements for the second-generation gliding robotic fish "Grace 2". These improvements have transformed the robots to underwater sensing platforms that can be modified to fit the requirements of a specific application with relative ease.We focus on the application of detecting and tracking live fish underwater, which is an important part of fishery research, as it helps scientists understands habitat use, migratory patterns, and spawning behavior of fishes. The gliding robotic fish has demonstrated its ability to detect special acoustic signals emulating tagged fish through a series of trials in Higgins Lake, Michigan. These tests have also validated a gliding-based strategy for navigating to a GPS waypoint, and offered insight into the limitations of the current design. Additional improvements are proposed to allow these robots to glide at larger depths and perform more interesting working patterns underwater.Motivated by the problem of tracking real fish, we consider the case where multiple robots localize and track a moving target without the need for a centralized node. We present theoretical treatment on how a network of robots can infer the location of an emitter (or target), and then track it, through a time-difference-of-arrival (TDOA) localization scheme in a fully distributed manner. In particular, we utilize a networked extended Kalman filter to estimate the target's location in a distributed manner, and establish that successful localization can be achieved under fixed and time-varying undirected communication topologies if every agent is part of a network with a minimum of 4 connected, non-coplanar agents. We further propose a movement control strategy based on the norm of the estimation covariance matrices, with a tuning parameter to balance the trade-off between estimation performance and the total distance traveled by the robots.Finally, motivated by the distributed localization problem, we investigate a more general problem of distributed estimation by a network of sensors. Specifically, we consider the class of consensus-based distributed linear filters (CBDLF) where each sensor updates its estimate in two steps: a consensus step dictated by a weighted and directed communication graph, followed by a local Luenberger filtering step. We show that the sub-optimal filtering gains that minimize an upper bound of a quadratic filtering cost are related to the convergence of a set of coupled Riccati equations. Then we show that the convergence of these coupled Riccati equations depends on the notion of squared detectability for the networked system, and proceed to provide necessary conditions that link the convergence of the coupled Riccati equations to the network topology and consensus weights of the communication graph.
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Title: Implementation of a high throughput low power MAC protocol in wireless sensor networks
Creator: Liu, Chin-Jung
Date: 2011
Collection: Electronic Theses & Dissertations
Description: This thesis presents the design, implementation, and evaluation of TATD-MAC, a TDMA-based low duty cycle synchronous MAC protocol that improves throughput by increasing channel uti- lization with a traffic-adaptive time slot scheduling method. Conventional time division multiple access (TDMA) introduces significant end-to-end packet delivery delay and its throughput is lim- ited. TATD-MAC achieves higher throughput by improving TDMA with a novel traffic-adaptive mechanism that assigns time...
Show moreThis thesis presents the design, implementation, and evaluation of TATD-MAC, a TDMA-based low duty cycle synchronous MAC protocol that improves throughput by increasing channel uti- lization with a traffic-adaptive time slot scheduling method. Conventional time division multiple access (TDMA) introduces significant end-to-end packet delivery delay and its throughput is lim- ited. TATD-MAC achieves higher throughput by improving TDMA with a novel traffic-adaptive mechanism that assigns time slots only to nodes that are expecting traffic. Our traffic-adaptive mechanism is a two-phase design, which decomposes the DATA period into traffic notification part and data transmission scheduling part. The two-phase design enables TATD-MAC to optimize the control packets and improve their energy efficiencies according to the characteristics of each phase. The source nodes inform all nodes on the routing path that these sources have outgoing traffic by transmitting traffic notification packets in a "pulse" fashion. With traffic notification packets, ev- ery node on the routing path claims time slots in data transmission part. Therefore, TATD-MAC is able to forward a packet over multiple hops in a single cycle and thus reduce the end-to-end delay. The data transmission scheduling mechanism only assigns time slots to nodes with traf- fic through an ordered schedule negotiation scheme. This innovative traffic-adaptive scheduling mechanism assigns time slots based on traffic and totally eliminates the idle listening slots on nodes with no traffic. Moreover, if any other nodes need more time slots, they are able to claim them, which further improves channel utilization and achievable throughput. We implemented a TATD-MAC prototype on Tmote-Sky running TinyOS 2.1.0. Performance evaluation shows that TATD-MAC significantly improves throughput compared to conventional TDMA and achieves the same throughput as TDMA with slot stealing while having 70% less power consumption.
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Title: Improving spectrum efficiency in heterogeneous wireless networks
Creator: Liu, Chin-Jung
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Over the past decades, the bandwidth-intensive applications that are previously confined to wired networks are now migrating to wireless networks. This trend has brought unprecedented high demand for wireless bandwidth. The wireless traffic is destined to dominate the Internet traffic in the future, but many of the popular wireless spectrum bands, especially the cellular and ISM bands, are already congested. On the other hand, some other wireless technologies, such as TV bands, often do not...
Show moreOver the past decades, the bandwidth-intensive applications that are previously confined to wired networks are now migrating to wireless networks. This trend has brought unprecedented high demand for wireless bandwidth. The wireless traffic is destined to dominate the Internet traffic in the future, but many of the popular wireless spectrum bands, especially the cellular and ISM bands, are already congested. On the other hand, some other wireless technologies, such as TV bands, often do not fully utilize their spectrum. However, the spectrum allocation is tightly regulated by the authority and adjusting the allocation is extremely difficult. The uneven utilization and the rigid regulation have led to the proposal of heterogeneous wireless networks, including cognitive radio networks (CRN) and heterogeneous cellular networks (HetNet). The CRNs that usually operate on different technologies from the spectrum owner attempt to reuse the idle spectrum (i.e., white space) from the owner, while HetNets attempt to improve spectrum utilization by smallcells. This dissertation addresses some of the challenging problems in these heterogeneous wireless networks.In CRNs, the secondary users (SU) are allowed to access the white spaces opportunistically as long as the SUs do not interfere with the primary users (PU, i.e., the spectrum owner). The CRN provides a promising means to improve spectral efficiency, which also introduces a set of new research challenges. We identify and discuss two problems in CRNs, namely non-contiguous control channel establishment and k-protected routing protocol design. The first problem deals with the need from SUs for a channel to transfer control information. Most existing approaches are channel-hopping (CH) based, which is inapplicable to NC-OFDM. We propose an efficient method for guaranteed NC-OFDM-based control channel establishment by utilizing short pulses on OFDM subcarriers. The results show that the time needed for establishing control channel is lower than that of CH-based approaches. The second problem deals with the interruption to a routing path in a CRN when a PU becomes active again. Existing reactive approaches that try to seek for an alternative route after PU returns suffer from potential long delay and possible interruption if an alternative cannot be found. We propose a k-protected routing protocol that builds routing paths with preassigned backups that are guaranteed to sustain from k returning PUs without being interrupted. Our result shows that the k-protected routing paths are never interrupted even when k PUs return, and have significantly shorter backup activation delays.HetNets formed by smallcells with different sizes of coverage and macrocells have been proposed to satisfy increased bandwidth demand with the limited and crowded wireless spectrum. Since the smallcells and macrocells operate on the same frequency, interference becomes a critical issue. Detecting and mitigating interference are two of the challenges introduced by HetNets. We first study the interference identification problem. Existing interference identification approaches often regard more cells as interferers than necessary. We propose to identify interference by analyzing the received patterns observed by the mobile stations. The result shows that our approach identifies all true interferers and excludes most non-interfering cells. The second research problem in HetNets is to provide effective solutions to mitigate the interference. The interference mitigation approaches in the literature mainly try to avoid interference, such as resource isolation that leads to significantly fewer resources, or power control that sacrifices signal quality and coverage. Instead of conservatively avoiding interference, we propose to mitigate the interference by precanceling the interfering signals from known interferers. With precancellation, the same set of resources can be shared between cells and thus throughput is improved.This dissertation addresses several challenges in heterogeneous wireless networks, including CRNs and HetNets. The proposed non-contiguous control channel protocol and k-protected routing protocol for CRNs can significantly improve the feasibility of CRNs in future wireless network applications. The proposed interference identification and interference precancellation approaches can effectively mitigate the interference and improve the throughput and spectrum utilization in HetNets. This dissertation aims at breaking the barriers for supporting heterogeneous wireless networks to improve the utilization of the precious and limited wireless spectrum.
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Title: Mobility and communication in wireless robot and sensor networks
Creator: Pei, Yuanteng
Date: 2011
Collection: Electronic Theses & Dissertations
Description: Mobility is a primary goal of many wireless communication systems. In recent years, mobile multi-hop wireless networks, such as mobile wireless sensor networks and wireless robot networks, have attracted increased attention and have been extensively studied. However, most current research does not consider the interdependence of communication and mobility and much assume an obstacle-free environment in their problem modeling and solving process.In this dissertation, we discuss several...
Show moreMobility is a primary goal of many wireless communication systems. In recent years, mobile multi-hop wireless networks, such as mobile wireless sensor networks and wireless robot networks, have attracted increased attention and have been extensively studied. However, most current research does not consider the interdependence of communication and mobility and much assume an obstacle-free environment in their problem modeling and solving process.In this dissertation, we discuss several research topics relevant to the above two issues of communication and mobility in wireless robot and sensor networks. First, we present multi-robot real-time exploration, which calls for the joint consideration of mobility and communication: it requires video and audio streams of a newly explored area be transmitted to the base station in a timely fashion as robots explore the area. Simulations show that our mobility model has achieved both improved communication quality and enhanced exploration efficiency.Second, we further investigate the above problem with two critical and real-world network conditions: (1) heterogeneous transmission ranges and link capacities, and (2) the impact of interference. The conditions increase the model complexity but significantly influence the actual available bandwidth and the required node size in placement. We jointly consider the relay placement and routing with these two critical conditions.Third, we introduce an online relay deployment paradigm to support remote sensing and control when mobile nodes migrate farther from the base station in a cost-effective system of mobile robots, static sensors and relays. A novel multi-robot real-time search method called STAtic Relay aided Search (STARS) is presented to allow robots to search in a known environment. Its solution is based on our near-optimal solution to a new variation of the multi-traveling salesman problem: precedence constrained two traveling salesman (PC2TSP).Fourth, we propose a heterogenous multi-robot exploration strategy with online relay deployment for an unknown environment called Bandwidth aware Exploration with a Steiner Traveler (BEST). In BEST, a relay-deployment node (RDN) tracks the FNs movement and places relays when necessary to support the video/audio streams aggregation to the base station. This problem inherits characteristics of both the Steiner minimum tree and traveling salesman problems. Extensive simulations show that BEST further enhances the exploration efficiency.While the first four topics deal with communication and mobility issues in powerful but expensive robotic systems, the fifth topic focuses on a special type of low cost, limited capability mobile sensors called hopping sensors, whose unique method of movement makes them suitable for rugged terrains. We present (1) a distributed message forwarding model called Binary Splitting Message Forwarding (BSMF) and (2) a grid based movement model unique to these hopping sensors. Simulation shows that our scheme significantly reduces the communication overhead and achieves relatively constant total energy consumption with varying amount of obstructions.Finally, we discuss the future work directions of this research work. We believe that a heterogeneous mobile platform to support real-time stream transmission by mobile robots, static sensor and communication devices, have great potential in various civilian and military applications, where the communication quality of service is critically important, as well as the mobility efficiency.
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Title: Network issues for 3D wireless sensor networks
Creator: Cintrón, Fernando J.
Date: 2013
Collection: Electronic Theses & Dissertations
Description: Wireless sensor networks (WSN) give the opportunity to monitor the environment by performing sensing tasks in places that are difficult to reach or dangerous for humans. Nevertheless, topographical characteristics of such places and the sensor node's limitations introduce new issues in WSN performance. Additionally, in scenarios where sensors are moving or in rugged terrain, there is a high chance for them to be out of communication range, causing network connectivity problems. Hence,...
Show moreWireless sensor networks (WSN) give the opportunity to monitor the environment by performing sensing tasks in places that are difficult to reach or dangerous for humans. Nevertheless, topographical characteristics of such places and the sensor node's limitations introduce new issues in WSN performance. Additionally, in scenarios where sensors are moving or in rugged terrain, there is a high chance for them to be out of communication range, causing network connectivity problems. Hence, solutions have to take into consideration the aspect of the topography consisting of its three dimensional characteristics, namely, type of terrain, terrain unevenness, and obstacles.This dissertation discusses several research topics addressing issues relevant to WSN connectivity and area coverage problems. First, changes in sensor communication range are studied by varying sensors' heights relative to the surface. A novel communication technique that relies on the jumping capabilities of sensors is proposed. While the jumping sensor robots are airborne, the change in elevation enhances their ability for a short time to successfully communicate with other sensors that are out of communication range at the ground level. Field experiments were conducted and results show a considerable improvement in wireless communication ranges.Second, the impact of network connectivity and area coverage in a jumping sensor network is further studied. A Hopping Sensor Network Model is defined to increase sensing area coverage along with the enhancement of network connectivity. A Hopping Sensor Routing Protocol is designed from the model that balances the energy consumption on active jumping sensor nodes. Results from simulations show the increase in area coverage obtained from jumping sensor networks, and the effectiveness of the routing protocol to optimize communication paths while balancing energy depletion in the network.Third, a distributed wireless sensor network organization to establish a functional network, without requiring initial topology information, is presented. Two decentralized algorithms that use the jumping capabilities of sensors are designed for the discovery of isolated sensors. Simulation results show the success of the algorithms to enhance base station reachability. Additionally, cluster to cluster (C-to-C) packet forwarding schemes relying on boundary jumping sensor gateways are defined and analyzed, showing remarkable savings in network energy consumption.Fourth, in order to have a functional network, it is important to address connectivity issues in an application oriented manner. This work presents an efficient node redeployment-decision process to produce a functionally heterogeneous (jumping and non-jumping sensors) WSN with a performance guarantee. Network performance is defined as a network fitness formula considering the network Quality of Connectivity (QoC). Decision making algorithms for node relocation and topology defragmentation are presented, along with a discussion of their performance.Fifth, a multi-step procedure to produce a direction oriented jumping sensor network is presented. A jumping sensor robot approach is introduced for collecting and processing signal strength data into relative geographical orientation information. A directional-orientation decision algorithm is defined to process the orientation information. Furthermore, an error identification and correction procedure is established. This has proven to accurately fix the true orientation of the nodes by using only a pair of location aware beacon nodes.
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Title: Off-network control processing for scalable routing in very large sensor networks
Creator: Wu, Tao
Date: 2008
Collection: Electronic Theses & Dissertations

Title: Power management and damage assessment techniques for self-powered sensing based on piezoelectric transduction
Creator: Rhimi, Mohamed
Date: 2013
Collection: Electronic Theses & Dissertations
Description: One major obstacle facing health monitoring systems is the ability to accurately predict remaining life after structural state diagnosis. Today, many remaining life prediction models rely on empirical data which limits their applicability. Moreover, the large scatter in material data, i.e., fatigue, combined with archaic instrumentation has hindered the development and validation of improved prediction models. There is a need for long term continuous monitoring techniques capable of rendering...
Show moreOne major obstacle facing health monitoring systems is the ability to accurately predict remaining life after structural state diagnosis. Today, many remaining life prediction models rely on empirical data which limits their applicability. Moreover, the large scatter in material data, i.e., fatigue, combined with archaic instrumentation has hindered the development and validation of improved prediction models. There is a need for long term continuous monitoring techniques capable of rendering a more precise and reliable stream of data that would enhance the modeling proficiencies and would ultimately help reduce maintenance cost, improve the longevity, and enhance the safety of civil infrastructures.Wireless sensors and sensor networks are emerging as sensing paradigms that the structural engineering field has begun to consider as substitutes for traditional tethered monitoring systems. A major consideration in using a dense sensor array for long term monitoring is the problem of providing power to the sensors. Piezoelectric energy powering has the added advantage to act both as the sensor and as the powering means, thereby reducing the power requirement and cost of the sensor system.Improving the piezoelectric power harvesting from civil structures' vibration while obeying environmental effects (temperature variation) is the first objective of this thesis; the application of a variable preloading condition is used as a solution to modify the cantilever piezoelectric harvester's properties. A generalized model that takes into account more than one vibration-mode shape is derived. Measured acceleration recordings from a concrete bridge deck under ambient loading and recordings from extreme events are used to show the gain in harvested energy when the harvester is in preloaded configuration. The effects of temperature variations on the piezoelectric (PZT) harvested energy from civil structures are also studied. A proposed mechanical tuning, based on the application of an axial load using Shape Memory Alloy to compensate the temperature effect, is presented.The work describing a fully deployed long-term piezoelectric based monitoring system with all needed attributes is the second objective of this work. The calibration and installation of the sensor is addressed. Defining the sensor output from real time loading distribution is shown. The evaluation of a full field data from a limited number of distributed sensor is studied. The damage prediction abilities of the long term self powered continuous monitoring system are evaluated. A slightly modified linear damage accumulation approach is then proposed using the damage index founded on continuum mechanics definition. The derivation of the damage index using sensor's output data is detailed with results from a set of laboratory tests, comparing the damage index prediction output from the sensor and values obtained using the complete time history data. Finally, a projection of the remaining life of tested specimens using reliability analysis was computed and it accuracy was evaluated by completing the test until failure and counting the total real observed cycles, showing very promising results for full field deployment and remaining life prediction with a reasonable accuracy.
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Title: Preserving source-location privacy in wireless sensor networks
Creator: Lightfoot, Leron J.
Date: 2010
Collection: Electronic Theses & Dissertations
Description: Wireless sensor networks (WSNs) can provide the world with a technology for real-time event monitoring for both military and civilian applications. One of the primary concerns that hinder the successful deployment of wireless sensor networks is source-location privacy. The privacy of the source location is vital and highly jeopardized by the usage of wireless communications.While message content privacy can be ensured through message encryption, it is much more difficult to adequately address...
Show moreWireless sensor networks (WSNs) can provide the world with a technology for real-time event monitoring for both military and civilian applications. One of the primary concerns that hinder the successful deployment of wireless sensor networks is source-location privacy. The privacy of the source location is vital and highly jeopardized by the usage of wireless communications.While message content privacy can be ensured through message encryption, it is much more difficult to adequately address the source-location privacy. For WSNs, source-location privacy service is further complicated by the fact that sensors consist of low-cost and energy efficient radio devices. Therefore, using computationally intensive cryptographic algorithms (such as public-key cryptosystems) and large scale broadcasting-based protocols are not suitable for WSNs.Many protocols have been proposed to provide source-location privacy but most of them are based on public-key cryptosystems, while others are either energy inefficient or have certain security flaws. In this thesis, after analyzing the security weakness of the existing scheme, we propose three routing-based source-location privacy schemes. The first scheme routes each message to a randomly selected intermediate node before it is transmitted to the SINK node. However, this scheme can only provide local source-location privacy. In the second scheme, a network mixing ring (NMR) is proposed to provide network-level source-location privacy. The third scheme achieve network-level source-location privacy through a technique we call the Sink Toroidal Region (STaR) routing. For each of these routing schemes, both security analysis and simulation results show that the proposed schemes are secure and efficient.
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