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Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 79-82). Also available on the World Wide Web.

Energy e ciency is a critical constraint in wireless sensor networks. Wireless sensor networks (WSNs) consist of a large number of battery-powered sensor nodes, connected to each other and equipped with low-power transmission radios. Usually, the sensor nodes closer to the sink are more likely to become overloaded and subject to draining their battery faster than the nodes farther away, creating a funneling e ect. The use of a mobile device as a sink node to perform data gathering is a well known solution to balance the energy consumption in the entire network. To address this problem, in this work we consider the use of an UAV as a mobile sink. An unmanned aircraft vehicle (UAV) is an aircraft without a human pilot on-board, popularly known as a Drone. In this thesis, besides the use of the UAV as a mobile sink node, we propose an UAV-aided algorithm for data gathering in wireless sensor networks, called Humming- bird. Our distributed algorithm is energy-e cient. Rather than using an arbitrary path, the UAV implements an approximation algorithm to solve the well-known NP- Hard problem, the Traveling Salesman Problem (or TSP), to setup the trajectory of node points to visit for data gathering. In our approach, both the path planning and the data gathering are performed by the UAV, and this is seamlessly integrated with sensor data reporting. The results, using ns-3 network simulator show that our algorithm improves the network lifetime compared to regular (non-UAV) data gathering, especially for data intensive applications. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Wireless sensor networks (WSNs) provide rapid, untethered access to information, eliminating the barriers of distance, time, and location for many applications in national security, civilian search and rescue operations, surveillance, border monitoring, and many more. Sensor nodes are resource constraint in terms of power, bandwidth, memory, and computing capabilities. Sensor nodes are typically battery powered and depending on the application, it may be impractical or even impossible to recharge them. Thus, it is important to develop mechanisms for WSN which are energy efficient, in order to reduce the energy consumption in the network. Energy efficient algorithms result in an increased network lifetime. Data gathering is an important operation in WSNs, dealing with collecting sensed data or event reporting in a timely and efficient way. There are various scenarios that have to be carefully addressed. In this dissertation we propose energy efficient algorithms for data gathering. We propose a novel event-based clustering mechanism, and propose several efficient data gathering algorithms for mobile sink WSNs and for spatio-temporal events. Border surveillance is an important application of WSNs. Typical border surveillance applications aim to detect intruders attempting to enter or exit the border of a certain region. Deploying a set of sensor nodes on a region of interest where sensors form barriers for intruders is often referred to as the barrier coverage problem. In this dissertation we propose some novel mechanisms for increasing the percentage of events detected successfully. More specifically, we propose an adaptive sensor rotation mechanism, which allow sensors to decide their orientation angle adaptively, based on the location of the incoming events. In addition, we propose an Unmanned Aerial Vehicle UAV aided mechanism, where an UAV is used to cover gaps dynamically, resulting in an increased quality of the surveillance. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Indiana University-Purdue University Indianapolis (IUPUI) / Sensor nodes forming a network and using wireless communications are highly useful in a variety of applications including battle field (military) surveillance, building security, medical and health services, environmental monitoring in harsh conditions, for scientific investigations on other planets, etc. But these wireless sensors are resource constricted: limited power supply, bandwidth for communication, processing speed, and memory space. One possible way of achieve maximum utilization of those constrained resource is applying signal processing and compressing the sensor readings. Usually, processing data consumes much less power than transmitting data in wireless medium, so it is effective to apply data compression by trading computation for communication before transmitting data for reducing total power consumption by a sensor node. However the existing state of the art compression algorithms are not suitable for wireless sensor nodes due to their limited resource. Therefore there is a need to design signal processing (compression) algorithms considering the resource constraint of wireless sensors. In our work, we designed a lightweight codec system aiming surveillance as a target application. In designing the codec system, we have proposed new design ideas and also tweak the existing encoding algorithms to fit the target application. Also during data transmission among sensors and between sensors and base station, the data has to be secured. We have addressed some security issues by assessing the security of wavelet tree shuffling as the only security mechanism.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This thesis explores two key aspects of wireless ad hoc networks. The first aspect concerns the topic of stimulating cooperation between nodes in a wireless ad hoc network. The functionality of a wireless ad hoc network depends entirely on the willingness of nodes to relay messages on behalf of other nodes. Network functionality depends on ensuring cooperation between nodes, so that each node benefits from continued participation in the network. This suggests an important question: how can cooperation among individual nodes be managed to improve overall wireless ad hoc network performance? The second aspect explored in this thesis concerns the concept of optimal resource utilisation. Wireless ad hoc networks are characterised by limited bandwidth and energy resources, which facilitates deployment in situations in which traditional infrastructure based networks are not practical. This suggests another important question: how can the use of the limited energy and bandwidth resources of wireless ad hoc networks be optimised? This research relies on the concept of a credit-based market economy. Nodes in simulated ad hoc networks use credits to pay for the cost of sending their own traffic and earn credits by forwarding traffic on behalf of other nodes. We show that a credit-based market economy approach can be employed to stimulate and regulate cooperation between nodes in a wireless ad hoc network. We show that this approach can be implemented in a simple decentralised manner and that it has several variants depending on which node is considered to be paying for the service, what the price of each service should be and how we route packets around the network using information derived from the credit-based economy. This thesis demonstrates that several variants of a credit-based scheme can be implemented in a packet based simulator and that these variants result in the stable operation of the network and improve the overall performance. The credit-based mechanisms also show significant improvement to network performance in resource constrained conditions and represent an effective means for optimising limited energy and bandwidth resource. The effectiveness of the credit-based mechanisms increases as the load on the networks increases. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek twee belangrike aspekte van draadlose ad hoc-netwerke. Die eerste aspek het betrekking op die onderwerp van 'n stimulerende samewerking tussen die nodusse in 'n draadlose ad hoc-netwerk. Dat die network funksioneer hang daarvan af om samewerking tussen die nodusse te verseker sodat elke nodus voordeel put uit voortgesette deelname in die netwerk. Dit dui op 'n belangrike vraag: Hoe kan die samewerking tussen die individuele nodusse bestuur word om die prestasie van 'n draadlose ad hoc-netwerk te verbeter? Die tweede aspek wat in hierdie tesis ondersoek word, behels die konsep van optimale hulpbronbenutting. Draadlose ad hoc-netwerke word gekenmerk deur beperkte bandwydte- en energie-hulpbronne, wat ontplooiing bewerkstellig in situasies waar tradisionele infrastruktuur-gebaseerde netwerke nie practise moontlik is nie. Dit dui op 'n ander belangrike vraag: Hoe kan die gebruik van die beperkte energie- en bandwydte-hulpbronne van draadlose ad hoc-netwerke optimaal bestuur word? Hierdie navorsing berus op die konsep van 'n krediet-gebaseerde markekonomie. Nodusse in gesimuleerde ad hoc-netwerke gebruik krediete om te betaal vir die versending van hul eie verkeer en nodusse verdien krediete deur die verkeer van ander nodusse aan te stuur. Ons wys dat die benadering van 'n krediet-gebaseerde markekonomie gebruik kan word om die samewerking tussen die nodusse in 'n draadlose ad hoc-netwerk te stimuleer en te reguleer. Ons wys dat hierdie benadering geïmplementeer kan word op 'n eenvoudige gedesentraliseerde wyse. Ons ondersoek verskeie variasies van die benadering, na gelang van watter nodus oorweeg word om vir die diens te betaal, wat die prys van elke diens moet wees en hoe inligting afgelei van die krediet-gebaseerde ekonomie gebruik kan word om pakkies in die netwerk te roeteer. Hierdie tesis toon dat verskeie variante van 'n krediet-gebaseerde skema geïmplementeer kan word in 'n netwerksimulator en dat hierdie variante die stabiele bedryf van en algehele verbetering in die prestasie van die network tot gevolg het. Die krediet-gebaseerde meganismes toon 'n beduidende verbetering in hulpbronbenutting en netwerkprestasie in omgewings met beperkte hulpbronne en verteenwoordig 'n doeltreffende manier om die beperkte energie- en bandwydte-hulpbronne optimaal te benut. Laastens, die doeltreffendheid van die krediet-gebaseerde meganismes word verhoog as die las op die netwerke word verhoog.

Wireless sensor networks are composed of sensor nodes, which can monitor an environment and observe events of interest. These networks are applied in various fields including but not limited to environmental, industrial and habitat monitoring. In many applications, the exact location of the sensor nodes is unknown after deployment. Localization is a process used to find sensor node's positional coordinates, which is vital information. The localization is generally assisted by anchor nodes that are also sensor nodes but with known locations. Anchor nodes generally are expensive and need to be optimally placed for effective localization. Passive localization is one of the localization techniques where the sensor nodes silently listen to the global events like thunder sounds, seismic waves, lighting, etc. According to previous studies, the ideal location to place anchor nodes was on the perimeter of the sensor network. This may not be the case in passive localization, since the function of anchor nodes here is different than the anchor nodes used in other localization systems. I do extensive studies on positioning anchor nodes for effective localization. Several simulations are run in dense and sparse networks for proper positioning of anchor nodes. I show that, for effective passive localization, the optimal placement of the anchor nodes is at the center of the network in such a way that no three anchor nodes share linearity. The more the non-linearity, the better the localization. The localization for our network design proves better when I place anchor nodes at right angles.

The objective of the proposed research is to analyze and develop energy optimized design techniques that can improve the operating efficiency for a wireless sensor device. To enhance the operating efficiency, all active functional blocks in a system should focus on energy conservation while achieving the required tasks. In addition, variations in the operating condition should be properly observed and compensated. Otherwise, a wireless sensor device would consume unnecessary energy for a given task or too little energy to meet the requirements. In this research, design strategies and some new circuit topologies are discussed in terms of ultra-low energy constraints. In particular, the signal processing unit, the memory unit, and the power unit in a conventional wireless sensor device will be main focus. As an example of the signal processing unit, a subthreshold current mode computation system has been designed and tested to prove the "low power consumption" feature of analog signal processing. For the memory unit, conventional SRAM cells are compared to a new fully-gated 10T-SRAM cell. For the power unit, a semi-active high-efficient CMOS rectifier with a reverse leakage control has been developed. It employs a cross-coupled NMOS pair and two leakage control comparators to reduce reverse charge leakage currents. In addition, the adaptive body bias control technique is utilized to improve the reliability of the rectifier. In addition, a novel link-variation sensing technique is proposed. The proposed technique can evaluate operational disturbances such as component mismatches and displacement variations so that the performance of a wireless sensor device in the actual environment can be close to the optimum without wasting an excessive amount of energy.

M. Tech. Electrical Engineering. / Aims to develope a detection procedure whose objective function is to try as much as possible not to impact heavily on the resource constrained sensor nodes.

The objective of this dissertation is to develop task scheduling guidelines and algorithms for wireless sensor nodes that harvest energy from ambient environment and use supercapacitor based storage systems to buffer the harvested energy. This dissertation makes five contributions. First, a physics based equivalent circuit model for supercapacitors is developed. The variable leakage resistance (VLR) model takes into account three mechanisms of supercapacitors: voltage dependency of capacitance, charge redistribution, and self-discharge. Second, the effects of time and supercapacitor initial state on supercapacitor voltage change and energy loss during charge redistribution are investigated. Third, the task scheduling problem in supercapacitor based environmentally powered wireless sensor nodes is studied qualitatively. The impacts of supercapacitor state and energy harvesting on task scheduling are examined. Task scheduling rules are developed. Fourth, the task scheduling problem in supercapacitor based environmentally powered wireless sensor nodes is studied quantitatively. The modified earliest deadline first (MEDF) algorithm is developed to schedule nonpreemptable tasks without precedence constraints. Finally, the modified first in first out (MFIFO) algorithm is proposed to schedule nonpreemptable tasks with precedence constraints. The MEDF and MFIFO algorithms take into account energy constraints of tasks in addition to timing constraints. The MEDF and MFIFO algorithms improve the energy performance and maintain the timing performance of the earliest deadline first (EDF) and first in first out (FIFO) algorithms, respectively.