A Wireless Sensor Network (WSN) consists of a number of nodes, each typically having a small amount of non-replenishable energy. Some of the nodes have sensors, which may be used to gather environmental data. A common network abstraction used in WSNs is the (source, sink) architecture in which data is generated at one or more sources and sent to one or more sinks using wireless communication, possibly via intermediate nodes. In such systems, wireless communication is usually implemented using radio. Transmitting or receiving, even on a low power radio, is much more energy-expensive than other activities such as computation and consequently, the radio must be used judiciously to avoid unnecessary depletion of energy. Eventually, the loss of energy at each node will cause it to stop operating, resulting in the loss of data acquisition and data delivery. Whilst the loss of some nodes may be tolerable, albeit undesirable, the loss of certain critical nodes in a multi-hop routing environment may cause network partitions such that data may no longer be deliverable to sinks, reducing the usefulness of the network. This thesis presents a new heuristic known as node reliance and demonstrates its efficacy in prolonging the useful lifetime of WSNs. The node reliance heuristic attempts to keep as many sources and sinks connected for as long as possible. It achieves this using a reliance value that measures the degree to which a node is relied upon in routing data from sources to sinks. By forming routes that avoid high reliance nodes, the usefulness of the network may be extended. The hypothesis of this thesis is that the useful lifetime of a WSN may be improved by node reliance routing in which paths from sources to sinks avoid critical nodes where possible.

Approved for public release, distribution is unlimited / This thesis details the critical need for deployable combat simulations for training in today's surge force environment. To truly realize deployment of these simulations on Naval vessels and in remote theaters, simulations for training must be wireless. Wireless standards 802.11/a/b/g are presented in detail to highlight the strengths and weaknesses of each. This thesis then investigates the viability of deploying combat simulations for training using wireless devices. To this end, the Joint Semi-Automated Forces (JSAF), combat simulation model and the Virtual Helicopter (VEHELO) training simulation entity are tested in an 802.11a wireless environment against the VEHELO application in a wired environment. 802.11a is proposed as part of an overall solution to deploy combat simulations for training. This is primarily because of its high data rates and ability to co-locate access points without interference. Testing reveals that operating JSAF and Virtual Helicopter via the High Level Architecture (HLA) with User Datagram Protocol (UDP) packets in an 802.11a environment provides ample bandwidth with which to deploy combat simulation for training for the simulations conducted. / Lieutenant, United States Navy

Approved for public release, distribution is unlimited / This thesis studies the feasibility of developing a closed-loop shipboard sensor calibration system with two main objectives. The first objective was to reduce the number of personnel required to calibrate a shipboard sensor by 50%. The second was to reduce the time required to complete the calibration process by 60%. This was achieved by displaying the sensor data and the calibration standard data on a tablet PC. Wireless technology was used to transmit the data from the sensor and the calibration standard to the tablet PC. The data from the sensor is sent via IEEE 802.11b wireless LAN using DataSocket protocol and the calibration standard is sent via Bluetooth protocol. The technology can be installed and used on current ships in the United States Navy. Four software programs were developed to accomplish these goals. One program runs on the tablet PC and the other three run on the network capable application processor (NCAP). These four programs accomplish the goals stated. / Lieutenant, United States Navy

Approved for public release, distribution is unlimited / Since its introduction in 1999, the Institute of Electrical and Electronics Engineers (IEEE) 802.11 Wireless Local Area Network (WLAN) has become the de-facto standard for wireless networking, providing convenient and low cost connectivity. Increasingly, enterprises are extending their networks with 802.11-based WLANs to provide mobility and information-on-the-move for its employees. However, the introduction of WLANs into enterprise networks has raised major concerns about security. A poorly implemented WLAN introduces weaknesses in the enterprise network which can be exploited by attackers, resulting in severe consequences for the enterprise. This thesis was sponsored by the DoD to study the problem of designing a secure wireless architecture for an enterprise network. The specific requirements for the enterprise network were based extensively on DoD and the intelligence community's security guidelines and policies. This thesis provides an indepth analysis into the 802.11 standard and measures how far the standard goes in meeting the specific requirements of the enterprise network. This thesis presents a layered-defense architecture to provide a scalable design for secure wireless networks. A prototype system utilizing XML to control the flow of classified information in wireless networks is also presented. . / Civilian, Defense Science and Technology Agency, Singapore

Sensor networks use a group of collaborating sensor nodes to collect information about real world phenomena. Sensor nodes use low-power short-range radio links to communicate with each other. Communication between sensor nodes shows significant variation over time and space. This can lead to unreliable and unpredictable network performance. These dynamic and lossy characteristics of wireless links pose major challenges for building reliable sensor networks and raise new issues that data delivery protocols must address. This thesis addresses the problems of designing protocols to overcome time-varying environmental conditions that lead to unpredictable network performance. The goal is to provide reliable data delivery in sensor networks and to minimise energy use. The major contributions of this thesis are: measuring the performance of wireless links in field trials on a time scale of weeks; systematic analysis of strengths and weaknesses of existing data delivery protocols; and the design, implementation and testing of a novel autonomic communication framework. We have measured link quality over time in experiments in unattended outdoor environments. Most previous work focused on spatial properties and experiments were not extensive, only lasting for a few hours. Besides common phenomena found in other work, such as the variation of network performance over time and the existence of asymmetric links, we find that links are independent over long time scales, and performance patterns of links are different. We also analyse the performance of data delivery protocols that use different techniques to improve reliability in sensor networks. Through systematic analysis of strengths and weaknesses of existing data delivery strategies, we find that networks using a single technique can only perform well for a limited range of link conditions. Different strategies are required in different operating conditions. Based on these experimental and theoretical studies, a novel autonomic communication framework (ACF) for wireless sensor networks is proposed. Nodes in this ACF are able to change their behaviour to adapt to time-varying environments so that optimal network performance can be achieved. Our framework provides a holistic solution for reliable data delivery to overcome time-varying wireless links. Our implementation and experimental evaluations demonstrate that this holistic framework is effective for reliable and energy-efficient data delivery in realistic sensor network settings.

Thesis (Ph.D.) -- Mississippi State University. College of Business and Industry. / Title from title screen. Includes bibliographical references. Also available in print.

Adaptive beamforming is a. powerful approach to receive or transmit signals of interest in a spatially selective way in the presence of interference and noise. Recently, there has been renewed interest in adaptive beamforming driven by applications in wireless communications, where multiple-input multiple-output (MEMO) techniques have emerged as one of the key technologies to accommodate the high number of users as well as the increasing demand for new high data rate services. Beamforming techniques promise to increase the spectral efficiency of next generation wireless systems and are currently being incorporated in future industry standards. Although a significant amount of research has focused on theoretical capacity analysis, little is known about the performance of such systems in practice. In thesis, I experimentally and analytically evaluate the performance of adaptive beamforming techniques on the downlink channel of a wireless LAN. To this end. I present the design and implementation of the first multi-user beam-forming system and experimental framework for wireless LANs. Next, I evaluate the benefits of such system in two applications. First, I investigate the potential of beamforming to increase the unicast throughput through spatial multiplexing. Using extensive measurements in an indoor environment, I evaluate the impact of user separation distance, user selection, and user population size on the multiplexing gains of multi-user beamforming. I also evaluate the impact of outdated channel information due to mobility and environmental variation on the multiplexing gains of multi-user beamforming. Further, I investigate the potential of beamforming to eliminate interference at unwanted locations and thus increase spatial reuse. Second, I investigate the potential of adaptive beamforming for efficient wireless multicasting. I address the joint problem of adaptive beamformer design at the PHY layer and client scheduling at the MAC layer by proposing efficient algorithms that are amenable to practical implementation. Next, I present the implementation of the beamforming based multicast system on the WARP platform and compare its performance against that of omni-directional and switched beamforming based multicast. Finally, I evaluate the performance of multicast beamforming under client mobility and infrequent channel feedback, and propose solutions that increase its robustness to channel dynamics.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Jayant, Nikil; Committee Member: Altunbasak, Yucel; Committee Member: Sivakumar, Raghupathy. Part of the SMARTech Electronic Thesis and Dissertation Collection.

M. Tech. Information Networks / This dissertation reports on a prototype implementation of an architecture that seamlessly integrates Wireless Body Area Networks with Web services for ubiquitous healthcare service provisioning. The prototype ubiquitous monitoring system proactively collects body physiological signals of remote patients to recommend diagnostic services. The technologies that are based upon Wireless Body Area Networks and Web services can provide ubiquitous accessibility to variety of services by allowing distributed healthcare resources to be massively reused. This contributes to improving quality of healthcare services and shields individuals from physically moving to locations where healthcare services are provided, except in a critical situation. In addition, the technology can reduce costs of healthcare services by allowing individuals to remotely access services to support their healthcare. Especially our system is designed for ubiquitous monitoring of elderly and patients in recovery (or rehabilitation). The Wireless Body Area Networks - Web services architecture is at crossroad of embedded engineering of hardware, software and networking protocols. Testing of the prototype was carried out on enthusiastic volunteers and it has shown to be an efficient, reliable and support state-of-art service provisioning of ubiquitous healthcare monitoring in health sector.

The objective of this research is to realize compact and reconfigurable antennas for next generation Ultra Wide Band (UWB) and Wireless Local Area Network (WLAN) applications. The contributions of this research are, a methodology for designing compact UWB antennas, a compact WLAN prototype antenna with reconfigurable characteristics in both radiation pattern and frequency of operation, and compact UWB antennas with reconfigurable WLAN band rejection characteristics. For the completion of this dissertation, five research projects have been studied. First, a double exponentially tapered slot antenna with conformal shape, high gain, and consistent radiation patterns is implemented. The radiation pattern consistency results in minimum distortion for any transmitted pulse. The second and third projects involve an elliptical slot with a tuning uneven U-shaped stub and two cactus-shaped monopoles. The elliptical slot demonstrates omni-directional radiation patterns and compact size. As an improved iteration of the elliptical slot antenna, two cactus-shaped monopoles are implemented. The two prototypes occupy only 60% and 40%, respectively, of the area that the original elliptical slot occupies resulting in a significant size reduction, while maintaining omni-directional radiation patterns. Through the cactus-shaped monopoles some general design methodologies for UWB antennas are introduced and successfully applied. The fourth research topic introduced, concerns the study of compact elliptical UWB monopoles. Several prototypes of different geometrical characteristics were designed and tested. Broadband matching techniques and the integration of reconfigurable features on the elliptical radiator are investigated. For the reconfigurable UWB antenna, resonating elements are used to create a rejection band in the frequency range that is occupied by WLAN applications. The performance of several of the introduced slot and monopole antennas are tested when the antennas under detection are mounted and operate on non-planar surfaces. Finally, a reconfigurable annular slot antenna operating at the wireless local area network (WLAN) band is implemented. The proposed antenna demonstrates reconfigurable characteristics in both radiation pattern and return loss. All of the UWB antennas are fabricated on liquid crystal polymer (LCP) and can be easily integrated with active components on the same module using system on package (SoP) technology.