PhD, University of Cincinnati, 2008, Engineering : Computer Science and Engineering

Wireless Ad Hoc Networks have emerged as an advanced networking paradigm based on collaborative efforts among multiple self-organized wireless communication devices. Without the requirement of a fixed infrastructure support, wireless ad hoc networks can be quickly deployed anywhere at any time when needed. The decentralized nature, minimal configuration and quick deployment of wireless ad hoc networks make them suitable for various applications, from disaster rescue, target tracking to military conflicts. Wireless ad hoc networks can be further categorized into mobile ad hoc networks (MANETs), wireless sensor networks (WSNs), and wireless mesh networks (WMNs) depending on their applications.Security is a big challenge in wireless ad hoc networks due to the lack of any infrastructure support, dynamic network topology, shared radio medium, and resource-constrained wireless users. Most existing security mechanisms applied for the Internet or traditional wireless networks are neither applicable nor suitable for wireless ad hoc network environments. In MANETs, routing security is an extremely important issue, as the majority of the standard routing protocols assume non-hostile environments. Once deployed in a hostile environment and working in an unattended mode, existing routing protocols are vulnerable to various attacks. To address these concerns, we propose an anonymous secure routing protocol for MANETs in this dissertation, which can be incorporated with existing routing protocols and achieve enhanced routing security with minimum additional overheads. In WSNs, key distribution and management is the core issue of any security approaches. Due to extremely resource-constrained sensor nodes and lack of any infrastructure support, traditional public-key based key distribution and management mechanisms are commonly considered as too expensive to be employed in WSNs. In this dissertation, we propose two efficient pairwise key pre-distribution and management mechanisms f (open full item for complete abstract)

Committee: Dharma Agrawal (Committee Chair); Jerome Paul (Committee Member); Wen-Ben Jone (Committee Member); Chia-Yung Han (Committee Member); Ernest Hall (Committee Member) Subjects: Communication; Computer Science

Doctor of Philosophy, Case Western Reserve University, 2020, EECS - Electrical Engineering

Methodologies for wireless power transfer (WPT) to implantable medical devices (IMDs) as an attractive solution toward obviating the need for primary battery have continuously evolved over the past decades. Capacitive WPT (C–WPT) is an emerging methodology that offers a higher dynamic range in power delivery when coping with biosafety limits as compared to its ultrasonic and inductive counterparts and introduces a unique advantage of flexible implementation with minimal costs on important link parameters. The C–WPT has been under investigation for delivering moderate-to-high levels of wireless power to centimeter-sized IMDs with an implantation depth of a few millimeters and thus suitable for IMDs in peripheral/autonomic applications. This work, for the first time, presents design and implementation of a complete C–WPT system for subcutaneously-implanted IMDs. That is a multidisciplinary research work involving co-design and co-development of capacitive link across a tissue layer and circuits/systems interfacing with the link on both external and implant sides including CMOS power management integrated circuits (PMICs) that interfaces with capacitive link on the implant side and performs efficient AC-to-DC conversion. One part of this work is focused on modeling, characterization, and development of a bio-safe capacitive link across tissue for C–WPT where an accurate circuit model for capacitive elements is proposed followed by a comprehensive circuit model for a series-resonant capacitive link setup. Electromagnetic simulations via ANSYS HFSS provide further insights into the capacitive link behavior and investigates the biosafety levels of the link. Flexible and conformal implementation of capacitive link on copper substrates is shown for ease of implantation. Following the link characterization, different PMIC designs are shown for capacitively-powered IMDs. First, a frequency-aware CMOS active rectifier IC with dual-loop adaptive delay compensation and (open full item for complete abstract)

Committee: Pedram Mohseni (Advisor); Hossein Miri Lavasani (Committee Member); Farncis Merat (Committee Member); Kevin Kilgore (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Design; Electrical Engineering; Electromagnetics; Energy; Engineering; Health Care

Doctor of Philosophy, The Ohio State University, 2018, Electrical and Computer Engineering

This dissertation gives guidelines for state-of-the-art power harvesters and for optimizing its components, e.g., rectifier, matching network, and antenna, in various applications. A single diode rectifier using a quarter-wave matching circuit with a measured efficiency of 73.7% is also presented. Several experimental demonstrations are included for powering a number of sensors and devices, such as a clock, computer mouse, calculator, thermometer, medical insulin pump, and super capacitor with power management circuitry. To increase the amount of RF harvested power, an array of rectifying antennas (rectennas) is presented and used in experiments up to 60 meters. Wireless power transfer demonstrations at near field distances are also presented. For the latter, we show a strong tolerance to misalignment while delivering high levels of power (1.2 mW over 42 cm). As an application, a medical pump is successfully powered over this distance. Further, bandwidth widening techniques are presented along with rectifier optimizations. To reduce the overall dimensions of the rectenna, miniaturization techniques are discussed. This leads to a rectenna size of 1.5 x 2.5 cm^2, making it ideal for medical or on-body applications. This rectenna was used to successfully activate a body-worn thermometer across 65 cm. In the case of implantable devices, a dielectric matching layer was found useful and validated using pig skin. A related SAR analysis ensured the safety of the proposed RF powering harvesting techniques.

Committee: John Volakis (Advisor); Asimina Kiourti (Advisor); Liang Guo (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Master of Science, Miami University, 2016, Computational Science and Engineering

Wireless power transfer (WPT) has become a common way to charge or power many types of devices, ranging from cell phones to electric toothbrushes. WPT became popular through the introduction of a transmission mode known as strongly coupled magnetic resonance (SCMR). This means of transmission is non-radiative and enables mid-range WPT. Shortly after the development of WPT via SCMR, a group of researchers introduced the concept of resonant repeaters, which allows power to hop from the source to the device. These repeaters are in resonance with the WPT system, which enables them to propagate the power wirelessly with minimal losses to the environment. Resonant repeaters have rekindled the dream of ubiquitous wireless power. Inherent risks come with the realization of such a dream. One of the most prominent risks, which we set out in this thesis to address, is that of accessibility to the WPT system. We propose the incorporation of a controlled access schema within a WPT system to prevent unwarranted use of wireless power. Our thesis discusses the history of electromagnetism, examines the inception of WPT via SCMR, evaluates recent developments in WPT, and further elaborates on the controlled access schema we wish to contribute to the field.

Committee: Dmitriy Garmatyuk PhD (Advisor); Mark Scott PhD (Committee Member); Herbert Jaeger PhD (Committee Member) Subjects: Computer Engineering; Electrical Engineering; Electromagnetics; Electromagnetism; Engineering

MS, University of Cincinnati, 2006, Engineering : Civil Engineering

Intelligent Transportation Systems, or ITS, is about using technology to solve transportation engineering problems. There is a major push by the Departments of Transportation to use wireless sensors all over the highways to provide accurate traffic information in real-time. Wireless Token Ring Protocol (WTRP), a wireless protocol based loosely on IEEE 802.4 [8] Token Bus Protocol, is an excellent Medium Access Control layer level protocol to prevent data collision in this wireless sensor network on the freeways. The distances between wireless sensors on the freeway were calculated, based on sensor frequency, sensitivity of the receiver and the transmitters, using the Free Space Path Loss Equation. Based on these calculations, it was found that Wireless Token Ring Protocol could fail, as the distances between the sensors was quite large and the data packets got lost, when being transmitted from the last sensor back to the first sensor. The Wireless Token Ring Protocol was modified such that instead of being uni-directional, transmitting data in one direction only; it became bi-directional, transmitting data in both directions. As such, during simulation, it was found that, the performance of the Modified Wireless Token Ring Protocol was better than that of Wireless Token Ring Protocol. The number of data packets that were lost in transmission or corrupted using Modified Wireless Token Ring Protocol was drastically less than that using Wireless Token Ring Protocol, over the same node positions. Hence, the Modified Wireless Token Ring Protocol is more effective than the Wireless Token Ring Protocol to prevent data collision and corruption on the field.

Committee: Dr. Prahlad Pant (Advisor) Subjects: Engineering, Civil

PhD, University of Cincinnati, 2006, Engineering : Computer Science and Engineering

One of the main challenges in next generation wireless networks is to integrate heterogeneous wireless technologies to provide seamless connectivity, with guaranteed Quality of Service (QoS), to mobile users “anytime, anywhere and with any device”. In this dissertation, we investigate the problem of integrating cellular networks and Wireless Local Area Networks (WLANs) with the multi-hop communication paradigm used in Mobile Ad hoc Networks (MANETs) to exploit all the connectivity alternatives available to different types of Mobile Stations (MSs). We propose an integrated architecture based on three basic functionalities, namely, topology discovery, gateway discovery, and link quality estimation. We combine these three functionalities into an integrated routing mechanism that exploits all connectivity alternatives available in a generic heterogeneous scenario. Then, we provide a simulation-based analysis of our architecture and integrated routing mechanism in different heterogeneous networking scenarios. Our results show improvements in network's capacity and coverage achieved by our architecture as compared to isolated networks. The results also highlight the importance of the link quality estimation in providing QoS to users, as well as indicate that multi-hop links can be exploited in a controlled network configuration, but the QoS in multi-hop routes cannot be always guaranteed. Furthermore, we address the problem of selecting the best connectivity opportunity for a given service type based on the applications' QoS requirements, as well as on the network condition and user mobility profile. We propose the Connectivity opportunity Selection Algorithm (CSA) that allows MSs to select the connectivity opportunity most appropriate for a given type of service and mobility profile. Furthermore, we describe how our proposed selection algorithm can be introduced into the IEEE 802.21 standard for Media Independent Handover services.

Committee: Dr. Dharma Agrawal (Advisor) Subjects: Computer Science

Doctor of Philosophy, The Ohio State University, 2024, Materials Science and Engineering

This dissertation presents biochemical sensing systems for wearable, implantable, and high-resolution chemical sensing applications. By integrating biorecognition elements, sensing interfaces, and wireless communication strategies, we aim to provide a low-cost, reliable, and highly accurate platform for real-time biochemical monitoring in clinical and experimental settings. We first demonstrate a wireless sensing system that is miniaturized, lightweight, and compatible with common biochemical sensing interfaces. Inspired by RF tuning circuits, our simple circuit design allows battery-free operation and accurate monitoring of multiple biomarkers. The modular design separates the inductive coupling unit and the electrochemical sensing interface, minimizing strain-induced changes and ensuring accurate recording. This system is compatible with common electrochemical sensing methods, including ion-sensitive membranes (ISM), aptamer-based sensors, and enzymatic interfaces. And allow for the detection of ions, neurotransmitters, and metabolites across different application scenarios. For instance, a "smart necklace" consists of glucose sensors, that are capable of wirelessly detecting sweat glucose during exercise. A wearable skin patch monitored cortisol levels in sweat showcases the functional adaptability for stress-related biomarker detection. Additionally, a miniaturized implant prototype illustrated the potential for continuous in vivo monitoring. Our work also introduces a portable vector network analyzer (pVNA) designed to overcome the size limitations of traditional VNAs. This research provides the design and working principle for a wearable reader, which allows for real-time monitoring of resonance frequency and Q factor of the inductive coupling wireless sensor. Furthermore, we introduce “NeuroThread”, a neurotransmitter-sensing platform that utilizes the cross-section of commercially available ultrathin microwires to serve as microelectrode. This cost (open full item for complete abstract)

Committee: Jinghua Li (Advisor); Heather Powell (Committee Member); Pelagia-Irene Gouma (Committee Member) Subjects: Engineering; Materials Science; Nanoscience; Neurosciences

Doctor of Philosophy, The Ohio State University, 2020, Electrical and Computer Engineering

The new generation of wireless networks is expected to be a key enabler of a myriad of new industries and applications. Disruptive technologies such as autonomous driving, cloud gaming, smart healthcare, and virtual reality are expected to rely on a robust wireless infrastructure to support those applications' vast and diverse communication requirements. The successful realization of a large number of those applications hinges on timely information exchange, and thus, Latency arises as the critical requirement essential to unlock the true potential of the new 5G wireless generation. In order to ensure reliable low latency communication, new network algorithms and protocols prioritizing latency need to be developed across different layers of the network stack. Furthermore, a theoretical framework is needed to better understand the behavior of delay at the wireless edge and the proposed solutions' performance. In this dissertation, we study the problem of designing algorithms for low latency communication by addressing traditional problems such as resource allocation and scheduling from a delay-oriented standpoint, as well as, new problems that arise from the new 5G architecture such as caching and Heterogeneous Networks (HetNets) access. We start by a addressing the problem of designing real-time cellular downlink resource allocation algorithms for flows with hard deadlines. Attempting to solve this problem brings about the following two key challenges: (i) The flow arrival and the wireless channel state information are not known to the Base Station (BS) apriori, thus, the allocation decisions need to be made in an online manner. (ii) Resource allocation algorithms that attempt to maximize a reward in the wireless setting will likely be unfair, causing unacceptable service for some users. We model the problem of allocating resources to deadline-sensitive traffic as an online convex optimization problem. We address the question of whether we can efficiently solve t (open full item for complete abstract)

Committee: Eylem Ekici (Advisor); Ness Shroff (Advisor); Atilla Eryilmaz (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2019, Electrical and Computer Engineering

This dissertation presents a new technology for batteryless and wireless neurorecording system which can be applied clinically. Two clinical issues of this type of neural implant are the 1) multichannel operation and 2) high impedance and DC voltage offset from the brain electrode impedance. To resolve these two problems, one wireless multichannel system and one brain electrode interface impedance-matching system are proposed respectively. To achieve multichannel operation, one photo-activated multiplexer is employed in the implant circuit. The interrogator additionally sends an infrared control signal for channel selection. Experimental results show that the proposed neuropotential recorder exhibits 20 uVpp sensitivity at all eight channels. The system is also in compliance with the strictest Federal Communications Commission standards for patient safety. Notably, the proposed approach is scalable to a much higher number of channels. On the other hand, to mitigate the high impedance and DC voltage offset of the brain-electrode interface, one self-biasing PNP Bipolar Junction Transistor (BJT) is adopted in the brain circuits. This self-biasing PNP BJT increases the overall system's impedance and maintains the system sensitivity while the high impedance is present. Measurement results demonstrate that emulated neuropotentials as low as 200 uVpp can be detected at a 33 kOhms electrode impedance. Together, these proposed techniques would lead the wireless neuro recorders to be applicable in real, in-vivo clinical applications.

Committee: John L. Volakis (Advisor); Asimina Kiourti (Advisor); Liang Guo (Committee Member); Daniel Rivers (Committee Member) Subjects: Biomedical Engineering; Electrical Engineering; Electromagnetics

Doctor of Philosophy, The Ohio State University, 2018, Electrical and Computer Engineering

Wireless communication networks have become ubiquitous in recent years. Current wireless applications are possible thanks to small WiFi cells that provide high-speed indoor coverage and outdoor macro-cells that support user mobility. Next generation wireless networks will use similar architectures to enable new applications such as augmented and virtual reality, the internet of things, ultra-high definition video streaming, and massive data transmission and storage. However, these applications require unprecedented high-speed data transfer capabilities enabled by large frequency bandwidths. Motivated by spectrum scarcity in bands below 6 GHz, previously unused millimeter-wave (mmWave) bands, where large bandwidths are available, are now considered for future wireless networks. The necessity for efficient communication techniques for such large bandwidths and mmWave frequencies is the main motivation for this dissertation, with a focus on the complex radiowave propagation conditions found in indoor environments. Propagation mechanisms such as multiple reflections, diffractions, and transmissions through walls are commonly found in indoor wireless communications, which cause variations in the received signal along its bandwidth (wideband or frequency-selective channels). Traditionally, antenna arrays have been used together with beamforming (linear processing) techniques to improve the system's performance. However, those techniques were designed for narrowband systems (e.g., zero-forcing or matched filtering) and their application to wideband systems requires additional processing that increases system's complexity. In the first part of this dissertation, we tackle the problem of beamforming in frequency-selective channels with two approaches: \emph{i}) we use the electromagnetic time-reversal (TR) effect to directly design novel wideband beamformers, and \emph{ii}) we generalize the block-diagonalization (BD) procedure used in narrowband channels to the freque (open full item for complete abstract)

Committee: Fernando Teixeira (Advisor) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2017, Computer Science and Engineering

It has long been believed that physical layer primitives extracted from wireless channel are not breakable given certain physical constraints. This belief is built upon the old faith in wireless channel's uncontrollability and unpredictability, and it is a cornerstone of physical layer security. Through our study, however, we find that the trust on an unauthenticated wireless channel's integrity is not valid. Here we propose various attacks and counterattacks on physical layer primitives including physical features about the environment and secret keys, and provide strong evidence that physical layer security solutions which purely rely on extracting these features from wireless channel need to be redesigned. In the thesis, we start with our finding that an in-band full-duplex forwarder can change wireless channel in fine granularity. We propose PhyCloak, which is a fine-grained channel controller. It works against a popular set of applications that relies on physical primitive extracted from the channel called communication based sensing. This work is the first to counter the threat of unwanted or even malicious communication based sensing: it proposes a blackbox sensor obfuscation technique which distorts only the physical information in the communication signal that leaks privacy. Moreover, the design allows coupling the PhyCloak module with legitimate sensors, so that their sensing is preserved, while that of illegitimate sensors is obfuscated. In the second part of the thesis, we focus on another popular set of applications that rely on physical primitives: channel based secret sharing. First, we introduce a channel based secret key extraction approach called Puzzle. In this part, we show how physical primitives can be extracted from the wireless channel, and be exploited to build a security solution. In addition, we will see more clearly what are the difficulties to break such channel based secret key extraction approaches. Next, in an effort to preserve (open full item for complete abstract)

Committee: Anish Arora (Advisor); Kannan Srinivasan (Advisor); Chunyi Peng (Committee Member); Ness Shroff (Committee Member); Yinqian Zhang (Committee Member) Subjects: Computer Science

PhD, University of Cincinnati, 2015, Engineering and Applied Science: Computer Science and Engineering

Wireless Body Area Network (WBAN) is a low-power Personal Area Network involving sensor nodes (SNs) that sense and relay physiological data to a central station. WBANs are new and still evolving. We try to address three open research areas involving WBANs. The limited energy budget in WBANs necessitates energy conservation to prolong the network lifetime. The first challenge we try to address is related to improvement of the lifetime of a WBAN, given the small sizes of body sensor nodes (SNs) and the limited battery power that they run on. We proposed a dual-prediction framework for improvement of network lifetime. The framework allows for minimizing data transmission involving four important body parameters by reconstructing their information by time series prediction at reception. A sample elimination algorithm further optimizes the framework performance. We enhanced the framework by reducing the sampling frequency and implementing the algorithm on top, increasing the network lifetime further. The missing samples were reconstructed by interpolation at the receiver. We probed the effects of adaptive sampling and evaluated the increase in battery lifetime in WBANs. We then tried to test the behavior of a WBAN in the presence of other WBANs around it and check the issues faced by WBANs. Wireless systems can face severe interference problems if they use the same communication channels at a time. There are issues related to data routing because the critical nature of WBAN data requires assured communication of body data. For optimum network utilization, efficient scheduling of transmissions in multiple co-existing WBANs is important in order to avoid intra and inter-WBAN interference and for a graceful coexistence. We propose that inter-WBAN interference can be avoided by a QoS based MAC scheduling approach and that intra-WBANs interference can be circumvented by fuzzy scheduling of intra-WBAN transmissions. We also propose to use interference to the benefit of WBA (open full item for complete abstract)

Committee: Dharma Agrawal D.Sc. (Committee Chair); Raj Bhatnagar Ph.D. (Committee Member); Prabir Bhattacharya Ph.D. (Committee Member); Chia Han Ph.D. (Committee Member); Marepalli Rao Ph.D. (Committee Member) Subjects: Computer Science

Master of Science in Engineering, University of Akron, 2014, Electrical Engineering

The communications industry has recently begun focusing on energy efficiency of networking devices, one of which is wireless local area network (WLAN) access points. Access points are continuously improving performance, but many aspects of the access point hardware and software consume more power as performance increases, namely power amplifiers (PAs), microprocessors, and security features. Multi-user multiple-input multiple-output (MU-MIMO) communication, transmitting disparate data to multiple receiving devices at the same time in the same frequency spectrum, has been researched for some time, but has just been standardized and is now starting to be implemented in WLAN access points. The benefits of this system performance enhancement do not come without cost, one of which is system power consumption. Investigations have begun on methods of reducing this additional power consumption and the impact those power reductions have on system performance. Some, like coding schemes that reduce power consumption can also increase system complexity and may not be practical without knowledge of the coding scheme at both ends of the link. Power reduction techniques such as optimizing user scheduling for energy efficiency, improving the energy efficiency of channel sounding, or turning off particular transmit chains have the potential to limit the effective capacity in the overall access network. Peak-to-average power ratio reduction often comes at the cost of system complexity, bit error rate increases, and even bandwidth limitations. Still, experimentation in this study shows that it is possible to decrease power consumption without sacrificing signal integrity by reducing peak-to-average power ratios and changing the bias point of select power amplifiers currently available and suitable for use in multi-user MIMO systems. Unfortunately, most available amplifiers do not facilitate external bias control to reap savings of lower peak-to-average power ratio signals. (open full item for complete abstract)

Committee: Nathan Ida Dr. (Advisor); Hamid Bahrami Dr. (Committee Member); Nghi Tran Dr. (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2014, Electrical and Computer Engineering

In a wireless network, the efficiency of scheduling algorithms over time-varying channels depends heavily on the accuracy of the Channel State Information (CSI), which is usually quite “costly” in terms of consuming network resources. In the meanwhile, communication channels in wireless systems typically fluctuate in a temporally-correlated manner. We hence consider scheduling in wireless networks with limited and imperfect channel state knowledge, where the scheduler can exploit the temporal-correlation inherent in channels with memory for better channel state knowledge. We consider the channel state acquisition mechanism with ARQ-styled feedback, whereby the channel states are revealed at the end of only scheduled users' transmissions. In the presence of temporally-correlated channel evolution, the desired scheduler must optimally balance the `exploitation-exploration trade-off', whereby it schedules transmissions both to exploit those channels with up-to-date CSI and to explore the current state of those with outdated CSI. We model the scheduling problems as Partially Observable Markov Decision Processes (POMDPs). POMDPs are known to be difficult to solve. We are able to analyze the problems in the framework of Restless Multi-armed Bandit Processes and utilize the Whittle's indexability analysis. Based on our analysis, we propose low-complexity scheduling algorithms that have optimality performance in different wireless networks. Our work reveals that, under limited and imperfect channel state information, exploiting channel memory and ARQ-styled feedback for scheduling can result in significant system-level performance gains and that the proposed polynomial-complexity algorithms have provably optimal performances in various settings.

Committee: Ness Shroff (Advisor); Atilla Eryilmaz (Advisor); Hesham El Gamal (Committee Member) Subjects: Computer Science; Electrical Engineering; Engineering; Operations Research

PhD, University of Cincinnati, 2014, Engineering and Applied Science: Computer Science and Engineering

Recent evolution of communication networks comprises of different segments and technologies, where each segment maybe implemented using different QoS. Further, the proposed all-IP core infrastructure of the future networks will offer varying QoS level multimedia services to the users. However, IP being a best effort service, seamless provision of end-to-end QoS guarantees is extremely important. In today's world, devices with multiple networking capabilities is quite common. The traditional approach in networking includes grouping identical traffic and allocating them to the network that has the maximum available data rate. This creates unbalanced traffic load in the network, leading to poor utilization of the associated resources. This problem can be greatly alleviated if the traffic can be allocated intelligently to the networks. For fair traffic distribution, we modeled the AP of each network as a single queuing server. Then, suitable equations and algorithms are designed to divide the incoming traffic flow into multiple subflows and allocated to the APs based on their available data rates. Network Selection in a Heterogeneous Cognitive Radio Wireless Network is a challenging task, since the users need to select the appropriate channels of the network in addition to the network itself. The varying levels of interference experienced by the secondary user (SUs) is due to the presence of primary user (PU)s in the adjacent channels. Hence, SUs transmitting highly sensitive data must find a channel that is interference free. In this dissertation, we develop a novel network and channel selection scheme that categorizes both the user applications and the network channels depending on their sensitivity level for interference and select them using a bipartite graph matching algorithm. The effectiveness of Cognitive Radios is based on opportunistic access of the licensed channels by SUs while protecting the PU transmission. But channel sensing incurs cost in terms (open full item for complete abstract)

Committee: Dharma Agrawal D.Sc. (Committee Chair); Raj Bhatnagar Ph.D. (Committee Member); Yizong Cheng Ph.D. (Committee Member); Chia Han Ph.D. (Committee Member); Yiming Hu Ph.D. (Committee Member) Subjects: Computer Science

Doctor of Philosophy, Case Western Reserve University, 2014, EECS - Electrical Engineering

This work describes the design and testing of a wireless implantable bladder pressure sensor suitable for chronic implantation in humans. The sensor was designed to fulfill the unmet need for a chronic bladder pressure sensing device in urological fields such as urodynamics for diagnosis and neuromodulation for bladder control. Neuromodulation would particularly benefit from a wireless bladder pressure sensor providing real-time pressure feedback to an implanted stimulator, resulting in greater bladder capacity while using less power. The pressure sensing system consists of an implantable microsystem, an external RF receiver, and a wireless battery charger. The implant is small enough to be cystoscopically implanted within the bladder wall, where it is securely held and shielded from the urine stream, protecting both the device and the patient. The implantable microsystem consists of a custom application-specific integrated circuit (ASIC), pressure transducer, rechargeable battery, and wireless telemetry and recharging antennas. Because the battery capacity is extremely limited, the ASIC was designed using an ultra-low-power methodology in which power is dynamically allocated to instrumentation and telemetry circuits by a power management unit. A low-power regulator and clock oscillator set the minimum current draw at 7.5 µA and instrumentation circuitry is operated at low duty cycles to transmit 100-Hz pressure samples while consuming 74 µA. An adaptive transmission activity detector determines the minimum telemetry rate to limit broadcast of unimportant samples. Measured results indicated that the power management circuits produced an average system current of 16 µA while reducing the number of transmitted samples by more than 95% with typical bladder pressure signals. The wireless telemetry range of the system was measured to be 35 cm with a bit-error-rate of 10-3, and the battery was wirelessly recharged at distances up to 20 cm. A novel biocompatible (open full item for complete abstract)

Committee: Steven Garverick (Advisor); Swarup Bhunia (Committee Co-Chair); Margot Damaser (Committee Member); Pedram Mohseni (Committee Member); Christian Zorman (Committee Member) Subjects: Biomedical Engineering; Electrical Engineering

Master of Science in Engineering, Youngstown State University, 2013, Department of Electrical and Computer Engineering

A network of wireless sensor nodes that are connected to a centralized base station is presented to conduct a study on reliability of data collection and transmission in wireless sensor networks (WSNs) with focus on data loss and data duplication. Software applications for specific sensor nodes called Sun SPOTs are presented, and programming techniques, for example packet transmitting time delay and data checking for loss and duplication, are implemented in these software applications to improve the functionality of the network. Acceleration data on a vibration plate are collected at sampling frequency of 100 Hz to validate the operation of the network. Additionally, the wireless sensor network is optimized to enhance the synchronization of data collection from different nodes. The result of this research shows that the reliability of the network is related to data sampling frequency, synchronization of the wireless data traffic, wireless sensor node signal strength, and wireless data routing protocols. The indoor tests on signal strength show the limitation of -70 dBm and higher for optimum data collection without data or packet loss.

Committee: Li Frank Ph.D. (Advisor); Munro Philip Ph.D. (Committee Member); Mossayebi Faramarz Ph.D. (Committee Member) Subjects: Computer Engineering; Electrical Engineering; Engineering; Information Technology

MS, University of Cincinnati, 2001, Engineering : Computer Science

Mobile computing has gained increasing attention recently as a variety of mobile terminals and convenient wireless connection becomes available. One of the major applications of mobile computing is information dissemination. The three fundamental methods of providing information on wireless communication channels are push, pull and hybrid push-pull. In a hybrid push-pull environment, the data of most interest is broadcast in the form of a broadcast disk, and the rest of the data is pulled from the server via explicit client requests. To achieve efficient data dissemination, the mobile server dynamically collects users' query access patterns and allocates data in broadcast disks. However, few studies have been conducted in the area of channel allocation and broadcast disk organization that considerate dynamic access pattern collection and utilization. In this study, we use a bit vector technique to represent mobile users' access patterns. We introduce a timestamp and a modification indicator to increase the accuracy of using bit vector technology. Algorithms for collecting access patterns are proposed and studied here. Algorithms for determining the optimal channel allocation and broadcast disk organization given a set of access patterns are proposed. The optimal allocation algorithm searches exhaustively for the optimal solution while the heuristic algorithm searches for a solution by finding the optimal number of broadcast channels first and then organizing the data pages on those channels. We also propose and investigate an algorithm for incremental broadcast disk reorganization. Performance studies are conducted using average access probe-wait time as a criterion. Performance studies indicate that the proposed algorithms always outperform the existing flat approach in channel allocation and broadcast disk organization. When the heuristic approach is compared with the optimal approach, experimental results demonstrate that no significant performance differences ar (open full item for complete abstract)

Committee: Dr. Karen C. Davis (Advisor) Subjects: Computer Science

MS, University of Cincinnati, 2010, Engineering and Applied Science: Computer Science

Wireless sensors are low power devices with small transmission range, restricted computation power, limited amount of memory and with portable power supply. Wireless Sensor Network (WSN) is a collection of such sensors where the number of sensors can vary from few hundreds to thousands. Performing secure pair-wise communication between sensors is a really difficult task due to inherent characteristics such as lack of any fixed infrastructure. As memory and power consumption are most stringent requirements for these devices, use of conventional techniques for secured communication are totally out of question. This thesis introduces scheme that enables a complete pair-wise secure connectivity between any two adjacent sensor nodes in spite of using small key ring (KR) for sensors. The Proposed Scheme (ELKPD) doesn't require any additional hardware while providing keys to the sensors irrespective of their location. Also, proposed scheme is easily scalable which allows enables addition of sensor nodes without any computational or hardware overheads. Due to the varying degree of mobility of Mesh Clients has provided much more flexibility in Wireless Mesh Networks. And establishing an Authentic Association among entities is a non -trivial problem. In this thesis, we introduce a Polynomial Based scheme which not only provides high pair-wise connectivity, low communication and storage overhead and high scalability but also makes on the fly Authentic Association feasible. The proposed scheme is also observed to be resilient against both the traffic analysis and the node capture attacks.

Committee: Dharma Agrawal DSc (Committee Chair); Raj Bhatnagar PhD (Committee Member); Carla Purdy, C PhD (Committee Member) Subjects: Computer Science

MS, University of Cincinnati, 2009, Engineering : Computer Science

In an integrated heterogeneous wireless network (IHWN), a user can connect itself to different types of networks on anytime, anywhere basis. Any of the following networks: cellular networks, WLANs, and ad hoc and sensor networks can constitute an IHWN network. The user is free to roam within networks seamlessly based on his needs and network availability. However, the security concerns associated with the IHWN count for some of the challenges involved in its implementation. These concerns combined with the different security requirements of various constituent wireless networks may have made security a serious issue. Seamless transfer of user's credentials is a major requirement when considering security during vertical handoff between two different types of networks. A security scheme that can fit all types of networks is difficult to propose. However, a reasonable architecture that keeps both security and user convenience into consideration can be designed. The existing security schemes fail to address mobility and scalability requirements. Considering the importance of these aspects in securing a global network, we propose a novel security scheme that uses two different security algorithms depending on the number of vertical handoffs made by the mobile node after the first authentication in the home network. It makes use of existing network elements, such as RADIUS and Diameter protocols and supports scalability, mobility, and secure key exchange. We also introduce a time factor which is pre-set between the home network and foreign network. It delegates the task of authorizing subsequent requests from mobile node to connect to a different foreign network. Finally, we evaluate the efficiency and scalability of the scheme and prove its superiority over the existing schemes. The simulation results show a significant improvement over messages exchanged during key distribution at the time of vertical handoff. They also show how the scheme provides an excellent solutio (open full item for complete abstract)

Committee: Raj Bhatnagar PhD (Committee Chair); George Purdy PhD (Committee Member); Ali Minai PhD (Committee Member); Qing An Zeng PhD (Committee Member) Subjects: Computer Science