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

Master of Science in Electrical Engineering (MSEE), Wright State University, 2024, Electrical Engineering

This research illustrates a high-security wireless communication method using a joint radar/communication waveform, addressing the vulnerability of traditional low probability of detection (LPD) waveforms to hostile receiver detection via cyclostationary processing (CSP). To mitigate this risk, RF steganography is used, concealing communication signals within linear frequency modulation (LFM) radar signals. The method integrates reduced phase-shift keying (RPSK) modulation and variable symbol duration, ensuring secure transmission while evading detection. Implementation is validated through software-defined radios (SDRs), demonstrating effectiveness in covert communication scenarios. Results include analysis of message reception and cyclostationary features, highlighting the method's ability to conceal messages from hostile receivers. Challenges encountered are discussed, with suggestions for future enhancements to improve real-world applicability.

Committee: Zhiqiang Wu Ph.D. (Advisor); Xiaodong Zhang Ph.D. (Committee Member); Bin Wang Ph.D. (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2022, Electrical and Computer Engineering

Over the past few decades, the ubiquity of radio-frequency (RF) devices has improved connectivity and productivity in our lives through wireless communication and sensing technologies. To this end, vehicle-to-everything (V2X) communication and vehicular radar imaging technologies have become the key enablers of Intelligent Transportation Systems (ITS) to promote safety, automation, and coordination in traffic. To enable V2X communication, a limited amount of bandwidth in the 5.9 GHz spectrum is dedicated to vehicles for the exchange of basic safety messages with low latency. However, with the large-scale deployment of connected vehicles, the V2X-dedicated band faces the spectrum scarcity problem that lowers the reliability of vehicular communication. The scarcity of dedicated spectrum also limits the feasibility and capabilities of more advanced vehicular applications that rely on broadband communication. Besides, up to 4 GHz of contiguous bandwidth is allocated as the vehicular radar spectrum that is dedicated solely to vehicles in the 76-81 GHz millimeter-wave (mmWave) bands. To supplement V2X communication, the under-utilized vehicular radar spectrum can be leveraged by joint radar-communication (JRC) systems. The objective of JRC is to perform both data transmission and radar imaging using the same \textit{joint} waveform and transceiver hardware. In this dissertation, we investigate transmission optimization and scheduling approaches to enable vehicular JRC in mmWave bands using adaptive orthogonal frequency-division multiplexing (OFDM). First, we study the joint waveform design problem for wideband vehicular JRC. By exploiting the frequency-selectivity in wideband channels, we adaptively design subcarrier coefficients of OFDM to achieve long-range detection and communication performance. We show that the problem is a non-convex quadratically constrained quadratic programming (QCQP), which is NP-hard. As an alternative to existing approaches, we propose time (open full item for complete abstract)

Committee: Eylem Ekici (Advisor); Ness Shroff (Committee Member); Can Emre Koksal (Committee Member) Subjects: Computer Engineering; Electrical Engineering

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

The explosive growth of the Internet, the advent of novel distributed applications, and an abundance of inexpensive hardware, have led to significant increases in the use of wireless networks. At present, different types of wireless networks are being used to support the requirements of several applications. WiFi networks are most widely used for universal access of the Internet. Vehicular networks that enable car-to-car communication have gained much attention because they can be utilized to develop a multitude of distributed applications to improve road safety and driving experience. Similarly, a dense deployment of inexpensive and battery-free (passive) radio frequency identification (RFID) tags is ideal for object tracking and monitoring in shopping malls and warehouses. Any wireless networks have to provide better performance when the number of users and applications increases rapidly. To meet this ever-increasing demand, we have proposed several protocols that utilize previously unused resources to gain additional information. Such information is beneficial for the design of collision-embracing protocols that allow simultaneous transmissions from multiple nodes for better resource utilization, resulting in improved performance. In our first work, a medium access control (MAC) protocol for WiFi networks, named BASIC, is devised. BASIC utilizes the high bandwidth Ethernet backbone networks that connect WiFi access points (APs). Multiple APs received packets from the same WiFi client, and several APs share this received signal among each other to maximize throughput from iia client. By working together, APs in enterprise WiFi networks can decode packets from several clients simultaneously, resulting in a considerable increment in the total throughput. As a continuation, a collision-embracing protocol, called CoReCast, is designed for vehicular networks and is suitable for broadcasting. CoReCast exploits the abundant power and the availabili (open full item for complete abstract)

Committee: Prasun Sinha (Advisor); Rajiv Ramnath (Committee Member); Can Koksal (Committee Member); Brent Sohngen (Committee Member) Subjects: Computer Engineering; Computer Science

Doctor of Philosophy, The Ohio State University, 2010, Electrical and Computer Engineering

We consider the problem of practical communication over a doubly selective (DS)channel, i.e., a time and frequency selective channel. The problem is approached in two different ways: coherent communication and noncoherent communication, and for each communication scheme we propose practical and near-optimal equalizers and maximum-diversity precoders. Toward these ends, we adopt 1) basis expansion (BE) modeling of the channel, which allows for an efficient and unied way of describing a DS channel in both time and frequency domain; and 2) tree-search algorithms (TSAs), which facilitate near-optimal performance with low complexity.For practical coherent communication, we focus on the pulse-shaped (PS) multicarrier modulation (MCM), where controlled inter-symbol-interference (ISI) and inter-carrier-interference (ICI) can be leveraged for computationally efficient receiver structures. Then, we propose a novel channel adaptive TSA with a novel fast minimum mean-squared error (MMSE) generalized decision-feedback equalizer (GDFE) preprocessing, and a rank-reduced channel estimation by using the BE channel model. Also, a new finding about optimality of MMSE-GDFE preprocessing is presented, which states that under constant modulus constellation the minimum distance property is preserved by the MMSE-GDFE preprocessing. Then, two practically realizable noncoherent equalization schemes are proposed: a sequential algorithm and a Bayesian expectation maximization (EM)-based algorithm. The sequential algorithm is derived from the optimal noncoherent metric, and made practical by a fast algorithm and a TSA to evaluate and search over the metric. The Bayesian EM-based noncoherent algorithm is derived from optimal maximum a posteriori (MAP) estimation of the BE parameters, and efficiently implemented via iteration between soft coherent equalizer and soft channel estimator. Efficient operations are accomplished using fast algorithms whose overall complexities grow linearly in the block (open full item for complete abstract)

Committee: Phil Schniter (Advisor); Hesham El-Gamal (Committee Member); Lee Potter (Committee Member) Subjects: Electrical Engineering

Master of Science in Computer Science, Miami University, 2025, Computational Science and Engineering

Wireless ad hoc networks (WANETs) are an essential development in providing high-speed data transfer in areas with little to no infrastructure. The conjunction of this technology with free space optical (FSO) transceivers has not only increased the speed of communication but has also greatly decreased the cost of implementation. Because FSO transceivers are highly directional, the problem of neighbor discovery in such systems has posed challenges in accuracy and runtime. In this thesis, we produce a novel neighbor discovery protocol using a supplementary omnidirectional channel and integrate an attack-detection method against several common network-layer attacks. We present an innovative approach that utilizes a low-bitrate, long-range (LoRa) omnidirectional communication channel to assist in coordinating the neighbor discovery process, allowing for the synchronization and establishment of directional FSO links among nodes. Secondly, provide a solution that utilizes the inherent properties of directional transceivers in order to implement attack detection in the neighbor discovery process.

Committee: Suman Bhunia (Advisor); Honglu Jiang (Committee Member); Khodakhast Bibak (Committee Member) Subjects: Computer Science

Master of Science in Electrical Engineering (MSEE), Wright State University, 2024, Electrical Engineering

This study examines the aging effects of GaN HEMTs, focusing on the CG2H40010 device under conditions that mimic the high-power, high-frequency environments of wireless communication systems. With the increasing adoption of GaN technology in RF applications, understanding its degradation mechanisms under CW stress and modulated signal characterization is essential for predicting device lifetime and ensuring performance standards for modern communication systems. RFALT was employed to stress the device using CW signals, while key performance metrics, such as gain compression, gate leakage, ACP, and EVM, were assessed using W-CDMA signals to replicate real-world dynamic stresses. The findings reveal that CW stress accelerates thermal and electrical degradation in GaN HEMTs, while W-CDMA characterization highlights the impact of complex modulation on linearity and spectral containment. Degradation mechanisms such as ohmic contact wear and dielectric failure significantly affect performance, especially under high peak-to-average ratio conditions. This research underscores the importance of combining CW-based RFALT with modulation-specific testing to evaluate device reliability comprehensively. By addressing thermal management, enhancing dielectric materials, and employing linearization techniques, these insights pave the way for optimizing GaN HEMTs to meet the stringent requirements of 5G and future wireless communication systems.

Committee: Yan Zhuang Ph.D. (Advisor); Weisong Wang Ph.D. (Committee Member); Marian K. Kazimierczuk Ph.D. (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Master of Science, The Ohio State University, 2006, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2006, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2006, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Sciences, Case Western Reserve University, 2020, EECS - Electrical Engineering

This thesis reports on the design and development of a Bluetooth Low Energy (BLE)-enabled neural microsystem suitable for activity-dependent stimulation applications in non-human primate models. The resulting microsystem is fabricated in all-rigid and rigid-flex substrates, operates autonomously from a 3.6V, 1.6A.h., lithium-ion battery, weighs approximately 48 grams (including the battery), consumes ~618μW under nominal operation, and is housed within a custom 3D-printed resin enclosure. An end-to-end BLE-enabled wireless communication protocol is developed to allow the user to wirelessly program the ICMS ASIC, measure stimulation rate, estimate electrode site impedance, and measure system power supply levels from a user base station. Comprehensive bench-top and in vitro tests demonstrate successful operation of the implemented hardware, software, and firmware. Additionally, initial results from in vivo experiments in awake squirrel monkeys are reported.

Committee: Pedram Mohseni (Committee Chair); Francis Merat (Committee Member); Soumyajit Mandal (Committee Member); Randolph Nudo (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

Master of Science, The Ohio State University, 2018, Electrical and Computer Engineering

We consider the problem of detecting the active wireless stations among a very large population. This problem is highly relevant in applications involving passive and active RFID tags and dense IoT settings. In this paper, we consider statistical activation models and formulate a general framework for investigating the limits of multi-station detection problem. We then evaluate the basic limits of achievable delay under two major activation models for Gaussian MAC channel and propose an order-optimal detection scheme in terms of detection delay. In contrast to a collisionavoiding and collision-resolving strategy for sequential detection, our scheme performs a interference-embracing strategy for simultaneous detection. More specifically, we assign each station a signature sequence, picked at random from a specific alphabet and have all active stations transmit their signatures simultaneously upon activation. The challenge at the detector is to detect all active stations from the combined signature signal with low probability of misdetection and false positives. We show that, such an interference embracing approach can substantially reduce the detection delay, at a vanishing probability of both types of detection errors, as the number of stations scale. We compare this paradigm with commonly-used interference avoiding (e.g., CSMA-based) approaches, which are designed to identify one station at a time. We show that interference avoiding approaches suffer from a reduction in delay scaling, even under highly optimistic situations. Finally, we discuss large-scale implementation issues such as the design of low-complexity detection schemes and present numerical investigations.

Committee: Atilla Eryilmaz (Advisor); Can Emre Koksal (Committee Member) Subjects: Computer Engineering; Electrical Engineering

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

The rapid development of demand for wireless data has lead to the development of numerous new applications, which the existing networks were not designed to handle. Dierent applications may have substantially dierent quality of service (QoS) requirements involving reliability, security, delay and throughput. Regardless of the required QoS, the perfect knowledge of source/channel conditions can always help to improve the performance. However, due to the intractability and unpredictability of the wireless communication environment, well-performed techniques under imperfect knowledge of source/channel information are more desirable from practical point of view, which is the focus of this research dissertation. First, we focus on wireless communication under imperfect source information problem. We consider a system in which two nodes take correlated measurements of a random source with time-varying and unknown statistics. The observations of the source at the rst node are to be losslessly replicated with a given probability of outage at the second node, which receives data from the rst node over a constant-rate errorless channel. We develop a system and associated strategies for joint distributed source coding (encoding and decoding) and transmission control in order to achieve low end-to-end delay. Slepian-Wolf coding in its traditional form cannot be applied in our scenario, since the encoder requires the joint statistics of the observations and the associated decoding delay is very high. We analytically evaluate the performance of our strategies and show that the delay achieved by them are order optimal, as the conditional entropy of the source approaches to the channel rate. We also evaluate the performance of our algorithms based on real-world experiments using two cameras recording videos of a scene at dierent angles. Having realized our schemes, we demonstrated that, even with a very low-complexity quantizer, a compression ratio of (open full item for complete abstract)

Committee: Can Koksal (Advisor); Atilla Eryilmaz (Committee Member); Yuejie Chi (Committee Member) Subjects: Electrical Engineering

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

Mobile devices such as smartphones are ubiquitous in society. According to Cisco Systems, there were eight billion mobile devices worldwide in 2016, which surpassed the human population. Mobile devices and wireless network infrastructure form an "electronic world" of signals that is part of daily life. However, navigating this world with users' devices is challenging. The volume of signals may confuse users, wireless communications often require manual connection establishment, and latency may be large (such as Bluetooth device discovery). Pervasive mobile device communications offer large-scale measurement opportunities when many devices connect to wireless networks. For example, base stations to which devices connect can indicate human mobility patterns. But existing work only studies coarse-grained cellular call records and datasets used in wireless local area network (WLAN) studies typically consist of laptops. Besides, existing vehicular communications technologies tend to be expensive and available for new vehicles only. This dissertation studies three topics that arise in the electronic world: unobtrusive communication among mobile devices without manual connection establishment; pervasive mobile device communications measurement; and cost-effective vehicular communication among mobile devices. First, we design Enclave that enables unobtrusive communication among mobile devices without network connections or configurations. Unobtrusive communication is efficient wireless communication that does not require user interruption such as manual device connection or network configuration. Enclave consists of a delegate mobile device (such as an unused phone) that interposes between a user's "master" device (such as her smartphone) and the electronic world. Enclave communicates between the master and delegate devices using wireless name communication and picture communication. Second, we study a new dataset with over 41 million anonymized (dis)association logs wit (open full item for complete abstract)

Committee: Dong Xuan Ph.D. (Advisor); Feng Qin Ph.D. (Committee Member); Ten-Hwang Lai Ph.D. (Committee Member) Subjects: Computer Science

Master of Science, The Ohio State University, 2017, Mathematics

Linear Programming has many applications in the domain of wireless communication. Many problems in this field consist of a very large number of variables and constraints and therefore fit in the platform of large scale linear programming. Advancements in computing over the past decade have allowed us to routinely solve linear programs in thousand of variables and constraints, using specialized methods from large scale linear programming. There are many software packages that implement such methods, e.g. AMPL, GAMS and Matlab. This dissertation gives A concise survey of linear programming fundamentals with a focus on techniques for large scale linear programming problems in the context of wireless communication. The dissertation explains some of these techniques, in particular the delayed column generation method and the decomposition method. It also draws on examples from the active field of wireless communication. The dissertation is concluded by giving concrete examples of how to use various software packages to solve large scale linear programming problems stemming from our examples in the context of wireless communication.

Committee: Ghaith Hiary (Advisor); Facundo Memoli (Committee Member) Subjects: Mathematics

Doctor of Philosophy, The Ohio State University, 2015, Computer Science and Engineering

There is an ever increasing demand for wireless communication. All wireless communication links access the same wireless medium. These multiple simultaneous transmissions increase the interference in the medium. This interference must be dealt with in today's wireless networks. Traditionally, to avoid the collision in wireless medium, different scheduling policies exist to ensure that no two transmitters in the same area transmit at the same time. The main focus of the dissertation is to explore alternative mechanisms to deal with interference: devices in the same neighbourhood collaborate by sharing channel information to control the collision of different independent wireless signals. Taming the interference collaboratively, we show we could improve the capability of WiFi system as well as explore new applications of wireless communications. This dissertation shows four systems taming the interference to improve our lives. First we propose Symphony to improve the uplink traffic performance in Enterprise Wireless LAN. It is a packet recovery architecture that encourages collisions among transmitters, and utilizes the unused capacity in the backbone to transmit recovered data packets and coordinate the efficient recovery of collided packets. Furthermore we start to look into the scenario when wireless devices are equipped with more than one RF chain. In this case there are several techniques that are possible; MIMO, full-duplex and interference alignment. We aim to unify these techniques into a single wireless node, called FlexRadio. A FlexRadio wireless node is fully flexible such that it can choose any number of its RF chains for transmission and the remaining for simultaneous reception. With the full duplex capability enabled in FlexRadio work, we further explore the case when multiple neighbour nodes are involved into collaboration. Specifically, we implement and deploy a wireless cut-through transmission system – AirExpress. Unli (open full item for complete abstract)

Committee: Kannan Srinivasan (Advisor); Dong Xuan (Committee Member); Anish Arora (Committee Member); Atanas Rountev (Committee Member) Subjects: Computer Science

Doctor of Philosophy (PhD), Ohio University, 2015, Electrical Engineering & Computer Science (Engineering and Technology)

Today's nanochips contain billions of transistors on a single die that integrates whole electronic systems as opposed to sub-system parts. Together with ever higher frequency performances resulting from transistor scaling and material improvements, it thus become possible to include on the same silicon chip analog functionalities and wireless communication circuitry that was once reserved to only an elite class of compound III-V semiconductors. It appears that the last stretch of Moore's scaling down to 5 nm range, these systems will only become more capable and faster, due to novel types of transistor geometries and functionalities as well as better integration of passive elements, antennas and novel isolation approaches. Accordingly, this dissertation is an example to how RF-CMOS integration may benefit from the use of a novel multi-gate transistors called FinFETs or Double Gate Metal Oxide Semiconductor Field Effect Transistors (DGMOSFETs). More specifically, this research is to validate how the performance of the radio frequency wireless communication integrated circuits can be improved by the use of this novel transistor architecture. To this end, in this dissertation, a wide range of radio frequency integrated circuits have been investigated in DG-MOSFETs which include Oscillators, On Off Keying (OOK) Modulator, Power Amplifier, Low Noise Amplifier, Envelope Detector, RF Mixer and Charge Pump Phase Frequency Detector. In all cases, the use of DG-MOSFET devices lead to reduction of transistor count and circuit complexity, while also resulting in tunable circuits owing to local back-gate control available in this device structure. Hence this work provides a unique insight as to how modest geometry changes and 3D device engineering may result in significant gains in analog/RF circuit engineering in the last stretch of Moore's scaling.

Committee: Savas Kaya (Advisor) Subjects: Electrical Engineering

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