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

Tremendous increase in throughput, reliability and security requirements in present and future wireless communication networks necessitates the migration towards the underutilized higher frequency bands. The premise of large scale multiple input multiple output (MIMO) technology deployment in these bands has the potential of fulfilling future network requirements. At the same time, large scale network deployment, or the so-called dense coverage (large number of small scale base stations), is another link level strategy that also has the potential of enhancing the overall network quality of service (QoS). Performance of MIMO communication systems is governed by the amount of channel state information (CSI) available at both transmitter and receiver especially when deployed in a dense coverage network which has the potential of high line of sight (LoS) opportunity. This thesis aims to address throughput, reliability and physical layer security aspects of MIMO communication systems deployed in a fading environment with a stable path between transmitter and receiver with limited CSI feedback. The research involves four major research directions: (1) Transmitter optimization for public messages with minimal form of CSI feedback, (2) Secrecy capacity and optimal transmission strategy for confidential messages under the same limited CSI feedback model with eavesdropper uncertainty, (3) Establishing fundamental limits of covert communication of MIMO AWGN channel and highlight the potential of having a dominant channel mode in establishing high covert rates, (4) Message source authentication over MIMO channel with dominant mode. We start by considering the MIMO channel with dominant LoS component where the only CSI available at the transmitter are the Rician factor and the physical direction of the receiver with respect to the transmitter antennas array. For this particular scenario, although the exact capacity still unknown in a closed form, we establish an upper bou (open full item for complete abstract)

Committee: Hesham El Gamal Professor (Advisor); Can Emre Koksal Professor (Advisor); Inder Gupta Professor (Committee Member); Sheila Morgan Professor (Committee Member) Subjects: Communication; Electrical Engineering; Information Science

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

The rapid growth in wireless communication systems has provided a flexibility of communication and content that has had a transformative impact to all aspects of society. However, the broadcast nature of the wireless medium makes these systems vulnerable to passive attacks in which the adversary attempts to eavesdrop on the transmitted messages, and to active attacks in which the adversary can intelligently manipulate legitimate transmissions, both of which can jeopardize a myriad of critical wireless services. Hence, it is imperative to design wireless networks with safeguards in place to ensure their resilience to attacks. To that end, this dissertation provides various perspectives in the domain of information theoretic secrecy and authentication, which provably guarantees security, regardless of the computational capabilities of the adversary. We strive to bridge the gap between the information theory of security and the practically implementable protocols within this paradigm. We first consider point to point secure communication over flat fading wireless channels under delay constraint. We extend the definition of outage capacity to account for the secrecy constraint and obtain sharp characterizations of the corresponding fundamental limits under different assumptions on the transmitter channel state information (CSI). The capacity achieving scheme relies on opportunistically exchanging private keys between the legitimate nodes. These keys are stored in a key buffer and used to secure delay sensitive data. We also characterize the optimal power control policies and analyze the effect of key buffer overflow on the overall outage probability. Next, we focus on investigating additional sources for generating secret key bits in mobile wireless networks. We propose an algorithm for secret key generation based on the observations of the relative locations between a pair of nodes. We test our algorithm in a vehicular setting based on observations made (open full item for complete abstract)

Committee: Can Emre Koksal (Advisor); Hesham El Gamal (Advisor); Ness Shroff (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2021, Electrical and Computer Engineering

Emerging technologies and infrastructure developments in information and communication systems have paved the way for the extraordinary exposure of information around the globe. Specifically, the ease and the reliable exchange of information have promoted cultural, social, and economic activities. Meanwhile, this exposure is being exploited against user privacy and data confidentiality. In response, there have been major activities in keeping information safe. These activities can be summarized under three main domains: 1) Authentication: granting only legitimate access to data at rest, 2) Confidentiality: protecting information from being leaked to unauthorized parties in transit, and 3) Privacy: concealing user identity and activities. Modern cryptography is a practical and standardized approach that provides a certain level of information security. Cryptosystems obfuscate data in a way that makes it almost impossible to recover the plaintext, even with significant computational resources, but they do not rule out brute force recovery of data. They are robust in the communication media, i.e., the attackers are ruled out to have access to the ciphertext without a problem. Another approach, which is based on the physical characteristics of the hardware and/or the location, has been emerged as a powerful technique that can achieve unconditional security, i.e., without any assumption on the computational resources of the attackers. These two approaches are complementary and future security approaches will likely utilize both. In this dissertation, we mainly focus on the physical layer approaches, in particular, hardware-aided approaches, and discuss ways on how they can be used to enhance encryption-based approaches. First, we study multiple-input multiple-output (MIMO)-aided covert communication (also referred to as communication with a low probability of detection): the session between two legitimate parties remains undetectable from an external eavesdropper. (open full item for complete abstract)

Committee: C. Emre Koksal (Advisor); Yingbin Liang (Committee Member); Daniel J. Gauthier (Committee Member) Subjects: Electrical Engineering; Information Science; Information Systems

Doctor of Philosophy, The Ohio State University, 2020, History

Americans paradoxically view intelligence as both the cause of and solution to many key challenges and controversies throughout U.S. history. As an open society that values government transparency, the United States periodically witnesses a great deal of its secret intelligence activities reach the public domain. In response, American citizens often question the methods and missions of the American intelligence establishment, especially as they pertain to the tenets of American liberalism, civil liberties, and constitutional principles. The American intelligence establishment also typically bears the brunt of the criticism for policies created by elected officials and supported—if only temporarily—by a mercurial American public. The fundamental issue in U.S. intelligence history is one of civil-intelligence relations. The study of civil-intelligence relations concerns the distribution of roles, responsibilities, and powers between intelligence and the rest of civil society and government. This dissertation examines the history and theory of American civil-intelligence relations in order to explain the critical connection and dynamic interaction between the spy and the state.

Committee: Jennifer Siegel (Advisor); Paula Baker (Committee Member); Peter Mansoor (Committee Member) Subjects: American History; History; Military History

Doctor of Philosophy, The Ohio State University, 2020, Business Administration

Secrecy, or an intention to conceal information from one or more individuals, is a ubiquitous social phenomenon which enshrouds a wide spectrum of human behavior. Inevitably, secrecy also infiltrates into the consumption domain of people's lives and constitutes an indispensable element in myriad consumption activities, ranging from throwing surprise parties and preparing surprise gifts, through purchasing counterfeit products on the sly, to covertly indulging in diet busters. Despite the prevalence of secrecy in consumption activities, scant research has examined the influences of secret keeping on consumer behavior. Given the temporal nature of secrecy which spans across a period of time from the point when the hiding begins to the moment when the secret is disclosed, secrecy can prolong a consumption activity from the consumption per se (or a single-episode activity) to a longer psychological experience that lingers on the secret keeper's mind. In light of such a unique feature of secrecy, this research investigates how keeping a consumption secret will influence the secret keeper's enjoyment through the prolonged psychological experience sustained by secrecy. Across eight studies, this research demonstrates that secrecy has a polarizing effect on a secret keeper's enjoyment. Specifically, when a consumption activity is expected to elicit positive social responses, keeping it as a secret (vs. not) increases consumption enjoyment. When a consumption activity is anticipated to elicit negative social responses, keeping it as a secret (vs. not) decreases consumption enjoyment. It reveals that such effects are jointly mediated by the secret keeper's anticipation of outcomes of secret revelation and the cognitive effort imposed by the process of secret keeping. It also examines preoccupation as a moderator and finds that when expected social responses are positive, a curvilinear relationship between level of preoccupation and enjoyment exists such that the secret consum (open full item for complete abstract)

Committee: Xiaoyan Deng (Committee Chair); Rebecca Reczek (Committee Member); Selin Malkoc (Committee Member); Xiaojing Yang (Committee Member) Subjects: Marketing; Psychology

Master of Science in Engineering, University of Akron, 2015, Electrical Engineering

Due to the broadcast nature of wireless channels, security and privacy are of utmost concern for future wireless technologies. However, securely transferring confidential information over a wireless network in the presence of adversaries still remains a challenging task. As one of the most important aspects of wireless communication security, Physical Layer (PHY) security has started gaining research attention in the past few years. In wireless PHY security, the breakthrough idea is to exploit the characteristics of wireless channels such as fading or noise to transmit a message from a source to an intended destination while trying to keep this message confidential from passive eavesdroppers. Unlike cryptographic methods, no computational constraints are placed on the eavesdroppers. Benefiting from information-theoretic studies in cooperative relaying communications, relaying strategies have also recently received considerable attention in the context of PHY security over wireless networks. Specifically, in wireless PHY security, relay nodes can be used as trusted nodes to support a secured transmission from a source to a destination in the presence of one or more eavesdroppers. This thesis studies a wireless relay network in which a source node wants to communicate securely to a destination node in the presence of an eavesdropper under the aid of an amplify-and-forward (AF) relay operating in full-duplex (FD) mode for further security enhancement. The focus is on the optimal power allocation (PA) schemes to maximize the secrecy rate in different wireless environments. The first part of the thesis considers the problem of optimizing the PA at the source node and the relay node to achieve the secrecy capacity for slowly varying fading channels. Under this consideration, the optimal PA problem is shown to be quasi-concave. As such, the globally optimal power allocation solution exists, and it is unique. A simple bisection method for root finding can then be used t (open full item for complete abstract)

Committee: Nghi Tran Dr. (Advisor); Shiva Sastry Dr. (Committee Member); Forrest Bao Dr. (Committee Member) Subjects: Electrical Engineering

Master of Arts (MA), Bowling Green State University, 2013, Psychology/Industrial-Organizational

The present study examined the association between pay secrecy and its outcomes. Based on theories of justice and equity, pay secrecy was hypothesized to positively influence the four facets of pay satisfaction (i.e., pay level, raises, benefits, and administration) through procedural and distributive justice. The pay secrecy-justice-pay satisfaction relationship was proposed to be conditional on the value of equity sensitivity, such that it would be the strongest for individuals with the highest sensitivity for inequity. Thus, utilizing a sample of 187 individuals, a moderated-mediation model of pay secrecy was tested. Results were inconsistent with the hypothesized model, in that equity sensitivity did not moderate the relationship between pay secrecy and the pay satisfaction facets, when it was mediated by procedural and distributive justice. Furthermore, neither procedural nor distributive justice mediated the pay secrecy-pay satisfaction relationship. Thus, the current findings suggest that there are no individual differences in the perceptions of justice and pay attitudes between equity sensitive and equity insensitive employees working in organizations with varying degrees of pay secrecy. The limitations of the study and future research directions are discussed.

Committee: Christopher Nye (Committee Chair); Margaret Brooks (Committee Member); Richard Anderson (Committee Member) Subjects: Psychology

Doctor of Philosophy, The Ohio State University, 2013, Political Science

Why do states use secrecy? Specifically, why do great powers often seem to create a kind of “backstage” area around local conflicts? That is, why create a kind of covert realm where external powers can meddle in local conflicts to pursue their security interests? This project generally analyzes how secrecy is used in international politics and why states are individually and collectively motivated to use it. Existing scholarship suggests states use secrecy to surprise their adversaries or insulate their leaders from dovish domestic political groups. I develop an alternative logic rooted in the desire to control conflict escalation risks. In the context of interventions in local conflicts by outside powers, I find intervening states use covert methods to maintain control over the perceptions and interpretations of outside audiences whose reactions determine the magnitude of external pressure on leaders to escalate further. Intervening in a secret, plausibly deniable manner makes restraint and withdrawal on the part of the intervening state easier. It also creates ambiguity about their role which can give the political space to responding states to ignore covert meddling and respond with restraint. Escalation control dynamics therefore make sense of why states intervene secretly and, more puzzling, why other states – even adversaries – may join in ignoring and covering up such covert activity (what I call “tacit collusion”). Drawing on Erving Goffman and others, I develop an “impression management” theory for why states individually and jointly use secrecy and political denial to achieve their goals. To illustrate several new concepts and evaluate the theory’s value-added, I use a sophisticated comparative case study research design that leverages within- and between-case variation in the Korean War, Spanish Civil War, and the civil war in Soviet-occupied Afghanistan. Each conflict hosts se (open full item for complete abstract)

Committee: Randall Schweller Ph.D. (Committee Chair); Richard Herrmann Ph.D. (Committee Member); Jennifer Mitzen Ph.D. (Committee Member) Subjects: International Relations; Political Science

Doctor of Philosophy, The Ohio State University, 2012, English

Abstract This project looks at confessional moments in three texts from the late Fourteenth and early Fifteenth centuries in which the subjectivities of the central figures shift noticeably in relation to challenges to orthodox behaviors and beliefs, both on a secular and a sacral level: John Gower's Confessio Amantis, the anonymously translated Partonope of Blois, and Geoffrey Chaucer's Troilus and Criseyde. In all these confessional moments, which involve secrecy and fear, the interiority of the confessant and that of the confessor contour the confesssion and reveal potentially subversive and political criticisms. Late medieval English poets use the very discourses of the institutions under scrutiny in order to challenge institutional corruption as well as cultural, social, and political corruption. By bringing an insular mechanism to challenge itself, such as confessional discourse to challenge confessional efficacy, poets enable a dual dialectic in order to illuminate the inefficacy of ideologies, social and cultural codes and structures, and institutional hierarchies; once brought under scrutiny, poets can position various subjectivities through mobile figurations in order to posit reformation on an individual level. Secrecy and fear are the primary investigatory foci of this project. My first point of entry in exploring poetic calls for personal, cultural, political, and institutional reformation is through the institial spaces that poets open within the confessional moments in the texts. In these institices, secrecy shapes the nature of the dialectic exchange primarily through the affective response of fear. Secrecy itself is premised on a liminal distinction between self and others, and its etymology reveals, it insists on things being held apart intentionally and separate from the knowledge of others. Within this definition, will and desire work in tandem, although they are not aligned under the same impulse. This cooperation seems too simplistic when con (open full item for complete abstract)

Committee: Lisa Kiser PhD (Committee Chair); Ethan Knapp PhD (Committee Member); Sarah-Grace Heller PhD (Committee Member) Subjects: Literature; Medieval Literature

Doctor of Philosophy, The Ohio State University, 2007, Electrical Engineering

The central theme of this dissertation is the impact of feedback on the performance of wireless networks. Wireless channels offer a multitude of new challenges and opportunities that are uncharacteristic of wireline systems. We reveal the crucial role of feedback in exploiting the opportunities and in overcoming the challenges posed by the wireless medium. In particular, we consider three distinct scenarios and demonstrate the different ways in which feedback helps improve performance. We first consider cellular multicast channels and show that the availability of feedback allows for the cross-layer design of efficient multicast schedulers. Here we focus on two types of feedback scenarios: perfect channel state information (CSI) feedback and automatic repeat request (ARQ) feedback. We propose low-complexity multicast schedulers that achieve near-optimal asymptotic throughput-delay tradeoffs for both feedback scenarios. We further propose a cooperative multicast scheduler, requiring perfect CSI feedback, that achieves the optimal asymptotic scaling of both throughput and delay with the number of users. Next, we consider fading eavesdropper channels and reveal the importance of feedback in establishing secure communications. We characterize the secrecy capacity of such channels under the assumptions of full CSI and main (legitimate) channel CSI knowledge at the transmitter, and propose optimal rate and power allocation strategies. Interestingly, we show that the availability of CSI feedback enables one to exploit the time-varying nature of the wireless medium and achieve a perfectly secure non-zero rate even when the eavesdropper channel is more capable than the legitimate receiver channel on the average. We also propose a low-complexity on/off power allocation strategy and establish its asymptotic optimality. We then consider a minimal ARQ feedback scenario and propose transmission schemes that leverage the ARQ feedback to achieve non-zero perfect secrecy rates. Fina (open full item for complete abstract)

Committee: Hesham El Gamal (Advisor) Subjects: