Doctor of Philosophy, The Ohio State University, 2024, Electrical and Computer Engineering

With rapidly increasing demands for high-speed and data-intensive wireless communications, mm-wave technology has become a promising way to provide unparalleled data rates, ultra-reliable low latency, and a massive increase in device connectivity. However, there are some fundamental challenges in the deployment of mm-wave networks. Considering the same communication distance, the mm-wave suffers from a higher free-space path loss due to its shortened wavelength. The path loss becomes an issue especially when the device is working in rural areas where a longer coverage distance is required. Also, a shorter wavelength can result in extra attenuation brought by random obstacles, for example, the raindrops whose diameter is comparable to the wavelength. For the mm-wave antenna systems with a fixed narrow beam, even light mechanical motions can cause misalignment between the transmitter and receiver leading to intermittent communication. To address these challenges, mm-wave antennas are designed to be highly directional, concentrating energy in narrow beams to combat the high path loss. Besides, beam-steerable antennas, which can dynamically adjust the radiation direction, have been developed to maintain reliable communication links. While the conventional phased array designs have a planar aperture with beam-forming capability, their usage in the mm-wave band is limited by its cost, potentially low efficiency, and high power consumption due to numerous active RF components. The reflector antennas, which have been widely adopted thanks to their decent gain level and high efficiency, face the challenges of a complex reflecting aperture and a large volume due to the separated feeding source. Similar limitations have been observed in other designs using metasurfaces or lenses as well. Therefore, there is an innovation gap for a simple low-cost, low-volume, high-efficiency, high gain, and beam-steerable antenna design for the next-generation mm-wave applications. A low-prof (open full item for complete abstract)

Committee: Chi-Chih Chen (Advisor); Scott Scheer (Committee Member); Fernando Teixeira (Committee Member); Kubilay Sertel (Committee Member) Subjects: Electrical Engineering; Electromagnetics

Doctor of Philosophy, Case Western Reserve University, 2024, EECS - Electrical Engineering

5G promises higher speed for data communication when Internet-of-Things (IoT) makes enormous number of devices connected to each other. Preserving the security and trust in such systems are one of the critical. To create secure and trustworthy system while preserving the low power nature of such circuits, this work introduces a novel concept: embedded analog Physically Unclonable Functions (PUFs). Embedded analog PUFs provide enable lower power consumption than conventional hardware security methods because they are implemented in target circuits such as Voltage Controlled Oscillator (VCO) or Low Noise Amplifier (LNA). Also, the proposed approach allows for using performance parameters of the target circuits to develop required unique Challenge-Response Pair (CRP) mechanisms instead of bit streams of conventional PUF designs. In this work, power hungry parts of a radio frequency front-end (RF-FE), i.e. VCO and LNA, are targeted. Prototype low power 28 GHz trusted VCO and trusted LNA are developed in 65-nm standard CMOS and 22-nm FDSOI processes. Embedded analog PUF in VCO and LNA allows adjusting the DC (e.g. current consumption) and AC (e.g. frequency and noise figure (NF)) properties of the VCO and LNA to authenticate the designs while providing competitive performance with the VCO achieving figure of merit (FoM) of 195.2 dBc/Hz @1 MHz offset, and LNA showing NF ~ 3.7 dB @ 28 GHz.

Committee: Hossein Miri Lavasani (Committee Chair); Francis Merat (Committee Member); David Kazdan (Committee Member); An Wang (Committee Member); Steve Majerus (Committee Member) Subjects: Computer Engineering; Electrical Engineering; Electromagnetics

Doctor of Philosophy (PhD), Wright State University, 2022, Electrical Engineering

5th generation wireless systems (5G) have expanded frequency band coverage with the low-band 5G and mid-band 5G frequencies spanning 600 MHz to 4 GHz spectrum. This dissertation focuses on a microelectronic implementation of CMOS 65 nm design of an All-Digital Phase Lock Loop (ADPLL), which is a critical component for advanced 5G wireless transceivers. The ADPLL is designed to operate in the frequency bands of 600MHz-930MHz, 2.4GHz-2.8GHz and 3.4GHz-4.2GHz. Unique ADPLL sub-components include: 1) Digital Phase Frequency Detector, 2) Digital Loop Filter, 3) Channel Bank Select Circuit, and 4) Digital Control Oscillator. Integrated with the ADPLL is a 90-degree active RC-CR phase shifter with on-line amplitude locked loop (ALL) calibration to facilitate enhanced image rejection while mitigating the effects of fabrication process variations and component mismatch. A unique high-sensitivity high-speed dynamic voltage comparator is included as a key component of the active phase shifter/ALL calibration subsystem. 65nm CMOS technology circuit designs are included for the ADPLL and active phase shifter with simulation performance assessments. Phase noise results for 1 MHz offset with carrier frequencies of 600MHz, 2.4GHz, and 3.8GHz are -130, -122, and -116 dBc/Hz, respectively. Monte Carlo simulations to account for process variations/component mismatch show that the active phase shifter with ALL calibration maintains accurate quadrature phase outputs when operating within the frequency bands 600MHz-930MHz, 2.4GHz-2.8GHz and 3.4GHz-4.2GHz.

Committee: Saiyu Ren Ph.D. (Advisor); Raymond E. Siferd Ph.D. (Committee Member); Yan Zhuang Ph.D. (Committee Member); Henry Chen Ph.D. (Committee Member); Marian K. Kazimierczuk Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science in Electrical Engineering, Cleveland State University, 2021, Washkewicz College of Engineering

In this thesis, we draw attention to the problem of cross-service attacks, that is, attacks that exploit information collected about users from one service to launch an attack on the same users on another service. With the increased deployment and use of what fundamentally are integrated-services networks, such as 4G/LTE networks and now 5G, we expect that cross-service attacks will become easier to stage and therefore more prevalent. As running example to illustrate the effectiveness and the potential impact of cross-service attacks we will use the problem of account association in 4G/LTE networks. Account association attacks aim at determining whether a target mobile phone number is associated with a particular online account. In the case of 4G/LTE, the adversary launches the account association attacks by sending SMS messages to the target phone number and analyzing patterns in traffic related to the online account. We evaluate the proposed attacks in both a local 4G/LTE testbed and a major commercial 4G/LTE network. Our extensive experiments show that the proposed attacks can successfully identify account association with close-to-zero false negative and false positive rates. Our experiments also illustrate that the proposed attacks can be launched in a way that the victim receives no indication of being under attack.

Committee: Ye Zhu (Committee Chair); Yongjain Fu (Committee Member); Sui-Tung Yau (Committee Member) Subjects: Computer Engineering; Computer Science; Electrical Engineering; Information Technology; Technology

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

With the increasing demands for wireless control, infotainment communication and telematics service, modern cars are equipped with more and more radio frequency (RF) systems such as Global Navigation Satellite System (GNSS), Satellite Digital Audio Radio Service (SDARS), Cellular, Vehicle-to-Everything (V2X), and Wireless Local Area Network (WLAN), for navigation, communication, and entrainment needs. Not only does the number of frequency bands increase, but also the operating frequency goes higher and higher for more bandwidths. However, operating at a higher frequency is accompanied by faster fading issue which can be mitigated via the utilization of diversity reception from multiple antennas with different pattern coverages, polarizations, and spatial locations. However, packing many antennas into a compact low-profile volume as demanded by automobile manufacturers is no easy task because 1) the dimensions of antennas are typically comparable to a quarter to one half of operating wavelengths, and 2) strong coupling and blockage effects occur when other antennas are in proximity (less than a quarter of wavelengths). In addition, the most critical practical requirements of the next generation automobile antennas are low cost, easy installation, low profile, small footprint, covers from 0.7 GHz to 6 GHz, and support up to 4 channels MIMO radios. Unlike the conventional approach of using different antennas for LTE cellular, WLAN, and V2X different systems, Our proposed a compact ultra-wide bandwidth (UWB) universal antenna system reduced the total number of antennas, and thus overall antenna volume, by combing LTE, WLAN, and V2X operations into the same antenna body due to their similarity in pattern coverage and polarization requirements. Note that this is actually very challenging since the antenna needs to work over a very wide bandwidth to support 4G LTE (700 MHz-960 MHz, 1700MHz-2100MHz, 2500MHz-2700MHz, 3400MHz-3700MHz), C-Band of 5G sub6 (3300MHz-5000 (open full item for complete abstract)

Committee: Chi-Chih Chen (Advisor); Nima Ghalichechian (Committee Member); Fernando Teixeira (Committee Member); C.K. Shum (Committee Member) Subjects: Electrical Engineering; Electromagnetics

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

Utility of wireless connectivity has been steadily increasing as broadband internet becomes widely available and having low-cost technology leads to more devices built with Wi-Fi capabilities and sensors. As the traditional radio-frequency (RF) bands (sub 3 GHz) become congested, the mmW band offering vast amount of spectrum, is poised to be the backbone of 5G wireless networks. Particularly, thanks to much smaller wavelengths, antenna-integrated transceivers are viable solutions for the future 5G wireless networks. However, key challenges still remain for on-chip implementation of efficient radiators at such high frequencies. Namely, poor antenna bandwidths, severely low radiation efficiencies, as well as laborious and expensive antenna-transceiver integration (wire bonds, flip-chip, ball grid arrays, etc.) limit the utility of truly-integrated on-chip antennas. To overcome these prevailing obstacles we present an ultra-wideband (UWB), low-profile, high efficiency, tightly-coupled array topology which is adopted from RF-frequency realizations and modified as a multilayered structure suitable for standard micro-fabrication process. Through this work, we show that on-chip radiation efficiency is well above 60% over the entire impedance bandwidth. The proposed array exhibits wideband performance, covering 35-75 GHz, achieving an unprecedented coverage that spans most of the bands allocated for mobile communications. Utilization of low-loss materials in such designs can address the substrate coupling issues and improve the radiation efficiency. Moreover, the structural support and packaging materials that exhibit low loss are indispensable for cost-effective realization of integrated high frequency systems. To effectively address these requirements, polymers are a natural, low-cost choice for structural support and packaging of microchips due to their favorable chemical, thermal, and mechanical properties. However, many polymers have not been studied for mmW and TH (open full item for complete abstract)

Committee: Kubilay Sertel (Advisor); Niru Nahar (Committee Member); Fernando Teixeira (Committee Member) Subjects: Electrical Engineering; Electromagnetics; Electromagnetism

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

Latency has emerged as one of the most important requirements for these services that are intertwined with our economy, entertainment, comfort, and education. In this dissertation, we investigate the fundamental limits and develop efficient algorithms for achieving ultra-low delay in two computer systems: (1) the 5G networks; (2) the cloud systems. In 5G networks, a fundamental challenge in wireless multicast has been how to simultaneously achieve high-throughput and low-delay for reliably serving a large number of users. In a line of works, we propose coding and rate control algorithms, which can simultaneously realize the following three benefits: (i) High throughput: We show that in the many-user many-channel asymptotic regime, to achieve a non-vanishing throughput, the multi-channel resources required by our scheme achieves an algorithm independent lower bound in an order sense. (ii) Low delay: Using large deviations theory, we show that the delay of our scheme decreases linearly as the number of channels grows, while the delay reduction of conventional schemes is bounded by a constant factor. (iii) Constant feedback overhead: The feedback overhead of our scheme is a constant that is independent of both the number of receivers in each session and the number of sessions in the network. Trace-driven simulation and numerical results are provided to demonstrate these benefits. Our research suggests that large-scale wireless multicast with high throughput and low delay guarantees could be achieved. The significant promise of wireless multicast may be finally realized in practice. In cloud systems, load balancing is a key component for achieving low delay performance. Heavy-traffic delay optimality is considered to be an important metric in evaluating the delay performance of load balancing schemes. We argue that heavy-traffic delay optimality is a coarse metric that does not necessarily imply good delay performance. Specifically, we show that any load balancing (open full item for complete abstract)

Committee: Ness Shroff (Advisor); Kannan Srinivasan (Advisor); Eryilmaz Atilla (Committee Member); Zhang Yinqian (Committee Member) Subjects: Computer Engineering; Computer Science

Master of Science in Computer Engineering, University of Dayton, 2018, Electrical and Computer Engineering

Device-to-device (D2D) communication is a promising technology to improve energy efficiency and spectrum efficiency of the next-generation mobile networks. In this thesis, we first propose a D2D data off-loading scheme using game theoretical approach to reduce energy consumption for a wireless mobile network service provider. In the meantime, our proposed scheme provides a fair incentive mechanism to motivate D2D relay users for participation. The D2D scenario studied in this work focuses on downlink communications from the service provider to some users who request the same service, e.g., live streaming of a sports game. As an incentive, the service provider rewards some data usage to D2D relay users. In particular, we formulate a Stackelberg game to find the optimal portion of off-loading data for the relay users and the optimal incentive mechanism settings for the base station. With the proposed D2D off-loading scheme, a base station can maximize the energy saving while providing the most attraction to D2D relay users.Moreover, we propose a security scheme on the physical layer. The simulation results demonstrate that our proposed scheme will enhance the network energy efficiency and be attractive to D2D relay users. In particular, this scheme is to protect the data receivers in D2D communication areas form the eavesdroppers. In the proposed scheme, we derive the optimal transmitting power for each D2D relay so that data receivers can be provided with the highest security capacity. For each D2D relay, we consider the data receiver at the edge of the D2D communication area as it has the lowest signal-to-noise-and-interference ratio (SINR) compared to other receivers in this D2D coverage. We propose a near-far problem to guarantee that all the data receivers on the edge of D2D communication areas have the same SINR. Thus, all the data receivers are equally protected. For the attackers, we consider the one with the highest receiving SINR. Simulation result demonstr (open full item for complete abstract)

Committee: Feng Ye (Advisor); Guru Subramanyam (Committee Member); Eric Balster (Committee Member) Subjects: Electrical Engineering

Master of Science, Miami University, 2017, Computational Science and Engineering

This thesis, provides for an enhanced version of the 5G Channel Simulator, NYUSIM, developed by NYU Wireless Lab for Millimeter Wave outdoor communications at New York University. This research is performed in the physical layer for Non-Line-of-Sight scenarios. Our goal is to increase the received signal power and establish a viable transmission link, reducing the degrading effects of multipath and atmospheric noise. To achieve this goal, a search algorithm is implemented to find the main spatial energy lobe with maximum power concentration and separate it from other spatial lobes that mostly contain noise. This will act as a reference point in order to perform adaptive beamforming needed for increasing the total received signal power and noise reduction.

Committee: Donald Ucci (Advisor); Dmitriy Garmatyuk (Committee Member); Qihou Zhou (Committee Member) Subjects: Electrical Engineering; Engineering

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

Many high performance wireless applications continue to be integrated onto increasingly small platforms, such as satellites, UAVs, and handheld devices. Lowprofile and ultra-wideband antenna arrays have emerged as a potential solution, by allowing many disparate functions to be consolidated into a shared, multi-functional aperture. Simultaneously, the demand for high data rate communications has driven these applications to higher frequencies, with many now exploring the use of the millimeter-wave spectrum. However, existing UWB arrays often utilize complex feed structures which cannot scale to these frequencies. The development of wideband millimeter-wave arrays compatible with low-cost commercial fabrication processes is critical to enabling these small and highly connected platforms. Tightly Coupled Arrays are one family of low-profile and wideband arrays which have demonstrated superior bandwidth and wide scanning capability. However, the feed design of these arrays is limited to operation below 5 GHz, and suffers from reduced efficiency when scanning. In this work, the feed is modified to improve efficiency by eliminating a Wilkinson power divider, and mitigating the resultant cavity resonances with the application of shorting pins. Likewise, strenuous fabrication requirements are relaxed, allowing fabrication at higher frequencies. This effort is approached initially through the intermediate frequencies in the X-, Ku- and Ka-bands, and is demonstrated to allow the new design to scale up 49 GHz. An 8x8 prototype operating over 3.5–18.5 GHz is fabricated and measured to validate the design. Infinite array simulations show VSWR < 2 across this band at broadside, with scanning to ±45deg in the H-plane (VSWR < 2.6) and as far 70deg in E-plane (VSWR < 2). At millimeter-wave frequencies, planar co-fabrication of the entire array is critical to achieving repeatable fabrication, by eliminating the need for complex assembly at such small scales. Simultaneously, (open full item for complete abstract)

Committee: John Volakis (Advisor); Robert Burkholder (Committee Member); Kubilay Sertel (Committee Member) Subjects: Electrical Engineering; Electromagnetics; Electromagnetism