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, 2017, Electrical and Computer Engineering

Vehicular Adhoc Networks (VANETs) promises to empower the future autonomous vehicles with a cooperative awareness facility that will help in avoiding accidents and alleviating traffic congestion. The foreseen collective awareness requires the vehicles to communicate with their neighbors and with the infrastructure; such communication will need the fulfillment of many requirements such as security, privacy, and efficiency. The Dedicated Short-Range Communication (DSRC) standard has been formulated to afford these requisites. On one hand, when focusing on the application layer, DSRC adopts the successful Internet-based Public Key Infrastructure (PKI) framework to safeguard the vehicles. However, PKI alone cannot comprehensively meet all of the security and privacy requirements. On the other hand, the DSRC 's Medium Access Control (MAC) layer adopts the IEEE 802.11p access mode, which also needs augmentation to fulfill the efficiency of communication when collisions arise for safety beacons. Since many issues have not been well addressed in DSRC, academic, industrial, and governmental research has flourished over the last two decades to complement the standard. As being part of such large research community, we also have been incentivized to contribute with our own solutions. Our contributions have been ranging between two limits: either finding solutions to acclimate with the available DSRC shortcomings or disregarding the bias that DSRC has towards using only specific standards by bringing other alternative frameworks into scene. With the first direction in mind, our efforts are a mixture of high-level re-arrangement protocols such as grouping and overhead omissions to minimize the PKI and Carrier Sense Multiple Access - Collision Avoidance (CSMA/CA) privacy and efficiency shortcomings. For the other direction, we especially address the application layer level. Since some frameworks have small communication overhead while others have high anonymous traits, we have at (open full item for complete abstract)

Committee: Fusun Ozguner Professor (Advisor); Can Emre Koksal Professor (Committee Member); Xiaorui Wang Professor (Committee Member) Subjects: Computer Engineering; Computer Science; Electrical Engineering; Transportation

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

Doctor of Philosophy, The Ohio State University, 2006, Electrical Engineering

In this dissertation, GPS based wireless communication protocols for two important problems in VANETs, namely broadcasting and Internet access, are proposed. The common feature of the new protocols is using the position information of vehicles in the MAC layer. Inter-Vehicle Communication Systems rely on multi-hop broadcast to disseminate information to locations beyond the transmission range of individual nodes. Our multi-hop broadcast protocols are proposed to address the broadcast storm, hidden node, and reliability problems of multi-hop broadcast in vehicular networks. In these proposed protocols, the functions of forwarding and acknowledging a broadcast packet are assigned to only one vehicle by dividing the road portion inside the transmission range into segments and choosing the vehicle in the furthest non-empty segment without a priori topology information. Assigning the forwarding function to only one vehicle is sufficient for successful broadcast in vehicular ad-hoc networks (VANETs) because of their special topology constrained by roads. For the Internet access problem, a new cross-layer communication protocol for vehicular Internet access along highways is introduced. The objective of the new Controlled Vehicular Internet Access (CVIA) protocol is to increase the end-to-end throughput while achieving fairness in bandwidth usage between road segments. To achieve this goal, the CVIA protocol eliminates contention in relaying packets over long distances. CVIA creates single-hop vehicle clusters and mitigates the hidden node problem by dividing the road into segments and controlling the active time of each segment. Using an analytical throughput estimation model, the protocol parameters are fine tuned to provide fairness among road segments. Finally, extentions to support QoS under the CVIA protocol are introduced. The new protocol, CVIA-QoS, uses admission control for soft-real time traffic to provide delay bounded throughput guarantees.

Committee: Fusun Ozguner (Advisor) Subjects: