Engineering Commons^™

Adaptive Transmission Protocols For Wireless Communication Systems With Fountain Coding, Jason Ellis

All Dissertations

We present low-complexity adaptive protocols for both unicast and multicast transmission in wireless communication systems that employ higher layer fountain codes. Our adaptive protocols respond to variations in channel conditions by adapting the modulation and channel coding of transmitted packets, and they provide efficient communication over wireless channels that experience fading, shadowing, and other time-varying propagation losses. The operation of our protocols is governed by simple receiver statistics that can be obtained during the demodulation of received packets. We present three adaptive protocols for fountain-coded unicast transmission, and compare the throughput performance of our protocols with that of fixed-rate systems, …

Study On Electromagnetic Scattering Of Cylinders Buried In A Half Space With Random Rough Surfaces Of Finite/Infinite Length, Yueyang Dai

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Analysis of electromagnetic scattering of buried objects is a subject of great interest due to its practical importance in both military and civil applications, such as subsurface investigation and target detection. In reality, the earth is of layered structure of random rough interfaces, which leads to a greatly increased complexity of the analysis. However, it is necessary to incorporate the nature of random rough surface and the layered structure because they both have substantial impact on the scattered signature and hence affect the study of inverse scattering and detection of buried objects. In this dissertation, a Monte-Carlo multidomain pseudospectral time …

Encapsulated And Monolithic Resonant Structures For Laser Applications, Aaron Pung

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Typically, the composition of a laser system includes a gain medium, a pump illumination source, and an external feedback cavity. This cavity consists of a highly reflective mirror and an outcoupler component. The geometry of the outcoupler can be engineered to tailor the reflected or transmitted beam's spatial and spectral distribution. Functionally, the transmitted beam profile is dependent on the laser application. Broadband reflection profiles can be obtained by utilizing a distributed Bragg reflector (DBR). A DBR device consists of multiple layers of alternating materials. Constructive interference of the reflected light off each interface between different materials produces the spectrally …

Design Of An Optical Position Sensor For Microfiber Actuators, Luxi Cheng

All Theses

This thesis introduces a new type of sensor that detects the position information of a paramagnetic microfiber and transforms it to computational electrical signal. The original purpose of the sensor is to solve the problem of feedback signal detection of the microfiber control system, which is the problem of detecting the position information for the microfiber. The microfiber will be presented as the experimental object of this sensor to test its capability. A novel optical based approach is used to transfer the position signal to a computer scrutable signal for further analysis.

The purpose of the sensor design comes from …

Adaptive Transmission For Ofdm, Michael Juang

All Theses

To respond to dynamic channel conditions caused by fading, shadowing, and other time-varying disturbances, orthogonal frequency division multiplexing (OFDM) packet radio systems should adapt transmission parameters on a packet-by-packet basis to maintain or improve performance over the channel. For this to be possible, there are three key ideas that must be addressed: first, how to determine the subchannel conditions; second, which transmission parameters should be adapted; and third, how to adapt those parameters intelligently. In this thesis, we propose a procedure for determining relative subchannel quality without using any traditional channel measurements. Instead, statistics derived solely from subcarrier error counts …

Speech Enhancement By Exploiting The Baseband Phase Structure Of Voiced Speech For Effective Non-Stationary Noise Estimation, Sanjay Patil

All Theses

Speech enhancement is one of the most important and challenging issues in the speech communication and signal processing field. It aims to minimize the effect of additive noise on the quality and intelligibility of the speech signal. Speech quality is the measure of noise remaining after the processing on the speech signal and of how pleasant the resulting speech sounds, while intelligibility refers to the accuracy of understanding speech. Speech enhancement algorithms are designed to remove the additive noise with minimum speech distortion.The task of speech enhancement is challenging due to lack of knowledge about the corrupting noise. Hence, the …

A Probabilistic Analysis Of Islanding Effects In A Modeled Distribution System With Renewable Resources, Paul Gooding

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For this research, an investigation was undertaken regarding the inclusion of renewable resources into the distribution system. This incorporated the increasing prevalence of solar and wind resources, as well as the development of islanding capabilities within distribution systems.

Offshore Wind Energy Study And Its Impact On South Carolina Transmission System, Tingting Wang

All Dissertations

As one of the renewable resources, wind energy is developing dramatically in last ten years. Offshore wind energy, with more stable speed and less environmental impact than onshore wind, will be the direction of large scale wind industry. Large scale wind farm penetration affects power system operation, planning and control. Studies concerning type III turbine based wind farm integration problems such as wind intermittency, harmonics, low voltage ride through capability have made great progress. However, there are few investigations concerning switching transient impacts of large scale type III turbine based offshore wind farm in transmission systems. This topic will gain …

A Hybrid Method Of Performing Electric Power System Fault Ride-Through Evaluations On Medium Voltage Multi-Megawatt Devices, John Fox

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This dissertation explores the design and analysis of a Hybrid Method of performing electrical power system fault ride-through evaluations on multi-megawatt, medium voltage power conversion equipment. Fault ride-through evaluations on such equipment are needed in order to verify and validate full scale designs prior to being implemented in the field. Ultimately, these evaluations will help in reducing the deployment risks associated with bringing new technologies into the marketplace. This is especially true for renewable energy and utility scale energy storage systems, where a significant amount of attention in recent years has focused on their ever increasing role in power system …

Bite Detection And Differentiation Using Templates Of Wrist Motion, Soheila Eskandari

All Theses

We introduce a new algorithm of bite detection during an eating activity based on template matching. The algorithm uses a template to model the motion of the wrist over a 6-second window centered on the time when a person takes a bite. We also determine if different types of bites (for example food vs. drink, or using different types of utensils) have different wrist motion templates. This method is implemented on 22,383 bites and 5 different types of templates are built. We then describe a method to recognize different types of bites using the set of templates. The obtained accuracy …

Fabrication And Characterization Of Radio-Frequency Sensors For Liquid Material Detection, Yuxi He

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This thesis presents a series of studies on fabrication and characterization of radio-frequency (RF) sensors. In the light of Electromagnetics and Transmission Line Theory, we designed multiple RF sensors with different detection capability emphasis and used them to detect various materials, especially liquid samples and materials in solutions such as dielectric thin films, confined liquids, red blood cells, and malarial pigments (hemozoin). Most sensors were fabricated under clean room environment following the standard process protocols. Proper process developments were also made to achieve special structures and functionalities of our novel sensors. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) …

Electromagnetic Scattering Of Three-Dimensional (3d) Objects Embedded In A Half Space With Random Rough Surface, Wei Liu

All Dissertations

ABSTRACT
This dissertation presents a Monte-Carlo multidomain pseudospectral time-domain (MPSTD) algorithm developed for the analysis of scattering from a two dimensional (2D) and three dimensional (3D) object buried below a random rough surface separating two half spaces. In the development, special attention is paid to the 3D computation domain decomposition, PML derivations, filtering technique and subdomain mapping involving the random rough surface as well as the subdomain patching along the rough surface. The Mote-Carlo MPSTD algorithm is then employed to determine the scattering of objects of various shapes and electromagnetic properties; embedded in the lower half space with different permittivity …

Reverse Engineering: Wimax And Ieee 802.16e, Katherine Cameron

All Theses

Wireless communications is part of everyday life. As it is incorporated into new products and services, it brings additional security risks and requirements. A thorough understanding of wireless protocols is necessary for network administrators and manufacturers. Though most wireless protocols have strict standards, many parts of the hardware implementation may deviate from the standard and be proprietary. In these situations reverse engineering must be conducted to fully understand the strengths and vulnerabilities of the communication medium.
New 4G broadband wireless access protocols, including IEEE 802.16e and WiMAX, offer higher data rates and wider coverage than earlier 3G technologies. Many security …

Analytical Evaluation Of Adaptive Transmission Protocols For Markov Models Of Channels With Fading And Moderate Shadowing, Sneha Latha Kottapalli

All Theses

Adaptive transmission protocols are often employed to communicate over wireless channels with fading and other time-varying propagation losses. The protocols compensate for the propagation losses and maintain high throughput by adjusting transmission parameters in response to the channel variations. Performance evaluations for practical adaptive transmission protocols typically require simulation of both the time-varying processes and the procedure by which the protocol derives information about the channel quality. In this thesis, we develop an analytical method to evaluate the performance of two practical protocols, an adaptive coding protocol and an adaptive modulation and coding protocol, which rely on statistics derived from …