Digital Commons Network^™

Ultra Wide Band Multiple Access Performance Using Th-Ppm And Ds-Bpsk Modulations, Courtney M. Canadeo

Theses and Dissertations

The increasing demand for portable, high data rate communications has focused much attention on wireless technology. Ultra Wide Band (UWB) waveforms have the ability to deliver megabits of information while maintaining low average power consumption. In accordance with recent FCC ruling, UWB systems are now allowed to operate in the unlicensed spectrum of 3.1 to 10.6 GHz, motivating renewed interest in the forty year old concept of impulse radio. Gaussian monocycles produce UWB waveforms occupying large bandwidths with multiple access (MA) capability enabled by spread spectrum techniques. Time Hopping (TH) and Direct Sequence (DS) modulations are considered here for UWB …

Theoretical Analysis Of Information Watermarking In Wavelet-Based Video Compression, Brendan K. Casey

Theses and Dissertations

Embedding audio bits into images for transmission of video data alleviates the synchronization problem common in video transmission techniques. We continue work combining audio or other information bits and images into one file using digital watermarking techniques to correct the synchronization problem. The system compresses the file by using wavelet image coefficients and implementing bit plane coding. Our research encompasses incorporating five free variables into the watermark/compression technique. These variables are watermark robustness, number of coding iterations, number of image coefficients, number of watermarked information bits, and number of watermarked error correcting bits. By altering these variables, four measurements of …

Using The Gps To Improve Trajectory Position And Velocity Determination During Real-Time Ejection Seat Design, Test And Evaluation, Christina G. Schutte

Theses and Dissertations

Test and evaluation of the United States Air Force’s latest aircraft escape system technology requires accurate position and velocity profiles during each test to determine the relative positions between the aircraft, ejection seat, manikin and the ground. Current rocket sled testing relies on expensive ground based multiple camera systems to determine the position and velocity profiles. While these systems are satisfactory at determining seat and manikin trajectories for sled testing, their accuracy decreases when they are used for in-flight testing, especially at high altitudes. This research presents the design and test results from a new GPS-based system capable of monitoring …

Development Of Variable Slope Piecewise-Based Brown Symbols For Application To Nonlinear Ambiguity Suppression, John Kurian

Theses and Dissertations

In 1962, Palermo used two conjugate Linear Frequency Modulated (LFM) pulses to demonstrate a Non-linear Ambiguity Suppression (NLAS) technique to reduce ambiguous energy in radar returns. Using conjugate LFM pulse coding does not readily extend to larger symbol families and thus is severely limited for M-channel (M> 2) NLAS applications. Larger families of optimal mutually dispersible codes with bigger time bandwidth products are needed to achieve the desired M-fold range ambiguity reduction. Using correlation function the time duration as an optimization metric, the recently proposed Brown's theorem formulates a deterministic process for designing optimal mutually dispersible symbol sets of arbitrary …

Analysis Of Broadband Higp-Impedance Ground Plane Antenna Designs, James W. Stewart

Theses and Dissertations

This research ties together computational and experimental analysis of two types of high-impedance ground plane (HIGP) antennas. One type of antenna consists of a proposed two-layer design. The structure consists of a bowtie antenna mounted over the surface of a HIGR The proposed structure was intended to achieve a resonant frequency of 3 GHz and a bandwidth of 48%; however, a design error results in a significant mismatch in operating bands between the antenna and HIGR Experiment results indicate the structure performs poorly across the entire measured band of 2-5 GHz. A new two-layer design is developed and presented. The …

An Advanced Ambiguity Selection Algorithm For Seawinds, David G. Long, David W. Draper

Faculty Publications

SeaWinds on QuikSCAT, a spaceborne Ku-band scatterometer, estimates ocean winds via the relationship between the normalized radar backscatter and the vector wind. Scatterometer wind retrieval generates several possible wind vector solutions or ambiguities at each resolution cell, requiring a separate ambiguity selection step to give a unique solution. In processing SeaWinds on QuikSCAT data, the ambiguity selection is "nudged" or initialized using numerical weather prediction winds. We describe a sophisticated new ambiguity selection approach developed at Brigham Young University (BYU) that does not require nudging. The BYU method utilizes a low-order data-driven Karhunen-Loeve wind field model to promote self-consistency. Ambiguity …

High-Resolution Measurements With A Spaceborne Pencil-Beam Scatterometer Using Combined Range/Doppler Discrimination Techniques, David G. Long, Michael W. Spencer, Wu-Yang Tsai

Faculty Publications

Conically scanning pencil-beam scatterometer systems, such as the SeaWinds radar, constitute an important class of instruments for spaceborne climate observation. In addition to ocean winds, scatterometer data are being applied to a wide range of land and cryospheric applications. A key issue for future scatterometer missions is improved spatial resolution. Pencil-beam scatterometers to date have been real-aperture systems where only range discrimination is used, resulting in a relatively coarse resolution of approximately 25 km. In this paper, the addition of Doppler discrimination techniques is proposed to meet the need for higher resolution. The unique issues associated with the simultaneous application …

Algan/Gan Hemts - Operation In The K-Band And Above, Ioulia P. Smorchkova, M. Wojtowicz, Rajinder Sandhu, R. Tsai, M. Barsky, C. Namba, P.-S. Liu, R. Dia, Minhdao Truong, D. Ko, J. Wang, H. Wange, Asif Khan

Faculty Publications

We report on the power and microwave noise performance of AlGan/GaN high electron-mobility transistors (HEMTs) at frequencies f > 18 GHz (K- and Ka-bands). At 20 GHz, a record continuous-wave output power of 1.6 W has been achieved on an eight-finger 500-mum total gate-periphery device. At 29 GHz, a 120-mum gate-periphery device showed a pulsed output density of 1.6 W/mm with an associated gain of 6.7 dB and power-added efficiency of 26%. Minimum noise figure of 1.5 dB has been achieved on a 0.2 mum x 200 mum device at 26 GHz. The data demonstrate the viability of AlGan/GaN HEMTs for …

Corp - A Method Of Concatenation And Optimization For Resource Reservation Path In Mobile Internet, Kyounghee Lee, Myungchul Kim, Samuel T. Chanson, Chansu Yu, Jonghyun Lee

Electrical and Computer Engineering Faculty Publications

Existing research related to RSVP with mobility support has mainly focused on maintaining reservation state along the routing path, which changes continuously with the movements of mobile host (MH), without much overhead and delay. However, problems such as deepening RSVP's inherent scalability problem and requiring significant changes in the existing network infrastructure have not been adequately addressed. In this paper, we propose a new approach, known as Concatenation and Optimization for Reservation Path (CORP), which addresses these issues. In CORP, each BS pre-establishes pseudo reservations to its neighboring BSs in anticipation of the MH's movement. When the MH moves into …

An All-Digital Clock-Smoothing Technique—Counting-Prognostication, Xiaoyi Qin, Hansheng Wang, Lieguang Zeng, Fuqin Xiong

Electrical and Computer Engineering Faculty Publications

This article presents a novel universal all-digital clock-smoothing technique - counting-prognostication. Operation principles, performance analysis, and comparisons are given. Analysis and measurement results show that this technique can efficiently smooth jitter and wander for a wide pull-in range and pull-out range, and jitter accumulation is small. A cycle-varying counting-prognostication method, which decreases pull-in time, is also suggested.

Network Lifetime Extension, Power Conservation And Interference Suppression For Next Generation Mobile Wireless Networks, Amer Catovic

Dissertations

Two major focus research areas related to the design of the next generation multihop wireless networks are network lifetime extension and interference suppression. In this dissertation, these two issues are addressed.

In the area of interference suppression, a new family of projection multiuser detectors, based on a generalized, two-stage design is proposed. Projection multiuser detectors provide efficient protection against undesired interference of unknown power, while preserving simple design, with closed-form solution for error probabilities. It is shown that these detectors are linearly optimal, if the interference power is unknown.

In the area of network lifetime extension, a new approach to …

Joint Buffer Management And Scheduling For Input Queued Switches, Dequan Liu

Dissertations

Input queued (IQ) switches are highly scalable and they have been the focus of many studies from academia and industry. Many scheduling algorithms have been proposed for IQ switches. However, they do not consider the buffer space requirement inside an IQ switch that may render the scheduling algorithms inefficient in practical applications.

In this dissertation, the Queue Length Proportional (QLP) algorithm is proposed for IQ switches. QLP considers both the buffer management and the scheduling mechanism to obtain the optimal allocation region for both bandwidth and buffer space according to real traffic load. In addition, this dissertation introduces the Queue …

Packet Data Communications Over Coded Cdma With Hybrid Type-Ii Arq, Seokhyun Yoon

Dissertations

This dissertation presents in-depth investigation of turbo-coded CDNIA systems in packet data communication terminology. It is divided into three parts; (1) CDMA with hybrid FEC/ARQ in deterministic environment, (2) CDMA with hybrid FEC/ARQ in random access environment and (3) an implementation issue on turbo decoding.

As a preliminary, the performance of CDMA with hybrid FEC/ARQ is investigated in deterministic environment. It highlights the practically achievable spectral efficiency of CDMA system with turbo codes and the effect of code rates on the performance of systems with MF and LMMSE receivers, respectively. For given ensemble distance spectra of punctured turbo codes, an …

Robust And Efficient Video/Image Transmission, Xi Min Zhang

Dissertations

The Internet has become a primary medium for information transmission. The unreliability of channel conditions, limited channel bandwidth and explosive growth of information transmission requests, however, hinder its further development. Hence, research on robust and efficient delivery of video/image content is demanding nowadays.

Three aspects of this task, error burst correction, efficient rate allocation and random error protection are investigated in this dissertation. A novel technique, called successive packing, is proposed for combating multi-dimensional (M-D) bursts of errors. A new concept of basis interleaving array is introduced. By combining different basis arrays, effective M-D interleaving can be realized. It has …

Vlsi Design Of Stability Routing Protocol For Sensors In Wireless Mobile Ad-Hoc Networks, Vishnu M. Mandava

Theses

This thesis gives a detailed description of the Application specific integrated circuit (ASIC) design of Stability routing protocol for sensors in mobile ad-hoc networks. The Stability routing protocol is based on the signal strength and position components during data transmission while considering sensors in an ad-hoc network. A general ad-hoc network has unpredictable and variable mobility patterns therefore the signal strength criteria is adopted for routing. Signal strength criteria has been proved to be efficient for communication between the mobile nodes without any data loss. In this thesis an architecture for a processor implementing stability routing protocol for effective communication …

Firewall Interface For Java Ftp Smtp And Http Servers, Ratan Kumar Erukulla

Theses

The objective of my thesis is to develop a firewall interface for FTP, HTTP and SMTP servers. A firewall interface is a graphical user interface (GUI) to configure the properties of the server. Using this interface, we can spy a user, block and unblock the IP address of a client, display statistics of user and server. We can track all the user actions while he is connected to the server. These actions are logged and based on the log data we can deny access to users performing illegal operations. All the servers and interfaces are written in Java. Java was …

An Interface Chip For Saw Based Sensor In An Ad-Hoc Network, Yagneshwara Ramakrishna Vadapalli

Theses

The design of a smart integrated chemical sensor system that will enhance sensor performance and compatibility to ad hoc network architecture remains a challenge. This work involves the design of an interface chip for a Surface Acoustic Wave (SAW) based chemical sensor where the sensor reflects the RF input and introduces a time delay proportional to the concentration of the vapors absorbed by it. The interface chip detects the frequency shift as a function of the chemical species absorbed by the sensor and alerts the ad hoc network controller when a monitored parameter exceeded some threshold, based on local processing …

Testing With Hostile Data Streams, Alan A. Jorgensen

Electrical Engineering and Computer Science Faculty Publications

This note describes a method of testing software for response to malicious data streams. Systems that process data streams obtained from an external source such as the Internet are vulnerable to security issues if malicious data is not processed correctly. This note describes a testing method that creates malicious data streams, applies them to a software application and checks the appropriateness of the application response. The note begins with a description of the problem: inadequate testing of software response to malicious data streams. I present a method of testing the response to malicious data streams and introduce the concepts of …

Heat: Runtime Interception Of Win32 Functions, Michael M. Andrews

Electrical Engineering and Computer Science Faculty Publications

When researching in any field, it is always important to build upon existing work. In most research disciplines, the core base is well defined and widely documented. However, the basis of innovative research in computer science, especially at the systems level, can often be proprietary information. This can be a major problem as unless you have source code available you must be granted access to the proprietary information (by usually signing non-disclosure documents) which comes with barriers on access, ownership and the ability to publish results. As an example, Microsoft's Windows operating system (all versions) can be a good base …

Observation Of Optical Phonon Instability Induced By Drifting Electrons In Semiconductor Nanostructures, W. Liang, K. T. Tsen, Otto F. Sankey, S. M. Komirenko, K. W. Kim, V. A. Kochelap, Meng-Chyi Wu, Chong-Long Ho, Wen-Jeng Ho, Hadis Morkoç

Electrical and Computer Engineering Publications

We have experimentally proven the Cerenkov generation of optical phonons by drifting electrons in a semiconductor. We observe an instability of the polar optical phonons in nanoscale semiconductors that occurs when electrons are accelerated to very high velocities by intense electric fields. The instability is observed when the electron drift velocity is larger than the phase velocity of optical phonons and rather resembles a “sonic boom” for optical phonons. The effect is demonstrated in p–i–nsemiconductor nanostructures by using subpicosecond Raman spectroscopy.

Logic Foundry: Rapid Prototyping For Fpga-Based Dsp Systems, Gary Spivey

Faculty Publications - Department of Electrical Engineering and Computer Science

We introduce the Logic Foundry, a system for the rapid creation and integration of FPGA-based digital signal processing systems. Recognizing that some of the greatest challenges in creating FPGA-based systems occur in the integration of the various components, we have proposed a system that targets the following four areas of integration: design flow integration, component integration, platform integration, and software integration. Using the Logic Foundry, a system can be easily specified, and then automatically constructed and integrated with system level software.

Improved Pattern Stability For Monopole Antennas With Ultrawideband Impedance Characteristics, Max Ammann

Conference papers

The requirement of future software defined and reconfigurable radio networks to operate in multiple, wide-ranging, frequency bands places heavy demands on antenna designs. Rather than using antennas tuned at the time of manufacture to operate in certain predefined frequency bands under predefined radio systems, which limits the possibilities of implementing new radio systems on a reconfigurable terminal, a wideband antenna is proposed. The use of a single antenna which can operate over many octaves is very desirable for future wireless communications systems. We discuss the characteristics of the planar monopole, an antenna with wideband properties. The addition of a second …

A Wide-Band Shorted Planar Monopole With Bevel, Max Ammann, Zhi Ning Chen

Articles

A new wide-band shorted planar monopole with a bevel is presented. The numerical simulations and measurements demonstrate that the impedance bandwidth of a wide-band planar square monopole is shown to increase dramatically by combining bevelling and a shorting technique. The radiation pattern stability is also discussed.

Improving Dsp Performance With A Small Amount Of Field Programmable Logic, John Y. Oliver, Venkatesh Akella

Electrical Engineering

We show a systematic methodology to create DSP + field-programmable logic hybrid architectures by viewing it as a hardware/software codesign problem. This enables an embedded processor architect to evaluate the trade-offs in the increase in die area due to the field programmable logic and the resultant improvement in performance or code size. We demonstrate our methodology with the implementation of a Viterbi decoder. A key result of the paper is that the addition of a field-programmable data alignment unit (FPDAU) between the register-file and the computational blocks provides 15%-22% improvement in the performance of a Viterbi decoder on the state-of-the-art …

Comparing Self-Efficacy And Metacognition As Indicators Of Performance, Deborah K. Smith, Jerry Cha-Jan Chang, Trevor T. Moores

Management, Entrepreneurship and Technology Faculty Research

We report the results of a pilot study that compared the computer self-efficacy construct with metacognition. While self-efficacy is primarily affective and refers to one’s beliefs about one’s ability to perform a task, metacognition is primarily cognitive and refers to one’s thoughts about one’s ability to perform a task. Given their similarity, both have been used as surrogate measures of knowledge or skill. We developed an instrument to measure both constructs and applied the instrument to a set of MIS students taking an Analysis and Design course. Factor analysis produced a five-factor model, with metacognition factoring out as a unidimensional …

A Discrete Dimming Ballast For Linear Fluorescent Lamps, Haiyan Wang

ETD Archive

No abstract provided.

Investigation On How To Improve Latent Semantic Analysis Performance, Thao Doan

Inquiry: The University of Arkansas Undergraduate Research Journal

Latent Semantic Analysis (LSA) is a matching technique capable of recognizing the semantic relationships of data that ordinary techniques such as string matching cannot. This is especially valuable for data integration applications, like those of Acxiom, where data items are usually related by context, rather than in a literal match. Even though it has been shown that LSA is 30% more effective in finding and ranking relevant pieces of information than existing string-by-string matching techniques (Deerwester et al., 1990; Dumais, 1995), the performance of the LSA seems to be affected by the presence of shared words, or “noise”, in data. …

A New Modified Smith Predictor Design, Pauline Sourdille, Aidan O'Dwyer

Conference papers

A new modified Smith predictor structure is presented with its associated tuning rules.

Automated Distribution And Management Of Software And Hardware Configurations For Heterogeneous Wireless Devices, Grainne Foley

Theses

The continuing evolution of wireless networks and services has increased the complexity and diversity of wireless networks and devices, placing significant emphasis on the need for flexible device configuration management. Widely varying wireless technologies currently operate independently worldwide, making global wireless network access for the mobile user confusing and unwieldy. New technologies, network access methodologies and improved services further obscure the evolving environment. The focus of effort for this thesis is the development of a system to automate the distribution and management of software and hardware configurations that enable different levels of wireless device reconfiguration. The scope of investigation will …

Optical Switches Using Electro-Optical Effects In Liquid Crystals, Yuliya Semenova, S. Dovgalets, Yuri Panarin, Gerald Farrell

Articles

A simple displacement sensor based on a bent singlemode-multimode-singlemode (SMS) fiber structure is proposed and experimentally investigated. The sensor offers a wider displacement range, not limited by the risk of fiber breakage, as well as a three-fold increase in displacement sensitivity by comparison with a straight SMS structure sensor. This sensor can be interrogated by either an optical spectral analyzer (OSA) or a ratiometric interrogation system: (1) if interrogated by an OSA assuming a resolution of 1 pm, it has a sensitivity of 28.2 nm for a displacement measurement range from 0 to 280 μm; (2) if interrogated by a …