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Title: PROTOTYPE OF COUPLING UNIT NETWORK FOR POWER LINE COMMUNICATIONS.
Creator: Srinivasan, Bharath, Wei, Lei, University of Central Florida
Abstract / Description: Power Line Communications has made impressive strides since its introduction. Power Line Communications (PLC) or Broadband over Power Lines (BPL) is the method of transmitting broadband signals over the power lines and making it available at the power outlet in homes. It provides last mile communication and makes use of existing power lines to transmit signals, thereby eliminating the need to lay cables all over again. PLC is fast becoming a commercial reality in the United States. The...
Show morePower Line Communications has made impressive strides since its introduction. Power Line Communications (PLC) or Broadband over Power Lines (BPL) is the method of transmitting broadband signals over the power lines and making it available at the power outlet in homes. It provides last mile communication and makes use of existing power lines to transmit signals, thereby eliminating the need to lay cables all over again. PLC is fast becoming a commercial reality in the United States. The Federal Communications Commission (FCC) is working toward making PLC a standard with particular emphasis on power emission issues and interference with nearby bands. Power companies, vendors and ISPs (Internet Service Providers) have tied up to bring this new technology to market. The Power line environment is inherently unpredictable due to interference, low signaling impedance and the highly linear operating environment that PLC transmitters require. The coupling unit in the PLC system acts as a filter and eliminates the harmful AC signal from interfering with the broadband signals. A coupling unit amplifier topology that provides gain equalization and wideband mitigation to the effects of low-impedance loads on PLC in the high frequency range has been explored in detail in this study. The amplifier is verified for its performance by means of circuit simulation using industry-standard software such as Agilent's Advanced Design System (ADS). The coupling unit has also been fabricated to verify the performance. An experimental setup for verifying the performance of the coupling unit using a PLC transmitter and PLC receiver has also been proposed.
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Date Issued: 2006
Identifier: CFE0001306, ucf:47029
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001306

Title: ULTRA-WIDE BAND IN COMMUNICATIONS: PERFORMANCE ANALYSIS AND ENHANCEMENTS.
Creator: Berksoy, Burak, WEI, Lei, University of Central Florida
Abstract / Description: Over the last ten years, Ultra-Wide Band (UWB) technology has attracted tremendous research attention. Frequency allocation of 3.1-10.6 GHz for UWB application by FCC made it apparent that UWB will be the technology for future wireless high speed communication applications. With the promise of high data rates (high channel capacity), UWB also offers advantages such as communication security, high multi-path resolution, good penetration capability, ability to coexist with other communication...
Show moreOver the last ten years, Ultra-Wide Band (UWB) technology has attracted tremendous research attention. Frequency allocation of 3.1-10.6 GHz for UWB application by FCC made it apparent that UWB will be the technology for future wireless high speed communication applications. With the promise of high data rates (high channel capacity), UWB also offers advantages such as communication security, high multi-path resolution, good penetration capability, ability to coexist with other communication schemes in the same band, and finally, circuit simplicity. The theoretical advantages of UWB has made it a great candidate for short distance communications, however, UWB communications have many challenges, for example, sub-nanosecond pulse generation, timing sensitivity of modulation and synchronization, flat antenna performance over a wide bandwidth, effect of existing systems on UWB systems. In order to experiment with various UWB modulation schemes, and to study transmitter and receiver structures, an accurate channel model need be established. In this dissertation, our first contribution is to evaluate and implement two major statistical channel models. The first model is proposed by AT\&T Labs and is in the form of an autoregressive IIR filter. Although this is an accurate channel model to represent UWB behavior, it is proposed before the allocation of 3.1-10.6 GHz frequency band, hence, it could not simulate the correct frequency spectrum. The second model is proposed by Saleh and Valenzuela, which has been widely accepted by UWB community to be the most accurate channel model for UWB systems. Recently disbanded task group 802.15.3a which was assigned to standardize a UWB communication scheme has also accepted the latter model. Our second contribution is to derive optimal pulses for PPM signals. Using the accurate channel model in computer simulations, we experimented on various UWB communication schemes. We found that the traditional UWB pulses being used in pulse position modulated UWB systems did not perform optimally. A set of optimized UWB pulses and the methodology to calculate optimal pulses for any modulation index for PPM systems have been proposed in this dissertation. It is found that the optimal pulse can improve the performance of UWB systems by as much as 0.7 dB. With the PPM pulse optimization, the theoretical performance limits of PPM systems are derived. The third contribution from this dissertation is to design near optimal practical implementable receiver structures. Some of the results obtained from PPM pulse optimization are found to be theoretical and not practical. More practical approach to the receiver structures were needed for industrial interest. We proposed simple sub-optimal receiver structures that are able to perform only a few dB less than the optimal receivers are proposed. These simple, low-cost receiver structures are strong alternatives to the complex traditional optimal receivers.
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Date Issued: 2008
Identifier: CFE0002106, ucf:47531
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002106

Title: ADVANCED CODING AND MODULATION FOR ULTRA-WIDEBAND AND IMPULSIVE NOISES.
Creator: Yang, Libo, Wei, Lei, University of Central Florida
Abstract / Description: The ever-growing demand for higher quality and faster multimedia content delivery over short distances in home environments drives the quest for higher data rates in wireless personal area networks (WPANs). One of the candidate IEEE 802.15.3a WPAN proposals support data rates up to 480 Mbps by using punctured convolutional codes with quadrature phase shift keying (QPSK) modulation for a multi-band orthogonal frequency-division multiplexing (MB-OFDM) system over ultra wideband (UWB) channels....
Show moreThe ever-growing demand for higher quality and faster multimedia content delivery over short distances in home environments drives the quest for higher data rates in wireless personal area networks (WPANs). One of the candidate IEEE 802.15.3a WPAN proposals support data rates up to 480 Mbps by using punctured convolutional codes with quadrature phase shift keying (QPSK) modulation for a multi-band orthogonal frequency-division multiplexing (MB-OFDM) system over ultra wideband (UWB) channels. In the first part of this dissertation, we combine more powerful near-Shannon-limit turbo codes with bandwidth efficient trellis coded modulation, i.e., turbo trellis coded modulation (TTCM), to further improve the data rates up to 1.2 Gbps. A modified iterative decoder for this TTCM coded MB-OFDM system is proposed and its bit error rate performance under various impulsive noises over both Gaussian and UWB channel is extensively investigated, especially in mismatched scenarios. A robust decoder which is immune to noise mismatch is provided based on comparison of impulsive noises in time domain and frequency domain. The accurate estimation of the dynamic noise model could be very difficult or impossible at the receiver, thus a significant performance degradation may occur due to noise mismatch. In the second part of this dissertation, we prove that the minimax decoder in \cite, which instead of minimizing the average bit error probability aims at minimizing the worst bit error probability, is optimal and robust to certain noise model with unknown prior probabilities in two and higher dimensions. Besides turbo codes, another kind of error correcting codes which approach the Shannon capacity is low-density parity-check (LDPC) codes. In the last part of this dissertation, we extend the density evolution method for sum-product decoding using mismatched noises. We will prove that as long as the true noise type and the estimated noise type used in the decoder are both binary-input memoryless output symmetric channels, the output from mismatched log-likelihood ratio (LLR) computation is also symmetric. We will show the Shannon capacity can be evaluated for mismatched LLR computation and it can be reduced if the mismatched LLR computation is not an one-to-one mapping function. We will derive the Shannon capacity, threshold and stable condition of LDPC codes for mismatched BIAWGN and BIL noise types. The results show that the noise variance estimation errors will not affect the Shannon capacity and stable condition, but the errors do reduce the threshold. The mismatch in noise type will only reduce Shannon capacity when LLR computation is based on BIL.
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Date Issued: 2007
Identifier: CFE0001836, ucf:47342
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001836

Title: COMPARISON OF SPARSE CODING AND JPEG CODING SCHEMES FOR BLURRED RETINAL IMAGES.
Creator: Chandrasekaran, Balaji, Wei, Lei, University of Central Florida
Abstract / Description: Overcomplete representations are currently one of the highly researched areas especially in the field of signal processing due to their strong potential to generate sparse representation of signals. Sparse representation implies that given signal can be represented with components that are only rarely significantly active. It has been strongly argued that the mammalian visual system is highly related towards sparse and overcomplete representations. The primary visual cortex has overcomplete...
Show moreOvercomplete representations are currently one of the highly researched areas especially in the field of signal processing due to their strong potential to generate sparse representation of signals. Sparse representation implies that given signal can be represented with components that are only rarely significantly active. It has been strongly argued that the mammalian visual system is highly related towards sparse and overcomplete representations. The primary visual cortex has overcomplete responses in representing an input signal which leads to the use of sparse neuronal activity for further processing. This work investigates the sparse coding with an overcomplete basis set representation which is believed to be the strategy employed by the mammalian visual system for efficient coding of natural images. This work analyzes the Sparse Code Learning algorithm in which the given image is represented by means of linear superposition of sparse statistically independent events on a set of overcomplete basis functions. This algorithm trains and adapts the overcomplete basis functions such as to represent any given image in terms of sparse structures. The second part of the work analyzes an inhibition based sparse coding model in which the Gabor based overcomplete representations are used to represent the image. It then applies an iterative inhibition algorithm based on competition between neighboring transform coefficients to select subset of Gabor functions such as to represent the given image with sparse set of coefficients. This work applies the developed models for the image compression applications and tests the achievable levels of compression of it. The research towards these areas so far proves that sparse coding algorithms are inefficient in representing high frequency sharp image features. So this work analyzes the performance of these algorithms only on the natural images which does not have sharp features and compares the compression results with the current industrial standard coding schemes such as JPEG and JPEG 2000. It also models the characteristics of an image falling on the retina after the distortion effects of the eye and then applies the developed algorithms towards these images and tests compression results.
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Date Issued: 2007
Identifier: CFE0001701, ucf:47328
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001701

Title: SUB-OPTIMAL ULTRA-WIDE BAND RECEIVERS.
Creator: Bhuvanendran, Nilesh, Lei Wei, Dr, University of Central Florida
Abstract / Description: Ultra-wide Band (UWB) has sparked a lot of interest lately from theindustry and academia. The growing capacity of the wireless industry is requires a new communication system that satis¯es the high data rate which does not interfere with existing RF systems. UWB promises to be this new technology. UWB also promises low power, low cost and °exibility. The UWB Channel opens up a huge new wireless channel with Giga Hertz Capacities as well as the highest spatial capacities measured in...
Show moreUltra-wide Band (UWB) has sparked a lot of interest lately from theindustry and academia. The growing capacity of the wireless industry is requires a new communication system that satis¯es the high data rate which does not interfere with existing RF systems. UWB promises to be this new technology. UWB also promises low power, low cost and °exibility. The UWB Channel opens up a huge new wireless channel with Giga Hertz Capacities as well as the highest spatial capacities measured in bits per hertz per square meter. When properly implemented UWB channel can share spectrum with traditional radio systems without causing harmful interference. In this thesiswe studied and compared several reduced complexity sub-optimal Ultra-Wide Band receivers. These receivers include auto correlation receiver, the square value detector and the absolute value detector are studied. We consider OOK and PPM modulation schemes. We examine these schemes and the receivers on Gaussian and UWB indoor channels. We compare the performance with optimal receivers.A transmitter receiver system using 0.1us pulses implemented usingexisting hardware. A packet consisting of 24 bits were transmitted and the received signal could be veri¯ed in real time using a vector signal analyzer. The results show sub-optimal receivers provide a better trade off between robust,complexity and performance.
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Date Issued: 2004
Identifier: CFE0000106, ucf:46186
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000106

Title: HIGH SPEED TURBO TCM OFDM FOR UWB AND POWERLINE SYSTEM.
Creator: WANG, YANXIA, Wei, Lei, University of Central Florida
Abstract / Description: Turbo Trellis-Coded Modulation (TTCM) is an attractive scheme for higher data rate transmission, since it combines the impressive near Shannon limit error correcting ability of turbo codes with the high spectral efficiency property of TCM codes. We build a punctured parity-concatenated trellis codes in which a TCM code is used as the inner code and a simple parity-check code is used as the outer code. It can be constructed by simple repetition, interleavers, and TCM and functions as standard...
Show moreTurbo Trellis-Coded Modulation (TTCM) is an attractive scheme for higher data rate transmission, since it combines the impressive near Shannon limit error correcting ability of turbo codes with the high spectral efficiency property of TCM codes. We build a punctured parity-concatenated trellis codes in which a TCM code is used as the inner code and a simple parity-check code is used as the outer code. It can be constructed by simple repetition, interleavers, and TCM and functions as standard TTCM but with much lower complexity regarding real world implementation. An iterative bit MAP decoding algorithm is associated with the coding scheme. Orthogonal Frequency Division Multiplexing (OFDM) modulation has been a promising solution for efficiently capturing multipath energy in highly dispersive channels and delivering high data rate transmission. One of UWB proposals in IEEE P802.15 WPAN project is to use multi-band OFDM system and punctured convolutional codes for UWB channels supporting data rate up to 480Mb/s. The HomePlug Networking system using the medium of power line wiring also selects OFDM as the modulation scheme due to its inherent adaptability in the presence of frequency selective channels, its resilience to jammer signals, and its robustness to impulsive noise in power line channel. The main idea behind OFDM is to split the transmitted data sequence into N parallel sequences of symbols and transmit on different frequencies. This structure has the particularity to enable a simple equalization scheme and to resist to multipath propagation channel. However, some carriers can be strongly attenuated. It is then necessary to incorporate a powerful channel encoder, combined with frequency and time interleaving. We examine the possibility of improving the proposed OFDM system over UWB channel and HomePlug powerline channel by using our Turbo TCM with QAM constellation for higher data rate transmission. The study shows that the system can offer much higher spectral efficiency, for example, 1.2 Gbps for OFDM/UWB which is 2.5 times higher than the current standard, and 39 Mbps for OFDM/HomePlug1.0 which is 3 times higher than current standard. We show several essential requirements to achieve high rate such as frequency and time diversifications, multi-level error protection. Results have been confirmed by density evolution. The effect of impulsive noise on TTCM coded OFDM system is also evaluated. A modified iterative bit MAP decoder is provided for channels with impulsive noise with different impulsivity.
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Date Issued: 2006
Identifier: CFE0000943, ucf:46745
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000943

Title: Prototype Development in General Purpose Representation and Association Machine Using Communication Theory.
Creator: Li, Huihui, Wei, Lei, Rahnavard, Nazanin, Vosoughi, Azadeh, Da Vitoria Lobo, Niels, Wang, Wei, University of Central Florida
Abstract / Description: Biological system study has been an intense research area in neuroscience and cognitive science for decades of years. Biological human brain is created as an intelligent system that integrates various types of sensor information and processes them intelligently. Neurons, as activated brain cells help the brain to make instant and rough decisions. From the 1950s, researchers start attempting to understand the strategies the biological system employs, then eventually translate them into machine...
Show moreBiological system study has been an intense research area in neuroscience and cognitive science for decades of years. Biological human brain is created as an intelligent system that integrates various types of sensor information and processes them intelligently. Neurons, as activated brain cells help the brain to make instant and rough decisions. From the 1950s, researchers start attempting to understand the strategies the biological system employs, then eventually translate them into machine-based algorithms. Modern computers have been developed to meet our need to handle computational tasks which our brains are not capable of performing with precision and speed. While in these existing man-made intelligent systems, most of them are designed for specific purposes. The modern computers solve sophistic problems based on fixed representation and association formats, instead of employing versatile approaches to explore the unsolved problems.Because of the above limitations of the conventional machines, General Purpose Representation and Association Machine (GPRAM) System is proposed to focus on using a versatile approach with hierarchical representation and association structures to do a quick and rough assessment on multitasks. Through lessons learned from neuroscience, error control coding and digital communications, a prototype of GPRAM system by employing (7,4) Hamming codes and short Low-Density Parity Check (LDPC) codes is implemented. Types of learning processes are presented, which prove the capability of GPRAM for handling multitasks.Furthermore, a study of low resolution simple patterns and face images recognition using an Image Processing Unit (IPU) structure for GPRAM system is presented. IPU structure consists of a randomly constructed LDPC code, an iterative decoder, a switch and scaling, and decision devices. All the input images have been severely degraded to mimic human Visual Information Variability (VIV) experienced in human visual system. The numerical results show that 1) IPU can reliably recognize simple pattern images in different shapes and sizes; 2) IPU demonstrates an excellent multi-class recognition performance for the face images with high degradation. Our results are comparable to popular machine learning recognition methods towards images without any quality degradation; 3) A bunch of methods have been discussed for improving IPU recognition performance, e.g. designing various detection and power scaling methods, constructing specific LDPC codes with large minimum girth, etc.Finally, novel methods to optimize M-ary PSK, M-ary DPSK, and dual-ring QAM signaling with non-equal symbol probabilities over AWGN channels are presented. In digital communication systems, MPSK, MDPSK, and dual-ring QAM signaling with equiprobable symbols have been well analyzed and widely used in practice. Inspired by bio-systems, we suggest investigating signaling with non-equiprobable symbol probabilities, since in bio-systems it is highly-unlikely to follow the ideal setting and uniform construction of single type of system. The results show that the optimizing system has lower error probabilities than conventional systems and the improvements are dramatic. Even though the communication systems are used as the testing environment, clearly, our final goal is to extend current communication theory to accommodate or better understand bio-neural information processing systems.
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Date Issued: 2017
Identifier: CFE0006758, ucf:51846
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006758

Title: "Design and Simulation of CMOS RF Active Mixers".
Creator: Gibson, Allen, Yuan, Jiann-Shiun, Wei, Lei, Sundaram, Kalpathy, University of Central Florida
Abstract / Description: This paper introduces a component of the Radio Frequency transceiver called the mixer. The mixer is a critical component in the RF systems, because of its ability for frequency conversion. This passage focuses on the design analysis and simulation of multiple topologies for the active down-conversion mixer. This mixer is characterized by its important design properties which consist of conversion gain, linearity, noise figure, and port isolation. The topologies that are given in this passage...
Show moreThis paper introduces a component of the Radio Frequency transceiver called the mixer. The mixer is a critical component in the RF systems, because of its ability for frequency conversion. This passage focuses on the design analysis and simulation of multiple topologies for the active down-conversion mixer. This mixer is characterized by its important design properties which consist of conversion gain, linearity, noise figure, and port isolation. The topologies that are given in this passage range from the most commonly known mixer design, to implemented design techniques that are used to increase the mixers important design properties as the demand of CMOS technology and the overall RF system rises. All mixer topologies were designed and simulated using TSMC 0.18 (&)#181;m CMOS technology in Advanced Design Systems, a simulator used specifically for RF designs.
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Date Issued: 2011
Identifier: CFE0004112, ucf:49086
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004112

Title: A Microwave Radiometer Roughness Correction Algorithm For Sea Surface Salinity Retrieval.
Creator: Hejazin, Yazan, Jones, W, Mikhael, Wasfy, Wei, Lei, University of Central Florida
Abstract / Description: The Aquarius/SAC-D is an Earth Science remote sensing satellite mission to measure global Sea Surface Salinity (SSS) that is sponsored by the NASA and the Argentine Space Agency (CONAE). The prime remote sensor is the Aquarius (AQ) L-band radiometer/scatterometer, which measures the L-band emitted blackbody radiation (brightness temperature) from the ocean. The brightness temperature at L-band is proportional to the ocean salinity as well as a number of physical parameters including ocean...
Show moreThe Aquarius/SAC-D is an Earth Science remote sensing satellite mission to measure global Sea Surface Salinity (SSS) that is sponsored by the NASA and the Argentine Space Agency (CONAE). The prime remote sensor is the Aquarius (AQ) L-band radiometer/scatterometer, which measures the L-band emitted blackbody radiation (brightness temperature) from the ocean. The brightness temperature at L-band is proportional to the ocean salinity as well as a number of physical parameters including ocean surface wind speed. The salinity retrieval algorithm make corrections for all other parameters before retrieving salinity, and the greatest of these is the increased brightness temperature due to roughness caused by surface wind speed. This thesis presents an independent approach for the AQ roughness correction, which is derived using simultaneous measurements from the CONAE Microwave Radiometer (MWR). When the wind blows over the ocean's surface, the brightness temperature is increased because of the ocean wave surface roughness. The MWR provides a semi-empirical approach by measuring the excess ocean emissivity at 36.5 GHz and then applying radiative transfer theory (improved ocean surface emissivity model) to translate this to the AQ 1.4 GHz frequency (L-band). The theoretical basis of the MWR algorithm is described and empirical results are presented that demonstrate the effectiveness in reducing the salinity measurement error due to surface roughness.
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Date Issued: 2012
Identifier: CFE0004212, ucf:49007
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004212

Title: Simulation Study of a GPRAM System: Error Control Coding and Connectionism.
Creator: Schultz, Steven, Wei, Lei, Lin, Mingjie, Yuan, Jiann-Shiun, University of Central Florida
Abstract / Description: A new computing platform, the General Purpose Reprsentation and Association Machine is studied and simulated. GPRAM machines use vague measurements to do a quick and rough assessment on a task; then use approximated message-passing algorithms to improve assessment; and finally selects ways closer to a solution, eventually solving it. We illustrate concepts and structures using simple examples.
Date Issued: 2012
Identifier: CFE0004437, ucf:49361
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004437

Title: Computationally Efficient Digital Backward Propagation for Fiber Nonlinearity Compensation.
Creator: Zhu, Likai, Li, Guifang, Schulzgen, Axel, Likamwa, Patrick, Wei, Lei, University of Central Florida
Abstract / Description: The next generation fiber transmission system is limited by fiber nonlinearity. A distributed nonlinearity compensation method, known as Digital Backward Propagation (DBP), is necessary for effective compensation of the joint effect of dispersion and nonlinearity. However, in order for DBP to be accurate, a large number of steps are usually required for long-haul transmission, resulting in a heavy computational load.In real time DBP implementation, the FIR filters can be used for dispersion...
Show moreThe next generation fiber transmission system is limited by fiber nonlinearity. A distributed nonlinearity compensation method, known as Digital Backward Propagation (DBP), is necessary for effective compensation of the joint effect of dispersion and nonlinearity. However, in order for DBP to be accurate, a large number of steps are usually required for long-haul transmission, resulting in a heavy computational load.In real time DBP implementation, the FIR filters can be used for dispersion compensation and account for most of the computation per step. A method of designing a complementary filter pair is proposed. The individual errors in the frequency response of the two filters in a complementary filter pair cancel each other. As a result, larger individual filter error can be tolerated and the required filter length is significantly reduced.Unequal step size can be used in DBP to minimize the number of steps. For unrepeatered transmission with distributed Raman amplification, the Raman gain as a function of the distance and the effective fiber length of each DBP step need to be calculated by solving the differential equations of Raman amplification. The split-step DBP is performed only for transmission where the signal power is high.In comparison with solving the nonlinear Schrodinger equation (NLSE) for the total field of the WDM signal, solving the coupled NLSE requires a smaller step number and a lower sampling rate. In addition, the phase-locking between the local oscillators is not necessary for solving the coupled NLSE. The XPM compensation of WDM long-haul transmission by solving the coupled NLSE is experimentally demonstrated.At the optimum power level of fiber transmission, the total nonlinear phase shift is on the order of 1 radian. Therefore, for transoceanic fiber transmission systems which consist of many ((>)100) amplified fiber spans, the nonlinear effects in each span are weak. As a result, the optical waveform evolution is dominated by the dispersion. Taking advantage of the periodic waveform evolution in periodically dispersion managed fiber link, the DBP of K fiber spans can be folded into one span with K times the nonlinearity. This method can be called (")distance-folded DBP("). Under the weakly nonlinear assumption, the optical waveform repeats at locations where accumulated dispersions are identical. Consequently, the nonlinear behavior of the optical signal also repeats at locations of identical accumulative dispersion. Hence for a fiber link with arbitrary dispersion map, the DBP steps can be folded according to the accumulated dispersion. Experimental results show considerable savings in computation using this (")dispersion-folded DBP(") method. Simulation results show that the dramatically reduced computational load makes the nonlinearity-compensated dispersion-managed fiber link a competitive candidate for the next-generation transmission systems.
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Date Issued: 2011
Identifier: CFE0004492, ucf:49272
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004492

Title: ACTION RECOGNITION USING PARTICLE FLOW FIELDS.
Creator: Reddy, Kishore, Shah, Mubarak, Sukthankar, Gita, Wei, Lei, Moore, Brian, University of Central Florida
Abstract / Description: In recent years, research in human action recognition has advanced on multiple fronts to address various types of actions including simple, isolated actions in staged data (e.g., KTH dataset), complex actions (e.g., Hollywood dataset), and naturally occurring actions in surveillance videos (e.g, VIRAT dataset). Several techniques including those based on gradient, flow, and interest-points, have been developed for their recognition. Most perform very well in standard action recognition...
Show moreIn recent years, research in human action recognition has advanced on multiple fronts to address various types of actions including simple, isolated actions in staged data (e.g., KTH dataset), complex actions (e.g., Hollywood dataset), and naturally occurring actions in surveillance videos (e.g, VIRAT dataset). Several techniques including those based on gradient, flow, and interest-points, have been developed for their recognition. Most perform very well in standard action recognition datasets, but fail to produce similar results in more complex, large-scale datasets. Action recognition on large categories of unconstrained videos taken from the web is a very challenging problem compared to datasets like KTH (six actions), IXMAS (thirteen actions), and Weizmann (ten actions). Challenges such as camera motion, different viewpoints, huge interclass variations, cluttered background, occlusions, bad illumination conditions, and poor quality of web videos cause the majority of the state-of-the-art action recognition approaches to fail. An increasing number of categories and the inclusion of actions with high confusion also increase the difficulty of the problem. The approach taken to solve this action recognition problem depends primarily on the dataset and the possibility of detecting and tracking the object of interest. In this dissertation, a new method for video representation is proposed and three new approaches to perform action recognition in different scenarios using varying prerequisites are presented. The prerequisites have decreasing levels of difficulty to obtain: 1) Scenario requires human detection and tracking to perform action recognition; 2) Scenario requires background and foreground separation to perform action recognition; and 3) No pre-processing is required for action recognition.First, we propose a new video representation using optical flow and particle advection. The proposed ``Particle Flow Field'' (PFF) representation has been used to generate motion descriptors and tested in a Bag of Video Words (BoVW) framework on the KTH dataset. We show that particle flow fields has better performance than other low-level video representations, such as 2D-Gradients, 3D-Gradients and optical flow. Second, we analyze the performance of the state-of-the-art technique based on the histogram of oriented 3D-Gradients in spatio temporal volumes, where human detection and tracking are required. We use the proposed particle flow field and show superior results compared to the histogram of oriented 3D-Gradients in spatio temporal volumes. The proposed method, when used for human action recognition, just needs human detection and does not necessarily require human tracking and figure centric bounding boxes. It has been tested on KTH (six actions), Weizmann (ten actions), and IXMAS (thirteen actions, 4 different views) action recognition datasets.Third, we propose using the scene context information obtained from moving and stationary pixels in the key frames, in conjunction with motion descriptors obtained using Bag of Words framework, to solve the action recognition problem on a large (50 actions) dataset with videos from the web. We perform a combination of early and late fusion on multiple features to handle the huge number of categories. We demonstrate that scene context is a very important feature for performing action recognition on huge datasets.The proposed method needs separation of moving and stationary pixels, and does not require any kind of video stabilization, person detection, or tracking and pruning of features. Our approach obtains good performance on a huge number of action categories. It has been tested on the UCF50 dataset with 50 action categories, which is an extension of the UCF YouTube Action (UCF11) Dataset containing 11 action categories. We also tested our approach on the KTH and HMDB51 datasets for comparison.Finally, we focus on solving practice problems in representing actions by bag of spatio temporal features (i.e. cuboids), which has proven valuable for action recognition in recent literature. We observed that the visual vocabulary based (bag of video words) method suffers from many drawbacks in practice, such as: (i) It requires an intensive training stage to obtain good performance; (ii) it is sensitive to the vocabulary size; (iii) it is unable to cope with incremental recognition problems; (iv) it is unable to recognize simultaneous multiple actions; (v) it is unable to perform recognition frame by frame. In order to overcome these drawbacks, we propose a framework to index large scale motion features using Sphere/Rectangle-tree (SR-tree) for incremental action detection and recognition. The recognition comprises of the following two steps: 1) recognizing the local features by non-parametric nearest neighbor (NN), and 2) using a simple voting strategy to label the action. It can also provide localization of the action. Since it does not require feature quantization it can efficiently grow the feature-tree by adding features from new training actions or categories. Our method provides an effective way for practical incremental action recognition. Furthermore, it can handle large scale datasets because the SR-tree is a disk-based data structure. We tested our approach on two publicly available datasets, the KTH dataset and the IXMAS multi-view dataset, and achieved promising results.
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Date Issued: 2012
Identifier: CFE0004626, ucf:49923
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004626

Title: Practical Issues in GPRAM Development.
Creator: Li, Yin, Wei, Lei, Wu, Xinzhang, Mikhael, Wasfy, University of Central Florida
Abstract / Description: In this thesis, two parts of practical issues in the GPRAM system design are included. The first part is the coding part. The sum-product decoding algorithm of LDPC codes has been refined to fit for the GPRAM hardware implementation. As we all know, communication channel has noise. The noise in telecom system is different from that in GPRAM systems. So the noise should be handled well in the GPRAM design. A noise look-up table was created for FPGA and those noises in the table are quantized....
Show moreIn this thesis, two parts of practical issues in the GPRAM system design are included. The first part is the coding part. The sum-product decoding algorithm of LDPC codes has been refined to fit for the GPRAM hardware implementation. As we all know, communication channel has noise. The noise in telecom system is different from that in GPRAM systems. So the noise should be handled well in the GPRAM design. A noise look-up table was created for FPGA and those noises in the table are quantized. The second part of the thesis is to convert perfect images in video stream to those similar to the coarse images in human vision. GPRAM is an animal like robot in which coarse images are needed more than the fine images in order for us to understand how to GPRAM progresses those images to generate as clear image as we experienced. We use three steps, Point Spread function, inserting Poisson Noise, and introducing Eye fixation movements to mimic the coarse images seen merely from our eyes at the retinal photo-receptor level, i.e., without any brain processing.
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Date Issued: 2014
Identifier: CFE0005200, ucf:50632
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005200

Title: Design, Simulation and Characterization of Novel Electrostatic Discharge Protection Devices and Circuits in Advanced Silicon Technologies.
Creator: Liang, Wei, Sundaram, Kalpathy, Fan, Deliang, Jin, Yier, Wei, Lei, Salcedo, Javier, University of Central Florida
Abstract / Description: Electrostatic Discharge (ESD) has been one of the major reliability concerns in the advanced silicon technologies and it becomes more important with technology scaling. It has been reported that more than 35% of the failures in integrated circuits (ICs) are ESD induced. ESD event is a phenomenon that a finite amount of charges transfer between two objects with different potential in a quite short time. Such event contains a large energy and the ICs without proper ESD protection could be...
Show moreElectrostatic Discharge (ESD) has been one of the major reliability concerns in the advanced silicon technologies and it becomes more important with technology scaling. It has been reported that more than 35% of the failures in integrated circuits (ICs) are ESD induced. ESD event is a phenomenon that a finite amount of charges transfer between two objects with different potential in a quite short time. Such event contains a large energy and the ICs without proper ESD protection could be destroyed easily, so ESD protection solutions are essential to semiconductor industry.ESD protection design consists of on-chip and off-chip ESD protection design, and the research works in this dissertation are all conducted in on-chip level, which incorporate the ESD protection devices and circuits into the microchip, to provide with basic ESD protection from manufacturing to customer use. The basic idea of ESD protection design is to provide a path with low impedance which directs most of the ESD current to flow through itself instead of the core circuit, and the ESD protection path must be robust enough to make sure that it does not fail before the core circuit. In this way, proper design on protection devices and circuits should be considered carefully. To assist the understanding and design of ESD protection, the ESD event in real world has been classified into a few ESD model including Human Body Model (HBM), Machine Model (MM), Charged Device Model (CDM), etc. Some mainstream testing method and industry standard are also introduced, including Transmission Line Pulse (TLP), and IEC 61000-4-2. ESD protection devices including diode, Gate-Grounded N-type MOSFET (GGNMOS), Silicon Controlled Rectifier (SCR) are basic elements for ESD protection design. In this dissertation, the device characteristics in ESD event and their applications are introduced. From the perspective of the whole chip ESD protection design, the concept of circuit level ESD protection and the ESD clamps are also briefly introduced. Technology Computer Aided Design (TCAD) and Simulation Program with Integrated Circuit Emphasis (SPICE) simulation is widely used in ESD protection design. In this dissertation, TCAD and SPICE simulation are carried out for a few times for both of pre-tapeout evaluation on characteristics of the proposed device and circuit and post-tapeout analysis on structure operating mechanism.Automotive electronics has been a popular subject in semiconductor industry, and due to the special requirement of the automotive applications like the capacitive pins, the ESD protection device used in such applications need to be specially designed. In this dissertation, a few SCRs without snapback are discussed in detail. To avoid core circuit damages caused the displacement current induced by the large snapback in conventional SCR, an eliminated/minimized snapback is preferred in a selection of the protection device. Two novel SCRs are proposed for High Voltage (HV), Medium Voltage (MV), and Low Voltage (LV) automotive ESD protection.The typical operating temperature for ICs is up to 125 (&)#186;C, however in automotive applications, the operating temperature may extend up to 850 (&)#186;C. In this way, the characteristics of the ESD protection device under the elevated temperatures will be an essential part to investigate for automotive ESD protection design. In this dissertation, the high temperature characteristics of ESD protection devices including diode and a few SCRs is measured and discussed in detail. TCAD simulation are also conducted to explain the underlying physical mechanism. This work provides with a useful insight and information to ESD protection design in high temperature applications.Besides the high temperature environment, ESD protection are also highly needed for electronics working in other extreme environment like the space. Space is an environment that contains kinds of radiation source and at the same time can generate abundant ESD. The ESD adhering to the space systems could be a potential threat to the space electronics. At the same time, the characteristics of the ESD protection part especially the basic protection device used in the space electronics could be influenced after the irradiation in the space. Therefore, the investigation of the radiation effects on ESD protection devices are necessary. In this dissertation, the total ionizing dose (TID) effects on ESD protection devices are investigated. The devices are irradiated with 1.5 MeV He+ and characterized with TLP tester. The pre- and post-irradiation characteristics are compared and the variation on key ESD parameters are analyzed and discussed. This work offers a useful insight on ESD devices' operation under TID and help with the device designing on ESD protection devices for space electronics.Single ESD protection devices are essential part constructing the ESD protection network, however the optimization on ESD clamp circuit design is also important on building an efficient whole chip ESD protection network. In this dissertation, the design and simulation of a novel voltage triggered ESD detection circuit are introduced. The voltage triggered ESD detection circuit is proposed in a 0.18 um CMOS technology. Comparing with the conventional RC based detection circuit, the proposed circuit realizes a higher triggering efficiency with a much smaller footprint, and is immune to false triggering under fast power-up events. The proposed circuit has a better sensitivity to ESD event and is more reliable in ESD protection applications.The leakage current has been a concern with the scaling down of the thickness of the gate oxide. Therefore, a proper design of the ESD clamp for power rail ESD protection need to be specially considered. In this dissertation, a design of a novel ESD clamp with low leakage current is analyzed. The proposed clamp realized a pretty low leakage current up to 12 nA, and has a smaller footprint than conventional design. It also has a long hold-on time under ESD event and a quick turn-off mechanism for false triggering. SPICE simulation is carried out to evaluate the operation of the proposed ESD clamp.
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Date Issued: 2017
Identifier: CFE0007126, ucf:52298
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007126

Title: An Emissive Antenna Correction for The Tropical Rainfall Measuring Mission Microwave Imager (TMI).
Creator: Alquaied, Faisal, Jones, W Linwood, Mikhael, Wasfy, Wei, Lei, Zec, Josko, Wilheit, Thomas, University of Central Florida
Abstract / Description: This dissertation deals with the radiometric calibration of a satellite microwave radiometer known as the TRMM Microwave Imager (TMI), which operated on NASA's Tropical Rainfall Measuring Mission (TRMM). This multi-frequency, conical-scanning, passive microwave, remote sensor measures the earth's blackbody emissions (brightness temperature, Tb) from a low earth orbit and covers the tropics ((&)#177;35(&)deg; latitude). The original scientific objective for TRMM's 3-year mission was to measure...
Show moreThis dissertation deals with the radiometric calibration of a satellite microwave radiometer known as the TRMM Microwave Imager (TMI), which operated on NASA's Tropical Rainfall Measuring Mission (TRMM). This multi-frequency, conical-scanning, passive microwave, remote sensor measures the earth's blackbody emissions (brightness temperature, Tb) from a low earth orbit and covers the tropics ((&)#177;35(&)deg; latitude). The original scientific objective for TRMM's 3-year mission was to measure the statistics of rainfall in the tropics. However, the mission was quite successful, and TRMM was extended for greater than 17 years to provide a long-term satellite rain measurements, which has contributed significantly to the study of global climate change.A significant part of the extended TRMM mission was the establishment of a constellation of satellite radiometer that provide frequent global rainfall measurements that enable severe storm warnings for operational hazard forecast by the international weather community. TRMM played a key role by serving as the radiometric calibration standard for the TRMM constellation microwave radiometers.The objective of this dissertation is to improve the radiometric calibration of TMI and to provide to NASA a new robust, physics-based algorithm for the legacy data processing of the TRMM brightness temperature data product, which will be called TMI 1B11 V8. Moreover, the results of this new procedure have been validated using the double difference techniques with the Global Precipitation Mission Microwave Imager (GMI), which is the replacement satellite mission to TRMM.
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Date Issued: 2017
Identifier: CFE0006711, ucf:51900
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006711

Title: nanoengineered energy harvesting and storage devices.
Creator: Li, Chao, Thomas, Jayan, Zhai, Lei, Yang, Yang, Gesquiere, Andre, Dong, Yajie, Sun, Wei, University of Central Florida
Abstract / Description: Organic and perovskite solar cells have recently attracted significant attention due to itsflexibility, ease of fabrication and excellent performance. In order to realize even betterperformance for organic and perovskite solar cells, rejuvenated effort towards developingnanostructured electrodes and high quality active layer is necessary.In this dissertation, several strategic directions of enhancing the performance of organicand perovskite solar cells are investigated. An introduction and...
Show moreOrganic and perovskite solar cells have recently attracted significant attention due to itsflexibility, ease of fabrication and excellent performance. In order to realize even betterperformance for organic and perovskite solar cells, rejuvenated effort towards developingnanostructured electrodes and high quality active layer is necessary.In this dissertation, several strategic directions of enhancing the performance of organicand perovskite solar cells are investigated. An introduction and background of organic andperovskite solar cells, which includes motivation, classification and working principles,nanostructured electrode materials and solvent effect on active materials, and devices fabrication,are presented. A facile method, called Spin-on Nanoprinting (SNAP), to fabricate highly orderedZnO-AgNW-ZnO electrode is introduced to enhance the performance of organic solar cell.Subsequently, a ternary solvent method is developed to fabricate high Voc thieno[3,4-b]thiophene/benzodithiophene (PTB7) and indene-C60 bisadduct (ICBA)solar cells. Theperformance of the devices improved about 20% compared to those made by binary solventmethod. In order to understand the fundamental properties of the materials ruling theperformance of the PSCs tested, AFM-based nanoscale characterization techniques includingPulsed-Force-Mode AFM (PFM-AFM) and Mode-Synthesizing AFM (MSAFM) are introduced.These methods are used to study the morphology and physical properties of the structuresconstitutive of the active layers of the PSCs. Conductive-AFM (cAFM) studies reveal localvariations in conductivity in the donor and acceptor phases as well as an increase in photocurrentmeasured in the PTB7:ICBA sample obtained with the ternary solvent processing technique.Moreover, efficient perovskite solar cells with good transparency in the visible wavelength rangehave been developed by a facile and low-temperature PCBM-assisted perovskite growth method.This method results in the formation of perovskite-PCBM hybrid material at the grain boundaries which is observed by EELS mapping and confirmed by steady-state photoluminescence (PL)spectra and transient photocurrent (TP) measurements. This method involves fewer steps andtherefore is less expensive and time consuming than other reported methods. In addition, wereport an all solid state, energy harvesting and storing (ENHANS) filament which integratesperovskite solar cell (PSC) on top of a symmetric supercapacitor (SSC) via a copper filamentwhich works as a shared electrode for direct charge transfer. Developing ENHANS on a copperfilament provides a low-cost solution for flexible self-sufficient energy systems for wearablesand other portable devices. Finally, a summary of this dissertation as well as some potentialfuture directions are presented.
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Date Issued: 2016
Identifier: CFE0006693, ucf:51912
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006693

Title: DESIGN OF HIGH EFFICIENCY BRUSHLESS PERMANENT MAGNET MACHINES AND DRIVER SYSTEM.
Creator: He, Chengyuan, Wei, Lei, Sundaram, Kalpathy, Zhou, Qun, Jin, Yier, Zou, Shengli, University of Central Florida
Abstract / Description: The dissertation is concerned with the design of high-efficiency permanent magnet synchronous machinery and the control system. The dissertation first talks about the basic concept of the permanent magnet synchronous motor (PMSM) design and the mathematics design model of the advanced design method. The advantage of the design method is that it can increase the high load capacity at no cost of increasing the total machine size. After that, the control method of the PMSM and Permanent magnet...
Show moreThe dissertation is concerned with the design of high-efficiency permanent magnet synchronous machinery and the control system. The dissertation first talks about the basic concept of the permanent magnet synchronous motor (PMSM) design and the mathematics design model of the advanced design method. The advantage of the design method is that it can increase the high load capacity at no cost of increasing the total machine size. After that, the control method of the PMSM and Permanent magnet synchronous generator (PMSG) is introduced. The design, simulation, and test of a permanent magnet brushless DC (BLDC) motor for electric impact wrench and new mechanical structure are first presented based on the design method. Finite element analysis based on the Maxwell 2D is built to optimize the design and the control board is designed using Altium Designer. Both the motor and control board have been fabricated and tested to verify the design. The electrical and mechanical design are combined, and it provides an analytical IPMBLDC design method and an innovative and reasonable mechanical dynamical calculation method for the impact wrench system, which can be used in whole system design of other functional electric tools. A 2kw high-efficiency alternator system and its control board system are also designed, analyzed and fabricated applying to the truck auxiliary power unit (APU). The alternator system has two stages. The first stage is that the alternator three-phase outputs are connected to the three-phase active rectifier to get 48V DC. An advanced Sliding Mode Observer (SMO) is used to get an alternator position. The buck is used for the second stage to get 14V DC output. The whole system efficiency is much higher than the traditional system using induction motor.
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Date Issued: 2018
Identifier: CFE0007334, ucf:52135
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007334

Title: Design of Low-Capacitance Electrostatic Discharge (ESD) Protection Devices in Advanced Silicon Technologies.
Creator: Dong, Aihua, Sundaram, Kalpathy, Fan, Deliang, Gong, Xun, Wei, Lei, Salcedo, Javier, University of Central Florida
Abstract / Description: Electrostatic discharge (ESD) related failure is a major IC reliability concern and this is particularly true as technology continues shrink to nano-metric dimensions. ESD design window research shows that ESD robustness of victim devices keep decreasing from 350nm bulk technology to 7nm FinFET technologies. In the meantime, parasitic capacitance of ESD diode with same It2 in FinFET technologies is approximately 3X compared with that in planar technologies. Thus transition from planar to...
Show moreElectrostatic discharge (ESD) related failure is a major IC reliability concern and this is particularly true as technology continues shrink to nano-metric dimensions. ESD design window research shows that ESD robustness of victim devices keep decreasing from 350nm bulk technology to 7nm FinFET technologies. In the meantime, parasitic capacitance of ESD diode with same It2 in FinFET technologies is approximately 3X compared with that in planar technologies. Thus transition from planar to FinFET technology requires more robust ESD protection however the large parasitic capacitance of ESD protection cell is problematic in high-speed interface design. To reduce the parasitic capacitance, a dual diode silicon controlled rectifier (DD-SCR) is presented in this dissertation. This design can exhibit good trade-offs between ESD robustness and parasitic capacitance characteristics. Besides, different bounding materials lead to performance variations in DD-SCRs are compared. Radio frequency (RF) technology is also demanded low capacitance ESD protection. To address this concern, a ?-network is presented, providing robust ESD protection for 10-60 GHz RF circuit. Like a low pass ? filter, the network can reflect high frequency RF signals and transmit low frequency ESD pulses. Given proper inductor value, networks can work as robust ESD solutions at a certain Giga Hertz frequency range, making this design suitable for broad band protection in RF input/outputs (I/Os). To increase the holding voltage and reduce snapback, a resistor assist triggering heterogeneous stacking structure is presented in this dissertation, which can increase the holding voltage and also keep the trigger voltage nearly as same as a single SCR device.
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Date Issued: 2018
Identifier: CFE0007172, ucf:52251
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007172

Title: Bootstrapping Cognitive Radio Networks.
Creator: Horine, Brent, Turgut, Damla, Wei, Lei, Boloni, Ladislau, Sukthankar, Gita, Garibay, Ivan, University of Central Florida
Abstract / Description: Cognitive radio networks promise more efficient spectrum utilization by leveraging degrees of freedom and distributing data collection. The actual realization of these promises is challenged by distributed control, and incomplete, uncertain and possibly conflicting knowledge bases. We consider two problems in bootstrapping, evolving, and managing cognitive radio networks. The first is Link Rendezvous, or how separate radio nodes initially find each other in a spectrum band with many degrees...
Show moreCognitive radio networks promise more efficient spectrum utilization by leveraging degrees of freedom and distributing data collection. The actual realization of these promises is challenged by distributed control, and incomplete, uncertain and possibly conflicting knowledge bases. We consider two problems in bootstrapping, evolving, and managing cognitive radio networks. The first is Link Rendezvous, or how separate radio nodes initially find each other in a spectrum band with many degrees of freedom, and little shared knowledge. The second is how radio nodes can negotiate for spectrum access with incomplete information.To address the first problem, we present our Frequency Parallel Blind Link Rendezvous algorithm. This approach, designed for recent generations of digital front-ends, implicitly shares vague information about spectrum occupancy early in the process, speeding the progress towards a solution. Furthermore, it operates in the frequency domain, facilitating a parallel channel rendezvous. Finally, it operates without a control channel and can rendezvous anywhere in the operating band. We present simulations and analysis on the false alarm rate for both a feature detector and a cross-correlation detector. We compare our results to the conventional frequency hopping sequence rendezvous techniques.To address the second problem, we model the network as a multi-agent system and negotiate by exchanging proposals, augmented with arguments. These arguments include information about priority status and the existence of other nodes. We show in a variety of network topologies that this process leads to solutions not otherwise apparent to individual nodes, and achieves superior network throughput, request satisfaction, and total number of connections, compared to our baselines. The agents independently formulate proposals based upon communication desires, evaluate these proposals based upon capacity constraints, create arguments in response to proposal rejections, and re-evaluate proposals based upon received arguments. We present our negotiation rules, messages, and protocol and demonstrate how they interoperate in a simulation environment.
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Date Issued: 2012
Identifier: CFE0004546, ucf:49240
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004546

Title: Performance Evaluation of Connectivity and Capacity of Dynamic Spectrum Access Networks.
Creator: Al-tameemi, Osama, Chatterjee, Mainak, Bassiouni, Mostafa, Jha, Sumit, Wei, Lei, Choudhury, Sudipto, University of Central Florida
Abstract / Description: Recent measurements on radio spectrum usage have revealed the abundance of under- utilized bands of spectrum that belong to licensed users. This necessitated the paradigm shift from static to dynamic spectrum access (DSA) where secondary networks utilize unused spectrum holes in the licensed bands without causing interference to the licensed user. However, wide scale deployment of these networks have been hindered due to lack of knowledge of expected performance in realistic environments and...
Show moreRecent measurements on radio spectrum usage have revealed the abundance of under- utilized bands of spectrum that belong to licensed users. This necessitated the paradigm shift from static to dynamic spectrum access (DSA) where secondary networks utilize unused spectrum holes in the licensed bands without causing interference to the licensed user. However, wide scale deployment of these networks have been hindered due to lack of knowledge of expected performance in realistic environments and lack of cost-effective solutions for implementing spectrum database systems. In this dissertation, we address some of the fundamental challenges on how to improve the performance of DSA networks in terms of connectivity and capacity. Apart from showing performance gains via simulation experiments, we designed, implemented, and deployed testbeds that achieve economics of scale. We start by introducing network connectivity models and show that the well-established disk model does not hold true for interference-limited networks. Thus, we characterize connectivity based on signal to interference and noise ratio (SINR) and show that not all the deployed secondary nodes necessarily contribute towards the network's connectivity. We identify such nodes and show that even-though a node might be communication-visible it can still be connectivity-invisible. The invisibility of such nodes is modeled using the concept of Poisson thinning. The connectivity-visible nodes are combined with the coverage shrinkage to develop the concept of effective density which is used to characterize the con- nectivity. Further, we propose three techniques for connectivity maximization. We also show how traditional flooding techniques are not applicable under the SINR model and analyze the underlying causes for that. Moreover, we propose a modified version of probabilistic flooding that uses lower message overhead while accounting for the node outreach and in- terference. Next, we analyze the connectivity of multi-channel distributed networks and show how the invisibility that arises among the secondary nodes results in thinning which we characterize as channel abundance. We also capture the thinning that occurs due to the nodes' interference. We study the effects of interference and channel abundance using Poisson thinning on the formation of a communication link between two nodes and also on the overall connectivity of the secondary network. As for the capacity, we derive the bounds on the maximum achievable capacity of a randomly deployed secondary network with finite number of nodes in the presence of primary users since finding the exact capacity involves solving an optimization problem that shows in-scalability both in time and search space dimensionality. We speed up the optimization by reducing the optimizer's search space. Next, we characterize the QoS that secondary users can expect. We do so by using vector quantization to partition the QoS space into finite number of regions each of which is represented by one QoS index. We argue that any operating condition of the system can be mapped to one of the pre-computed QoS indices using a simple look-up in Olog (N) time thus avoiding any cumbersome computation for QoS evaluation. We implement the QoS space on an 8-bit microcontroller and show how the mathematically intensive operations can be computed in a shorter time. To demonstrate that there could be low cost solutions that scale, we present and implement an architecture that enables dynamic spectrum access for any type of network ranging from IoT to cellular. The three main components of this architecture are the RSSI sensing network, the DSA server, and the service engine. We use the concept of modular design in these components which allows transparency between them, scalability, and ease of maintenance and upgrade in a plug-n-play manner, without requiring any changes to the other components. Moreover, we provide a blueprint on how to use off-the-shelf commercially available software configurable RF chips to build low cost spectrum sensors. Using testbed experiments, we demonstrate the efficiency of the proposed architecture by comparing its performance to that of a legacy system. We show the benefits in terms of resilience to jamming, channel relinquishment on primary arrival, and best channel determination and allocation. We also show the performance gains in terms of frame error rater and spectral efficiency.
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Date Issued: 2016
Identifier: CFE0006063, ucf:50980
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006063

UWB (4)	+ -
Cognitive Radio (2)	+ -
ESD (2)	+ -
OFDM (2)	+ -
TRMM (2)	+ -

Temperature (2)	+ -
connectivity (2)	+ -
(2D)^2PCA (1)	+ -
2DPCA (1)	+ -
Active Mixer (1)	+ -
Advanced Coding (1)	+ -
Amplifier (1)	+ -
Aquarius (1)	+ -
Argumentation (1)	+ -
Battery (1)	+ -
CFD (1)	+ -
CMOS (1)	+ -
CONOE Microwave Radiometer (1)	+ -
Channel Model (1)	+ -
Charge Injection (1)	+ -
Coherent Fiber Communication (1)	+ -
Compressive Sensing (1)	+ -
Coupling Unit (1)	+ -
DCT (1)	+ -
Density Evolution (1)	+ -
Digital Backward Propagation (1)	+ -
Digital Modulation (1)	+ -
Diode (1)	+ -
Discrete Cosine Transform (1)	+ -
Discrete Multiwavelet Transform (1)	+ -

University of Central Florida (32)	+ -
Wei, Lei (29)	+ -
Mikhael, Wasfy (8)	+ -
Sundaram, Kalpathy (7)	+ -
Atia, George (4)	+ -

Jones, W Linwood (4)	+ -
Rahnavard, Nazanin (4)	+ -
Vosoughi, Azadeh (4)	+ -
Lin, Mingjie (3)	+ -
Yuan, Jiann-Shiun (3)	+ -
Chatterjee, Mainak (2)	+ -
Chow, Louis (2)	+ -
Fan, Deliang (2)	+ -
Jin, Yier (2)	+ -
Myers, Brent (2)	+ -
Qu, Zhihua (2)	+ -
Salcedo, Javier (2)	+ -
Sukthankar, Gita (2)	+ -
Turgut, Damla (2)	+ -
Wahid, Parveen (2)	+ -
Wilheit, Thomas (2)	+ -
Wu, Thomas (2)	+ -
Wu, Xinzhang (2)	+ -
Al-tameemi, Osama (1)	+ -
Alabri, Said (1)	+ -
Aldhahab, Ahmed (1)	+ -
Alquaied, Faisal (1)	+ -
Alrasheed, Waleed (1)	+ -
Bassiouni, Mostafa (1)	+ -
Berksoy, Burak (1)	+ -

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