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1 
A Fast Sphere Decoding Algorithm for Rank Deficient MIMO SystemsAhmed, Ahmed January 2007 (has links)
The problem of rank deficient multiple input multiple out (MIMO) systems arises when the number of transmit antennas M is greater than number of receive antennas N or when the channel gains are strongly correlated.
Most of the optimal algorithms that deal with uncoded rankdeficient (underdetermined) VBLAST MIMO systems (e.g. Damen ,Meraim and Belfiore) suffer from high complexity and large processing time. Recently, some new optimal algorithms were introduced with low complexity for small constellations like 4QAM yet they still suffer from very high complexity and processing time with large constellations like the 16 QAM.
In order to reduce the complexity and the processing time of the decoding algorithms, some suboptimal algorithms were introduced. One of the most efficient suboptimal solutions for this problem is based on the Minimum mean square error decisionfeedback equalizer (MMSEDFE) followed by either sphere decoder or fano decoder. The performance of these algorithms is shown to be a fraction of dB from the maximum likelihood decoders while offering outstanding reduction in complexity compared to the most efficient ML algorithms (e.g. Cui and Tellambura algorithm).
These suboptimal algorithms employ a two stage approach. In the first stage, the channel is preprocessed to transform the original decoding problem into a simpler form which facilitates the search decoding step. The second stage is basically the application of the sphere decoding search algorithm in the case of MMSEDFE sphere decoding step or Fano decoder in the case of MMSEDFE Fano decoder.
In this study, various algorithms which deal with rank deficient MIMO systems such as Damen,Meraim and Belfiore algorithm ,Dayal and Varansi algorithm, and Cui and Tellambura algorithm are discussed and compared. Moreover, the MMSEDFE sphere decoding algorithm and MMSEDFE fano decoding algorithm are applied on uncoded VBLAST rank deficient MIMO systems. The optimality of MMSEDFE sphere decoding algorithm is analyzed in the case of VBLAST 4QAM. Furthermore, Simulation results show that when these algorithms are extended to cover large constellations, their performance falls within a fraction of dB behind the ML while achieving a significant decrease in the processing time by more than an order of magnitude when compared to the least

2 
Short Wavelength aSi:H Photodetector for Biomolecular Fragment SizingKhodami, Ida 12 1900 (has links)
A gel electrophoresis technology based on absorption of ultraviolet radiation for fragment sizing of biomolecular segments such as protein and nucleic acid is introduced for the first time. The new technology has the potential to improve conventional gel electrophoresis method by lowering the cost and increasing the throughpxcvfut. A cost effective, high sensitivity, short wavelength selective detector is an essential component to enable the proposed technology. In this thesis, hydrogenated amorphous silicon (aSi:H) metal semiconductor metal(MSM) are investigated as the short wavelength detector of choice. The operation of planar MSM photoconductorbased photo detectors with very thin aSi:H film thickness and aluminium electrodes is investigated. Experimental results of photocurrent measurements as well as responsivity and quantum efficiency are presented. The MSM photodetectors presented are fully compatible with stateoftheart staggered gate thin film transistor (TFT) fabrication processes to enable large area pixel arrays for biomolecular imaging.

3 
Access Network Selection in a 4G Networking EnvironmentLiu, Yang January 2008 (has links)
An allIP pervasive networking system provides a comprehensive IP solution where voice, data and streamed multimedia can be delivered to users at anytime and anywhere. Network selection is a key issue in this converged heterogeneous networking environment. A traditional way to select a target network is only based on the received signal strength (RSS); however, it is not comprehensive enough to meet the various demands of different multimedia applications and different users. Though some existing schemes have considered multiple criteria (e.g. QoS, security, connection cost, etc.) for access network selection, there are still several problems unsettled or not being solved perfectly. In this thesis, we propose a novel model to handle this network selection issue. Firstly, we take advantage of IEEE 802.21 to obtain the information of neighboring networks and then classify the information into two categories: 1) compensatory information and 2) noncompensatory information; secondly, we use the noncompensatory information to sort out the capable networks as candidates. If a neighboring network satisfies all the requirements of noncompensatory criteria, the checking of the compensatory information will then be triggered; thirdly, taking the values of compensatory information as input, we propose a hybrid ANP and RTOPSIS model to rank the candidate networks. ANP elicit weights to compensatory criteria and eliminates the interdependence impact on them, and RTOPSIS resolves the rank reversal problem which happens in some multiple criteria decision making (MCDM) algorithms such as AHP, TOPSIS, and ELECTRE. The evaluation study verifies the usability and validity of our proposed network selection method. Furthermore, a comparison study with a TOPSIS based algorithm shows the advantage and superiority of the proposed RTOPSIS based model.

4 
Upper Bounds to the Capacity of Wireless NetworksChu, Xiaoyu January 2008 (has links)
In this thesis, I mainly focus on the evaluation of the upper bounds to the capacity of wireless networks. With the consideration of the two measures, the maximal transmission rate for any sourcedestination pair and the transport capacity of wireless networks, I summarize the most recent results to the upper bounds of these two measures first in this thesis. At the same time, I also improve and modify the previous results given in these papers. Moreover, I present a proof to the upper bound of maximal transmission rate with high probability by taking the fading of the channel into account when the full CSI is only known to the receivers. With a simple extension of the result, I derive an upper bound to the transport capacity of wireless networks without full CSI at the receiver side. A linear scaling of the upper bound to transport capacity is also derived when the path loss exponent is greater than three. Compared with the previous results, it is shown that the upper bound given in this thesis is much better for relatively large alpha and a minimum distance constraint.

5 
Economical and Environmentally Friendly Geocast Routing in Vehicular NetworksAlsabaan, Maazen January 2013 (has links)
The volatile world economy has greatly affected fuel prices, while pollution and gas emissions are increasing to negatively impact global warming. Rising fuel costs have made drivers more concerned about how much of their monthly budgets are allocated for gasoline. In terms of the air pollution problem, greenhouse gas (GHG) emissions from vehicles are considered to be one of the main contributing sources. Carbon dioxide (CO₂) is the largest component of GHG emissions. As a result, it is important to develop and implement effective strategies to reduce fuel expenditure and prevent the expected increase of CO₂ emission from vehicles.
Vehicular networks offer a promising approach that can be applied in transportation systems to reduce fuel consumption and emissions. One of the major applications of vehicular networks is intelligent transportation systems (ITS). To exchange and distribute messages, geocast routing protocols have been proposed for ITS applications. Most of these protocols focus on improving networkcentric performance measures (e.g., message delay, packet delivery ratio, etc.) instead of focusing on improving the performance measures that are meaningful to both the scientific community and the general public (e.g., fuel consumption and CO₂ emission).
Stopandgo conditions, high acceleration, and unnecessary speed are uneconomical and environmentally unfriendly (UEU) actions that increase the amount of vehicle fuel consumed and the CO₂ emission. These actions can happen frequently for vehicles approaching a traffic light signal (TLS). This thesis proposes a new protocol named Economical and Environmentally Friendly Geocast (EEFG), which focuses on minimizing CO₂ emission and fuel consumption from vehicles approaching a TLS. The goal of this protocol is to deliver useful information to approaching vehicles inside the regions of interest (ROIs). Based on the information sent, the vehicle receiving the message adapts its speed to a recommended speed (Sʀ), which helps the vehicle reduce its UEU actions.
To determine the value of Sʀ, a comprehensive optimization model that is applicable in both vehicletovehicle (V2V) communication and traffic light signaltovehicle (TLS2V) communication is developed. The objective function is to minimize fuel consumption by and emissions from vehicles. The speed that can achieve this goal is the optimum Sʀ
(Sʀ*). The thesis also proposes efficient heuristic expressions to compute the optimum or nearoptimum value of Sʀ.
An extensive performance study of the EEFG protocol is performed. It shows the impact of using EEFG in a modeled realworld network for urban and suburban areas in the city of Waterloo, Ontario, Canada. Four case studies have been considered: (1) a suburban environment at the maximum traffic volume hour of the day; (2) a suburban environment at the minimum traffic volume hour of the day; (3) an urban environment at the maximum traffic volume hour of the day; (4) an urban environment at the minimum traffic volume hour of the day. The results show that EEFG saves fuel and CO₂ emission in all four cases. In addition, the thesis studies the effect of communication parameters (e.g., transmission range, packet delay, and packet dropping rate) on vehicle fuel consumption
and CO₂ emission. Having high transmission range, low packet delay, and low packet dropping rate, can save more fuel and CO₂ emission.

6 
Geometric Modeling and Optimization Over Regular Domains for Graphics and Visual ComputingWan, Shenghua 09 September 2013 (has links)
The effective construction of parametric representation of complicated geometric objects can facilitate many design,
analysis, and simulation tasks in ComputerAided Design (CAD), ComputerAided Manufacturing (CAM), and ComputerAided Engineering (CAE).
Given a 3D shape, the procedure of finding such a parametric representation upon a canonical domain is called geometric parameterization.
Regular geometric regions, such as polycubes and spheres, are desirable domains for parameterization.
Parametric representations defined upon regular geometric domains have many desirable mathematical properties
and can facilitate or simplify various surface/solid modeling and processing computation.
This dissertation studies the construction of parameterization on regular geometric domains and explores their applications in shape modeling and computeraided design.
Specifically, we studies (1) the surface parameterization on the spherical domain for closed genuszero surfaces;
(2) the surface parameterization on the polycube domain for general closed surfaces;
and (3) the volumetric parameterization for 3Dmanifolds embedded in 3D Euclidean space.
We propose novel computational models to solve these geometric problems.
Our computational models reduce to nonlinear optimizations with various geometric constraints.
Hence, we also need to explore effective optimization algorithms.
The main contributions of this dissertation are threefolded.
(1) We developed an effective progressive spherical parameterization algorithm, with an efficient nonlinear optimization scheme subject to the spherical constraint.
Compared with the stateoftheart spherical mapping algorithms, our algorithm demonstrates the advantages of great efficiency,
lower distortion, and guaranteed bijectiveness, and we show its applications in spherical harmonic decomposition and shape analysis.
(2) We propose a first topologypreserving polycube domain optimization algorithm that simultaneously optimizes polycube domain together
with the parameterization to balance the mapping distortion and domain simplicity.
We develop effective nonlinear geometric optimization algorithms dealing with variables with and without derivatives.
This polycube parameterization algorithm can benefit the regular quadrilateral mesh generation and crosssurface parameterization.
(3) We develop a novel quaternionbased optimization framework for 3D frame field construction and volumetric parameterization computation.
We demonstrate our constructed 3D frame field has better smoothness, compared with stateoftheart algorithms,
and is effective in guiding lowdistortion volumetric parameterization and highquality hexahedral mesh generation.

7 
Heterogeneous Volumetric Data Mapping and its Medical ApplicationsXu, Huanhuan 09 July 2013 (has links)
With the advance of data acquisition techniques, massive solid geometries are being collected routinely in scientific tasks, these complex and unstructured data need to be effectively correlated for various processing and analysis.
Volumetric mapping solves bijective lowdistortion correspondence between/among 3D geometric data, and can serve as an important preprocessing step in many tasks in computeaided design and analysis, industrial manufacturing, medical image analysis, to name a few.
This dissertation studied two important volumetric mapping problems: the mapping of heterogeneous volumes (with nonuniform inner structures/layers) and the mapping of sequential dynamic volumes.
To effectively handle heterogeneous volumes, first, we studied the featurealigned harmonic volumetric mapping. Compared to previous harmonic mapping, it supports the point, curve, and isosurface alignment, which are important lowdimensional structures in heterogeneous volumetric data.
Second, we proposed a biharmonic model for volumetric mapping. Unlike the conventional harmonic volumetric mapping that only supports positional continuity on the boundary, this new model allows us to have higher order continuity $C^1$ along the boundary surface. This suggests a potential model to solve the volumetric mapping of complex and big geometries through divideandconquer.
We also studied the medical applications of our volumetric mapping in lung tumor respiratory motion modeling. We were building an effective digital platform for lung tumor radiotherapy based on effective volumetric CT/MRI image matching and analysis. We developed and integrated in this platform a set of geometric/image processing techniques including advanced image segmentation, finite element meshing, volumetric registration and interpolation. The lung organ/tumor and surrounding tissues are treated as a heterogeneous region and a dynamic 4D registration framework is developed for lung tumor motion modeling and tracking.
Compared to the previous 3D pairwise registration, our new 4D parameterization model leads to a significantly improved registration accuracy. The constructed deforming model can hence approximate the deformation of the tissues and tumor.

8 
Achievable Secrecy Enhancement Through Joint Encryption and Privacy AmplificationSowti Khiabani, Yahya 18 June 2013 (has links)
In this dissertation we try to achieve secrecy enhancement in communications by resorting
to both cryptographic and information theoretic secrecy tools and metrics. Our objective
is to unify tools and measures from cryptography community with techniques and metrics
from information theory community that are utilized to provide privacy and confidentiality
in communication systems. For this purpose we adopt encryption techniques accompanied
with privacy amplification tools in order to achieve secrecy goals that are determined based
on information theoretic and cryptographic metrics.
Every secrecy scheme relies on a certain advantage for legitimate users over adversaries
viewed as an asymmetry in the system to deliver the required security for data transmission.
In all of the proposed schemes in this dissertation, we resort to either inherently existing asymmetry in the system or proactively created advantage for legitimate users over a passive eavesdropper to further enhance secrecy of the communications. This advantage is manipulated by means of privacy amplification and encryption tools to achieve secrecy goals for the
system evaluated based on information theoretic and cryptographic metrics.
In our first work discussed in Chapter 2 and the third work explained in Chapter 4, we
rely on a proactively established advantage for legitimate users based on eavesdroppers lack of knowledge about a shared source of data. Unlike these works that assume an errorfree
physical channel, in the second work discussed in Chapter 3 correlated erasure wiretap
channel model is considered. This work relies on a passive and internally existing advantage
for legitimate users that is built upon statistical and partial independence of eavesdroppers channel errors from the errors in the main channel. We arrive at this secrecy advantage for legitimate users by exploitation of an authenticated but insecure feedback channel.
From the perspective of the utilized tools, the first work discussed in Chapter 2 considers
a specific scenario where secrecy enhancement of a particular block cipher called Data Encryption
standard (DES) operating in cipher feedback mode (CFB) is studied. This secrecy enhancement is achieved by means of deliberate noise injection and wiretap channel encoding as a technique for privacy amplification against a resource constrained eavesdropper. Compared to the first work, the third work considers a more general framework in terms of both metrics and secrecy tools. This work studies secrecy enhancement of a general cipher based on universal hashing as a privacy amplification technique against an unbounded adversary. In this work, we have achieved the goal of exponential secrecy where information leakage to adversary, that is assessed in terms of mutual information as an information theoretic measure and Eves distinguishability as a cryptographic metric, decays at an exponential rate. In the second work generally encrypted data frames are transmitted through Automatic Repeat reQuest (ARQ) protocol to generate a common random source between legitimate users that later on is transformed into information theoretically secure keys for encryption by means of privacy amplification based on universal hashing.
Towards the end, future works as an extension of the accomplished research in this dissertation
are outlined. Proofs of major theorems and lemmas are presented in the Appendix.

9 
High Capacity Digital Beam Steering TechnologyHebert, Daniel James 19 June 2013 (has links)
A novel method is described in detail for steering light in many directions without moving mechanical parts. The method involves a combination of liquid crystal cells and polarizing beam splitters. The polarization at each beam splitter is controlled by applying a signal to its corresponding liquid crystal cell.
A study of light steering techniques is described for efficient beam placement, in a line and plane.
These techniques permit accurate, nonmechanical, beam steering limited by the response time of the liquid crystal cells. A theoretical limit to the number of discrete directions is described and closely approached for a one dimensional system.

10 
Threshold Voltage Instability and Relaxation in Hydrogenated Amorphous Silicon Thin Film TransistorsAkhavan Fomani, Arash January 2005 (has links)
This thesis presents a study of the biasinduced threshold voltage metastability phenomenon of the hydrogenated amorphous silicon (aSi:H) thin film transistors (TFTs). An application of gate bias stress shifts the threshold voltage of a TFT. After the bias stress is removed, the threshold voltage eventually returns to its original value. The underlying physical mechanisms for the shift in threshold voltage during the application of the bias and after the removal of the bias stress are investigated. <br /><br /> The creation of extra defect states in the band gap of aSi:H close to the gate dielectric interface, and the charge trapping in the silicon nitride (SiN) gate dielectric are the most commonly considered instability mechanisms of threshold voltage. In the first part of this work, the defect state creation mechanism is reviewed and the kinetics of the charge trapping in the SiN is modelled assuming a simplified monoenergetic and a more realistic Gaussian distribution of the SiN traps. The charge trapping in the monoenergetic SiN traps was approximated by a logarithmic function of time. However, the charge trapping with a Gaussian distribution of SiN traps results in a more complex behavior. <br /><br /> The change in the threshold voltage of a TFT after the gate bias has been removed is referred to threshold voltage relaxation, and it is investigated in the second part of this work. A study of the threshold voltage relaxation sheds more light on the metastability mechanisms of aSi:H TFTs. Possible mechanisms considered for the relaxation of threshold voltage are the annealing of the extra defect states and the charge detrapping from the SiN gate dielectric. The kinetics of the charge detrapping from a monoenergetic and a Gaussian distribution of the SiN traps are analytically modelled. It is shown that the defect state annealing mechanisms cannot explain the observed threshold voltage relaxation, but a study of the kinetics of charge detrapping helps to bring about a very good agreement with the experimentally obtained results. Using the experimentally measured threshold voltage relaxation results, a Gaussian distribution of gap states is extracted for the SiN. This explains the threshold voltage relaxation of TFT after the bias stress with voltages as high as 50V is removed. <br /><br /> Finally, the results obtained from the threshold voltage relaxation make it possible to calculate the total charge trapped in the SiN and to quantitatively distinguish between the charge trapping mechanism and the defect state creation mechanisms. In conclusion, for the TFTs used in this thesis, the charge trapping in the SiN gate dielectric is shown to be the dominant threshold voltage metastability mechanism caused in short bias stress times.

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