Dissertations / Theses on the topic 'Error propagation'
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1
Robinson, Anthony John. "Dynamic error propagation networks." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303145.
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Lu, Chun. "The error propagation in robots." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5871.
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The accuracy of a robot manipulator has been receiving scrutinity since the widespread acceptance of robot manipulators. The relationship between two consecutive joint coordinate frames of a robot manipulator can be completely defined by five link parameters; one is the joint variable and the other four are the geometric parameters. The basis for the open-loop manipulator control is often the relationship between the Cartesian coordinates of the end-effector and the joint coordinates; therefore, the accuracy of the Cartesian position and orientation of the end-effector with regard to the real world depends on the errors of the five link parameters for each link. For design optimization and robot calibration, it is very important to develop a model for quantitative characterization and evaluation of the positioning and orientational errors of the end-effector. A static error propagation model is developed in order to describe the relationships between the six Cartesian errors and the five independent kinematic errors for each link. In this thesis, a general method for evaluating the end-effector errors produced by a mix of arbitrarily distributed errors is presented. Based on this method, any different combinations of biased and mixed error distributions can be dealt with directly to give a quantative error propagation analysis. Numerical results are presented for one, two and three degrees-of-freedom robot manipulators. Comparison of the results of the proposed model with other published model are presented and analyzed.
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Deslandes, Jeffrey E. "Error propagation through digital demultiplexers." Thesis, University of Essex, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280874.
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Garufi, David (David J. ). "Error propagation in concurrent product development." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118550.
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Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, System Design and Management Program, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (page 68).
System dynamics modelling is used to explore varying levels of concurrency in a typical design-build-produce project introducing a new product. Faster product life-cycles and demanding schedules have introduced the importance of beginning downstream work (build/manufacturing) while upstream work (design) is incomplete. Conceivably, this project concurrency improves project schedule and cost by forcing rework to be discovered and completed earlier in the project life. Depending on the type of project, some design errors may only be discoverable once the build phase has begun its work. Namely, systemic errors and assembly errors that cannot be easily discovered within the design phase. Pushing build activity earlier in the project allows the rework to be discovered earlier in the project, shortening the overall effort required to complete the project. A mathematical simulation, created using Vensim@ system modeling software, was created by James Lyneis to simulate two-phase rework cycles. The model was tuned to match data based on a disguised real project. Various start dates (as a function of project percentage complete) for downstream phases were explored to find optimal levels of concurrency. Project types were varied by exploring three levels of "rework discoverable within the design phase" to cover a range of project types. The simulation found that for virtually all project types, significant schedule and effort benefits can be gained by introducing the downstream phase as early as 30% to 40% into the project progress and ramping downstream effort over an extended period of time.
by David Garufi.
S.M. in Engineering and Management
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Utcke, Sven. "Error propagation in geometry-based grouping." [S.l. : s.n.], 2006.
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Dumont, Pascal. "Error propagation calculation in groundwater vulnerability models." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27212.
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Blukacz, Edyta Agnes. "Error propagation in ecology, an aquatic example." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58714.pdf.
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Morgan, Keith S. "SEU-Induced Persistent Error Propagation in FPGAs." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1377.pdf.
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Alboabidallah, Ahmed Hussein Hamdullah. "Error propagation analysis for remotely sensed aboveground biomass." Thesis, University of Plymouth, 2018. http://hdl.handle.net/10026.1/13074.
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Above-Ground Biomass (AGB) assessment using remote sensing has been an active area of research since the 1970s. However, improvements in the reported accuracy of wide scale studies remain relatively small. Therefore, there is a need to improve error analysis to answer the question: Why is AGB assessment accuracy still under doubt? This project aimed to develop and implement a systematic quantitative methodology to analyse the uncertainty of remotely sensed AGB, including all perceptible error types and reducing the associated costs and computational effort required in comparison to conventional methods. An accuracy prediction tool was designed based on previous study inputs and their outcome accuracy. The methodology used included training a neural network tool to emulate human decision making for the optimal trade-off between cost and accuracy for forest biomass surveys. The training samples were based on outputs from a number of previous biomass surveys, including 64 optical data based studies, 62 Lidar data based studies, 100 Radar data based studies, and 50 combined data studies. The tool showed promising convergent results of medium production ability. However, it might take many years until enough studies will be published to provide sufficient samples for accurate predictions. To provide field data for the next steps, 38 plots within six sites were scanned with a Leica ScanStation P20 terrestrial laser scanner. The Terrestrial Laser Scanning (TLS) data analysis used existing techniques such as 3D voxels and applied allometric equations, alongside exploring new features such as non-plane voxel layers, parent-child relationships between layers and skeletonising tree branches to speed up the overall processing time. The results were two maps for each plot, a tree trunk map and branch map. An error analysis tool was designed to work on three stages. Stage 1 uses a Taylor method to propagate errors from remote sensing data for the products that were used as direct inputs to the biomass assessment process. Stage 2 applies a Monte Carlo method to propagate errors from the direct remote sensing and field inputs to the mathematical model. Stage 3 includes generating an error estimation model that is trained based on the error behaviour of the training samples. The tool was applied to four biomass assessment scenarios, and the results show that the relative error of AGB represented by the RMSE of the model fitting was high (20-35% of the AGB) in spite of the relatively high correlation coefficients. About 65% of the RMSE is due to the remote sensing and field data errors, with the remaining 35% due to the ill-defined relationship between the remote sensing data and AGB. The error component that has the largest influence was the remote sensing error (50-60% of the propagated error), with both the spatial and spectral error components having a clear influence on the total error. The influence of field data errors was close to the remote sensing data errors (40-50% of the propagated error) and its spatial and non-spatial Overall, the study successfully traced the errors and applied certainty-scenarios using the software tool designed for this purpose. The applied novel approach allowed for a relatively fast solution when mapping errors outside the fieldwork areas.
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Pan, Zhao. "Error Propagation Dynamics of PIV-based Pressure Field Calculation." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6353.
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Particle Image Velocimetry (PIV) based pressure field calculation is becoming increasingly popular in experimental fluid dynamics due to its non-intrusive nature. Errors propagated from PIV results to pressure field calculations are unavoidable, and in most cases, non-negligible. However, the specific dynamics of this error propagation process have not been unveiled. This dissertation examines both why and how errors in the experimental data are propagated to the pressure field by direct analysis of the pressure Poisson equation. Error in the pressure calculations are bounded with the error level of the experimental data. The error bounds quantitatively explain why and how many factors (i.e., geometry and length scale of the flow domain, type of boundary conditions) determine the resulting error propagation. The reason that the type of flow and profile of the error matter to the error propagation is also qualitatively illustrated. Numerical and experimental validations are conducted to verify these results. The results and framework introduced in this research can be used to guide the optimization of the experimental design, and potentially estimate the error in the reconstructed pressure field before performing PIV experiments.
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Chan, Abraham. "Error propagation analysis of multithreaded programs using likely invariants." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62713.
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Error Propagation Analysis (EPA) is a technique for understanding how errors affect
a program’s execution and result in program failures. For this purpose, EPA
usually compares the traces of a fault-free (golden) run with those from a faulty
run of the program. This makes existing EPA approaches brittle for multithreaded
programs, which do not typically have a deterministic golden run. In this thesis, we
study the use of likely invariants generated by automated approaches as alternatives
for golden run based EPA in multithreaded programs. We present Invariant Propagation
Analysis (IPA), an approach and a framework for automatically deriving
invariants for multithreaded programs, and using the invariants for EPA.We evaluate
the invariants derived by IPA in terms of their coverage for different fault types
across six representative programs through fault injection experiments. We find
that stable invariants can be inferred in all six programs, although their coverage of
faults depends on the application and the fault type.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Kon, Henry B. "Data quality management : foundations in error measurement and propagation." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/9838.
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Palaniappan, Karthik. "Propagation of updates to replicas using error correcting codes." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1915.
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Thesis (M.S.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains vi, 68 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 67-68).
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Wyant, Timothy Joseph. "Numerical study of error propagation in Monte Carlo depletion simulations." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44809.
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Improving computer technology and the desire to more accurately model the heterogeneity of the nuclear reactor environment have made the use
of Monte Carlo depletion codes more attractive in recent years, and feasible (if not practical) even for 3-D depletion simulation. However, in this case statistical uncertainty is combined with error propagating through the calculation from previous steps. In an effort to understand this error propagation, four test problems were developed to test error propagation in
the fuel assembly and core domains. Three test cases modeled and tracked individual fuel pins in four 17x17 PWR fuel assemblies. A fourth problem
modeled a well-characterized 330MWe nuclear reactor core. By changing the code's initial random number seed, the data produced by a series of 19 replica runs of each test case was used to investigate the true and apparent variance in k-eff, pin powers, and number densities of several isotopes. While this study does not intend to develop a predictive model for error
propagation, it is hoped that its results can help to identify some common regularities in the behavior of uncertainty in several key parameters.
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Wang, Rujiang. "Mitigating error propagation of decision feedback equalization in boradband communications." Doctoral thesis, Université Laval, 2008. http://www.theses.ulaval.ca/.
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Wang, Rujiang. "Mitigating Error Propagation of Decision Feedback Equalization in Broadband Communications." Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25328/25328.pdf.
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Lloyd, Jeffrey (Jeffrey M. ). "Error propagation of optimal system design in a hierarchical enterprise." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/43096.
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Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2007.Includes bibliographical references (p. 62-63).
Increased computing power has helped virtual engineering become common practice amongst product development firms. However, while capabilities increase, the desire to simulate even larger systems has increased as well. To deal with the complexity and size of these systems, several techniques have been developed to decompose the system into smaller, more tractable subsystems. The drawback of this approach is a substantial decrease in computational efficiency. Therefore the use of simplified models is encouraged and often required to reach convergence.In this thesis, a test model is introduced where different forms of error can be introduced at each level. Error derived from both measurement inaccuracy and modeling inaccuracy is examined coupled with the effect of system constraints as well. A hierarchical decomposition method is selected for its similarity to a typical enterprise organizational structure. In this manner, the results of the examination should be applicable to both system engineering methods and enterprise level problems. The direction of error propagation within the hierarchical decomposition is determined and the effects of robust design considerations and simple system constraints are revealed.
by Jeffrey Lloyd.
S.M.
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Krishnan, Vignesh. "Analysis of Error Propagation in Differential Satellite Based Positioning Systems." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1102711243.
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Anderson, Travis V. "Efficient, Accurate, and Non-Gaussian Error Propagation Through Nonlinear, Closed-Form, Analytical System Models." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2675.
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Uncertainty analysis is an important part of system design. The formula for error propagation through a system model that is most-often cited in literature is based on a first-order Taylor series. This formula makes several important assumptions and has several important limitations that are often ignored. This thesis explores these assumptions and addresses two of the major limitations. First, the results obtained from propagating error through nonlinear systems can be wrong by one or more orders of magnitude, due to the linearization inherent in a first-order Taylor series. This thesis presents a method for overcoming that inaccuracy that is capable of achieving fourth-order accuracy without significant additional computational cost. Second, system designers using a Taylor series to propagate error typically only propagate a mean and variance and ignore all higher-order statistics. Consequently, a Gaussian output distribution must be assumed, which often does not reflect reality. This thesis presents a proof that nonlinear systems do not produce Gaussian output distributions, even when inputs are Gaussian. A second-order Taylor series is then used to propagate both skewness and kurtosis through a system model. This allows the system designer to obtain a fully-described non-Gaussian output distribution. The benefits of having a fully-described output distribution are demonstrated using the examples of both a flat rolling metalworking process and the propeller component of a solar-powered unmanned aerial vehicle.
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Alter, Tao Daniel. "The role of saliencey and error propagation in visual object recognition." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38055.
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Tharek, A. R. "Propagation and bit error rate measurements in the millimetre wave band about 60GHz." Thesis, University of Bristol, 1988. http://hdl.handle.net/1983/1b39cd0b-e371-46a5-9ce4-463e2167a6b5.
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Watkins, Adam Christopher. "RADIATION INDUCED TRANSIENT PULSE PROPAGATION USING THE WEIBULL DISTRIBUTION FUNCTION." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/811.
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In recent years, studying soft errors has become an issue of greater importance. There have been many methods developed that estimate the Soft Error Rate. Those methods are either deterministic or statistical. The proposed deterministic model aims to improve Soft Error Rate estimation by accurately approximating the generated pulse and all subsequent pulses. The generated pulse is approximated by a piecewise function consisting of two Weibull cumulative distribution functions. This method is an improvement over existing methods as it offers high accuracy while requiring less pre-characterization. The proposed algorithm reduces pre-characterization by allowing the beta Weibull parameter to be calculated during runtime using gate parameters such as the gate delay.
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Khatami, Mehrdad. "combined Modulation and Error Correction Decoder for TDMR Using Generalized Belief Propagation." International Foundation for Telemetering, 2013. http://hdl.handle.net/10150/579681.
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ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NVConstrained codes also known as modulation codes are a key component in the digital magnetic recording systems. The constrained codes forbid particular input data patterns which lead to some of the dominant error events or higher media noise. In data recording systems, a concatenated approach toward the constrained code and error-correcting code (ECC) is typically used and the decoding is done independently. In this paper, we show the improvement in combining the decoding of the constrained code and the ECC using generalized belief propagation (GBP) algorithm. We consider the performance of a combined modulation constraints and the ECC on a binary symmetric channel (BSC). We show that combining demodulation and decoding results in a superior performance compared to concatenated schemes. Furthermore, we compute the capacity of the joint ECC and modulation codes for 1-D and 2-D constraints.
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McDonald, Robert Alan. "Error Propagation and Metamodeling for a Fidelity Tradeoff Capability in Complex Systems Design." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11568.
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Complex man-made systems are ubiquitous in modern technological society. The national air transportation infrastructure and the aircraft that operate within it, the highways stretching coast-to-coast and the vehicles that travel on them, and global communications networks and the computers that make them possible are all complex systems.
It is impossible to fully validate a systems analysis or a design process. Systems are too large, complex, and expensive to build test and validation articles. Furthermore, the operating conditions throughout the life cycle of a system are impossible to predict and control for a validation experiment.
Error is introduced at every point in a complex systems design process. Every error source propagates through the complex system in the same way information propagates, feedforward, feedback, and coupling are all present with error.
As with error propagation through a single analysis, error sources grow and decay when propagated through a complex system. These behaviors are made more complex by the complex interactions of a complete system. This complication and the loss of intuition that accompanies it make proper error propagation calculations even more important to aid the decision maker.
Error allocation and fidelity trade decisions answer questions like: Is the fidelity of a complex systems analysis adequate, or is an improvement needed, and how is that improvement best achieved? Where should limited resources be invested for the improvement of fidelity? How does knowledge of the imperfection of a model impact design decisions based on the model and the certainty of the performance of a particular design?
In this research, a fidelity trade environment was conceived, formulated, developed, and demonstrated. This development relied on the advancement of enabling techniques including error propagation, metamodeling, and information management. A notional transport aircraft is modeled in the fidelity trade environment. Using the environment, the designer is able to make design decisions while considering error and he is able to make decisions regarding required tool fidelity as the design problem continues. These decisions could not be made in a quantitative manner before the fidelity trade environment was developed.
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Kindervatter, Tim. "Survey of Ionospheric Propagation Effects and Modeling Techniques for Mitigation of GPS Error." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1515106508878179.
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Wolting, Duane. "MULTIVARIATE SYSTEMS ANALYSIS." International Foundation for Telemetering, 1985. http://hdl.handle.net/10150/615760.
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International Telemetering Conference Proceedings / October 28-31, 1985 / Riviera Hotel, Las Vegas, NevadaIn many engineering applications, a systems analysis is performed to study the effects of random error propagation throughout a system. Often these errors are not independent, and have joint behavior characterized by arbitrary covariance structure. The multivariate nature of such problems is compounded in complex systems, where overall system performance is described by a q-dimensional random vector. To address this problem, a computer program was developed which generates Taylor series approximations for multivariate system performance in the presence of random component variablilty. A summary of an application of this approach is given in which an analysis was performed to assess simultaneous design margins and to ensure optimal component selection.
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Mutha, Chetan V. "Software fault failure and error analysis at the early design phase with UML." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1296597871.
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Rainey, Cameron Scott. "Error Estimations in the Design of a Terrain Measurement System." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/50501.
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Terrain surface measurement is an important tool in vehicle design work as well as pavement classification and health monitoring. �Non-deformable terrains are the primary excitation to vehicles traveling over it, and therefore it is important to be able to quantify these terrain surfaces. Knowledge of the terrain can be used in combination with vehicle models in order to predict force loads the vehicles would experience while driving over the terrain surface. �This is useful in vehicle design, as it can speed the design process through the use of simulation as opposed to prototype construction and durability testing. �Additionally, accurate terrain maps can be used by highway engineers and maintenance personnel to identify deterioration in road surface conditions for immediate correction. �Repeated measurements of terrain surfaces over an extended length of time can also allow for long term pavement health monitoring.Many systems have been designed to measure terrain surfaces, most of them historically single line profiles, with more modern equipment capable of capturing three dimensional measurements of the terrain surface. �These more modern systems are often constructed using a combination of various sensors which allow the system to measure the relative height of the terrain with respect to the terrain measurement system. �Additionally, these terrain measurement systems are also equipped with sensors which allow the system to be located in some global coordinate space, as well as the angular attitude of that system to be estimated. �Since all sensors return estimated values, with some uncertainty, the combination of a group of sensors serves to also combine their uncertainties, resulting in a system which is less precise than any of its individual components. �In order to predict the precision of the system, the individual probability densities of the components must be quantified, in some cases transformed, and finally combined in order to predict the system precision. �This thesis provides a proof-of-concept as to how such an evaluation of final precision can be performed.
Master of Science
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Boisvert, Mario. "Minimizing state error propagation in low-bit rate speech codec for voice over IP." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26360.
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Today's Internet and intranets are packet-switched networks where the Internet Protocol (IP) is the most widespread of all network protocols in use. Such network protocol poses serious constraints on the real-time transmission of packets such as in the case of voice applications, namely Voice over IP (VoIP) applications. The "best effort" delivery mechanism and the lack of guarantee of Quality of Service (QoS) of packet networks are known to cause packet arrival problems that result in packet losses. Obviously, the loss of packets impairs the quality of the speech at the receiving end.
In this thesis, we focus on two main areas in the implementation of VoIP systems. Initially, we review speech compression techniques to better understand the operation and characteristics of speech codecs. This allows us to select a promising speech codec, namely, the ITU-T G.729A speech codec that will be used during our demonstrations and investigations. Secondly, we review the operation of packet-switched networks, more specifically IP networks, for the purpose of understanding the degradation effects they cause to VoIP systems. With this knowledge, we formalize a set of constraints and requirements that allows us to properly analyze the effect of packet losses over IP networks.
Finally, we propose a closed-loop over the network method to assist the codec in improving its speech quality performance in periods of packet losses. The method, named State Error Correction (SEC), is described in detail and its performance is assessed through simulations.
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Tan, Chin Khee. "System Performance of an Over-Water Propagation for an LMDS Link." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32131.
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The growth of broadband Internet access has paved the way for the development of many newer existing technologies. As the costs of implementing broadband access soar, the best alternative will be to use wireless technologies. At a carrier frequency of about 28 GHz, the potential benefits of Local Multipoint Distribution Service (LMDS) will eventually outweigh those of its current competitors in the wired market. Since the rural communities will reap the most benefits from this technology due to its low costs, studies on the channel behavior and terrain relationships must be done.
This thesis aims to provide a preliminary study on the effects of propagating an LMDS signal over a lake surface. Currently, there is not enough information to prove the feasibility of deploying an LMDS system for this terrain. Some background on the technology and rough surface theory is provided for the reader to better understand the environment that is being investigated. Simulation results are presented as a guide to assist future researchers to conduct a field measurement campaign. A block diagram of a potential measurement system is also provided to aid in the development of the tools necessary for the measurement of an actual channel.Master of Science
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Esperon, Miguez Manuel. "Financial and risk assessment and selection of health monitoring system design options for legacy aircraft." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8062.
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Aircraft operators demand an ever increasing availability of their fleets with
constant reduction of their operational costs. With the age of many fleets
measured in decades, the options to face these challenges are limited.
Integrated Vehicle Health Management (IVHM) uses data gathered through
sensors in the aircraft to assess the condition of components to detect and
isolate faults or even estimate their Remaining Useful Life (RUL). This
information can then be used to improve the planning of maintenance
operations and even logistics and operational planning, resulting in shorter
maintenance stops and lower cost. Retrofitting health monitoring technology
onto legacy aircraft has the capability to deliver what operators and maintainers
demand, but working on aging platforms presents numerous challenges. This
thesis presents a novel methodology to select the combination of diagnostic and
prognostic tools for legacy aircraft that best suits the stakeholders’ needs based
on economic return and financial risk. The methodology is comprised of
different steps in which a series of quantitative analyses are carried out to reach
an objective solution. Beginning with the identification of which components
could bring higher reduction of maintenance cost and time if monitored, the
methodology also provides a method to define the requirements for diagnostic
and prognostic tools capable of monitoring these components. It then continues
to analyse how combining these tools affects the economic return and financial
risk. Each possible combination is analysed to identify which of them should be
retrofitted. Whilst computer models of maintenance operations can be used to
analyse the effect of retrofitting IVHM technology on a legacy fleet, the number
of possible combinations of diagnostic and prognostic tools is too big for this
approach to be practicable. Nevertheless, computer models can go beyond the
economic analysis performed thus far and simulations are used as part of the
methodology to get an insight of other effects or retrofitting the chosen toolset.
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Kennedy, Rodney Andrew, and rodney kennedy@anu edu au. "Operational Aspects of Decision Feedback Equalizers." The Australian National University. Research School of Physical Sciences and Engineering, 1989. http://thesis.anu.edu.au./public/adt-ANU20050418.151329.
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The central theme is the study of error propagation effects in decision feedback equalizers (DFEs). The thesis contains: a stochastic analysis of error propagation in a tuned DFE; an analysis of the effects of error propagation in a blindly adapted DFE; a deterministic analysis of error propagation through input-output stability ideas; and testing procedures for establishing correct tap convergence in blind adaptation. To a lesser extent, the decision directed equalizer (DDE) is also treated.¶ Characterizing error propagation using finite state Markov process (FSMP) techniques is first considered. We classify how the channel and DFE parameters affect the FSMP model and establish tight bounds on the error probability and mean error recovery time of a tuned DFE. These bounds are shown to be too conservative for practical use and highlight the need for imposing stronger hypotheses on the class of channels for which a DFE may be effectively used.¶ In blind DFE adaptation we show the effect of decision errors is to distort the adaptation relative to the use of a training sequence. The mean square error surface in a LMS type setting is shown to be a concatenation of quadratic functions exposing the possibility of false tap convergence to undesirable DFE parameter settings. Averaging analysis and simulation are used to verify this behaviour on some examples.¶ Error propagation in a tuned DFE is also examined in a deterministic setting. A finite error recovery time problem is set up as an input-output stability problem. Passivity theory is invoked to prove that a DFE can be effectively used on a channel satisfying a simple frequency domain condition. These results give performance bounds which relate well with practice.¶ Testing for false tap convergence in blind adaptation concludes our study. Simple statistic output tests are shown to be capable of discerning correct operation of a DDE. Similar tests are conjectured for the DFE, supported by proofs for the low dimensional cases.
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Haugen, Paul Alan. "Evaluation of an instructional unit utilizing the worst case method in improving students' understanding of uncertainty analysis and propagation of error." Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/503.
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The objective of most physics laboratory exercises is to investigate the validity of a physical law or theory. Students compare predictions, based on theoretical grounds, with experimental results and are often confronted with a discrepancy between these two. Instead of submitting an analysis or a conclusion that incorporates uncertainty analysis, students will often resort to a list of excuses to explain the difference, such as equipment malfunctions or human error. They fail to recognize that their results may support the theory, even without perfect correlation.Physics teachers are challenged to provide instruction on uncertainty analysis rigorous enough to analyze laboratory data while, at the same time, understandable to entry-level students. This study focused on evaluating the effects of an algebra-based instruction unit on student understanding of uncertainty analysis and propagation of error. A comparison of scores on a pretest and posttest showed a statistically significant improvement in scores. In Phase Two of the study, student laboratory assignments were evaluated for changes in the level of understanding. Students demonstrated improved ability to incorporate uncertainty analysis and propagation of error in their laboratory reports, but most did not obtain an in-depth level of understanding. In a similar manner, conceptual change was evident at the lower level of assimilation, but few students achieved a complete conceptual change regarding uncertainty analysis.
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Kilcoyne, Deirdre Kathleen. "Link Adaptation for Mitigating Earth-to-Space Propagation Effects on the NASA SCaN Testbed." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71362.
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In Earth-to-Space communications, well-known propagation effects such as path loss and atmospheric loss can lead to fluctuations in the strength of the communications link between a satellite and its ground station. Additionally, a less-often considered effect of shadowing due to the geometry of the satellite and its solar panels can also lead to link degradation. As a result of these anticipated channel impairments, NASA's communication links have been traditionally designed to handle the worst-case impact of these effects through high link margins and static, lower rate, modulation formats. This thesis first characterizes the propagation environment experienced by a software-defined radio on the NASA SCaN Testbed through a full link-budget analysis. Then, the following chapters propose, design, and model a link adaptation algorithm to provide an improved trade-off between data rate and link margin through varying the modulation format as the received signal-to-noise ratio fluctuates.Master of Science
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Ben, Hassine Seif. "Multipath and receiver models for assessing the VOR bearing error : application to wind farms." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30047.
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L'implémentation des éoliennes à proximité des systèmes VOR (VHF Omnidirectional Range) est une préoccupation importante pour l'aviation civile. Les éoliennes constituent une source de multitrajets qui peuvent produire des erreurs sur l'information d'azimut estimée par le récepteur d'avion. Dans la littérature, l'erreur VOR est calculée à partir de paramètres multitrajets en utilisant l'expression analytique proposée par Odunaiya et Quinet. Dans cette thèse de doctorat, nous avons développé un modèle d'un récepteur IQ numérique qui peut reproduire la réponse d'un récepteur VOR lorsque les multitrajets varient dans le temps tout au long d'une trajectoire réaliste d'avion. Le Chapitre 1 présente les principes de base des systèmes : VOR conventionnel (VORC) et VOR Doppler (VORD). Le phénomène de multitrajets générés par les éoliennes à proximité des stations VOR est détaillé en présentant ses paramètres et certaines méthodes de modélisation associées qui existent dans la littérature. Un aperçu des récepteurs VOR est présenté en décrivant la structure classique d'un récepteur VOR et les étapes du traitement du signal appliquées afin d'extraire l'information d'azimut. Les expressions de l'erreur VOR proposées par Odunaiya et Quinet pour les systèmes VORC et VORD sont données et illustrées. Dans le Chapitre 2, nous présentons notre modèle de récepteur IQ numérique. Un générateur de séries temporelles au long d'une trajectoire réaliste d'avion est présenté. Un critère échantillonnage est également proposé pour être sûr de capturer toutes les variations de multitrajets dans l'espace. Le modèle de récepteur IQ numérique est détaillé en décrivant ses composantes. Afin d'analyser l'effet et dynamique de multitrajets sur le récepteur VOR, un test d'illustration est donné en comparant la réponse du modèle avec l'expression d'Odunaiya. Dans le Chapitre 3, le comportement de notre modèle de récepteur IQ numérique est analysé en le comparant avec un récepteur de calibration (R&S EVS300) à l'aide de deux mesures de laboratoire. La première mesure est effectuée dans la bande des fréquences VHF en traitant un multitrajet canonique. La seconde mesure est effectuée en utilisant des signaux en bande de base IQ générées à partir d'une simulation d'un scénario complexe. Les résultats des mesures montrent un bon accord entre les récepteurs. Une analyse critique de récepteur VOR est présentée dans le Chapitre 4. Pour le VORC, nous présentons une méthode permettant de déterminer le domaine de validité de l'expression statique d'Odunaiya afin de calculer l'erreur VOR. Pour le VORD, nous montrons que l'erreur VOR est sensible au type de démodulateur FM en développant et en validant une expression alternative de l'erreur Doppler analytique qui est cohérente avec notre démodulateur FM. Enfin, nous évaluons l'analyse de Bredemeyer qui indique que l'effet et des multitrajets sur le signal de référence doit être pris en compte dans le calcul de l'erreur VORD. Dans le Chapitre 5, nous proposons un modèle statistique d'erreur VOR dont les seuls paramètres sont les positions de l'avion et de l'éolienne et les autres paramètres suivent des distributions statistiques. Ce modèle permet de réduire le temps de simulation électromagnétique. Tout d'abord, nous déterminons les distributions statistiques associées aux paramètres multitrajets. Ensuite, la distribution statistique associée à l'erreur VOR est déduite. Enfin, nous effectuons des simulations de Monte Carlo pour évaluer les paramètres des distributions statistiquesThe implementation of wind turbines close to VHF Omnidirectional Range (VOR) systems is an important concern for civil aviation. The wind turbines constitute a source of multipath that can yield bearing errors in the azimuth estimated by aircraft receivers. In the literature, the bearing error is computed from the multipath characteristics by means of the analytic expression proposed by Odunaiya and Quinet. In this PhD thesis, we have developed a digital IQ receiver model which can reproduce the response of a VOR receiver when the multipath change in time along a realistic aircraft trajectory. In Chapter 1, the basic principle of the Conventional VOR (CVOR) and Doppler VOR (DVOR) is pre-sented. The multipath phenomenon generated by the wind turbines in the vicinity of VOR stations is detailed by presenting its parameters and some associated modeling methods that exist in the literature. An overview of the VOR receivers is presented by describing the standard structure of a VOR receiver and the signal processing steps to extract the azimuth information. The analytical expressions proposed by Odunaiya and Quinet for the CVOR and DVOR systems are given and illustrated. In Chapter 2, we present our digital IQ receiver model. A time series generator along a realistic aircraft trajectory is presented. A sampling criterion is also proposed to be sure to capture all the multipath variations in space. The digital IQ receiver model is detailed by describing its components. In order to analyze the effect of multipath dynamics on the VOR receiver, an illustration test is given by comparing the receiver model response with the Odunaiya expression. In Chapter 3, the behavior of our digital IQ receiver model is analyzed by comparing with a calibration receiver (R&S EVS300) from two laboratory measurements. The first one is performed in the VHF frequency band for one canonical multipath. The second one is performed using baseband IQ signals in a complex scenario. The measurements results are shown a good agreement between receivers. A CVOR and DVOR analysis are given in Chapter 4. For CVOR, we present a method to determine the validity domain of the static Odunaiya expression for computing the bearing error. For DVOR, we show that the bearing error is sensitive to the type of FM demodulator by developing and validating an alternative expression of the analytic Doppler error which is consistent with our FM demodulator. Finally, we evaluate the analysis of Bredemeyer which indicates that the effect of multipath on the reference signal must be considered in the DVOR error computation. In Chapter 5, we propose a statistical model for the bearing error with which the only parameters are the aircraft and wind turbine positions and the other parameters follow statistical distributions. This model allows to reduce the electromagnetic simulation time. Firstly, we determine the statistical distributions associated with the multipath parameters. Secondly, the statistical distribution associated with the bearing error is deduced. Finally, we perform Monte Carlo simulations to assess the parameters of the statistical distributions
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Sargelis, Kęstas. "Klaidos skleidimo atgal algoritmo tyrimai." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090630_094557-88383.
Full textAbstract:
Šiame darbe detaliai išanalizuotas klaidos skleidimo atgal algoritmas, atlikti tyrimai. Išsamiai analizuota neuroninių tinklų teorija. Algoritmui taikyti ir analizuoti sistemoje Visual Studio Web Developer 2008 sukurta programa su įvairiais tyrimo metodais, padedančiais ištirti algoritmo daromą klaidą. Taip pat naudotasi Matlab 7.1 sistemos įrankiais neuroniniams tinklams apmokyti. Tyrimo metu analizuotas daugiasluoksnis dirbtinis neuroninis tinklas su vienu paslėptu sluoksniu. Tyrimams naudoti gėlių irisų ir oro taršos duomenys. Atlikti gautų rezultatų palyginimai.The present work provides an in-depth analysis of the error back-propagation algorithm, as well as information on the investigation carried out. A neural network theory has been analysed in detail. For the application and analysis of the algorithm in the system Visual Studio Web Developer 2008, a program has been developed with various investigation methods, which help to research into the error of the algorithm. For training neural networks, Matlab 7.1 tools have been used. In the course of the investigation, a multilayer artificial neural network with one hidden layer has been analysed. For the purpose of the investigation, data on irises (plants) and air pollution have been used. Comparisons of the results obtained have been made.
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Li, Huanlin. "Studies on Lowering the Error Floors of Finite Length LDPC codes." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1305126490.
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Hannah, Bruce M. "Modelling and simulation of GPS multipath propagation." Thesis, Queensland University of Technology, 2001. https://eprints.qut.edu.au/15782/1/Bruce_Hannah_Thesis.pdf.
Full textAbstract:
Multipath remains a dominant error source in Global Positioning System (GPS) applications that require high accuracy. With the use of differential techniques it is possible to remove many of the common-mode error sources, but the error effects of multipath have proven much more difficult to mitigate. The research aim of this work is to enhance the understanding of multipath propagation and its effects in GPS terrestrial applications, through the modelling of signal propagation behaviour and the resultant error effects.
Multipath propagation occurs when environmental features cause combinations of reflected and/or diffracted replica signals to arrive at the receiving antenna. These signals, in combination with the original line-of-sight (LOS) signal, can cause distortion of the receiver correlation function and ultimately the discrimination function and hence errors in range estimation.
To date, a completely satisfactory mitigation strategy has yet to be developed. In the search for such a mitigation strategy, it is imperative that a comprehensive understanding of the multipath propagation environment and the resultant error effects exists. The work presented here, provides a comprehensive understanding through the use of new modelling and simulation techniques specific to GPS multipath.
This dissertation unites the existing theory of radio frequency propagation for the GPS L1 signal into a coherent treatment of GPS propagation in the terrestrial environment.
To further enhance the understanding of the multipath propagation environment and the resultant error effects, this dissertation also describes the design and development of a new parabolic equation (PE) based propagation model for analysis of GPS multipath propagation behaviour.
The propagation model improves on previous PE-based models by incorporating terrain features, including boundary impedance properties, backscatter and time-domain decomposition of the field into a multipath impulse response. The results provide visualisation as well as the defining parameters necessary to fully describe the multipath propagation behaviour.
These resultant parameters provide the input for a correlation and discrimination model for visualisation and the generation of resultant receiver error measurements. Results for a variety of propagation environments are presented and the technique is shown to provide a deterministic methodology against real GPS data.
The unique and novel combined modelling of multipath propagation and reception, presented in this dissertation, provides an effective set of tools that have enhanced the understanding of the behaviour and effect of multipath in GPS applications, and ultimately should aid in providing a solution to the GPS multipath mitigation problem.
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Hannah, Bruce M. "Modelling and Simulation of GPS Multipath Propagation." Queensland University of Technology, 2001. http://eprints.qut.edu.au/15782/.
Full textAbstract:
Multipath remains a dominant error source in Global Positioning System (GPS) applications that require high accuracy. With the use of differential techniques it is possible to remove many of the common-mode error sources, but the error effects of multipath have proven much more difficult to mitigate. The research aim of this work is to enhance the understanding of multipath propagation and its effects in GPS terrestrial applications, through the modelling of signal propagation behaviour and the resultant error effects. Multipath propagation occurs when environmental features cause combinations of reflected and/or diffracted replica signals to arrive at the receiving antenna. These signals, in combination with the original line-of-sight (LOS) signal, can cause distortion of the receiver correlation function and ultimately the discrimination function and hence errors in range estimation. To date, a completely satisfactory mitigation strategy has yet to be developed. In the search for such a mitigation strategy, it is imperative that a comprehensive understanding of the multipath propagation environment and the resultant error effects exists. The work presented here, provides a comprehensive understanding through the use of new modelling and simulation techniques specific to GPS multipath. This dissertation unites the existing theory of radio frequency propagation for the GPS L1 signal into a coherent treatment of GPS propagation in the terrestrial environment. To further enhance the understanding of the multipath propagation environment and the resultant error effects, this dissertation also describes the design and development of a new parabolic equation (PE) based propagation model for analysis of GPS multipath propagation behaviour. The propagation model improves on previous PE-based models by incorporating terrain features, including boundary impedance properties, backscatter and time-domain decomposition of the field into a multipath impulse response. The results provide visualisation as well as the defining parameters necessary to fully describe the multipath propagation behaviour. These resultant parameters provide the input for a correlation and discrimination model for visualisation and the generation of resultant receiver error measurements. Results for a variety of propagation environments are presented and the technique is shown to provide a deterministic methodology against real GPS data. The unique and novel combined modelling of multipath propagation and reception, presented in this dissertation, provides an effective set of tools that have enhanced the understanding of the behaviour and effect of multipath in GPS applications, and ultimately should aid in providing a solution to the GPS multipath mitigation problem.
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Planjery, Shiva Kumar. "Iterative Decoding Beyond Belief Propagation of Low-Density Parity-Check Codes." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/305883.
Full textAbstract:
The recent renaissance of one particular class of error-correcting codes called low-density parity-check (LDPC) codes has revolutionized the area of communications leading to the so-called field of modern coding theory. At the heart of this theory lies the fact that LDPC codes can be efficiently decoded by an iterative inference algorithm known as belief propagation (BP) which operates on a graphical model of a code. With BP decoding, LDPC codes are able to achieve an exceptionally good error-rate performance as they can asymptotically approach Shannon's capacity. However, LDPC codes under BP decoding suffer from the error floor phenomenon, an abrupt degradation in the error-rate performance of the code in the high signal-to-noise ratio region, which prevents the decoder from achieving very low error-rates. It arises mainly due to the sub-optimality of BP decoding on finite-length loopy graphs. Moreover, the effects of finite precision that stem from hardware realizations of BP decoding can further worsen the error floor phenomenon. Over the past few years, the error floor problem has emerged as one of the most important problems in coding theory with applications now requiring very low error rates and faster processing speeds. Further, addressing the error floor problem while taking finite precision into account in the decoder design has remained a challenge. In this dissertation, we introduce a new paradigm for finite precision iterative decoding of LDPC codes over the binary symmetric channel (BSC). These novel decoders, referred to as finite alphabet iterative decoders (FAIDs), are capable of surpassing the BP in the error floor region at a much lower complexity and memory usage than BP without any compromise in decoding latency. The messages propagated by FAIDs are not quantized probabilities or log-likelihoods, and the variable node update functions do not mimic the BP decoder. Rather, the update functions are simple maps designed to ensure a higher guaranteed error correction capability which improves the error floor performance. We provide a methodology for the design of FAIDs on column-weight-three codes. Using this methodology, we design 3-bit precision FAIDs that can surpass the BP (floating-point) in the error floor region on several column-weight-three codes of practical interest. While the proposed FAIDs are able to outperform the BP decoder with low precision, the analysis of FAIDs still proves to be a difficult issue. Furthermore, their achievable guaranteed error correction capability is still far from what is achievable by the optimal maximum-likelihood (ML) decoding. In order to address these two issues, we propose another novel class of decoders called decimation-enhanced FAIDs for LDPC codes. For this class of decoders, the technique of decimation is incorporated into the variable node update function of FAIDs. Decimation, which involves fixing certain bits of the code to a particular value during decoding, can significantly reduce the number of iterations required to correct a fixed number of errors while maintaining the good performance of a FAID, thereby making such decoders more amenable to analysis. We illustrate this for 3-bit precision FAIDs on column-weight-three codes and provide insights into the analysis of such decoders. We also show how decimation can be used adaptively to further enhance the guaranteed error correction capability of FAIDs that are already good on a given code. The new adaptive decimation scheme proposed has marginally added complexity but can significantly increase the slope of the error floor in the error-rate performance of a particular FAID. On certain high-rate column-weight-three codes of practical interest, we show that adaptive decimation-enhanced FAIDs can achieve a guaranteed error-correction capability that is close to the theoretical limit achieved by ML decoding.
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Walker, Edward A. "Factors affecting the bit error rate performance of the indoor radio propagation channel for 2.3-2.5 GHz frequency band." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2002. https://ro.ecu.edu.au/theses/726.
Full textAbstract:
The use of wireless in buildings based on microwave radio technology has recently become a viable alternative to the traditional wired transmission media. Because of the portable nature of radio transceivers, the need for extensive cabling of buildings with either twisted pair, coaxial, or optical fibre cable is eliminated. This is particularly desirable where high user mobility occurs and existing wiring is not in place, or buildings are heritage in nature and extensive cabling is seen as intrusive. Economic analysis bas also shown that significant labour cost savings can result by using a radio system or a hybrid mix of cable and radio for personal communication. The use of wireless systems within buildings introduces a new physical radio wave propagation medium, namely the indoor radio propagation channel. This physical medium has significantly different characteristics to some of the other forms of radio channels where elevated antennas, longer propagation path distances, and often minimally obstructed paths between transmit and receive antenna are common. Radio waves transmitted over the indoor channel at microwave frequencies behave much like light rays, they are blocked, scattered, and reflected by objects in the environment. As a direct result of this several phenomena unique to this form of physical medium become apparent, and they must be accounted for in the design and modelling of the indoor radio propagation channel transmission performance. In this thesis we analyse and characterise the indoor radio channel as a physical medium for data transmission. The research focuses on the influence of the radio physics aspects of an indoor microwave channel on the data transmission quality. We identify the associated statistical error performance for both time varying and temporally stationary indoor channels. Together with the theoretical analysis of the channel, a series of propagation measurements within buildings are completed to permit empirical validation of the theoretical predictions of how the indoor microwave channel should perform. The measurements are performed in the frequency range 2.3-2.5 GHz, which includes the 2.4-2.4835 GHz band allocated by spectrum management authorities for industrial scientific and medical radio use, (ISM band). As a direct result of our measurements, statistics related to channel noise, fading, and impulse response for the indoor microwave channel are obtained. The relationship between data transmission error statistics and the aforementioned phenomena is quantified and statistically analysed for the indoor radio channel and phase shift keyed (PSK) modulation. The results obtained from this research provide input data for the development of a simulation model of an indoor wireless mobile channel. Our measurements identify microwave ovens as a channel noise source of sufficient magnitude to corrupt data transmission in the ISM band, and an in depth analysis of the effect of noise emissions from operational microwave ovens on PSK modulation is presented in this thesis. As a result of this analysis, the estimated data error rates are calculated. Channel fading measurements provide results that will be used as the input data for the design of antennas for use on the indoor microwave channel. We also show that a data rate of eight megabits/second is possible over the typical indoor radio channel, with no requirement for adaptive delay equalisation to counter multipath signal delay spread.
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Dutta, Rahul Kumar. "A Framework for Software Security Testing and Evaluation." Thesis, Linköpings universitet, Institutionen för datavetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-121645.
Full textAbstract:
Security in automotive industry is a thought of concern these days. As more smart electronic devices are getting connected to each other, the dependency on these devices are urging us to connect them with moving objects such as cars, buses, trucks etc. As such, safety and security issues related to automotive objects are becoming more relevant in the realm of internet connected devices and objects. In this thesis, we emphasize on certain factors that introduces security vulnerabilities in the implementation phase of Software Development Life Cycle (SDLC). Input invalidation is one of them that we address in our work. We implement a security evaluation framework that allows us to improve security in automotive software by identifying and removing software security vulnerabilities that arise due to input invalidation reasons during SDLC. We propose to use this framework in the implementation and testing phase so that the critical deficiencies of software in security by design issues could be easily addressed and mitigated.
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Iltis, Ronald A. "Decoding and Turbo Equalization for LDPC Codes Based on Nonlinear Programming." International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/605945.
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ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, CaliforniaDecoding and Turbo Equalization (TEQ) algorithms based on the Sum-Product Algorithm (SPA) are well established for LDPC codes. However there is increasing interest in linear and nonlinear programming (NLP)-based decoders which may offer computational and performance advantages over the SPA. We present NLP decoders and Turbo equalizers based on an Augmented Lagrangian formulation of the decoding problem. The decoders update estimates of both the Lagrange multipliers and transmitted codeword while solving an approximate quadratic programming problem. Simulation results show that the NLP decoder performance is intermediate between the SPA and bit-flipping algorithms. The NLP may thus be attractive in some applications as it eliminates the tanh/atanh computations in the SPA.
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Klempner, Scott. "Statistical modeling of radiometric error propagation in support of hyperspectral imaging inversion and optimized ground sensor network design /." Online version of thesis, 2008. http://hdl.handle.net/1850/7859.
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Decouvreur, Vincent. "Updating acoustic models: a constitutive relation error approach." Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210572.
Full textAbstract:
In the global framework of improving vibro-acoustic numerical prediction quality together with the need to decrease the number of prototyping stages, this manuscript focuses on achieving greater accuracy for acoustic numerical simulations by making use of a parametric updating technique, which enables tuning the model parameters inside physically meaningful boundaries. The improved model is used for the next prototyping stages, allowing more accurate results within reduced simulation times. The updating technique is based on recent works dealing with the constitutive relation error method (CRE) applied to acoustics. The updating process focuses on improving the acoustic damping matrix related to the absorbing properties of the materials covering the borders of the acoustic domain.Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
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Alejo, Eleuterio Roberto. "Análisis del error en redes neuronales: Corrección de los datos y distribuciones no balanceadas." Doctoral thesis, Universitat Jaume I, 2010. http://hdl.handle.net/10803/10490.
Full textAbstract:
El problema del desbalance de las clases aparece cuando existen muchos más elementos de una o algunas clases, que de la otra u otras clases (dos o múltiples clases). Esta desproporción en el tamaño de las diferentes clases en un mismo conjunto de datos, puede ocasionar una disminución en la efectividad del clasificación sobre las clases menos representadas. En el caso específico de las redes neuronales artificiales, el desbalance de las clases ocasiona lentitud en la convergencia de las clases minoritarias, lo que se traduce en una pobre capacidad de generalización del clasificador. En este trabajo se estudia y trata el problema del desbalance de las clases en el ámbito de las redes neuronales artificiales. Para ello se entrena la red con el algoritmo back-propagation con procesamiento por grupos desde tres enfoques distintos: (a) Incluyendo funciones de coste al proceso de entrenamiento, (b) aplicando redes neuronales modulares (descomposición del problema), y (c) reduciendo la región de solapamiento de las clases menos representadas. En síntesis, este trabajo presenta un estudio empírico comparativo de los efectos y posibles tratamientos del problema del desbalance de las clases sobre tres modelos de red neuronal artificial.
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Yarkinoglu, Gucuk Oya. "Modelling And Analyzing The Uncertainty Propagation In Vector-based Network Structures In Gis." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608845/index.pdf.
Full textAbstract:
Uncertainty is a quantitative attribute that represents the difference between reality
and representation of reality. Uncertainty analysis and error propagation modeling reveals
the propagation of input error through output.
Main objective of this thesis is to model the uncertainty and its propagation for
dependent line segments considering positional correlation.
The model is implemented as a plug-in, called Propagated Band Model (PBM)
Plug-in, to a commercial desktop application, GeoKIT Explorer. Implementation of the
model is divided into two parts. In the first one, model is applied to each line segment of
the selected network, separately. In the second one, error in each segment is transmitted
through the line segments from the start node to the end node of the network. Outcomes are
then compared with the results of the G-Band model which is the latest uncertainty model
for vector features. To comment on similarities and differences of the outcomes,
implementation is handled for two different cases. In the first case, users digitize the
selected road network. In the second case recently developed software called Interactive
Drawer (ID) is used to allow user to define a new network and simulate this network
through Monte Carlo Simulation Method. PBM Plug-in is designed to accept the outputs of
these implementation cases as an input, as well as generating and visualizing the
uncertainty bands of the given line network.
Developed implementations and functionality are basically for expressing the
importance and effectiveness of uncertainty handling in vector based geometric features,
especially for line segments which construct a network.
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Li, Ding. "ESA ExoMars Rover PanCam System Geometric Modeling and Evaluation." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1420788556.
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WAKAKI, Shigeyuki. "Estimation of optimal isotopic compositions of Sr, Ba, Nd and Sm spikes for double spike thermal ionization mass spectrometry by error propagation simulation." Dept. of Earth and Planetary Sciences, Nagoya University, 2012. http://hdl.handle.net/2237/20538.
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Xie, Meiling. "Indoor radio propagation modeling for system performance prediction." Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0074/document.
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Cette thèse a pour but de proposer toutes les avancées possibles dans l’utilisation du modèle de propagation Multi-Resolution Frequency-Domain ParFlow (MR-FDPF). Etant un modèle de propagation radio déterministe, le modèle MR-FDPF possède un haut niveau de précision, mais souffre des limitations communes à tous les modèles déterministes. Par exemple, un canal radio réel n’est pas déterministe, mais un processus aléatoire à cause par exemple des personnes ou objets mobiles, et ne peut donc être décrit fidèlement par un modèle purement déterministe. Dans cette thèse, un modèle semi-déterministe est proposé, basé sur le modèle MR-FDPF, qui introduit une part stochastique pour tenir compte des aspects aléatoires du canal radio réaliste. La partie déterministe du modèle est composée du path loss (atténuation d’espace), et la partie stochastique venant du shadow fading (masquage) et du small scale fading (évanouissement). De même, de nombreux simulateurs de propagation radio ne proposent que la prédiction de la puissance moyenne. Mais pour une simulation précise de la propagation radio il convient de prédire également des informations de fading permettant dès lors une prédiction précise du taux d’erreur binaire (BER) potentiel. Dans cette thèse, l’information de fading est déduite des simulations MR-FDPF et par la suite des valeurs réalistes de BER sont données. Enfin, ces données réalistes de BER permettent d’évaluer l’impact de schémas de modulation adaptatifs. Des résultats sont présentés dans trois configurations : systèmes SISO (mono-antenne à l’émission et à la réception), systèmes à diversité de type MRC, et systèmes large bande de type OFDMThis thesis aims at proposing all the possible enhancements for the Multi-Resolution Frequency-Domain ParFlow (MR-FDPF) model. As a deterministic radio propagation model, the MR-FDPF model possesses the property of a high level of accuracy, but it also suffers from some common limitations of deterministic models. For instance, realistic radio channels are not deterministic but a kind of random processes due to, e.g. moving people or moving objects, thus they can not be completely described by a purely deterministic model. In this thesis, a semi-deterministic model is proposed based on the deterministic MR-FDPF model which introduces a stochastic part to take into account the randomness of realistic radio channels. The deterministic part of the semi-deterministic model is the mean path loss, and the stochastic part comes from the shadow fading and the small scale fading. Besides, many radio propagation simulators provide only the mean power predictions. However, only mean power is not enough to fully describe the behavior of radio channels. It has been shown that fading has also an important impact on the radio system performance. Thus, a fine radio propagation simulator should also be able to provide the fading information, and then an accurate Bit Error Rate (BER) prediction can be achieved. In this thesis, the fading information is extracted based on the MR-FDPF model and then a realistic BER is predicted. Finally, the realistic prediction of the BER allows the implementation of the adaptive modulation scheme. This has been done in the thesis for three systems, the Single-Input Single-Output (SISO) systems, the Maximum Ratio Combining (MRC) diversity systems and the wideband Orthogonal Frequency-Division Multiplexing (OFDM) systems