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1
Valieva, Inna. « Spectrum Sensing for Dynamic Spectrum Access in Cognitive Radio ». Licentiate thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-52881.
Texte intégralRésumé :
Abstract. The number of mobile devices is constantly growing, and the exclusivestatic spectrum allocation approach is leading to the spectrum scarcity problem whensome of the licensed bands are heavily occupied and others are nearly unused.Spectrum sharing and opportunistic spectrum access allow achieving more efficientspectrum utilization. Radio scene analysis is a first step in the cognitive radiooperation required to employ opportunistic spectrum access scenarios such as thedynamic spectrum access or frequency hopping spread spectrum. The objective of thiswork is to develop and virtual prototype the subset of radio scene analysis algorithmsintended to be used for deployment of opportunistic spectrum access in our targetapplication: a cognitive radio network consisting of multiple software-defined radionodes BitSDR. The proposed radio scene analysis algorithms are devoted to solvingtwo radio scene analysis problems: 1. detection of vacant frequency channels toimplement spectrum sharing scenarios; 2. waveform estimation including modulationtype, symbol rate, and central frequency estimation. From the subset of two radioscene analysis problems two hypotheses are formulated: the first is related to thevacant band identification and the second to waveform estimation. Then sevenresearch questions related to the trade-off between the sensing accuracy and real-time operation requirement for the proposed radio scene analysis algorithms, the nature of the noise, and assumptions used to model the radio scene environment such as the AWGN channel. In the scope of this work, Hypothesis 1, dedicated to vacant frequency band detection, has been proven. Research questions related to the selection of the observation bandwidth, vacant channels detection threshold, and the optimal algorithm have been answered. We have proposed, prototyped, and tested a vacant frequency channels detection algorithm based on wavelet transform performing multichannel detection in the wide band of 56 MHz based on the received signal observed during500 microseconds. Detection accuracy of 91 % has been demonstrated. Detection has been modeled as a binary hypothesis testing problem. Also, energy detection and cyclostationary feature extraction algorithms have been prototyped and tested, however, they have shown lower classification accuracy than wavelets. Answering research question 7 revealed the advantage of using wavelets due to the potential of the results of wavelet transform to be applied for solving the waveform estimation problem including symbol rate and modulation type. Test data samples have been generated during the controlled experiment by the hardware signal generator and received by proprietary hardware based on AD9364 Analog Devices transceiver. To test Hypothesis 2 research questions related to the waveform estimation have been elaborated. We could not fully prove Hypothesis 2 in the scope of this work. The algorithm and features that have been chosen for modulation type classification have not met the required classification accuracy to classify between five studied modulation classes 2FSK, BPSK, QPSK, 8PSK, and 16PSK. To capture more of the fine differences between the received signal modulated into different linear modulations it has been suggested to use the spectral features derived from the time-series signal observed during 500 microseconds or less observation time in the scope of the future work. However, the binary classification between 2FSK and BPSKpresented in Paper 1 could be performed based on instantaneous values and SNRinput: ensemble boosted trees and decision trees have shown an average classification accuracy of 86.3 % and 86.0 % respectively and classification speed of 1200000objects per second, what is faster than required 2000 objects per second.3The prototyping and testing of the proposed algorithm for symbol rate estimation based on deep learning have been performed to answer research question 2. Wavelet transform feature extraction has been proposed to be applied as a preprocessing step for deep learning-based estimation of the symbol rate for 2FSK modulated signals. This algorithm has shown an improvement in the accuracy of the symbol rate estimation in comparison with cyclostationary based detection. The validation accuracy of the symbol rate classification has reached 99.7 %. During testing, the highest average classification accuracy of 100 % has been observed for the signals with SNR levels 25-30 dB, while for signals with SNR 20-25 dB it was 96.3 %.
2
Tercero, Vargas Miurel. « Topics in Dynamic Spectrum Access : Market Based Spectrum Sharing and Secondary User Access in Radar Bands ». Licentiate thesis, KTH, Kommunikationssystem, CoS, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33791.
Texte intégralRésumé :
The steady growth in demand for spectrum has increased research interest in dynamic spectrum access schemes. This thesis studies some challenges in dynamic spectrum access based on two strategies: open sharing and hierarchical access. (1) In the open sharing model, the channels are allocated based on an auction process, taking into account the propagation characteristics of the channels, termed as channel heterogeneity. Two distributed dynamic spectrum access schemes are evaluated, sequential and concurrent. We show that the concurrent accessmechanismperforms better in terms of channel utilization and energy consumption, especially in wireless cellular network with an energy constraint. (2) In the hierarchical model, we assess the opportunities for secondary access in the radar band at 5.6GHz. The primary user is a meteorological radar and WLANs are the secondary users. The secondary users implement an interference protection mechanism to protect the radar, such that the WLAN’s transmission is regulated by an interference threshold. We evaluate the aggregate interference caused to the radar from multiple WLANs transmitting. We derive a mathematicalmodel to approximate the probability distribution function of the aggregate interference at the primary user, considering two cases: when secondary users are homogeneously distributed, and when they are heterogeneously distributed. The heterogeneous distribution of secondary users is modeled using an annulus sector with a higher density, called a hot zone. Finally, we evaluate opportunities for secondary access when WLANs employ an interference protection mechanism that considers the radar’s antenna pattern, such that temporal opportunities for transmission exist. The analytical probability distribution function of the interference is verified showing a good agrement with a Monte Carlo simulation. We show that the aggregate interference is sensitive to the propagation environment, thus in the rural case interference is more severe when compared to the urban case. In the evaluation of the hot zonemodel, we observe that the heterogenous distribution of secondary users has impact on the aggregate interference if the hot zone is near to the radar. The mathematical framework presented in this thesis can easily be adapted to assess interference to other types of primary and secondary users.QC 20110523
3
San, Jose Caceres Antonia. « Information processing, intelligence and social learning in autism spectrum disorder ». Thesis, King's College London (University of London), 2012. https://kclpure.kcl.ac.uk/portal/en/theses/information-processing-intelligence-and-social-learning-in-autism-spectrum-disorder(0dfaa229-73b3-4184-b342-c981ded6ad66).html.
Texte intégralRésumé :
Autism Spectrum Disorder (ASD) is a life-long developmental disorder, which affects communication, social interaction, and flexible behaviour. Kanner’s and Asperger’s original descriptions suggested a hidden intelligence in Autism, reflected in islets of ability. However, for more than three decades it has been documented that ASD has a strong association with Intellectual Disability (ID) and low measured IQ: a high percentage of cases of ASD have intellectual disability, and risk of ASD increases with reduced IQ. The current study aimed to investigate the underlying cognitive potential in ASD, using a simple measure of processing efficiency. The thesis reports studies testing the notion that learning and acquisition of skills is hampered by poor social insight in ASD, which curtails ordinary social learning mechanisms. This general framework further predicts that the basic processing mechanism is not impaired in ASD, and that learning will proceed more efficiently through non-social than through social routes. The Inspection Time (IT) task was used to assess processing efficiency and speed of processing, free of social demands. ITs were predicted to be significantly better than expected from standard IQ in children with ASD and ID, but not in those with ID alone. A novel photograph version of a well-known receptive vocabulary test was developed, predicting that this less socio-communicative version would specifically aid children with ASD, compared to the traditional line drawing format (which may be more determined by the author’s own interpretation and/or drawing ability). Finally, learning in novel social and non-social odd-one-out tasks was tested in children with ID with and without ASD. Learning performance was examined in relation to performance on standard IQ tests, IT, Theory of Mind, and report of everyday life skills and deficits. Results showed that ASD individuals outperformed ID individuals in the IT task despite matched IQ. However, IT did not predict better non-social learning than IQ did. Implications of these results and future directions are further discussed.
4
Au, Yeung Sheena. « Eye movements during complex information processing in autism spectrum disorder ». Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/377982/.
Texte intégral
5
Kumar, Avinash. « GENERALIZING DIRECT SEQUENCE SPREAD-SPECTRUM WITH MACHINE LEARNING FOR SECRECY ». Cleveland State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=csu1600186456691124.
Texte intégral
6
Jamasebi-Jahromi, Ali. « Code synchronisation in spread spectrum communication systems ». Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257305.
Texte intégral
7
Charbit, Gilles Gerald. « Error protection techniques for frequency-hopping Spread-Spectrum ». Thesis, Lancaster University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238955.
Texte intégral
8
Ravi, K. V. « Sequential detection methods for spread-spectrum code acquisition ». Thesis, University of Bath, 1991. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292854.
Texte intégral
9
Tooze, Alana. « Visual information processing by high functioning individuals with autistic spectrum condition ». Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/347433/.
Texte intégralRésumé :
People with Autistic Spectrum Condition (ASC) have sometimes been found to show a local-processing bias on certain visual tasks. This bias has been associated with superior task performance on tasks where it confers an advantage. However, this finding is far from universal; especially when the research participants with ASC have an average to above average level of general intellectual functioning. This thesis comprises a literature review of research examining the processing of visual information by people with ASC, and an empirical paper examining the performance of people with ASC on the Rey-Osterrieth Complex Figure. The literature review considers various models of ASC with the predictions they make for processing of complex visual stimuli. The evidence which supports or refutes these theories is described. Several methodologies have been used to explore visual processing in people with ASC and the information and understanding which each methodology has provided is discussed. Finally, the literature review considers what still remains unknown, and potential directions for future research. The empirical paper is a quantitative study using the Boston Qualitative Scoring System and eye tracking methodology to investigate the potential presence of a local-processing bias, evidenced by increased lower level cognitive processing during completion of the Rey-Osterrieth Complex Figure. A local-processing bias was not found. This study does not support the presence of this bias in high functioning individuals with ASC. The study findings are discussed in relation to the existing literature and the Underconnectivity Hypothesis of ASC.
10
Smythe, Colin. « Direct sequence spread spectrum techniques in local area networks ». Thesis, Durham University, 1985. http://etheses.dur.ac.uk/6804/.
Texte intégralRésumé :
This thesis describes the application of a direct sequence spread spectrum modulation scheme to the physical layer of a local area networks subsequently named the SS-LAN. Most present day LANs employ erne form or another of time division multiplexing which performs well in many systems but which is limited by its very nature in real time, time critical and time demanding applications. The use of spread spectrum multiplexing removes these limitations by providing a simultaneous multiple user access capability to the channel which permits each and all nodes to utilise the channel independent of the activity being currently supported by that channel. The theory of spectral spreading is a consequence of the Shannon channel capacity in which the channel capacity may be maintained by the trading of signal to noise ratio for bandwidth. The increased bandwidth provides an increased signal dimensionality which can be utilised in providing noise immunity and/or a simultaneous multiple user environment: the effects of the simultaneous users can be considered as noise from the point of view of any particular constituent signal. The use of code sequences at the physical layer of a LAN permits a wide range of mapping alternatives which can be selected according to the particular application. Each of the mapping techniques possess the general spread spectrum properties but certain properties can be emphasised at the expense of others. The work has Involved the description of the properties of the SS-LAN coupled with the development of the mapping techniques for use In the distribution of the code sequences. This has been followed by an appraisal of a set of code sequences which has resulted in the definition of the ideal code properties and the selection of code families for particular types of applications. The top level design specification for the hardware required in the construction of the SS-LAN has also been presented and this has provided the basis for a simplified and idealised theoretical analysis of the performance parameters of the SS-LAN. A positive set of conclusions for the range of these parameters has been obtained and these have been further analysed by the use of a SS-LAN computer simulation program. This program can simulate any configuration of the SS-LAN and the results it has produced have been compared with those of the analysis and have been found to be in agreement. A tool for the further analysis of complex SS-LAN configurations has therefore been developed and this will form the basis for further work.
11
Mattingley-Scott, Mark Alistair. « A code division multiple spread spectrum local area network ». Thesis, Durham University, 1989. http://etheses.dur.ac.uk/1451/.
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12
Lu, Huimei. « Study and Comparison of Spectrum Sensing Methods ». Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177361.
Texte intégralRésumé :
Efficient utilization of frequency bands has attracted more and more attention. Most of the licensed spectrum nowadays is under-utilized and some unlicensed services are allowed to use the available spectrum without causing harmful interference to the primary users. Therefore, unlicensed users should be able to detect spectrum holes reliably. Spectrum sensing and estimation is an important factor to achieve this. In this thesis, several spectrum sensing and estimation methods are compared based on receiver operating characteristics. Simulation results show that there is a trade-off among different methods.
13
Özyagci, Ali. « Selfish Dynamic Spectrum Access in Multichannel Wireless Networks : Complete and incomplete information analysis ». Licentiate thesis, KTH, Kommunikationssystem, CoS, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50738.
Texte intégralRésumé :
The increasing popularity and widespread deployment of wireless data systems fuel the increasing demand for more spectrum. On the other hand, various studies measuring spectrum utilization show that there is a huge variation in spectrum utilization at different times and locations. In view of this, various dynamic spectrum access (DSA) methods have been proposed in order to achieve more efficient utilization of spectrum resources by virtue of exploiting the variations in spectrum demand over time and space. Implementing DSA systems in a centralized way can lead to complexity and scalability problems due to the extensive control signaling involved. Therefore distributed implementations of DSA systems in which the users can access the system resources at their own discretion have been proposed. These distributed mechanisms typically incorporate cognitive radio systems which act as agents on behalf of users to measure the radio environment and make decisions based on these measurements. On the other hand, the freedom of the users in distributed systems to form their actions can lead each user to try to maximize its benefit from the system without regard the overall performance of the DSA system. Therefore, selfish behavior can prevail in distributed systems, which is likely to degrade the system performance.In this thesis we investigate the implications of selfish decision making in dynamic spectrum access systems. To address this broad problem, we focus our analysis on a particular system which can represent the essential properties of DSA systems and thus can shed light on the performance of the broad class of DSA systems with selfish users. Specifically, we model a DSA system as a multichannel random access system which uses ALOHA for medium access, and we analyze the behavior of the selfish users by modeling the system as a non-cooperative game. In this analysis we incorporate the effect of channel state information on the decision making of the users; we consider both cases when the users act on global (complete) and on local (incomplete) information. We determine the behavior of the selfish users at the Nash equilibria of the non-cooperative game and measure the performance of the system in terms of sum and individual utilities for various user loads and amount of available resources. We try to identify how the performance of the DSA system with selfish users compares with its cooperative counterpart. By performing these analyses we provide insights into the broader question of whether selfish users can utilize spectrum resources in a DSA system as well as cooperative users.QC 20111208
MultiOperator Dynamic Spectrum access (MODyS)
14
Rosenblau, Gabriela [Verfasser]. « Social information processing in naturalistic settings : Insights from Autism Spectrum Disorders / Gabriela Rosenblau ». Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1047097567/34.
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15
Fletcher-, Watson Sue. « Understanding attention to social information in adults with and without autism spectrum disorders ». Thesis, Durham University, 2008. http://etheses.dur.ac.uk/2278/.
Texte intégralRésumé :
This thesis aims to further our understanding of social attention, and its manifestation in adults with autism spectrum disorders (ASD) and their typically-developed (TD) peers. Atypicalities in social attention have been proposed to play a crucial role in the development of autism. If social attention difficulties persist across the life-span, we would also expect them to impair ongoing social interactions in adolescents and adults with ASD. However, social attention in adulthood has been little examined. Instead, research tends to focus on more complex social cognitive difficulties, or to investigate attention to social stimuli presented in isolation. Our understanding of the role of social attention in autism is further inhibited by conflicting evidence on the influence of high-level input and low-level stimulus properties on selecting the focus of attention in TD individuals. The studies presented here tackle these issues by assessing social attention in adults using stimuli which: present social information in a realistic context; measure spontaneous attentional processes; and provide control over the low-level properties of stimuli. Three studies each employed a method newly applied to the study of social attention. These were: a free- description task that coded verbal accounts of social scenes; a social change detection task that recorded change detection speed and accuracy for alterations to social and non-social aspects of a person; and a preferential-looking task that presented social and non-social scenes side-by-side, while recording eye-movements. It was predicted that findings from each study would indicate a social attention bias in TD adults, while people with ASD would have either a weaker social attention bias or no bias at all. In contrast to predictions, these results showed that people with ASD spontaneously attend to social stimuli, as revealed by the social content of their verbal descriptions and their rapid and accurate detection of changes to eye-gaze direction. However, eye-tracking data in the preferential-looking task indicate that the social attention bias is subtly different in people with ASD, who show a reduced attentional priority for social information, and less persistence in looking at social stimuli over time, compared to TD participants. A series of cross-task analyses examining relationships between tasks indicated that a single social attention construct which operates across tasks and scenarios may not exist. These studies also emphasise the need to make distinctions between different types of social information and the idea of a hierarchy of social stimuli available in the real world is proposed. Taken together, the studies reported in this thesis provide new data indicating that social attentional difficulties found in children with autism do not continue in adulthood. Strong attentional preferences for social information, which override the influence of low-levelstimulus properties, are found in both TO and ASD groups. The findings also contribute a new way of thinking about the construct of social attention, in particular indicating that different types of social information may interact with individual attentional preferences. These data are interpreted in the context of recent findings of perceptual atypicalities in people with ASD, which may interact with their social difficulties. The motion and multisensory properties of real-life social interaction may present specific processing difficulties for people with ASD. If so, the mild group differences found in our studies could translate into profound problems for people with ASD in the real world, and this is an area ripe for futureresearch.
16
Peiris, Bemini Hennadige Janath. « Resource allocation in DS-CDMA systems with side information at the transmitter ». Texas A&M University, 2006. http://hdl.handle.net/1969.1/5004.
Texte intégralRésumé :
In a multiuser DS-CDMA system with frequency selectivity, each userâÂÂs spreading
sequence is transmitted through a different channel and the autocorrelation and
the cross correlation properties of the received sequences will not be the same as
that of the transmitted sequences. The best way of designing spreading sequences
for frequency selective channels is to design them at the receiver exploiting the usersâÂÂ
channel characteristics. By doing so, we can show that the designed sequences outperform
single user AWGN performance.
In existing sequence design algorithms for frequency selective channels, the design
is done in the time domain and the connection to frequency domain properties
is not established. We approach the design of spreading sequences based on their
frequency domain characteristics. Based on the frequency domain characteristics of
the spreading sequences with unconstrained amplitudes and phases, we propose a
reduced-rank sequence design algorithm that reduces the computational complexity,
feedback bandwidth and improves the performance of some existing sequence design
algorithms proposed for frequency selective channels.
We propose several different approaches to design the spreading sequences with constrained amplitudes and phases for frequency selective channels. First, we use the
frequency domain characteristics of the unconstrained spreading sequences to find a
set of constrained amplitude sequences for a given set of channels. This is done either
by carefully assigning an already existing set of sequences for a given set of users or by
mapping unconstrained sequences onto a unit circle. Secondly, we use an information
theoretic approach to design the spreading sequences by matching the spectrum of
each userâÂÂs sequence to the water-filling spectrum of the userâÂÂs channel.
Finally, the design of inner shaping codes for single-head and multi-head magnetic
recoding channels is discussed. The shaping sequences are designed considering them
as short spreading codes matched to the recoding channels. The outer channel code
is matched to the inner shaping code using the extrinsic information transfer chart
analysis.
In this dissertation we introduce a new frequency domain approach to design
spreading sequences for frequency selective channels. We also extend this proposed
technique to design inner shaping codes for partial response channels.
17
Al-Rawas, Layth. « The design of synchronisation and tracking loops for spread-spectrum communication systems ». Thesis, University of Bath, 1985. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370459.
Texte intégralRésumé :
The work reported in this thesis deals with aspects of synchronisation and tracking in direct sequence spread spectrum systems used in ranging and communications applications. This is regarded as a major design problem in such systems and several novel solutions are presented. Three main problem areas have been defined: i) reduction of the acquisition time of code sychronisation in the spread spectrum receiver; ii) reduction of the receiver complexity; iii) improvement of the signal to noise ratio performance of the system by better utilisation of the power spectrum in the main lobe of the transmitted signal. Greater tolerance to Doppler shift effects is also important. A general review of the spread spectrum concept and past work is first given in Chapter One, and common methods of synchronisation and tracking are reviewed in Chapter Two. There, current performance limitations are also included. In Chapter Three a novel method is given for increasing the speed of synchronisation between locally generated and received codes, using a technique of controlling the loop's error curve during acquisition. This method is applied to different width delay lock loops, and a significant increase in maximum search rate is obtained. The effect of the width of the discriminator characteristics and damping ratio on the maximum search rate are also examined. The technique is applied to data modulated spread spectrum systems which use either synchronous or asynchronous data communication systems. All methods have been tested experimentally and found to perform as predicted theoretically. Several novel spread sprectrum configurations are given in Chapter Four which employ multi-level sequences. Some configurations have reduced the complexity and cost of the spread spectrum receivers. Others show some improvement in the maximum search rate as well as the signal to noise ratio performance. Some of these configurations have been implemented experimentally. In Chapter Five, the generation and properties of the composite (Kronecker) sequences are explained. Several types of component sequences are examined. And the reception of these composite sequences are discussed. In particular, a technique is introduced for achieving a rapid acquisition of phase synchronisation using these codes. The effect of white Gaussian noise on the acquisition performance of the delay lock loop is given in Chapter Six. Experimental results are obtained for both digital and analogue correlators. Chapter Seven gives a final summary of the conclusions, and further work suggestions.
18
BARNES, LARRY. « Review of Spectrum Support Information for U.S. Air Force Telemetry Equipment Development and Procurement ». International Foundation for Telemetering, 1986. http://hdl.handle.net/10150/615381.
Texte intégralRésumé :
International Telemetering Conference Proceedings / October 13-16, 1986 / Riviera Hotel, Las Vegas, NevadaThis paper presents a review of spectrum support information as it pertains to the development and procurement of U. S. Air Force Telemetry Equipment. Highlights of this review include: Definitions of terms used in this paper that are peculiar to spectrum management; frequency bands encouraged by the U. S. Air Force for Telemetry Equipment Development and Procurement for use in the United States including station, channeling, and bandwidth information; frequency bands discouraged by the U. S. Air Force for Telemetry Equipment Development and Procurement for use in the United States; summary of Telemetry Equipment Electromagnetic Compatibility (EMC) Parameters required when requesting certification of spectrum support in the United States; and finally a summary of telemetry equipment EMC standards associated with the certification of spectrum support in the United States.
19
Elshaer, Ehab. « Millimetre-Wave Spectrum Sharing in Future Mobile Networks : Techno-Economic Analysis ». Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-206078.
Texte intégralRésumé :
Mobile operators passed through many phases in the market over the last several years, since the beginning of mobile broadband services. When the first smart phone was introduced in 2007, it caused a huge increase in the traffic and the users demand kept on increasing. This exponential growth has led to a severe shortage in the available capacity which caused that mobile users don’t have their promised quality of service and coverage. Operators began to put different scenarios for the next-generation mobile networks, putting in consideration the expected increase in the number of users along with their high demand.As a new proposed solution to the scarcity of empty spectrum slots, operating in higher frequency bands (noted as mmwave) emerged as a solution that will provide larger bandwidths with lower prices for the license. Mmwave will provide users with high data rates but on the other hand, has a low penetration rate that can be fixed by increasing the base stations. Another technique for the operators to follow is that they share their own spectrum with each other, by changing the classic way of exploiting the spectrum which proved a low efficiency and high cost, operators can increase their spectrum and coverage with lower cost.To get a clear understanding of how the operators will decide their future strategies, a technical analysis of the new strategies will not be enough, a technical one also will make it clearer and will help the operators in making the decision. The objective of this thesis is to perform a Techno-Economic analysis to get a full image of the system performance. Our system will consist of 2 operators working in mmwave band with antennas equipped with directional beamforming and the base station transmitters will consist of small cells serving outdoor users only. The main question we want to answer is what will be the effect of decreasing the beamwidth on the system performance and when the operators will need to share their spectrum with each other. The performance evaluation will be based on measuring the downlink achievable rate. As we will be performing an economical evaluation, the number of base stations required in each strategy will be an important parameter to evaluate its economic feasibility and cost savings. The different scenarios will include variations of the beamwidth and coordination between the operators with an objective of seeking the best performance along with cost savings. The results should give us a clear look on how the operators will decide for a certain strategy depending on downlink data rate as a KPI and the number of deployed base stations as a limiting factor.
20
Velasco, Diego. « Full spectrum information operations and the information professional officer intermediate qualification process : filling the gap to ensure the continued leadership of the information professional community in the area of information dominance / ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FVelasco.pdf.
Texte intégral
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Lasso, Juan Pablo. « Alternative Mobile Broadband Deployment in Countries with Low Spectrum Allocation and Low Fixed Line Penetration ». Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-143494.
Texte intégralRésumé :
The research work presented in this document deals with the problem of implementing high capacity mobile networks that are able to accommodate the ever increasing amounts of data traffic produced by mobile broadband users, given the dramatic expansion this service has experienced in the recent past due to the popularity of smartphones and tablets. Moreover, the analysis focuses in the feasibility of considering alternative deployment strategies that may render cost-efficient solutions while overcoming the challenges posed by the low amount of spectrum allocated to operators and the limited number of fixed telephone and internet lines available, which are characteristic of developing countries. In this context, an assessment in the scenario of the Telecommunications market in Ecuador is provided, for three specific strategies: network sharing, the use of secondary spectrum in TV white spaces, and offloading of traffic to local networks. The main factors considered are the economic situation, the penetration of fixed and mobile services, the regulatory environment, and the set up of the mobile operators in the market. Descriptions and comparisons with Chile and Sweden are included, as they present scenarios with higher levels of development, giving the opportunity to look at the way they have managed to improve the conditions in their markets and provide suggestions to allow Ecuador to follow their steps. The results show that network sharing could be feasible mostly in the way of passive sharing, given regulatory restrictions. Also, the introduction of at least one new operator could provide better conditions for this strategy. On the other hand, the use of secondary spectrum would be a great solution, but it may be hard to implement it due to regulatory delays and economic issues related to the potentially high costs mobile phones supporting cognitive radio technologies may have. Finally, offloading of traffic to local networks is possible, but limited to urban areas where the density of fixed internet and telephone lines may support the deployment of femtocells or Wi-Fi networks.
22
Souza, Higor Amario de. « Assessment of spectrum-based fault localization for practical use ». Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-17082018-153806/.
Texte intégralRésumé :
Debugging is one of the most time-consuming activities in software development. Several fault localization techniques have been proposed in the last years, aiming to reduce development costs. A promising approach, called Spectrum-based Fault localization (SFL), consists of techniques that provide a list of suspicious program elements (e.g., statements, basic blocks, methods) more likely to be faulty. Developers should inspect a suspiciousness list to search for faults. However, these fault localization techniques are not yet used in practice. These techniques are based on assumptions about the developer\'s behavior when inspecting such lists that may not hold in practice. A developer is supposed to inspect an SFL list from the most to the least suspicious program elements (e.g., statements) until reaching the faulty one. This assumption leads to some implications: the techniques are assessed only by the position of a bug in a list; a bug is deemed as found when the faulty element is reached. SFL techniques should pinpoint the faulty program elements among the first picks to be useful in practice. Most techniques use ranking metrics to assign suspiciousness values to program elements executed by the tests. These ranking metrics have presented similar modest results, which indicates the need for different strategies to improve the effectiveness of SFL. Moreover, most techniques use only control-flow spectra due to the high execution costs associated with other spectra, such as data-flow. Also, little research has investigated the use of SFL techniques by practitioners. Understanding how developers use SFL may help to clarify the theoretical assumptions about their behavior, which in turn can collaborate with the proposal of techniques more feasible for practical use. Therefore, user studies are a valuable tool for the development of the area. The goal of this thesis research was to propose strategies to improve spectrum-based fault localization, focusing on its practical use. This thesis presents the following contributions. First, we investigate strategies to provide contextual information for SFL. These strategies helped to reduce the amount of code to be inspected until reaching the faults. Second, we carried out a user study to understand how developers use SFL in practice. The results show that developers can benefit from SFL to locate bugs. Third, we explore the use of data-flow spectrum for SFL. Data-flow spectrum singles out faults significantly better than control-flow spectrum, improving the fault localization effectiveness.Depuração é uma das atividades mais custosas durante o desenvolvimento de programas. Diversas técnicas de localização de defeitos têm sido propostas nos últimos anos com o objetivo de reduzir custos de desenvolvimento. Uma abordagem promissora, chamada Localização de Defeitos baseada em Espectro (LDE), é formada por técnicas que fornecem listas contendo elementos de código (comandos, blocos básicos, métodos) mais suspeitos de conter defeitos. Desenvolvedores deveriam inspecionar uma lista de suspeição para procurar por defeitos. No entanto, essas técnicas de localização de defeitos ainda não são usadas na prática. Essas técnicas baseiam-se em suposições sobre o comportamento de desenvolvedores durante a inspeção de tais listas que podem não ocorrer na prática. Um desenvolvedor supostamente inspeciona uma lista de LDE a partir do elemento mais suspeito para o menos suspeito até atingir o elemento defeituoso. Essa suposição leva a algumas implicações: as técnicas são avaliadas somente pela posição dos defeitos nas listas; um defeito é considerado como encontrado quando o elemento defeituoso é atingido. Técnicas de LDE deveriam posicionar os elementos de código defeituosos entre as primeiras posições para serem úteis na prática. A maioria das técnicas usa métricas de ranqueamento para atribuir valores de suspeição aos elementos executados pelos testes. Essas métricas de ranqueamento têm apresentado resultados semelhantes, o que indica a necessidade de estratégias diferentes para melhorar a eficácia de LDE. Além disso, a maioria das técnicas usa somente espectros de fluxo de controle devido ao alto custo de execução associado a outros espectros, tais como fluxo de dados. Também, poucas pesquisas têm investigado o uso de técnicas de LDE por programadores. Entender como desenvolvedores usam LDE pode ajudar a esclarecer as suposições teóricas sobre seu comportamento, o que por sua vez pode para colaborar para a proposição de técnicas mais viáveis para uso prático. Portanto, estudos com usuários são importantes para o desenvolvimento da área. O objetivo desta pesquisa de doutorado foi propor estratégias para melhorar a localização de defeitos baseada em espectro focando em seu uso prático. Esta tese apresenta as seguintes contribuições originais. Primeiro, nós investigamos estratégias para fornecer informação de contexto para LDE. Essas estratégias ajudaram a reduzir quantidade de código a ser inspecionado até atingir os defeitos. Segundo, nós realizamos um estudo com usuários para entender como desenvolvedores usam LDE na prática. Os resultados mostram que desenvolvedores podem beneficiar-se de LDE para localizar defeitos. Terceiro, nós exploramos o uso de espectros de fluxo de dados para LDE. Mostramos que o espectro de fluxo de dados seleciona defeitos significamente melhor que espectro de fluxo de controle, aumentando a eficácia de localização de defeitos.
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Switzer, Earl R., John Wrin et James Huynh. « COMBINING TECHNOLOGIES TO FOSTER IMPROVED TSPI ACCURACY AND INCREASE SHARING OF THE FREQUENCY SPECTRUM ». International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/608757.
Texte intégralRésumé :
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, NevadaThe loss of radio frequency (RF) spectrum for use in testing has steadily increased the likelihood that users of the few remaining frequencies available to test ranges will experience scheduling conflicts and interference with nontest users. A gradual increase in the base of test customers engaged in scientific, military, and commercial R&D, point toward a near term situation in which more test customers will be competing for fewer frequencies. The test ranges, often operating in close geographical proximity with other communications-intensive functions as well as with each other, will also encounter increasing out-of-band and adjacent-channel interference. This projected growth of R&Drelated testing constrained to operate in a diminished RF spectrum (and a more confined test space), will undoubtedly stimulate the development of new products that make more efficient use of the RF spectrum. This paper describes one such innovative approach to spectrum sharing. The authors assess the operational need for an affordable miniaturized avionics instrument package based on a C-band radar transponder integrated with a Global Positioning System/Inertial Measurement Unit (GPS/IMU). The proposed approach would make use of frequencies already allocated for use by existing C-band aeronautical transponders. It would augment the format of the transponder output data to include the vehicle position obtained from an onboard GPS/IMU. Existing range instrumentation radars, such as the venerable AN/FPS-16, could be modified with lowcost upgrade kits to provide uniformly higher accuracy over the entire transponder coverage range.
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Sephus, Nashlie H. « A framework for exploiting modulation spectral features in music data mining and other applications ». Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52243.
Texte intégralRésumé :
When a signal is decomposed into frequency bands, demodulated into modulator and carrier pairs, and portrayed in a carrier frequency-versus modulator frequency domain, significant information may be automatically observed about the signal. We refer to this domain as the modulation spectral domain. The modulation spectrum is referred to as a windowed Fourier transform across time that produces an acoustic frequency versus modulation frequency representation of a signal. Previously, frameworks incorporating the discrete short-time modulation transform (DSTMT) and modulation spectrum have been designed mostly for filtering of speech signals. This modulation spectral domain is rarely, if ever, discussed in typical signal processing courses today, and we believe its current associated tools and applications are somewhat limited. We seek to revisit this domain to uncover more intuition, develop new concepts to extend its capabilities, and increase its applications, especially in the area of music data mining.
A recent interest has risen in using modulation spectral features, which are features in the modulation spectral domain, for music data mining. The field of music data mining, also known as music information retrieval (MIR), has been rapidly developing over the past decade or so. One reason for this development is the aim to develop frameworks leveraging the particular characteristics of music signals instead of simply copying methods previously applied to its speech-centered predecessors, such as speech recognition, speech synthesis, and speaker identification. This research seeks to broaden the perspective and use of an existing modulation filterbank framework by exploiting modulation features well suited for music signals.
The objective of this thesis is to develop a framework for extracting modulation spectral features from music and other signals. The purpose of extracting features from these signals is to perform data mining tasks, such as unsupervised source identification, unsupervised source separation, and audio synthesis. More specifically, this research emphasizes the following: the usefulness of the DSTMT and the modulation spectrum for music data mining tasks; a new approach to unsupervised source identification using modulation spectral features; a new approach to unsupervised source separation; a newly introduced analysis of FM features in an AM-dominated modulation spectra; and other applications.
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Firman, Fikri. « Outdoor Small Cell Deployment with Complementary Spectrum Authorizations, Licensed (LSA) and Unlicensed (LAA) : Techno-Economic Analysis ». Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207140.
Texte intégralRésumé :
The significant increase in mobile data traffc has put a considerable load on the wireless mobile networks. In the current highly competitive market, Mobile Network Operators (MNOs) have to strive to provide additional capacityof their network, by also considering the cost factor to make their business sustainable. Along with advances in spectrum-efficient technologies, small cells deployment have provided cost-efficient methods to provide additional capacity for indoor and outdoor subscribers. The gain of better spectrum utilization and opportunistic spectrum access have motivated the deployment of wireless networks utilizing below 6GHz spectrum, where there are opportunities for mobile networks to access the spectrum by co-existing with incumbent users and technologies. Two emerging complementary spectrum authorizations have attracted industry and academia, Licensed Shared Access (LSA) and License Assisted Access(LAA). In this thesis, the techno-economic aspects of operating under individual authorization (LSA) and general authorization (LAA) regimes are investigated and compared. The dynamics of operating under unlicensed spectrum are represented considering the scenario of two MNOs co-existing following the regulatory requirements. The results show that choosing the appropriate channel selection mechanism is of high importance when operating under the unlicensed regime (LAA). The results indicate that LAA can be an alternative for cost-efficient deployment method in some scenarios, for example when there is a low or moderate availability of LSA bandwidth. For the future work, we suggest an optimized user association to the small cells to provide a better load balancing mechanism.Den avsevärda ökningen av den mobila datatrafiken har skapat stor belastning på de trådlösa mobilnäten. I den nuvarande mycket konkurrensutsatta marknaden, måste mobiloperatörerna (MNO) sträva efter att skapa ytterligare kapacitet i deras nätverk, samtidigt som de måste tänka på kostnadsfaktorerför att göra sin verksamhet hållbar. Tillsammans med framsteginom spektrumeffektiv teknik och driftsättning av små basstationer, ha rman fått fram kostnadseffektiva metoder för att öka kapaciteten för inom- och utomhusanvändare. Fördelen av bättre spektrumanvändning för frekvenser under 6 GHz och opportunistiska tillgång av spektrum, har motiverat utbyggnaden av trådlösanätverk. Detta möjliggör för mobila nätverk att använda spektrumet genom att samexistera med etablerade användare och tekniker. Två nya kompletterande spektrumtillstånd har lockat industrin och den akademiska världen, Licensed Shared Access (LSA) och License Assisted Access (LAA). I denna avhandling, har de tekno-ekonomiska aspekterna av LSA och LAA regimer undersökts och jämförts. Dynamiken av drift i olicensierat spektrum representeras i scenariot av två mobilnätsoperatörer samexisterar och följer lagkraven. Resultaten indikerar att valet av lämplig mekanism t.ex. val av rätt kanal är av stor betydelse vid användning av olicensierad regim (LAA). Resultatentyder på att LAA kan vara ett alternativ för kostnadseffektiv distributionsmetod i vissa scenarier, till exempel när det finns en låg eller måttlig tillgång på LSA bandbredd. För det framtida arbetet, föreslår vi en optimerad användarassociation till de små cellerna för att ge en bättre lastbalansering mekanism.
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Wang, Ji. « Imperfect Monitoring in Multi-agent Opportunistic ChannelAccess ». Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71789.
Texte intégralRésumé :
In recent years, extensive research has been devoted to opportunistically exploiting spectrum in a distributed cognitive radio network. In such a network, autonomous secondary users (SUs) compete with each other for better channels without instructions from a centralized authority or explicit coordination among SUs. Channel selection relies on channel occupancy information observed by SUs, including whether a channel is occupied by a PU or an SU. Therefore, the SUs' performance depends on the quality of the information. Current research in this area often assumes that the SUs can distinguish a channel occupied by a PU from one occupied by another SU. This can potentially be achieved using advanced signal detection techniques but not by simple energy detection. However, energy detection is currently the primary detection technique proposed for use in cognitive radio networks. This creates a need to design a channel selection strategy under the assumption that, when SUs observe channel availability, they cannot distinguish between a channel occupied by a PU and one occupied by another SU. Also, as energy detection is simpler and less costly than more advanced signal detection techniques, it is worth understanding the value associated with better channel occupancy information.
The first part of this thesis investigates the impact of different types of imperfect information on the performance of secondary users (SUs) attempting to opportunistically exploit spectrum resources in a distributed manner in a channel environment where all the channels have the same PU duty cycle. We refer to this scenario as the homogeneous channel environment. We design channel selection strategies that leverage different levels of information about channel occupancy. We consider two sources of imperfect information: partial observability and sensing errors. Partial observability models SUs that are unable to distinguish the activity of PUs from SUs. Therefore, under the partial observability models, SUs can only observe whether a channel was occupied or not without further distinguishing it was occupied by a PU or by SUs. This type of imperfect information exists, as discussed above, when energy detection is adopted as the sensing technique. We propose two channel selection strategies under full and partial observability of channel activity and evaluate the performance of our proposed strategies through both theoretical and simulation results. We prove that both proposed strategies converge to a stable orthogonal channel allocation when the missed detection rate is zero. The simulation results validate the efficiency and robustness of our proposed strategies even with a non-zero probability of missed detection.
The second part of this thesis focuses on computing the probability distribution of the number of successful users in a multi-channel random access scheme. This probability distribution is commonly encountered in distributed multi-channel communication systems. An algorithm to calculate this distribution based on a recursive expression was previously proposed. We propose a non-recursive algorithm that has a lower execution time than the one previously proposed in the literature.
The third part of this thesis investigates secondary users (SUs) attempting to opportunistically exploit spectrum resources in a scenario where the channels have different duty cycles, which we refer to as the heterogeneous channel environment. In particular, we model the channel selection process as a one shot game. We prove the existence of a symmetric Nash equilibrium for the proposed static game and design a channel selection strategy that achieves this equilibrium. The simulation results compare the performance of the Nash equilibrium to two other strategies(the random and the proportional strategies) under different PU activity scenarios.Master of Science
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Juntti, J. (Juhani). « Performance analysis of suboptimal soft decision DS/BPSK receivers in pulsed noise and CW jamming utilizing jammer state information ». Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514273869.
Texte intégralRésumé :
Abstract
The problem of receiving direct sequence (DS) spread spectrum, binary phase shift keyed (BPSK) information in pulsed noise and continuous wave (CW) jamming is studied in additive white noise. An automatic gain control is not modelled. The general system theory of receiver analysis is first presented and previous literature is reviewed. The study treats the problem of decision making after matched filter or integrate and dump demodulation. The decision methods have a great effect on system performance with pulsed jamming. The following receivers are compared: hard, soft, quantized soft, signal level based erasure, and chip combiner receivers. The analysis is done using a channel parameter D, and bit error upper bound. Simulations were done in original papers using a convolutionally coded DS/BPSK system. The simulations confirm that analytical results are valid. Final conclusions are based on analytical results.
The analysis is done using a Chernoff upper bound and a union bound. The analysis is presented with pulsed noise and CW jamming. The same kinds of methods can also be used to analyse other jamming signals. The receivers are compared under pulsed noise and CW jamming along with white gaussian noise. The results show that noise jamming is more harmful than CW jamming and that a jammer should use a high pulse duty factor. If the jammer cannot optimise a pulse duty factor, a good robust choice is to use continuous time jamming.
The best performance was achieved by the use of the chip combiner receiver. Just slightly worse was the quantized soft and signal level based erasure receivers. The hard decision receiver was clearly worse. The soft decision receiver without jammer state information was shown to be the most vulnerable to pulsed jamming. The chip combiner receiver is 3 dB worse than an optimum receiver (the soft decision receiver with perfect channel state information).
If a simple implementation is required, the hard decision receiver should be used. If moderate complex implementation is allowed, the quantized soft decision receiver should be used. The signal level based erasure receiver does not give any remarkable improvement, so that it is not worth using, because it is more complex to implement. If receiver complexity is not limiting factor, the chip combiner receiver should be used.
Uncoded DS/BPSK systems are vulnerable to jamming and a channel coding is an essential part of antijam communication system. Detecting the jamming and erasing jammed symbols in a channel decoder can remove the effect of pulsed jamming. The realization of erasure receivers is rather easy using current integrated circuit technology.
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Ivey, Michelle Louise. « Priming as a Means of Increasing Spontaneous Verbal Language in Children with Autism Spectrum Disorder ». Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/epse_diss/56.
Texte intégralRésumé :
ABSTRACT THE EFFECTS OF PRIMING ON SPONTANEOUS VERBAL LANGUAGE IN CHILDREN WITH AUTISM SPECTRUM DISORDERS by Michelle L. Ivey A multi-element design was used to investigate the effect of priming on spontaneous verbal communication in children with Autism Spectrum Disorders (ASD). Three children with ASD engaged in 20-minute thematic activity sessions (ACT) with the investigator. Prior to the ACTs, they met with another trained researcher for 10-minute presessions. Half of the presessions incorporated the conventions of priming with materials to be used in the upcoming ACT (i.e., related presessions; RP). During the other half of the presessions, participants were not primed for the upcoming ACT (i.e., unrelated presesessions; UP). The researcher conducted presessions so the investigator was blind to the condition. Procedural fidelity checks of the presessions, based on a checklist of the critical components of priming, revealed 100% adherence to procedures. Participants’ utterances during ACT were recorded, transcribed, and coded based on functionality. The dependent variables were spontaneous comments, requests, topic initiations, social information seeking, and total. Once the criterion of a 30% increase from the mean of the first 3 UP was achieved for three consecutive sessions, priming was withdrawn and then reinstated to demonstrate a functional relation. Additionally, Cohen's d was calculated to determine effect size for the intervention. Reliability was assessed for transcription and coding. There were fewer than 10 word disagreements on any transcript, which did not affect coding. A line by line comparison of the coding across the dependent variables yielded an average reliability of 85%. Visual inspection of the data and statistical analysis revealed that two of the three participants reached criterion for spontaneous comments (Cohen's d = .32 and .95), one reached criterion for total utterances (Cohen's d = 2.99), the other achieved the goal during the reinstatement following the withdrawal (Cohen’s d = 1.00). None increased requesting. Topic initiation and social information seeking did not occur with sufficient frequency for meaningful analyses. Similar to most interventions with individuals with ASD, priming was effective for increasing spontaneous verbal comments for some but not all of the participants. Priming was highly effective for two of the participants. This ground-breaking study creates momentum for further investigation and examination of the variables that affect benefit.
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Abouei, Mina. « Enhancing emotional communication between autistic and non-autistic individuals through assistive Information Technology ». Thesis, Uppsala universitet, Institutionen för informatik och media, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-447877.
Texte intégralRésumé :
Recognising people’s emotions is a promising research area in human-computer interaction as emotional communication plays a crucial role in humans’ lives. One of the main reasons for ineffective emotional communication is a deficit in understanding emotional signals such as facial expressions and body posture. There is a bidirectional challenge between autistic and non-autistic individuals since they display their emotional signals differently. This thesis discovers differences in emotional signals, in particular facial expressions, body posture, and physiological signals. Based on the interviews and questionnaires conducted in this thesis, the need to design an aid tool to assist autistic and non-autistic participants during their emotional communication is identified. Therefore, Emognition, a smartwatch, and its mobile application is designed to blur these differences and enhance the emotional communication between them. Furthermore, Emognition’s user evaluation indicates that the smartwatch could successfully detect nonautistic participants’ sadness and happiness. Also, they found the mobile application useful and aesthetically motivating to interact with. Even though we could not evaluate how well the Emognition recognises autistic participants’ sadness and happiness, it is promising to measure their emotions successfully by accurate sensors and, more importantly, by finding their autonomic response patterns to different emotions and enhance emotional communication between autistic and nonautistic people by Emognition.
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Donaldson, Amy Lynn. « An investigation of assessment methods for examining the production of requests for information by young children with autism spectrum disorders / ». Thesis, Connect to this title online ; UW restricted, 2005. http://hdl.handle.net/1773/8244.
Texte intégral
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Torku, Thomas K. « Takens Theorem with Singular Spectrum Analysis Applied to Noisy Time Series ». Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etd/3013.
Texte intégralRésumé :
The evolution of big data has led to financial time series becoming increasingly complex, noisy, non-stationary and nonlinear. Takens theorem can be used to analyze and forecast nonlinear time series, but even small amounts of noise can hopelessly corrupt a Takens approach. In contrast, Singular Spectrum Analysis is an excellent tool for both forecasting and noise reduction. Fortunately, it is possible to combine the Takens approach with Singular Spectrum analysis (SSA), and in fact, estimation of key parameters in Takens theorem is performed with Singular Spectrum Analysis. In this thesis, we combine the denoising abilities of SSA with the Takens theorem approach to make the manifold reconstruction outcomes of Takens theorem less sensitive to noise. In particular, in the course of performing the SSA on a noisy time series, we branch of into a Takens theorem approach. We apply this approach to a variety of noisy time series.
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Rao, Raghunandan M. « Enhancing Performance of Next-Generation Vehicular and Spectrum Sharing Wireless Networks : Practical Algorithms and Fundamental Limits ». Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/99796.
Texte intégralRésumé :
Over the last few decades, wireless networks have morphed from traditional cellular/wireless local area networks (WLAN), into a wide range of applications, such as the Internet-of-Things (IoT), vehicular-to-everything (V2X), and smart grid communication networks. This transition has been facilitated by research and development efforts in academia and industry, which has resulted in the standardization of fifth-generation (5G) wireless networks. To meet the performance requirements of these diverse use-cases, 5G networks demand higher performance in terms of data rate, latency, security, and reliability, etc. At the physical layer, these performance enhancements are achieved by (a) optimizing spectrum utilization shared amongst multiple technologies (termed as spectrum sharing), and (b) leveraging advanced spatial signal processing techniques using large antenna arrays (termed as massive MIMO). In this dissertation, we focus on enhancing the performance of next-generation vehicular communication and spectrum sharing systems.
In the first contribution, we present a novel pilot configuration design and adaptation mechanism for cellular vehicular-to-everything (C-V2X) networks. Drawing inspiration from 4G and 5G standards, the proposed approach is based on limited feedback of indices from a codebook comprised of quantized channel statistics information. We demonstrate significant rate improvements using our proposed approach in terrestrial and air-to-ground (A2G) vehicular channels.
In the second contribution, we demonstrate the occurrence of cellular link adaptation failure due to channel state information (CSI) contamination, because of coexisting pulsed radar signals that act as non-pilot interference. To mitigate this problem, we propose a low-complexity semi-blind SINR estimation scheme that is robust and accurate in a wide range of interference and noise conditions. We also propose a novel dual CSI feedback mechanism for cellular systems and demonstrate significant improvements in throughput, block error rate, and latency, when sharing spectrum with a pulsed radar.
In the third contribution, we develop fundamental insights on underlay radar-massive MIMO spectrum sharing, using mathematical tools from stochastic geometry. We consider a multi-antenna radar system, sharing spectrum with a network of massive MIMO base stations distributed as a homogeneous Poisson Point Process (PPP) outside a circular exclusion zone centered around the radar. We propose a tractable analytical framework, and characterize the impact of worst-case downlink cellular interference on radar performance, as a function of key system parameters. The analytical formulation enables network designers to systematically isolate and evaluate the impact of each parameter on the worst-case radar performance and complements industry-standard simulation methodologies by establishing a baseline performance for each set of system parameters, for current and future radar-cellular spectrum sharing deployments.
Finally, we highlight directions for future work to advance the research presented in this dissertation and discuss its broader impacts across the wireless industry, and policy-making.Doctor of Philosophy
The impact of today's technologies has been magnified by wireless networks, due to the standardization and deployment of fifth-generation (5G) cellular networks. 5G promises faster data speeds, lower latency and higher user security, among other desirable features. This has made it capable of meeting the performance requirements of key infrastructure such as smart grid and mission-critical networks, and novel consumer applications such as smart home appliances, smart vehicles, and augmented/virtual reality. In part, these capabilities have been achieved by (a) better spectrum utilization among various wireless technologies (called spectrum sharing), and (b) serving multiple users on the same resource using large multi-antenna systems (called massive MIMO). In this dissertation, we make three contributions that enhance the performance of vehicular communications and spectrum sharing systems. In the first contribution, we present a novel scheme wherein a vehicular communication link adapts to the channel conditions by controlling the resource overhead in real-time, to improve spectral utilization of data resources. The proposed scheme enhances those of current 4G and 5G networks, which are based on limited feedback of quantized channel statistics, fed back from the receiver to the transmitter. In the second contribution, we show that conventional link adaptation methods fail when 4G/5G networks share spectrum with pulsed radars. To mitigate this problem, we develop a comprehensive signal processing framework, consisting of a hybrid SINR estimation method that is robust and accurate in a wide range of interference and noise conditions. Concurrently, we also propose a scheme to pass additional information that captures the channel conditions in the presence of radar interference, and analyze its performance in detail. In the third contribution, we focus on characterizing the impact of 5G cellular interference on a radar system in shared spectrum, using mathematical tools from stochastic geometry. We model the worst-case interference scenario, and study the impact of the system parameters on the worst-case radar performance. In summary, this dissertation advances the state-of-the-art in vehicular communications and spectrum sharing, through (a) novel contributions in protocol design and (b) development of mathematical tools for performance characterization.
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Lim, Yi Huey. « The Postural Control System in Individuals with Autism Spectrum Disorder : Insights from Exploring the Effects of Visual Information on Postural Control ». Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/78788.
Texte intégralRésumé :
The thesis examined the effects of static and dynamic visual information on postural control in individuals with autism spectrum disorder (ASD). The results suggest that the visual-motor mechanism adopted by ASD individuals to control posture is different from typically-developed individuals. Evidence of postural control impairments was also identified in ASD individuals. The findings advance the understanding of postural control in ASD and may guide the development of effective postural control interventions for ASD individuals.
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Arasteh, Davoud. « Computational Intelligence and Complexity Measures for Chaotic Information Processing ». ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/834.
Texte intégralRésumé :
This dissertation investigates the application of computational intelligence methods in the analysis of nonlinear chaotic systems in the framework of many known and newly designed complex systems. Parallel comparisons are made between these methods. This provides insight into the difficult challenges facing nonlinear systems characterization and aids in developing a generalized algorithm in computing algorithmic complexity measures, Lyapunov exponents, information dimension and topological entropy. These metrics are implemented to characterize the dynamic patterns of discrete and continuous systems. These metrics make it possible to distinguish order from disorder in these systems. Steps required for computing Lyapunov exponents with a reorthonormalization method and a group theory approach are formalized. Procedures for implementing computational algorithms are designed and numerical results for each system are presented. The advance-time sampling technique is designed to overcome the scarcity of phase space samples and the buffer overflow problem in algorithmic complexity measure estimation in slow dynamics feedback-controlled systems. It is proved analytically and tested numerically that for a quasiperiodic system like a Fibonacci map, complexity grows logarithmically with the evolutionary length of the data block. It is concluded that a normalized algorithmic complexity measure can be used as a system classifier. This quantity turns out to be one for random sequences and a non-zero value less than one for chaotic sequences. For periodic and quasi-periodic responses, as data strings grow their normalized complexity approaches zero, while a faster deceasing rate is observed for periodic responses. Algorithmic complexity analysis is performed on a class of certain rate convolutional encoders. The degree of diffusion in random-like patterns is measured. Simulation evidence indicates that algorithmic complexity associated with a particular class of 1/n-rate code increases with the increase of the encoder constraint length. This occurs in parallel with the increase of error correcting capacity of the decoder. Comparing groups of rate-1/n convolutional encoders, it is observed that as the encoder rate decreases from 1/2 to 1/7, the encoded data sequence manifests smaller algorithmic complexity with a larger free distance value.
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Van, Den Biggelaar Olivier. « Distributed spectrum sensing and interference management for cognitive radios with low capacity control channels ». Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209612.
Texte intégralRésumé :
Cognitive radios have been proposed as a new technology to counteract the spectrum scarcity issue and increase the spectral efficiency. In cognitive radios, the sparse assigned frequency bands are opened to secondary users, provided that interference induced on the primary licensees is negligible. Cognitive radios are established in two steps: the radios firstly sense the available frequency bands by detecting the presence of primary users and secondly communicate using the bands that have been identified as not in use by the primary users.In this thesis we investigate how to improve the efficiency of cognitive radio networks when multiple cognitive radios cooperate to sense the spectrum or control their interferences. A major challenge in the design of cooperating devices lays in the need for exchange of information between these devices. Therefore, in this thesis we identify three specific types of control information exchange whose efficiency can be improved. Specifically, we first study how cognitive radios can efficiently exchange sensing information with a coordinator node when the reporting channels are noisy. Then, we propose distributed learning algorithms allowing to allocate the primary network sensing times and the secondary transmission powers within the secondary network. Both distributed allocation algorithms minimize the need for information exchange compared to centralized allocation algorithms.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Ullah, Farooq Kifayat. « New Generation of Vibration Experiments Remotely Controlled Over the Internet:Development of Labview based Spectrum Analyzer and Interface ». Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2509.
Texte intégralRésumé :
This thesis is part of the on going work at BTH (Blekinge Technical University) to develop a remote lab for Sound and Vibration Experiments. The aim of this undertaking is to develop a Spectrum Analyzer that can simultaneously take inputs from 10 sensors and be able to measure the Power Spectral Density, Cross correlation, Frequency Response Functions (FRF) and coherence. The Interface and analysis algorithms are developed inLabview programming language. The thesis starts by introducing the overall aim of the project and its scope, the place of this particular thesis in the whole picture and the algorithms used for analysis are introduced. In the second part of the thesis the development of the software is explained and the main aim is to thoroughly document the software. This part of the thesis explains Labview programming concepts in detail to make it easier for other students who want to undertake theses to continue this work and who may not have experience of Labview programming.Two versions of the spectrum analyzer were developed. The third part explains theexperimental set up and results obtained and compares measurements to those obtained using other spectrum analyzers. An accurate Spectrum Analyzer Virtual Instrument has been developed and tested during this thesis project and it can be used as a component of the proposed Sound and vibration analysis laboratory and also for general Spectral Analysis tasks.Good guide to learn Labview and sound and vibration analysis..
fkul08@gmail.com Is my email and i can be contacted via messenger usually at farooq_kifayat@hotmail.com And i can also be contacted via skype using farooqkifayat as my name. I move around a lot so i have no permanent address that stays longer than half a year .
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Baksh, Rehman Asaad. « Edinburgh Social Cognition Test (ESCoT) : a new test of theory of mind and social norm understanding ». Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31385.
Texte intégralRésumé :
Social cognitive abilities are needed to process and understand social information in order to respond appropriately in everyday social interactions. While there are a number of tests that have been developed to measure social cognition in the literature, many have important limitations such as only assessing one ability, performance being predicted by measures of intelligence and exhibiting low ecological validity. To address some of these limitations, I developed a new test called the Edinburgh Social Cognition Test (ESCoT). The ESCoT is an animated test that assesses four domains of social cognition: cognitive Theory of Mind (ToM) (What is X thinking?); affective ToM (How does X feel at the end of the animation?); interpersonal understanding of social norms (Did X behave as other people should behave?); and intrapersonal understanding of social norms (Would you have acted the same as X in the animation?). The aims of this thesis were to examine the validity of the ESCoT as a test of social cognition and to further investigate social cognitive processes in healthy and neurological populations. The ESCoT was firstly administered to a healthy population of older, middle-aged and younger adults to examine the effects of ageing on social abilities. This study found that the ESCoT was sensitive to age; poorer performances on cognitive and affective ToM and also interpersonal but not intrapersonal understanding of social norms were predicted by older age. Furthermore unlike traditional tests used in the study, performance was not predicted by measures of intelligence. Instead, the sex of participants and autistic-like traits, in addition to age were found to be important for performance. The ESCoT was then validated in a sample of adults with Autism Spectrum Disorder (ASD), and performance was compared to performance on established social cognition tests. Convergent validity was demonstrated in the study and the ESCoT was sensitive to social cognitive difficulties found in ASD. This study also showed that the ESCoT was more effective than existing tests at differentiating ASD adults and neurotypical controls. The interplay of social anxiety and empathy on ESCoT performance in addition to further exploring sex and autistic-like traits were then examined in a younger adult population. Social anxiety and empathy were not significant predictors of performance on the ESCoT. Similar to the results of the ageing study, this study found that women were better than men on affective ToM. However, unlike the ageing study, better cognitive ToM performance was predicted by older age. Better performance on interpersonal understanding of social norms and ESCoT total scores were predicted by more years of education. The subsequent chapter then examined the clinical efficacy of the ESCoT in a patient population (Alzheimer's disease, behavioural-variant Frontotemporal dementia and amnestic mild cognitive impairment). Here performance on the ESCoT was compared between the patients and neurotypical controls. It was found that patients performed poorer than neurotypical controls on ESCoT total scores, affective ToM, inter-and intrapersonal understanding of social norms. The final chapter returned to healthy ageing to more closely investigate the consequences of healthy ageing on social cognitive processes, by examining the positivity bias (preference for positive over negative stimuli) found in older adults using an attention paradigm. There was no evidence of the positivity bias in older, middle-aged and younger adults in regards to reaction time or accuracy. However, older and middle-aged adults differed in accuracy across stimuli type compared to younger adults. This thesis offers novel insights into the social cognitive abilities of various populations. The ESCoT presents a new, informative and validated test of social cognition for researchers and clinicians to use, which has many advantages over established tests of social cognition.
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Chammem, Afef. « Robust watermarking techniques for stereoscopic video protection ». Phd thesis, Institut National des Télécommunications, 2013. http://tel.archives-ouvertes.fr/tel-00917964.
Texte intégralRésumé :
The explosion in stereoscopic video distribution increases the concerns over its copyright protection. Watermarking can be considered as the most flexible property right protection technology. The watermarking applicative issue is to reach the trade-off between the properties of transparency, robustness, data payload and computational cost. While the capturing and displaying of the 3D content are solely based on the two left/right views, some alternative representations, like the disparity maps should also be considered during transmission/storage. A specific study on the optimal (with respect to the above-mentioned properties) insertion domain is also required. The present thesis tackles the above-mentioned challenges. First, a new disparity map (3D video-New Three Step Search - 3DV-NTSS) is designed. The performances of the 3DV-NTSS were evaluated in terms of visual quality of the reconstructed image and computational cost. When compared with state of the art methods (NTSS and FS-MPEG) average gains of 2dB in PSNR and 0.1 in SSIM are obtained. The computational cost is reduced by average factors between 1.3 and 13. Second, a comparative study on the main classes of 2D inherited watermarking methods and on their related optimal insertion domains is carried out. Four insertion methods are considered; they belong to the SS, SI and hybrid (Fast-IProtect) families. The experiments brought to light that the Fast-IProtect performed in the new disparity map domain (3DV-NTSS) would be generic enough so as to serve a large variety of applications. The statistical relevance of the results is given by the 95% confidence limits and their underlying relative errors lower than er<0.1
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Craescu, Constantin. « Etudes par **(1)h rmn a haute resolution de la structure et de la dynamique des hemoglobines humaines ». Paris 6, 1987. http://www.theses.fr/1987PA066323.
Texte intégral
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Pillutla, Laxminarayana S. « Resource management in wireless networks ». Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2829.
Texte intégralRésumé :
This thesis considers resource management issues in wireless sensor networks (WSNs),
wireless local area networks (WLANs), and cognitive radio (CR) networks. Since energy
is a critical resource in WSNs, we consider energy minimization techniques based on
explicit node cooperation and distributed source coding (DSC). The explicit node cooperation based on space time block codes (STBC) improves energy efficiency of WSNs,
by reducing the energy consumption per bit of each sensor node. The DSC on the other
hand exploits the spatial correlation in WSNs, and thus reduces the data generated in
a WSN. For the purpose of our analysis, we model the spatial correlation according to
a linear Gauss-Markov model. Through our numerical results, we observe that the node
cooperation combined with DSC can improve energy efficiency for many cases of interest.
A unique aspect of our work is we obtain important structural results using the concepts from monotone comparative statics. These structural results provide insights into the general design of WSNs. Through our numerical results, we also demonstrate that,
the cooperation based transmission can achieve better mutual information (MI)-energy
tradeoff than the non-cooperation based transmission scheme. From the perspective of
WLANs, we propose a price based approach to regulate the channel occupancy of low rate
users, which is known to be the primary cause for low overall throughput in WLANs. Owing to the decentralized nature of WLANs we use non-cooperative game theory as a tool for analysis. Specifically, we use supermodular game theory. Through our analysis, we show that an increase in price leads to an increase in rate of WLAN users. We also prove that the best response dynamics indeed converge to the Nash equilibrium of the
underlying non-cooperative game. Through our numerical results, we demonstrate that
by proper tuning of the price, the proposed price based approach can lead to an improvement in overall throughput of a WLAN. Finally from the perspective of CR networks, we consider the impact of number of channels captured by a secondary user on its transmission control protocol (TCP) throughput. From our simulation results it was found that, there exists a definite optimal number of channels a secondary user needs to capture, to maximize its TCP throughput.
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Jansson, Lena. « Bibliotek tillgängliga för alla ? : En undersökning av bibliotekens upplevda tillgänglighet för användare med autismspektrumtillstånd ». Thesis, Uppsala universitet, Institutionen för ABM, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-400259.
Texte intégralRésumé :
The aim of this master’s thesis is to study how a group of people diagnosed with autism spectrum disorder experience a visit to the library. By interviewing them I hoped to hear their thoughts on noise, lighting and the over all library environment. Did the informants get a fair treament by the library staff or did they feel stigmatized? The thesis is also aiming to expose how accessible the libraries’ websites are. Two librarians shared their insights about accessibility from the library in which they work. The interview showed there are still many aspects that need to improve until the library is autism friendly. The study shows that the informants prefer a silent library compared to a noisy one. They did not experience any stigmatization in the library. The informants use the digital services offered by the library in order to renew their books and to request new ones. However, the websites are not customized for people with Austism spectrum disorder. The informants main concern when visiting the library are loud noise and insufficient signs. This study is a two years master’s thesis in Library and Information Science.
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Alder, Frank A. « Symbol assignment and performance of simplex signaling in high dimensional trellis-coded modulation ». Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1177008035.
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Mora, Guiard Joan. « Full-body interaction and autism : design, development and evaluation of experiences as tools for intervention on motivation and social initiation for ASD children ». Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/395173.
Texte intégralRésumé :
This thesis focuses on the design, development and evaluation of a series of full-body interaction experiences as tools for intervention on motivation and social initiation for children with Autism. Autism Spectrum Disorders are characterized by challenges in social communication. Thus, it is necessary to provide support tools for motivating the learning and use of social behaviors. We developed three systems to explore the characteristics and limitations of the full-body interaction medium for the development of such tools.
This thesis analyzes the characteristics of full-body interaction technologies by focusing on different physical settings, and different interaction design approaches. We have focused our research on motivation, through promoting engagement and exploration attitudes, and social behaviors, by fostering social initiation and collaboration in multi-user environments. This thesis is a first step to design full-body interaction systems for promoting motivation and social behaviors.Aquesta tesis es focalitza en el disseny, desenvolupament i avaluació d'una sèrie d'experiències d'interacció a cos sencer com a eines d'intervenció en motivació i inicialització social en nens amb Autisme. El Trastorn de l'Espectre Autista es caracteritza per dificultats en la socialització i comunicació. Per tant, és necessari de proveir eines de suport per a motivar l'aprenentatge i ús de conductes socials. Hem desenvolupat tres sistemes per a explorar les característiques i limitacions dels mitjans d'interacció a cos sencer per al desenvolupament d'aquestes eines. Aquesta tesis analitza les característiques de les tecnologies d'interacció a cos sencer a través de focalitzar-se en diferents configuracions físiques, i diferents aproximacions de disseny d'interacció. Hem focalitzat la nostra investigació en la motivació, a través del compromís i actituds exploradores, i actituds socials, a través d'encoratjar la iniciació social i la col·laboració en entorns multi usuari. Aquesta tesis és un primer pas en el disseny de sistemes d'interacció a cos sencer per a promoure la motivació i conductes socials.
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Salihou, Adamou Ismaila. « Error exponent bounds and practical short-length coding schemes for Distributed Hypothesis Testing (DHT) ». Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2024. http://www.theses.fr/2024IMTA0446.
Texte intégralRésumé :
Dans les réseaux de communication distribués, les données sont collectées, compressées, et transmises depuis des nœuds distants vers un serveur central pour un traitement ultérieur. Cependant, l’objectif du serveur n’est pas toujours de reconstruire les données originales, mais plutôt de prendre des décisions à partir des données codées reçues. Dans ce contexte, le Test d’Hypothèses Distribué se concentre sur le cas particulier de deux sources et vise à effectuer une prise de décision directement à partir des données compressées, sans passer par une reconstruction préalable. Comme dans le test d’hypothèses classique, deux types d’erreurs sont pris en compte pour évaluer les performances : l’erreur de Type I (fausse alarme) et l’erreur de Type II (décision manquée). Le Test d’Hypothèses Distribué prend en compte une contrainte de débit sur le lien de communication, et l’objectif est de concevoir un schéma de codage afin de maximiser la décroissance exponentielle, appelée exposant d’erreur, de la probabilité d’erreur de Type II, tout en maintenant la probabilité d’erreur de Type I en dessous d’un seuil spécifié. Dans la littérature, ce cadre a principalement été étudié sous un angle théorique de l’information, et la plupart des travaux existants analysent les performances des schémas du Test d’Hypothèses Distribué en supposant des sources indépendantes et identiquement distribuées (i.i.d.).Dans la première partie de cette thèse, nous abordons un modèle plus réaliste et général de sources non-i.i.d. Ce modèle englobe des sources non stationnaires et non ergodiques, reflétant mieux les scénarios réels par rapport au cas i.i.d. Nous dérivons des bornes génériques sur l’exposant d’erreur pour le Test d’Hypothèses Distribué à l’aide d’outils du spectre de l’information pour ce modèle général de sources. Nous montrons la cohérence de ces bornes avec le cas i.i.d. et les caractérisons plus précisément pour deux modèles spécifiques de sources : les sources gaussiennes non-i.i.d., et les sources de type Gilbert-Elliot. De plus, l’étude du Test d’Hypothèses Distribué ne se limite pas à l’analyse des limites théoriques de l’information, mais inclut aussi le développement de schémas de codage pratiques pour ce cadre. Ainsi, dans la deuxième partie de cette thèse, nous développons et implémentons des schémas de codage pratiques de courte longueur, spécialement conçus pour le Test d’Hypothèses Distribué, qui n’avaient pas encore été étudiés dans la littérature. Ces schémas de codage sont basés sur des codes linéaires en blocs et visent des longueurs très courtes, appropriées pour le Test d’Hypothèses Distribué (moins de 100 bits). En outre, nous fournissons des expressions analytiques exactes pour les probabilités d’erreurs de Type I et Type II pour chaque schéma de codage proposé, offrant ainsi des outils utiles pour la conception optimale future de codes DHT. Le travail réalisé dans cette thèse pourrait servir de base à l’investigation théorique et pratique de schémas de codage dédiés à des tâches d’apprentissage plus complexes, telles que la classificationIn distributed communication networks, data is gathered, compressed, and transmitted from remote nodes to a central server for further processing. However, often, the objective of the server is not to reconstruct the original data, but rather to make decisions based on the received coded data. In this context, Distributed Hypothesis Testing (DHT) focuses on the particular case of two sources and addresses decision-making directly from compressed data without prior reconstruction. As in conventional hypothesis testing, two types of errors are considered for performance evaluation: Type-I error (false alarm) and Type-II error (missed detection). DHT considers a rate-limited communication link, and the objective is to design a coding scheme so as to maximize the exponential decay, termed error exponent, of Type-II error probability, while keeping Type-I error probability below a specified threshold. In the literature, this setup was mostly investigated from an information-theoretic perspective, and most existing work analyze the performance of DHT schemes under the assumption of i.i.d. sources. In the first part of this PhD thesis, we address a more realistic and general model of non-i.i.d. sources. This model encompasses non-stationary and non-ergodic sources, and better reflects real-world scenarios compared to the i.i.d. case. We derive generic error exponent DHT bounds using information spectrum tools for the considered general source model. We show the consistency of these bounds with the i.i.d. case and further characterize these bounds for two specific source models: non-i.i.d. Gaussian sources, and Gilbert-Elliot sources. In addition, addressing DHT requires not only the investigation of information-theoretic limits, but also the development of practical coding schemes for this setup. Therefore, in the second part of this thesis, we develop and implement practical short-length coding schemes specifically for DHT, which had not yet been investigated in the literature. These coding schemes are based on linear block codes, and they target very short length which are appropriate for DHT (less than 100 bits). Additionally, we provide tights analytical expressions for the Type-I and Type-II error probabilities for each proposed coding scheme, which provides useful tools for further optimal DHT code designs. The work carried out in this PhD may serve as a basis for the theoretical and practical investigation of coding schemes dedicated to more complex learning tasks such as classification
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Dang, Hieu. « Adaptive multiobjective memetic optimization : algorithms and applications ». Journal of Cognitive Informatics and Natural Intelligence, 2012. http://hdl.handle.net/1993/30856.
Texte intégralRésumé :
The thesis presents research on multiobjective optimization based on memetic computing and its applications in engineering. We have introduced a framework for adaptive multiobjective memetic optimization algorithms (AMMOA) with an information theoretic criterion for guiding the selection, clustering, and local refinements. A robust stopping criterion for AMMOA has also been introduced to solve non-linear and large-scale optimization problems. The framework has been implemented for different benchmark test problems with remarkable results.
This thesis also presents two applications of these algorithms. First, an optimal image data hiding technique has been formulated as a multiobjective optimization problem with conflicting objectives. In particular, trade-off factors in designing an optimal image data hiding are investigated to maximize the quality of watermarked images and the robustness of watermark. With the fixed size of a logo watermark, there is a conflict between these two objectives, thus a multiobjective optimization problem is introduced. We propose to use a hybrid between general regression neural networks (GRNN) and the adaptive multiobjective memetic optimization algorithm (AMMOA) to solve this challenging problem. This novel image data hiding approach has been implemented for many different test natural images with remarkable robustness and transparency of the embedded logo watermark. We also introduce a perceptual measure based on the relative Rényi information spectrum to evaluate the quality of watermarked images.
The second application is the problem of joint spectrum sensing and power control optimization for a multichannel, multiple-user cognitive radio network. We investigated trade-off factors in designing efficient spectrum sensing techniques to maximize the throughput and minimize the interference. To maximize the throughput of secondary users and minimize the interference to primary users, we propose a joint determination of the sensing and transmission parameters of the secondary users, such as sensing times, decision threshold vectors, and power allocation vectors. There is a conflict between these two objectives, thus a multiobjective optimization problem is used again in the form of AMMOA. This algorithm learns to find optimal spectrum sensing times, decision threshold vectors, and power allocation vectors to maximize the averaged opportunistic throughput and minimize the averaged interference to the cognitive radio network.February 2016
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Xu, Chenzhi. « Optical Spectrocopy on Nanostructrured Materials ». Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-174866.
Texte intégralRésumé :
Solar cells are designed to transform the optical energy into electrical energy. Using solar energy is the best way for humans to solve the energy shortage problem. Dye sensitized solar cell(DSSC) has a low cost and helps people to obtain the solar energy expediently. The DSSC is based on nano structured TiO2 ; and dye molecules help the particles of TiO2 to absorb more photons. Hence DSSC has higher efficiency than SC(solar cell without dye). This thesis elaborates and analyzes the dye which is sensitized to TiO2. The absorption spectrum of the dye was achieved. Two kinds of dye sample were made on the basis of their places in structure of TiO2. One dye sample is solution, nanopowder of the dye in aceton. The other dye sample is film, thin film on a quartz plate. The absorption spectrums of the samples have been measured in laboratory. The measurement suggests that the dye works improves the absorption of solar energy in DSSC. This thesis mainly contains the following sections: Chapter I reviews the solar energy technology development, the research purposes, and the principles of DSSC. Chapter II introduces the theory of optical spectroscopy. Chapter III and Chapter IV describe the apparatus employed in this experimental system, the experimental method, and the testing results. Chapter V gives the conclusions drawn from the experiments.
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Retief, Francois Jacques. « Methods for multi-spectral image fusion : identifying stable and repeatable information across the visible and infrared spectra ». Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20636.
Texte intégralRésumé :
Fusion of images captured from different viewpoints is a well-known challenge in computer vision with many established approaches and applications; however, if the observations are captured by sensors also separated by wavelength, this challenge is compounded significantly. This dissertation presents an investigation into the fusion of visible and thermal image information from two front-facing sensors mounted side-by-side. The primary focus of this work is the development of methods that enable us to map and overlay multi-spectral information; the goal is to establish a combined image in which each pixel contains both colour and thermal information. Pixel-level fusion of these distinct modalities is approached using computational stereo methods; the focus is on the viewpoint alignment and correspondence search/matching stages of processing. Frequency domain analysis is performed using a method called phase congruency. An extensive investigation of this method is carried out with two major objectives: to identify predictable relationships between the elements extracted from each modality, and to establish a stable representation of the common information captured by both sensors. Phase congruency is shown to be a stable edge detector and repeatable spatial similarity measure for multi-spectral information; this result forms the basis for the methods developed in the subsequent chapters of this work. The feasibility of automatic alignment with sparse feature-correspondence methods is investigated. It is found that conventional methods fail to match inter-spectrum correspondences, motivating the development of an edge orientation histogram (EOH) descriptor which incorporates elements of the phase congruency process. A cost function, which incorporates the outputs of the phase congruency process and the mutual information similarity measure, is developed for computational stereo correspondence matching. An evaluation of the proposed cost function shows it to be an effective similarity measure for multi-spectral information.
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Dellapiazza, Florine. « Etude du traitement atypique de l’information sensorielle dans le trouble du spectre de l’autisme à partir de la cohorte ELENA : impact et spécificité ». Thesis, Montpellier 3, 2019. http://www.theses.fr/2019MON30084.
Texte intégralRésumé :
Etude du traitement atypique de l’information sensorielle dans le trouble du spectre de l’autisme à partir de la cohorte ELENA : impact et spécificité.L’objectif général de ce travail de doctorat en psychologie du développement est d’étudier le traitement atypique de l’information sensorielle dans le trouble du spectre de l’autisme. En partant du constat de l’apparition précoce de particularités sur le plan du traitement de l’information sensorielle chez les enfants avec un trouble du spectre de l’autisme, nous nous interrogeons sur leur impact au cours du développement. Ce travail de thèse a consisté dans un premier temps à mener une analyse des apports de la littérature sur cette question, avec la réalisation d’une revue systématique sur les liens entre le traitement sensoriel atypique et les capacités adaptatives d’une part et l’attention d’autre part. Dans un second temps, nous avons conduit deux études à partir des données issues d’une cohorte pédiatrique sur le trouble du spectre de l’autisme, la cohorte ELENA. La première étude avait pour objectif d’investiguer l’impact du traitement de l’information sensorielle sur les capacités adaptatives ainsi que sur la présence de comportements problèmes. Pour cela, un échantillon de 197 enfants ayant un trouble du spectre de l’autisme a été étudié. Par ailleurs, nous nous interrogeons sur le caractère spécifique du traitement de l’information sensorielle atypique dans la symptomatologie autistique. Dès lors, l’objectif de notre seconde étude était de comparer le traitement de l’information sensorielle dans quatre groupes d’enfants : 43 enfants présentant un trouble du spectre de l’autisme, 28 enfants présentant un trouble du déficit de l’attention avec ou sans hyperactivité, 18 enfants présentant les deux diagnostics, et 31 enfants typiques. Les résultats révèlent une forte prévalence du traitement sensoriel atypique chez les enfants présentant un trouble du spectre de l’autisme et chez ceux présentant un trouble de l’attention comparativement aux enfants typiques. Nous retrouvons une relation significative entre le traitement atypique et les capacités adaptatives, et avec l’attention, ainsi qu’un impact sur les comportements problèmes. Ainsi, l’évaluation de ces particularités sensorielles est essentielle pour le diagnostic clinique, mais également pour proposer des aménagements adaptés. Enfin, ce travail de thèse ouvre des perspectives de recherche sur le traitement sensoriel dans le trouble du spectre de l’autisme et dans les autres troubles neuro-développementaux.Mots clés : Trouble du spectre autistique, Traitement information sensorielle, Trouble de l’attention, Capacités adaptatives, Psychologie du développement, AttentionAtypical sensory processing in autism spectrum disorder, data from ELENA cohort: impact and specificity.The overall goal of this thesis in developmental psychology is to study atypical sensory processing in autism spectrum disorder. The observation of the early detection of atypical sensory processing in children with autism spectrum disorder raises questions about their impact on their development. This work consisted initially to conduct an analysis of the literature through a systematic review on the links between atypical sensory processing and adaptive functioning and attention. Then, we conducted two studies based on data from a pediatric cohort on autism spectrum disorder, the ELENA Cohort. The first study aimed to investigate the impact of atypical sensory processing on adaptive functioning as well as the presence of maladaptive behaviors. That is the reason why, we examine the specific character of atypical sensory processing in a sample of 197 children with autistic disorder. Therefore, the aim of our second study was to compare sensory processing in four groups of children: 43 children with autism spectrum disorder, 28 children with attention deficit disorder with or without hyperactivity, 18 children presenting both diagnosis, and 31 typically developing children. The results reveal a high prevalence of atypical sensory processing in children with autism spectrum disorder and in those with attention deficit compared to typical children. We find a significant relationship between atypical sensory processing and adaptive functioning and with attention, as well as an impact on maladaptive behaviors. Consequently, the assessment of sensory processing is essential for the clinical diagnosis but also to propose adapted interventions. Finally, this thesis opens up research perspectives on sensory processing in autism spectrum disorder and other neurodevelopmental disorders.Key words: Autism spectrum disorder, Sensory processing, Attention deficit disorder, Adaptive functioning, Developmental psychology, Attention
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Sestok, Charles K. (Charles Kasimer). « Speech enhancement with spectral magnitude side information ». Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80117.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (p. 43-44).
by Charles Kasimer Sestok, IV.
S.M.
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Wu, Long. « Separating Load Torque Oscillation and Rotor Faults in Stator Current Based-Induction Motor Condition Monitoring ». Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14545.
Texte intégralRésumé :
Stator current spectral analysis techniques are usually used to detect rotor faults in induction machines. Magnetic field anomalies in the airgap due to the rotor faults result in characteristic side-band harmonic components in the stator current spectrum, which can be measured as rotor fault signatures. A position-varying load torque oscillation at multiples of the rotational speed, however, has exactly the same effect. Stator current harmonics due to a load torque oscillation often obscure and even overwhelm rotor eccentricity fault detection since the magnitude of load oscillation induced harmonics is usually much larger.
Although previous research has suggested some methods to differentiate between these two effects, most of them rely heavily on the accurate estimation of motor parameters. The objective of this research is to develop a far more practical and computationally efficient method to detect rotor faults effectively in the presence of a load torque oscillation. A significant advantage of the proposed scheme is that it does not need any knowledge of motor parameters. The normalized negative sequence information induced by a mixed rotor eccentricity in the stator current or terminal voltage space vector spectra, serves as a reliable rotor fault indicator to eliminate load oscillation effects.
Detailed airgap magnetic field analysis for an eccentric motor is performed and all machine inductance matrices as well as their derivatives are reformulated accordingly. Careful observation of these inductance matrices provides a fundamental understanding of motor operation characteristics under a fault condition. Simulation results based on both induction motor dynamic model and Maxwell 2D Finite Element Model demonstrate clearly the existence of the predicted rotor fault indicator. Extensive experimental results also validate the effectiveness and feasibility of the proposed detection scheme.