• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 36
  • 11
  • 9
  • 5
  • 5
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 90
  • 26
  • 14
  • 14
  • 14
  • 13
  • 12
  • 12
  • 12
  • 11
  • 11
  • 11
  • 10
  • 10
  • 9
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Paramètres spectraux à LPC Paramètres Mapping : approches multi-linéaires et GMM (appliqué aux voyelles françaises) / Spectral Parameters to Cued Speech Parameters Mapping : Multi-linear and GMM approaches (applied to French vowels)

Ming, Zuheng 24 June 2013 (has links)
Le langage parlé complété (LPC) est un système de communication visuel qui utilise des formes de main placés dans différentes positions près du visage, en combinaison avec le discours de la lecture labiale naturel, pour améliorer la perception de la parole à partir de l'entrée visuelle pour les personnes sourdes. Cependant l'un des défis importants est la question de la communication de la parole entre les personnes normo-entendant qui ne pratiquent pas LPC mais produisent discours acoustique et les personnes sourdes qui utilisent la lecture labiale complété par code LPC pour la perception de la parole sans audition résiduelle. Dans notre travail, nous appliquons la méthode de régression linéaire multiple (MLR) et modèle gaussien de mélange (GMM) approche pour mapper des paramètres spectraux acoustiques à la position de la main dans LPC et la forme de la lèvre d’accompagnement. Nous donc contribué à la mise au point d'un système de traduction automatique dans le cadre de la synthèse de la parole visuelle.Cela prouve que l'approche MLR est bonne pour l'estimation des paramètres pour les lèvres à partir des paramètres spectraux car il y a forte corrélation linéaire entre les paramètres des lèvres et des paramètres spectraux. Cependant, la performance de l'approche MLR pour estimer la position de la main est faible car il n'y a pas de relation entre les positions de la main et des paramètres spectraux. En introduisant un espace intermédiaire, il s'avère que la structure de topologie similaire est la clé de la MLR. Afin de libérer de la contrainte linéaire de l'approche MLR, nous appliquons la méthode de cartographie basée sur GMM qui possède à la fois les propriétés de classification et de régression. Les paramètres de GMM sont estimés par les méthodes de formation supervisées, non supervisées et semi- supervisés séparément dans la vue de la théorie de l'apprentissage de la machine. La méthode de formation supervisée montre une grande efficacité et une bonne robustesse. Le Minimum Mean Square Error (MMSE) et Maximum A Posteriori Probabilité (MAP) sont utilisés comme critères de régression séparément dans l'approche de la cartographie basée sur GMM. Cela prouve que l'approche MLR est un cas particulier de l'approche de GMM lorsque le nombre de gaussiennes est égal à un. Ainsi, l'approche de la cartographie sur GMM peut améliorer la performance significative en comparaison avec le MLR en augmentant le nombre de gaussiennes. Enfin, les différentes approches de cartographie utilisées dans ce travail sont comparées dans une transition continue. Il montre que l'approche sur GMM peut effectuer bien grâce à la propriété de classification lorsque les données source et cible n'a pas de " relation" comme dans le cas de l'estimation de la position de la main, et il peut également améliorer les performances par la propriété de régression local lorsque la source et les données cible a forte corrélation comme dans le cas du paramètre de lèvre estimation. En outre, une prédiction directe de la géométrie des lèvres comporte de l'image naturelle de la bouche région d'intérêt (ROI) sur la base de la 2D transformée en cosinus discrète (DCT) combinée à une analyse en composante principale (ACP) est proposé. Les résultats montrent la possibilité d'estimer les caractéristiques géométriques de la lèvre avec une bonne précision en utilisant un ensemble réduit de prédicteurs dérivés des coefficients DCT. / Cued Speech (CS) is a visual communication system that uses hand shapes placed in different positions near the face, in combination with the natural speech lip-reading, to enhance speech perception from visual input for deaf people. However one of the important challenges is the question of speech communication between normal hearing people who do not practice CS but produce acoustic speech and deaf people who use lip-reading complemented by CS code for speech perception with no residual audition. In our work, we apply the multi-linear regression approach (MLR) and Gaussian Mixture Model (GMM)-based mapping approach to map acoustic spectral parameters to the hand position in CS and the accompanying lip shape. We hence contributed to the development of automatic translation system in the framework of visual speech synthesis. It proves that the MLR approach is good for estimating the lip parameters from the spectral parameters since there is strong linear correlation between the lip parameters and spectral parameters. However, the performance of MLR approach for estimating the hand position is poor since there is no relationship between the hand positions and spectral parameters. By introducing an intermediate space, it proves that the similar topology structure is the key of the MLR. In order to release the linear constraint of the MLR approach, we apply the GMM-based mapping approach which has both the classification-partition and regression properties. The parameters of GMM are estimated by the supervised, unsupervised and semi-supervised training methods separately in the view of the machine learning theory. The supervised training method shows high efficiency and good robustness. The Minimum Mean Square Error (MMSE) and Maximum A Posteriori Probability (MAP) are used as regression criteria separately in GMM-based mapping approach. It proves that the MLR approach is a special case of GMM-based mapping approach when the number of the Gaussians equals to one. Thus the GMM-based mapping approach can improve the performance significantly in comparison with the MLR by increasing the number of the Gaussians. Finally, a continuous transition achieved by the linear interpolation in the acoustic space is introduced to compare the different mapping approaches used in this work. It shows that the GMM-based mapping approach can perform well thanks to the classification-partitioning property when the source and target data has “no relationship” such as the case of the hand position estimation; and it can also improve the performance by the local regression property when the source and target data has strong correlation such as the case of the lip parameter estimation. Besides, a direct prediction of lip geometry features from the natural image of mouth region-of-interest (ROI) based on the 2D Discrete Cosine Transform (DCT) combined with a Principal Component Analysis (PCA) is proposed. The results show the possibility to estimate the geometric lip features with good accuracy using a reduced set of predictors derived from the DCT coefficients.
22

Cognitive impairment in 873 patients with idiopathic Parkinson’s disease: Results from the German Study on Epidemiology of Parkinson’s Disease with Dementia (GEPAD)

Riedel, Oliver, Klotsche, Jens, Spottke, Annika, Deuschl, Günther, Förstl, Hans, Henn, Fritz, Heuser, Isabella, Oertel, Wolfgang, Reichmann, Heinz, Riederer, Peter, Trenkwalder, Claudia, Dodel, Richard, Wittchen, Hans-Ulrich January 2008 (has links)
Background: Parkinson’s disease (PD) is often accompanied by non-motor complications, such as dementia, depression, and psychotic symptoms, which worsen the prognosis and increase the personal and socioeconomic burden of disease. Prevalence estimates of these complications are quite variable and are lacking for the outpatient care sector. Methods: As part of a larger, nationwide, cross-sectional epidemiological study in n=315 neurological outpatient settings in Germany, this paper estimates the frequency of dementia and cognitive impairment in n=873 outpatients meeting the UK Brain Bank criteria for idiopathic PD. Assessments were based on a clinical interview and neuropsychological assessments, including the Hoehn & Yahr rating and Unified Parkinson’s Disease Rating Scale (UPDRS). Cognitive impairment was assessed by the Mini-Mental State Exam (MMSE), Clock Drawing Test (CDT) and the Parkinson Neuropsychometric Dementia Assessment (PANDA) and the clinician’s diagnosis of dementia was based on the diagnostic criteria of DSMIV. Results Using standardized cutoff scores, the prevalence of cognitive impairment in the study sample as measured by various methods was 17.5% by MMSE (≤ 24), 41.8% by CDT (≥ 3), 43.6% by PANDA (≤ 14), and 28.6% met the DSM-IV criteria for dementia. All estimates increased with age and PD severity. Gender was an inconsistent contributor while illness duration had no significant impact on cognition. Multiple regression analyses revealed PD severity to be the strongest predictor of dementia risk (OR=4.3; 95 % CI: 2.1–9.1), while neuropsychiatric syndromes had independent, although modest additional contributions (OR=2.5, 95% CI: 1.6–3.8). Conclusion: Estimates of cognitive impairment and dementia in PD patients are largely dependent on the diagnostic measure used. Using established clinical diagnostic standards for dementia the overall rate on routine outpatient neurological care is 28.6%, but using more sensitive neuropsychological measures, rates for cognitive impairment might be up to 2-fold higher. The MMSE revealed strikingly low sensitivity. Neuropsychiatric syndromes, in addition to PD severity and age, have an independent – although modest – additional contribution to patients’ risk for cognitive impairment and dementia.
23

Receiver architectures for MIMO wireless communication systems based on V-BLAST and sphere decoding algorithms

Tade, Foluwaso Olunkunle January 2011 (has links)
Modern day technology aspires to always progress. This progression leads to a lot of research in any significant area of improvement. There is a growing amount of end-users in the wireless spectrum which has led to a need for improved bandwidth usage and BER values. In other words, new technologies which would increase the capacity of wireless systems are proving to be a crucial point of research in these modern times. Different combinations of multiuser receivers are evaluated to determine performance under normal working conditions by comparing their BER performance charts. Multiple input, multiple output (MIMO) systems are incorporated into the system to utilise the increased capacity rates achievable using the MIMO configuration. The effect of MIMO on the technologies associated with modern day technological standards such as CDMA and OFDM have been investigated due to the significant capacity potentials these technologies normally exhibit in a single antenna scenario. An in-depth comparison is established before comparison is made with a conventional maximum likelihood (ML) detector. The complexity of the ML detector makes its realization evaluated in such a manner to achieve the same or near ML solution but with lower computational complexity. This was achieved using a proposed modification of the Schnorr-Euchner Sphere decoding algorithm (SE-SDA). The proposed sphere decoder (P-SD) adopts a modification of the radius utilised in the SE-SDA to obtain a near ML solution at a much lower complexity compared to the conventional ML decoder. The P-SD was configured to work in different MIMO antenna configurations. The need for the highest possible data rates from the available limited spectrum led to my research into the multi-user detection scenario and MIMO.
24

Rastreamento cognitivo por instrumento baseado no MEEM em idosos não institucionalizados residentes em Batatais-SP / “Cognitive screening by instrument based on MMMSE in non institutionalized elderly living in Batatais.”

Gurian, Maria Beatriz Ferreira 23 January 2003 (has links)
O transtorno cognitivo no idoso acarreta repercussões na sua vida, na família e na relação com a sociedade. Um instrumento de avaliação cognitiva amplamente utilizado é o MEEM - Mini Exame do Estado Mental - que é um teste de rastreamento com o objetivo de selecionar pessoas com provável déficit cognitivo. Uma amostra representativa da população de 394 idosos do município de Batatais SP foi avaliada através de inquérito domiciliar em relação às condições socioeconômicas e de saúde, e foi feito rastreamento dos sintomas depressivos e do desempenho cognitivo através de um instrumento baseado no MEEM. A maioria dos entrevistados era do sexo feminino (66%), sendo que 75,4% dos idosos pertenciam a uma faixa etária de 60-74 anos, chamada idoso jovem. Com relação à escolaridade a grande maioria (62.2%) cursou o primeiro grau. Com relação aos analfabetos 77,1% eram mulheres e 22,9% eram homens. Para o estado conjugal a diferença foi na proporção da viuvez 80.2% para o sexo feminino e 19.8% para o masculino. Quanto à renda familiar, 43.7% da população recebiam menos de 2,5 salários mínimos. Para avaliação do desempenho cognitivo usou um ponto de corte ? a 23 para o MEEM. Observou-se que 81.7% ficaram acima deste ponto e 18.3% ficaram abaixo. Os idosos que tiveram os escores mais elevados foram associados aos fatores como idade (60-69 anos), maior nível escolaridade, ter hábito de leitura, ter boa relação social principalmente com parentes, não ter hipertensão arterial, diabete, incontinência urinária, catarata e ausência de sintomas depressivos. / The cognitive impairment in the old has its effects on their lives, families and relationships with society. A widely used instrument of cognitive assessment is the MMSE- Mini Mental State - that is a screening test whose aim is to select people with probable cognitive deficiency. A significant sample of the population of 394 old people from Batatais - SP, was evaluated through a home survey considering the socioeconomic and health conditions and a screening of depressive symptoms and cognitive performance was done through an instrument based on MMSE. The great majority of people who were interviewed were female (66%) and 75.4% of the old belonged to an age group from 60 to 74 years old, being considered \"younger old\". Regarding scholarship, most of them had attended primary school (62.2%). Considering the illiterate 77.1% were women and 22.9% were men. Concerning marital status a huge difference between the proportion of widows (80.2%) and widowers (19.8%) was found. With reference to familiar income 43.7% of the population earned less than 2.5 minimum wages. To evaluate the cognitive performance a cut off ? 23 for MMSE was used. It was observed that 81.7% of the old were above and 18.3% were under this point. The old who achieved the highest scores had factors such as age (60-69 years old), better scholarship level, reading habits, a good social relationship (mainly with relatives), no high blood pressure, no diabetes, no urinary incontinence, no cataract and absence of depressive symptoms.
25

Adaptação e validação discriminante do instrumento Mini Exame do Estado Mental (MEEM) para avaliação neuropsicológica em adultos angolanos com diagnóstico clínico de acidente vascular cerebral (AVC) e epilepsia / Adaptation and discriminant validation of the instrument Mini Mental State Examination (MMSE) for neuropsychological assessment in Angolan adults with a clinical diagnosis of stroke (CVA) and epilepsy

Luemba, Martinho 26 June 2017 (has links)
Doenças como AVC e Epilepsia estão constantemente associadas à manifestação de comprometimentos cognitivos e demência, tendo como característica principal os déficits de memória. Atualmente,o instrumento Mini Exame do Estado Mental (MEEM) é o teste de rastreio de comprometimento cognitivo mais utilizado no mundo, individualmente ou como parte integrante em baterias de avaliação neuropsicológica. Devido afalta de instrumentos específicos pararastreiode comprometimento cognitivo de indivíduos com sintomas de demênciavítimas de AVC e/ou Epilepsia em Angola, África, fez se necessária aadaptação evalidação de instrumentos confiáveis.O presente estudoteve por objetivo a avaliação clínicada versão brasileira do instrumento MEEM adaptado por Brucki, para uso na população adulta de Angola.Trata-se de um estudo clínico comparado, envolvendo três populações. Foram incluídos neste estudo 85 indivíduos acometidos por AVC, 40 por Epilepsia e como grupo de comparação, 87 indivíduos de 20 a 65 anos de idade, supostamente saudáveis. A escolaridade mínima para inclusão do estudo foi definida em 4 anos de ensino formal. O presente estudo foi desenvolvido em parceria com o Serviço de Neurologia do Hospital Américo Boavida e com a Faculdade de Medicina da Universidade Agostinho Neto (FMUAN), ambos localizados ao norte da cidade de Luanda, capital de Angola, África.Toda a amostra foi submetida à coleta de dados sócio demográficos e avaliação neuropsicológica, através do instrumento MEEM. O instrumento consistiu no rastreio de comprometimento cognitivo, contemplando funções como orientação temporal e espacial, memória, cálculo, linguagem e capacidade construtivavisual.No presente estudo, encontramos dados que apontam um desempenho significativamente pior das funções cognitivas em pacientes acometidos por AVC quando comparados a pacientes com Epilepsia e grupo dossaudáveis. Esses achados confirmam a validade do instrumento MEEM, em função das características apresentadas pela doença, sendo possível discriminar com clareza os grupos AVC, Epilepsia e Controles Saudáveis. Os dados obtidos indicam uma boa qualidade da versão na língua portuguesa angolana, sendo a consistência interna da versão adaptada com ? de Cronbach = 0,736, semelhante aos dados de referência. Este estudo pioneiro preenche uma importante lacuna na produção de conhecimento em Angola, abrindo um leque de possibilidades para outros trabalhos científicos no país, facilitando a aplicação dos resultados tanto na área acadêmica-científica, quanto na clínica. É necessário aos profissionais de saúde que se apropriem de mais conhecimentos, para que possam propor intervenções adequadas, que auxiliam nos direitos de saúde e bem-estarda população angolana. / Diseases such as stroke and epilepsy are constantly associated with the manifestation of cognitive impairment and dementia, having as main feature the memory deficits (Caramelli & Castro, 2005). Currently, the instrument Mini Mental State Examination (MMSE) is the screening test of cognitive impairment most used in the world, individually or as an integrated part in neuropsychological assessment battery (Melo & Barbosa, 2015). Due to the lack of specific instruments for screening cognitive impairment of individuals with dementia symptoms victims of stroke and / or epilepsy in Angola, Africa, it was necessary to adapt and validate reliable instruments. The presentestudy had as objective the clinical evaluationof the brazilian version of the MMSE instrument adapted by Brucki et al. (2003), for use in the adult population of Angola, Africa. It is a comparative clinical study involving three populations. This studyincluded 85 individuals affected by stroke, 40 by Epilepsy, and as a comparison group, 87 individuals, 20 to 65 years of age, who were supposed to be healthy. The minimum schooling for inclusion of the study was defined in 4 years of formal education. Thepresent study was developed in partnership with the Neurology Service of the Américo Boavida Hospital and the Faculty of Medicine of the Agostinho Neto University (FMUAN), both located north of the city of Luanda, the capital of Angola, Africa. All the sample was submitted to the collection of sociodemographic data and neuropsychological evaluation, through the MMSE instrument. The instrument consisted in the screening of cognitive impairment, including functions such as temporal and spatial orientation, memory, calculus, language and visual constructive capacity.In the presente study, we found data that indicate a significantly worse performance of cognitive functions in patients with stroke when compared to patients with epilepsy and healthy group. These findings confirm the validity of theinstrument MMSE in, due to the characteristics of the disease, being possible to discriminate with clarity the groups Stroke, Epilepsy and Healthy Controls. The data obtained indicate a good quality of the Angolan Portuguese language version, being the internal consistency of the adapted versionwhit the Cronbach\'s alpha = 0.736, similar to the reference data.This pioneering study fills animportant gap in knowledge production in Angola, opening up a range of possibilities for other scientific papers in the country, facilitating the application of the results both in the academic and scientific area, as at the clinic. It is necessary that health professional take ownership of more knowledge, so that they can propose appropriate interventions that assist in health and welfare rights of the Angolan population.
26

Adaptação e validação discriminante do instrumento Mini Exame do Estado Mental (MEEM) para avaliação neuropsicológica em adultos angolanos com diagnóstico clínico de acidente vascular cerebral (AVC) e epilepsia / Adaptation and discriminant validation of the instrument Mini Mental State Examination (MMSE) for neuropsychological assessment in Angolan adults with a clinical diagnosis of stroke (CVA) and epilepsy

Martinho Luemba 26 June 2017 (has links)
Doenças como AVC e Epilepsia estão constantemente associadas à manifestação de comprometimentos cognitivos e demência, tendo como característica principal os déficits de memória. Atualmente,o instrumento Mini Exame do Estado Mental (MEEM) é o teste de rastreio de comprometimento cognitivo mais utilizado no mundo, individualmente ou como parte integrante em baterias de avaliação neuropsicológica. Devido afalta de instrumentos específicos pararastreiode comprometimento cognitivo de indivíduos com sintomas de demênciavítimas de AVC e/ou Epilepsia em Angola, África, fez se necessária aadaptação evalidação de instrumentos confiáveis.O presente estudoteve por objetivo a avaliação clínicada versão brasileira do instrumento MEEM adaptado por Brucki, para uso na população adulta de Angola.Trata-se de um estudo clínico comparado, envolvendo três populações. Foram incluídos neste estudo 85 indivíduos acometidos por AVC, 40 por Epilepsia e como grupo de comparação, 87 indivíduos de 20 a 65 anos de idade, supostamente saudáveis. A escolaridade mínima para inclusão do estudo foi definida em 4 anos de ensino formal. O presente estudo foi desenvolvido em parceria com o Serviço de Neurologia do Hospital Américo Boavida e com a Faculdade de Medicina da Universidade Agostinho Neto (FMUAN), ambos localizados ao norte da cidade de Luanda, capital de Angola, África.Toda a amostra foi submetida à coleta de dados sócio demográficos e avaliação neuropsicológica, através do instrumento MEEM. O instrumento consistiu no rastreio de comprometimento cognitivo, contemplando funções como orientação temporal e espacial, memória, cálculo, linguagem e capacidade construtivavisual.No presente estudo, encontramos dados que apontam um desempenho significativamente pior das funções cognitivas em pacientes acometidos por AVC quando comparados a pacientes com Epilepsia e grupo dossaudáveis. Esses achados confirmam a validade do instrumento MEEM, em função das características apresentadas pela doença, sendo possível discriminar com clareza os grupos AVC, Epilepsia e Controles Saudáveis. Os dados obtidos indicam uma boa qualidade da versão na língua portuguesa angolana, sendo a consistência interna da versão adaptada com ? de Cronbach = 0,736, semelhante aos dados de referência. Este estudo pioneiro preenche uma importante lacuna na produção de conhecimento em Angola, abrindo um leque de possibilidades para outros trabalhos científicos no país, facilitando a aplicação dos resultados tanto na área acadêmica-científica, quanto na clínica. É necessário aos profissionais de saúde que se apropriem de mais conhecimentos, para que possam propor intervenções adequadas, que auxiliam nos direitos de saúde e bem-estarda população angolana. / Diseases such as stroke and epilepsy are constantly associated with the manifestation of cognitive impairment and dementia, having as main feature the memory deficits (Caramelli & Castro, 2005). Currently, the instrument Mini Mental State Examination (MMSE) is the screening test of cognitive impairment most used in the world, individually or as an integrated part in neuropsychological assessment battery (Melo & Barbosa, 2015). Due to the lack of specific instruments for screening cognitive impairment of individuals with dementia symptoms victims of stroke and / or epilepsy in Angola, Africa, it was necessary to adapt and validate reliable instruments. The presentestudy had as objective the clinical evaluationof the brazilian version of the MMSE instrument adapted by Brucki et al. (2003), for use in the adult population of Angola, Africa. It is a comparative clinical study involving three populations. This studyincluded 85 individuals affected by stroke, 40 by Epilepsy, and as a comparison group, 87 individuals, 20 to 65 years of age, who were supposed to be healthy. The minimum schooling for inclusion of the study was defined in 4 years of formal education. Thepresent study was developed in partnership with the Neurology Service of the Américo Boavida Hospital and the Faculty of Medicine of the Agostinho Neto University (FMUAN), both located north of the city of Luanda, the capital of Angola, Africa. All the sample was submitted to the collection of sociodemographic data and neuropsychological evaluation, through the MMSE instrument. The instrument consisted in the screening of cognitive impairment, including functions such as temporal and spatial orientation, memory, calculus, language and visual constructive capacity.In the presente study, we found data that indicate a significantly worse performance of cognitive functions in patients with stroke when compared to patients with epilepsy and healthy group. These findings confirm the validity of theinstrument MMSE in, due to the characteristics of the disease, being possible to discriminate with clarity the groups Stroke, Epilepsy and Healthy Controls. The data obtained indicate a good quality of the Angolan Portuguese language version, being the internal consistency of the adapted versionwhit the Cronbach\'s alpha = 0.736, similar to the reference data.This pioneering study fills animportant gap in knowledge production in Angola, opening up a range of possibilities for other scientific papers in the country, facilitating the application of the results both in the academic and scientific area, as at the clinic. It is necessary that health professional take ownership of more knowledge, so that they can propose appropriate interventions that assist in health and welfare rights of the Angolan population.
27

Mental Status and Functional Behavior In Male Geriatric Patients

Mayer, Gregory Lee 01 May 1989 (has links)
It was the goal of this study to examine the ecological validity of a number of measures of mental status for geriatric individuals. Subjects were 40 alert, ambulatory male VA patients. Mental status instruments included the Mini-Mental State Examination (MMSE), the Wechsler Memory Scale (WMS) and the Vocabulary subtest of the WAIS-R. Measures of functional behavior included the Woodcock-Johnson Scales of Independent Behavior (SIB) and the Parachek Geriatric Behavior Rating Scale (PGBRS). Significant relationships were found between the MMSE and the SIB, between the WMS and the SIB, and between the WMS and the PGBRS. It was found that estimation of functional behavior can be enhanced significantly through the use of battery of mental status instruments.
28

Equalisation for carrierless amplitude and phase modulation

Gao, Jason January 2002 (has links)
Carrierless amplitude and phase (CAP) modulation is generally regarded as a bandwidth efficient two-dimensional (2-D) passband line code. It is closely related to the pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM) schemes. CAP has been proposed for various digital subscriber loop (DSL) systems over unshielded twisted pairs of copper wires. In this thesis, our main focus is on the minimum mean-square error (MMSE) performance of the ideal (i.e., infinite length) linear and non-linear (decision feedback) CAP receivers/equalisers in the presence of additive, coloured Gaussian noise, and/or data-like cross-talks. An in-depth analysis is given on the performance of both receiver structures. In the case of the linear receiver, one possible view of the overall CAP transceiver system which includes both data and cross-talk transmission paths is that it is a linear multiple-input multiple-output (MIMO) system. Accordingly, the existing MMSE results for a general MIMO system are applicable also to CAP systems. However, up to date, this approach was shown to be unsuccessful in the sense that the derived MMSE expressions are too complex and offer little insights. In our analysis, in order to find a more incisive MMSE expression, we reconsider the problem of minimisation of the MSEs at slicers. By exploiting the Hilbert transform pair relationship between the impulse responses of the inphase and quadrature transmit shaping filters, we are able to obtain an elegant and more meaningful MMSE expression, as well as the corresponding transfer functions of the optimum linear receive filters. In the case of the nonlinear, or decision feedback equaliser (DFE), receiver, we start our analysis with the receiver structure of a generic multidimensional (>/= 3) CAP-type system. / This receiver consists of a bank of analog receive filters, the number of which equals the dimension of the CAP line code, and a matrix of cross-connected, infinite-length, baud-spaced feedback filters. It is shown that the optimum filters and the corresponding MMSE of the DFE receiver require the factorisation of a discrete-time channel spectral matrix. This mathematically intractable step can be avoided, however, when the DFE results are specialised to a standard 2-D CAP system where we are able to again exploit the Hilbert transform pair relationship to derive a further and more useful MMSE expression. Three sets of numerical studies are given on the MMSE performance of the CAP receivers. In the first set of studies. we model the sum of all crosstalks as an additive, Gaussian noise source and select three test transmission channels over which we compare the MMSE performance of the linear and DFE receiver structures. In the second set of studies, we compare the performance of the two receiver structures, but in a data-like cross-talk environment. The results demonstrate the importance of NEXT equalisation in the design of CAP receivers operating in a NEXT dominant environment. In the final set of studies which follows from the second set of studies, we investigate the relationship between the MMSE performance of the DFE receiver and system parameters which include excess bandwidth, data rate, CAP scheme. and relative phase between the received signal and the NEXT signal. The results show that data-like cross-talks can be effectively suppressed by using a large excess bandwidth (alpha > 1 in the case of a RC transmit shaping filter) alone. / The relative phase also affect; the receiver performance. but to a lesser degree. In addition to the MMSE performance analysis. implementation issues of an adaptive linear CAP receiver are also considered. We propose a novel linear receiver by appending two fixed analog filters to the front-end of the existing adaptive linear receiver using fractionally-spaced equalisers (FSE). We show that if the analog filters are matched to the transmit shaping filters, then inphase and quadrature finite-length FSEs in the proposed receiver have the same NINISE solution. We further propose a modified least-mean-square (LMS) algorithm which takes advantage of this feature. The convergence analysis of the proposed LMS algorithm is also given. We show that the modified LMS algorithm converges approximately twice as fast as the standard LMS algorithm, given the same misadjustment, or alternatively, it halves the misadjustment, given the same initial convergence rate.
29

Turbo Equalization for HSPA / Turboutjämning för HSPA

Konuskan, Cagatay January 2010 (has links)
<p>New high quality mobile telecommunication services are offered everyday and the demand for higher data rates is continuously increasing. To maximize the uplink throughput in HSPA when transmission is propagated through a dispersive channel causing self-interference, equalizers are used. One interesting solution, where the equalizer and decoder exchange information in an iterative way, for improving the equalizer performance is Turbo equalization.</p><p>In this thesis a literature survey has been performed on Turbo equalization methods and a chosen method has been implemented for the uplink HSPA standard to evaluate the performance in heavily dispersive channels. The selected algorithm has been adapted for multiple receiving antennas, oversampled processing and HARQ retransmissions. The results derived from the computer based link simulations show that the implemented algorithm provide a gain of approximately 0.5 dB when performing up to 7 Turbo equalization iterations. Gains up to 1 dB have been obtained by disabling power control, not using retransmission combining and utilizing a single receiver antenna. The algorithm has also been evaluated considering alternative dispersive channels, Log-MAP decoding, different code rates, number of Turbo equalization iterations and number of Turbo decoding iterations.</p><p>The simulation results do not motivate a real implementation of the chosen algorithm considering the increased computational complexity and small gain achieved in a full featured receiver system. Further studies are needed before concluding the HSPA uplink Turbo equalization approach.</p>
30

Snabb automatiserad benämning som screeninginstrument vid kognitiva störningar : En klinisk studie baserad på AQT

Backlund, Josefine, Lindqvist, Anna January 2009 (has links)
<p><em>A Quick Test </em>(AQT)<em> Färg och Form</em> är ett test av snabb automatiserad benämning avsett att detektera kognitiva störningar. Det består av tre delar som var och en utgörs av 40 visuella stimuli som skall benämnas så snabbt som möjligt. Tidigare studier har indikerat att AQT skiljer personer med Alzheimers sjukdom från friska kontroller med högre precision än det ofta använda <em>Mini-Mental-Testet </em>(MMT). I denna studie undersöktes för första gången om AQT-resultat kunde predicera diagnosen hos en konsekutiv serie patienter vid en minnesklinik samt relationen mellan AQT-resultat och biomarkörer (likvorproteiner) för neurodegenerativ sjukdom. 492 svarsblanketter från <em>AQT Färg och Form</em> analyserades och diagnostisk prediktion samt korrelation med nivån av likvorproteiner fastställdes för de 374 första patienterna i serien. Resultaten tyder på att <em>AQT Färg och Form</em> kan vara känsligt för vissa lindriga kognitiva sviktsymptom som förekommer hos personer remitterade för minnesbesvär men inte alltid känsligt för lindriga grader av demens. AQT-data korrelerade måttligt med nivån av patologiska likvorproteiner, troligen avspeglande förhöjda nivåer i Alzheimergruppen. Ytterligare forskning på konsekutiva fallserier behövs för att fastställa testets diagnostiska diskriminationsförmåga i klinisk praxis.</p> / <p><em>A Quick Test </em>(AQT)<em> Color-Form </em>is a test that uses rapid automatized naming in order to identify cognitive impairment. It is divided into three parts, each of which consists of 40 stimuli that are to be named as quickly as possible. Previous studies have indicated that AQT separates patients with Alzheimer’s disease from normal controls with higher accuracy than the commonly used <em>Mini-Mental State Examination </em>(MMSE). The purpose of this study was to investigate, for the first time, whether AQT results collected from a consecutive series of patients at a Memory Clinic would be able to predict the diagnosis. Another aim was to study the possible relation between AQT results and Cerebrospinal Fluid (CSF) biomarkers for neurodegenerative diseases. 492 forms from <em>AQT Color-Form</em> tests were analyzed and diagnostic prediction and correlation with level of CSF biomarkers were determined for the first 374 patients. The results imply that <em>AQT Color-Form</em> may be sensitive to some symptoms of benign memory impairment that is found in patients admitted to a Memory Clinic, but that it is not always sensitive to mild degrees of dementia. Further research consecutive series of patients is needed in order to determine the diagnostic abilities of discrimination in clinical practice.</p>

Page generated in 0.0597 seconds