• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 58
  • 8
  • 6
  • 5
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 101
  • 101
  • 40
  • 28
  • 27
  • 20
  • 17
  • 15
  • 14
  • 12
  • 12
  • 12
  • 11
  • 10
  • 10
  • 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.
81

Avaliação da qualidade do Sistema de Educação Superior Brasileiro em tempos de mercantilização : período 1994-2003

Bertolin, Julio Cesar Godoy January 2007 (has links)
Este estudo teve como objetivo elaborar uma proposta de indicadores para avaliação da qualidade do sistema de educação superior brasileiro e, com base nestes indicadores elaborados, medir e avaliar o desenvolvimento da sua qualidade no período 1993-2004. Considerou-se que o período escolhido está associado à intensificação do fenômeno da mercantilização da educação superior no Brasil. Para caracterizar o fenômeno, o estudo apóia-se nas perspectivas teóricas de Boaventura de Sousa Santos sobre as crises da universidade, de Ana Maria Seixas acerca das transformações privatistas e dos autores David Dill, Pedro Teixeira, Bem Jonbloed e Alberto Amaral sobre os mercados da educação superior. Os temas da qualidade e da avaliação da qualidade têm como referência principal os trabalhos de Ronald Barnett, Lee Harvey e Diana Green. Foram estudados os indicadores e sistemas de indicadores de educação adotados pelas agências internacionais, tais como Unesco e OCDE. Com essas referências foi elaborado um sistema de indicadores para avaliação do desenvolvimento da qualidade do Sesb, que compreende as categorias eqüidade, relevância, diversidade e eficácia. O estudo apresenta o sistema de indicadores elaborado e sua aplicação no período 1993-2004. Os resultados explicam a hipótese de trabalho, ou seja, em tempos de mercantilização da educação superior a qualidade da educação superior brasileira não se desenvolveu positivamente, visto que no período 1994- 2003 não foram encontradas evidências claras de melhorias do Sesb em termos de eqüidade, relevância, diversidade e eficácia. / The present study was carried out with the aiming to elaborate a proposal of indicators for assessing quality in Brazilian system for higher education and, based on those indicators, measure and evaluate the development of such quality in the period ranging from 1993 to 2004. It was considered the chosen period as associated to the increasing of the commodification of higher education in Brazil. In order to characterize that phenomena, the study used as grounds the theories developed by Boaventura de Sousa Santos, about the university crisis; by Ana Maria Seixas, about the privatizing transformations; and by David Dill, Pedro Teixeira, Bem Jonbloed, and Alberto Amaral, on the higher education markets. The matters involving quality and quality assessment have the main studies by Ronald Barnett, Lee Harvey, and Diana Green as references. The indicators and systems of education indicators adopted by international agencies such as Unesco and OCDE, were also studied. Based on those references a system of indicators for the evaluation of quality development in Sesb was elaborated, and it includes the following categories: equity, relevance, diversity, and efficiency. This study presents that indicators system as well as its application during the period 1993-2004. The results explain the hypothesis upon which work was developed, that is, in times of commodification of higher education, the quality of such education in Brazil has not developed positively. That is said based on the fact that during the period 1993-2004 there could not be found clear evidences of improvement in Sesb in what concerns equity, relevance, diversity, and efficiency.
82

Avaliação da qualidade do Sistema de Educação Superior Brasileiro em tempos de mercantilização : período 1994-2003

Bertolin, Julio Cesar Godoy January 2007 (has links)
Este estudo teve como objetivo elaborar uma proposta de indicadores para avaliação da qualidade do sistema de educação superior brasileiro e, com base nestes indicadores elaborados, medir e avaliar o desenvolvimento da sua qualidade no período 1993-2004. Considerou-se que o período escolhido está associado à intensificação do fenômeno da mercantilização da educação superior no Brasil. Para caracterizar o fenômeno, o estudo apóia-se nas perspectivas teóricas de Boaventura de Sousa Santos sobre as crises da universidade, de Ana Maria Seixas acerca das transformações privatistas e dos autores David Dill, Pedro Teixeira, Bem Jonbloed e Alberto Amaral sobre os mercados da educação superior. Os temas da qualidade e da avaliação da qualidade têm como referência principal os trabalhos de Ronald Barnett, Lee Harvey e Diana Green. Foram estudados os indicadores e sistemas de indicadores de educação adotados pelas agências internacionais, tais como Unesco e OCDE. Com essas referências foi elaborado um sistema de indicadores para avaliação do desenvolvimento da qualidade do Sesb, que compreende as categorias eqüidade, relevância, diversidade e eficácia. O estudo apresenta o sistema de indicadores elaborado e sua aplicação no período 1993-2004. Os resultados explicam a hipótese de trabalho, ou seja, em tempos de mercantilização da educação superior a qualidade da educação superior brasileira não se desenvolveu positivamente, visto que no período 1994- 2003 não foram encontradas evidências claras de melhorias do Sesb em termos de eqüidade, relevância, diversidade e eficácia. / The present study was carried out with the aiming to elaborate a proposal of indicators for assessing quality in Brazilian system for higher education and, based on those indicators, measure and evaluate the development of such quality in the period ranging from 1993 to 2004. It was considered the chosen period as associated to the increasing of the commodification of higher education in Brazil. In order to characterize that phenomena, the study used as grounds the theories developed by Boaventura de Sousa Santos, about the university crisis; by Ana Maria Seixas, about the privatizing transformations; and by David Dill, Pedro Teixeira, Bem Jonbloed, and Alberto Amaral, on the higher education markets. The matters involving quality and quality assessment have the main studies by Ronald Barnett, Lee Harvey, and Diana Green as references. The indicators and systems of education indicators adopted by international agencies such as Unesco and OCDE, were also studied. Based on those references a system of indicators for the evaluation of quality development in Sesb was elaborated, and it includes the following categories: equity, relevance, diversity, and efficiency. This study presents that indicators system as well as its application during the period 1993-2004. The results explain the hypothesis upon which work was developed, that is, in times of commodification of higher education, the quality of such education in Brazil has not developed positively. That is said based on the fact that during the period 1993-2004 there could not be found clear evidences of improvement in Sesb in what concerns equity, relevance, diversity, and efficiency.
83

Techniques de réduction de la consommation d'un récepteur radio adaptatif et impacts sur ses performances / Low power techniques applied to an adaptive radio receiver and impacts on its performances

Pons, Jean-François 05 November 2015 (has links)
L’engouement actuel pour les applications de type réseaux de capteurs sans-fil ou internet des objets (IoT) relance la nécessité, alors initiée par les applications mobiles, de concevoir des émetteurs-récepteurs radio à basse consommation. Dans ce contexte, l’objet des travaux de thèse est de proposer des techniques de réduction de la consommation des récepteurs radio tout en minimisant l’impact sur leur architecture de manière à pouvoir adapter leur consommation aux besoins de performance.Pour ce faire, l’utilisation intermittente du convertisseur analogique numérique (ADC) a, dans un premier temps, été étudiée puis celle-ci a été généralisée à l’ensemble du récepteur. Pour chacune de ces approches, une modélisation de la dégradation des performances en termes de taux d’erreur (BER) a été confrontée à une estimation de la réduction de la consommation engendrée. Par ailleurs, l’impact de l’ajout de modules spécifiques aux techniques proposées est décrit à l’aide de résultats concernant leurs complexités et leurs consommations. L’ensemble de ces résultats s’inscrit pleinement dans le domaine de recherche des récepteurs adaptatifs pour lesquels les performances sont adaptées au canal de transmission en temps réel.Finalement, une technique de compensation digitale des défauts de quadrature a été proposée, rendant possible l’utilisation d’une PLL moins énergivore mais avec des performances dégradées. Cette technique utilise une recherche par dichotomie des poids de compensation des défauts de quadrature, lui permettant de converger suffisamment rapidement pour pouvoir réaliser la compensation sur une portion connue du message reçu et ainsi éviter une perte d’information. / The recent craze for the Wireless Sensor Networks (WSN) and the Internet of Things (IoT) applications boosts the necessity, previously introduced by the mobile applications, to design low power transceivers. In this context, the purpose of this thesis is to propose some techniques to reduce the power consumption of RF receivers while minimizing the impact on their architecture in order to be able to adapt their power consumption to the required performances.To do so, the study of the intermittent use of the analog-to-digital converter (ADC) is firstly proposed and then extended to the whole receiver. In each case, the degradation of the receiver performances in terms of bit error rate (BER) is compared to an estimate of the obtained decrease of the power consumption. Moreover, the complexity and the overhead power consumption of the modules involved in the processing of the proposed techniques are also estimated and discussed. All these results are part of the field of research called “adaptive receiver” that tries to adapt the receiver performances to its environment in real time.Finally, a digital compensation technique of the quadrature imbalances was proposed. It allows using a less energy-consuming PLL but with degraded quadrature performances and compensating the mismatches in the digital domain. This technique uses a dichotomic search of the compensation weights allowing a fast convergence in order for the compensation to be done during the reception of a known portion of the received message and therefore avoiding a loss of information.
84

A Formal Fault Model for Component-Based Models of Embedded Systems

Fischer, Marco 14 May 2007 (has links)
Der vierte Band der wissenschaftlichen Schriftenreihe Eingebettete Selbstorganisierende Systeme widmet sich der Entwicklung von Fehlermodellen für eingebettete, verteilte Multi – Prozessorsysteme. Diese werden zu einem hierarchischen Netzwerk zur Steuerung von Flugzeugen (Avionik) verbunden und mehr und mehr im Automotive Bereich eingesetzt. Hier gilt es höchste Sicherheitsstandards einzuhalten und maximale Verfügbarkeit zu garantieren. Herr Fischer integriert die Modellierung von möglichen Fehlern in den Entwurfsprozess. Auf Grundlage des π-Kalküls entwickelt Herr Fischer ein formales Fehlermodell, das eine einheitliche Modellierung von Fehlerfällen unterstützt. Dabei werden interessante Bezüge zur Bi-Simulation sowie zu Methoden des Modell Checkings hergestellt. Die theoretischen Ergebnisse werden an einem komplexen Beispiel anschaulich illustriert. So kann der Leser die Mächtigkeit des entwickelten Ansatzes nachvollziehen und wird motiviert, die entwickelte Methodik auf weitere Anwendungsfälle zu übertragen. / The 4th volume of the scientific series Eingebettete, selbstorganisierende Systeme (Embedded Self-Organized Systems) outlines the design of fault models for embedded distributed multi processor systems. These multi processor systems will be connected to a hierarchical network to control airplanes (avionics) and also be used more and more in the automotive area. Here it is essential to meet highest safety standards and to ensure the maximum of availability. Mr Fischer integrates the modelling of potential faults into the design process. Based on the pi-calculus, he develops a formal framework, which supports a standardised modelling of faults. Thereby, interesting connections to the Bi-Simulation as well as to methods of the Model checking are established. The theoretical results are depicted on a complex example. So it is possible for the reader to understand the complexity of this approach and is motivated to use the developed methodology in other applications. I am glad that Mr Fischer publishes his important research in this scientific series.
85

Large-scale Numerical Optimization for Comprehensive HEV Energy Management - A Three-step Approach

Vishwanath, Aashrith 17 February 2022 (has links)
No description available.
86

Développement d'une approche multi-échelle de modélisation de dispositifs thermoélectriques : application à des systèmes de capteurs sans fils autonomes sur le corps humain / Development of a multiscale approach for thermoelectric devices modelling : application to wearable wireless autonomous sensors systems

Bella, Malika 14 December 2016 (has links)
Les dispositifs thermoélectriques, basés sur la conversion d'énergie thermique, offrent des perspectives intéressantes pour le développement de systèmes autonomes. Les principaux défis pour le développement de telles technologies reposent sur l'obtention de dispositifs flexibles, écologiquement et économiquement viables pouvant alimenter des appareils électroniques à faible consommation d'énergie. Le but de cette thèse a donc été de proposer une méthodologie pour l'analyse globale de dispositifs thermoélectriques pour des applications à température ambiante. Dans un premier temps, une approche multi-échelle pour la modélisation de dispositifs thermoélectriques a été développée. A cet effet, trois niveaux d'abstraction ont été considérés. A l'échelle du système, un modèle compact a été développé afin d'évaluer les performances du dispositif dans son environnement. A l'échelle du dispositif, des prototypes virtuels de TEG ont été évalués par le biais de la simulation numérique. A l'échelle des matériaux, la DFT combinée à une approche semi-classique basée sur l'équation de transport de Boltzmann ont été utilisées afin de calculer les propriétés électroniques. La tétraédrite et la famatinite ont été sélectionnées en raison de leurs propriétés prometteuses à température ambiante ainsi que de leur abondance et faible coût. Dans un second temps, des travaux expérimentaux sur la synthèse de nanoparticules de Cu-Sb-S ont été menés. Des nanoparticules quasi-monodisperses avec des tailles inférieures à 50 nm ont été obtenues grâce à la mise au point d'un procédé basé sur la synthèse solvothermale avec surfactant, une méthode faible coût et facilement adaptable à grande échelle. / Thermoelectric devices, capitalizing on waste heat conversion, offer good prospects for the development of autonomous systems. The main challenges for technology development are to obtain flexible, environmentally friendly and low-cost thermoelectric devices with performances sufficient enough to power small electronic devices. The aim of this thesis was thus to propose a methodology for the global analysis of thermoelectric devices for ambient temperature applications. The developed methodology enables the evaluation of key parameters impact on the global system. First, a multiscale approach for thermoelectric devices modelling is developed. In this scope, three parallel levels of modeling are addressed. At the system level, a compact model is developed in order to evaluate overall system efficiency as a function of the thermal environment. At the device level, virtual prototypes of printed devices are built and their performances are evaluated via a finite-element simulation tool. Low temperature gradient has to be dealt with by appropriate architecture design. At the material level, quantum DFT is used in conjunction with semi-classical approach using Boltzmann transport theory to calculate electronic properties. Tetrahedrite and famatinite compounds are chosen due to their promising thermoelectric properties at room temperature and their relative abundance and low cost. Secondly, an experimental work has been conducted on the synthesis of sulphide nanoparticles. Quasi-monodisperse nanoparticles with a size not exceeding 50 nm have successfully been fabricated via a low cost and easily scalable surfactant assisted solvothermal technique.
87

Analysis of 5G Mobile Broadband Solutions in Rural and Remote Areas : A Case Study of Banten, Indonesia

Sarah, Annisa January 2017 (has links)
Providing a broadband access anytime and anywhere is one of the visions of the future 5G network. However, deploying a reliable network connection in remote/rural areas has been a challenging task because of its wide area that needed to be covered and a low density of user compared to urban area. Different geography and traffic condition may need different system solution. In this thesis, we analyze several solutions to providing a broadband access network in practical remote and rural area in Banten, Indonesia: Leuwidamar (remote) and Panimbang (rural). Two approaches are discussed, first one is fulfilling futuristic traffic demand by having LTE System, and the second one is by having 5G System. We included three key technology components in a 5G network: occupying wide bandwidth in high frequency, applying UE-Specific Beamforming, and implementing Carrier Aggregation (CA) scheme. We also account a rain attenuation when deploying a network in high operating frequency, since Indonesia has a high rain rate thus it is important to be considered. We compared five cases of solution: Case 1 is Single Carrier (SC) LTE 1.8 GHz system; Case 2 is Carrier Aggregation (CA) LTE 1.8 GHz + 2.6 GHz; Case 3 is SC 5G 15GHz; Case 4 is SC 5G 28 GHz; Case 5 is CA LTE 1.8 GHz + 5G 15 GHz. Basedon the evaluation, in Leuwidamar scenario, Case 5 gives us the least number of BS needed in order to meet the futuristic requirement with only 1.6 x densification from the current network. In Panimbang, the least number of BS neededis offered by two cases, Case 3 and Case 5 without any additional BS needed(1x densification). However, the solution with the lowest energy consumption for both area is Case 3. This is due to the fact that the carrier aggregation scenario needs additional power to generate the second system. Furthermore, if we introduce cell DTX ability in the 5G network, the Case 3 can give us impressive amount of energy saving, with 97% saving for Leuwidamar and 94% saving for Panimbang, compared to Case 1 solution without any DTX Capability. / Att tillhandahålla bredbandsanslutning när som helst och var som helst är en av visionerna för det framtida 5G-nätverket. Att använda en tillförlitlig nätverksanslutning i avlägsna- eller landsbygdsområden har dock varit en utmanande uppgift på grund av det breda området som måste täckas och den låga täthetenav användare jämfört med stadsområden. Olika geografiska förhållanden och trafikförhållanden kan behöva olika systemlösningar. I denna avhandling analyserarvi flera lösningar för att tillhandahåller ett bredbandsnätverk i verkligt avlägset eller landsbygdsområde i Banten, Indonesien: Leuwidamar (avlägset) och Panimbang (landsbygd). Två strategier diskuteras, den första uppfyller framtida trafikbehov genom att ha LTE-system och den andra är genom att ha5G System. Vi inkluderade tre viktiga teknikkomponenter i 5G-nätverk: bredbandbredd och hög frekvens, tillämpar UE-specifik strålformning och implementeringav carrier aggregation (CA). Vi redovisar också en dämpning av regn när nätverket används i hög bärvågsfrekvens, eftersom Indonesien har en hög regnhastighet och det är viktigt att överväga. Vi jämförde fem fall av lösning:Fall 1 är Single Carrier (SC) eller Enkelbärare LTE 1.8 GHz system; Fall 2 är bärareaggregation (CA) LTE 1,8 GHz + 2.6 GHz; Fall 3 är SC 5G 15 GHz;Fall 4 är SC 5G 28 GHz; Fall 5 är CA LTE 1.8 GHz + 5G 15 GHz. Baserat på utvärderingen, i Leuwidamar-scenariot,ger Fall 5 oss det minsta antalet BSsom behövs för att möta det futuristiska kravet med endast 1.6 gångers förtätning från nuvarande nätverk. I Panimbang erbjuds det minsta antalet BS somkrävs i två fall, fall 3 och fall 5 utan ytterligare BS behövs (1 gångers förtätning). Lösningen med den lägsta energiförbrukningen för båda områdena är fall 3. Detta beror på att bäraraggregations scenariot behöver ytterligare effekt för att generera det andra systemet. Om vi introducerar cell DTX-funktionen i 5G-nätverket kan Fall 3 ge oss en imponerande energibesparing, med 97% minskning för Leuwidamar och 94% för Panimbang jämfört med Fall 1-lösning utan DTX-funktion.
88

Modelling and Analysis of Substrate Noise in Delta Sigma ADCs

Darda, Abu January 2017 (has links)
The rapid development in the semiconductors industry has enabled the placement of multiple chips on a single die. This has helped boost the functionality of modernday application specific integrated circuits (ASICs). Thus, digital circuits are being increasingly placed along-side analog and RF circuits in what are known as mixed signal circuits. As a result, the noise couplings through the substrate now have an increased role in mixed-signal ASIC design. Therefore, there is a need to study the effects of substrate noise and include them in the traditional design methodology. ∆Σ analog-to-digital converters (ADCs) are a perfect example of digital integration in traditionally analog circuits. ADCs, used to interface digital circuits to an analog world, are indispensable in mixed-signal systems and therefore set an interesting case study. A ∆Σ ADC is used in this thesis to study the effects of substrate noise. A background study is presented in the thesis to better understand ∆Σ modulators and substrate couplings. An intensive theoretical background on generation, propagation and reception of substrate noise is presented in light of existing researches. System and behavioural level models are proposed to include the effects of substrate noise in the design stages. A maximum decay of 10dB is seen due to injection of substrate noise system level simulations while a decay of 12dB is seen in behavioural simulations. A solution is proposed using controlled clock tree delays to overcome the effects of substrate noise. The solution is verified on both the system and behavioural levels. The noise models used to drive the studies can further be used in mixed-signal systems to design custom solutions. / Den snabba utvecklingen inom halvledarindustrin har möjliggjort placering av flera marker på en enda dö. Detta har hjälpt till att öka funktionaliteten hos moderna applikationsspecifika integrerade kretsar. Sålunda placeras digitala kretsar i allt högre grad parallella och RF-kretsar i de så kallade blandade signalkretsarna. Som ett resultat har bullerkopplingarna genom substratet nu en ökad roll i ASICdesign med blandad signal. Därför finns det behov av att studera effekterna av substratbuller och inkludera dem i den traditionella designmetoden. ∆Σ analog-till-digital omvandlare är ett perfekt exempel på digital integration i traditionellt analoga kretsar. ADC, som används för att gränssnitta digitala kretsar till en analog värld, är oumbärliga i blandningssignalsystem och är därför en intressant fallstudie. A ∆Σ arkitektur används i denna avhandling för att studera effekterna av substratstörning. En bakgrundsstudie presenteras i avhandlingen för att bättre förstå ∆Σ modulatorer och substratkopplingar. En intensiv teoretisk bakgrund på generering, förökning och mottagande av substratbuller presenteras i ljuset av befintliga undersökningar. Systemoch beteendemodellmodeller föreslås inkludera effekterna av substratbuller i konstruktionsstadiet. Ett maximalt förfall på 10dB ses på grund av injektion av substratbuller på systemnivå medan ett förfall av 12dB ses i beteende simuleringar.En lösning föreslås med hjälp av kontrollerade klockträdfördröjningar för att övervinna effekterna av substratbuller. Lösningen är verifierad på både system och beteendenivåer. De brusmodeller som används för att driva studierna kan vidare användas i blandningssignalsystem för att designa anpassade lösningar.
89

An analysis of 5G orchestration : Defining the role of software orchestrators in 5G networks, and building a method to compare implementations of 5G orchestrators / En analys av 5G orkestrering : Hur orkestreringsprogramvaror används i 5G nätverk, och ett sätt att jämföra varianter av orkestreringsprogramvaror.

Lex-Hammarskjöld, Justin January 2021 (has links)
Software orchestrators like Kubernetes are growing in popularity with computer engineers for deploying and running complex software systems. Interestingly, there are now new technical standards being proposed for the telecom industry to begin utilizing software orchestration for the software that runs inside cellular networks. The telecom industry is currently transitioning from 4G to 5G technology. One of the central pieces of this development work is implementing a software orchestrator for 5G networks. This raises some questions about how and why the telecom industry will use software orchestration in their cellular networks. Software orchestration is a complex technology and it is challenging to develop an implementation of a software orchestrator. Some important questions that this thesis addresses are: What do network operators need from this technology? Furthermore, telecom vendors, like Ericsson and Huawei, have developed their own versions of a 5G software orchestrator, which orchestrator should the network operators choose? Furthermore, we investigate what 5G is, why the telecom industry is developing software orchestrators for the 5G roll-out, and importantly, we determine the design requirements that the telecom industry has for these "5G orchestration systems". We interpret and break down technical whitepapers from the industry, and we build a picture of the IT stack of upcoming 5G networks. In our research, we find that software orchestration is being used to deploy and maintain complex software stacks such as software-defined networking (SDN) system that is central to 5G networks. We uncover some of the specializations needed in a software orchestrator for the telecom industry, such as modularity, high-availability, and specialized system integration. With this information, we make feature and design recommendations for 5G orchestrators, and we compile a list of criteria that network operators can use to assess and compare different 5G orchestrators. / Orkestreringsprogramvaror som Kubernetes växer i popularitet med IT ingenjörer för att installera och köra komplexa mjukvarasystem. På grund av pågående transitionen från 4G till 5G, används orkestreringsprogramvaror nu också i mobilnäten. I den här uppsatsen undersöks vad är 5G, varför telekombranschen använder orkestreringsprogramvaror för nya 5G nätverk, och vad krav har telekombranschen på denna "5G orkestreringsprogramvaror". Denna undersökning utförs genom en litteraturstudie. Genom den här undersökningen, det visar sig att orkestreringsprogramvaror används för att installera och köra komplexa mjukvarasystem som är centralt till 5G nätverk. Specialiseringskrav för orkestreringsprogramvaror i telekombranschen upptäcks, som modularitet, hög tillgänglighet, och specialiserad API-hookar. Rekommendationer görs för 5G orkestreringsprogramvarors funktioner, och en lista sammanställas av kriterier som telekomoperatör kan använda för att bedöma och jämföra 5G orkestreringsprogramvaror.
90

Applications of Adaptive Antennas in Third-Generation Mobile Communications Systems

Lau, Buon Kiong January 2002 (has links)
Adaptive antenna systems (AAS's) are traditionally of interest only in radar and sonar applications. However, since the onset of the explosive growth in demand for wireless communications during the 1990's, researchers are giving increasing attention to the use of AAS technology to overcome practical challenges in providing the service. The main benefit of the technology lies in its ability to exploit the spatial domain, on top of the temporal and frequency domains, to improve on transceiver performance. This thesis presents a unified study on two classes of preprocessing techniques for uniform circular arrays (UCA's). UCA's are of interest because of their natural ability to provide a full azimuth (i.e. 360') coverage found in typical scenarios for sensor array applications, such as radar, sonar and wireless communications. The two classes of preprocessing techniques studied are the Davies transformation and the interpolated array transformations. These techniques yield a mathematically more convenient form - the Vandermonde form - for the array steering vector via a linear transformation. The Vandermonde form is useful for different applications such as direction-of-arrival (DOA) estimation and optimum or minimum variance distortionless response (MVDR) beamforming in correlated signal environment and beampattem synthesis. A novel interpolated array transformation is proposed to overcome limitations in the existing interpolated array transformations. A disadvantage of the two classes of preprocessing techniques for UCA's with omnidirectional elements is the lack of robustness in the transformed array steering vector to array imperfections under certain conditions. In order to mitigate the robustness problem, optimisation problems are formulated to modify the transformation matrices. / Suitable optimisation techniques are then applied to obtain more robust transformations. The improved transformations are shown to improve robustness but at the cost of larger transformation errors. The benefits of the robustification procedure are most apparent in DOA estimation. In addition to the algorithm level studies, the thesis also investigates the use of AAS technology with respect to two different third generation (3G) mobile communications systems: Enhanced Data rates for Global Evolution (EDGE) and Wideband Code Division Multiple Access (WCDMA). EDGE, or more generally GSM/EDGE Radio Access Network (GERAN), is the evolution of the widely successful GSM system to provide 3G mobile services in the existing radio spectrum. It builds on the TDMA technology of GSM and relies on improved coding and higher order modulation schemes to provide packet-based services at high data rates. WCDMA, on the other hand, is based on CDMA technology and is specially designed and streamlined for 3G mobile services. For WCDMA, a single-user approach to DOA estimation which utilises the user spreading code and the pulse-shaped chip waveform is proposed. It is shown that the proposed approach produces promising performance improvements. The studies with EDGE are concerned with the evaluation of a simple AAS at the system and link levels. / Results from, the system and link level simulations are presented to demonstrate the effectiveness of AAS technology in the new mobile communications system. Finally, it is noted that the WCDMA and EDGE link level simulations employ the newly developed COST259 directional channel model, which is capable of producing accurate channel realisations of macrocell environments for the evaluation of AAS's.

Page generated in 0.1424 seconds