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Oh, Jun. "Limited." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1328121668.
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Knutsson, Philip. "Piercing the corporate veil : limits of limited liability." Thesis, Stockholms universitet, Juridiska institutionen, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-153357.
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Green, Antony D. "Phonology limited." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2007/1551/.
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Phonology Limited is a study of the areas of phonology where the application of optimality theory (OT) has previously been problematic. Evidence from a wide variety of phenomena in a wide variety of languages is presented to show that interactions involving more than just faithfulness and markedness are best analyzed as involving language-specific morphological constraints rather than universal phonological constraints. OT has proved to be a highly insightful and successful theory of linguistics in general and phonology in particular, focusing as it does on surface forms and treating the relationship between inputs and outputs as a form of conflict resolution. Yet there have also been a number of serious problems with the approach that have led some detractors to argue that OT has failed as a theory of generative grammar. The most serious of these problems is opacity, defined as a state of affairs where the grammatical output of a given input appears to violate more constraints than an ungrammatical competitor. It is argued that these problems disappear once language-specific morphological constraints are allowed to play a significant role in analysis. Specifically, a number of processes of Tiberian Hebrew traditionally considered opaque are reexamined and shown to be straightforwardly transparent, but crucially involving morphological constraints on form, such as a constraint requiring certain morphological forms to end with a syllabic trochee, or a constraint requiring paradigm uniformity with regard to the occurrence of fricative allophones of stop phonemes.
Language-specific morphological constraints are also shown to play a role in allomorphy, where a lexeme is associated with more than one input; the constraint hierarchy then decides which input is grammatical in which context. For example, [ɨ]/[ə] and [u]/[ə] alternation found in some lexemes but not in others in Welsh is attributed to the presence of two inputs for the lexemes with the alternation. A novel analysis of the initial consonant mutations of the modern Celtic languages argues that mutated forms are separately listed inputs chosen in appropriate contexts by constraints on morphology and syntax, rather than being outputs that are phonologically unfaithful to their unmutated inputs.
Finally, static irregularities and lexical exceptions are examined and shown to be attributable to language-specific morphological constraints. In American English, the distribution of tense and lax vowels is predictable in several contexts; however, in some contexts, the distributions of tense [ɔ] vs. lax [a] and of tense [æ] vs. lax [æ] are not as expected. It is shown that clusters of output-output faithfulness constraints create a pattern to which words are attracted, which however violates general phonological considerations. New words that enter the language first obey the general phonological considerations before being attracted into the language-specific exceptional pattern.
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Lilico, Andrew. "Limited foresight." Thesis, University College London (University of London), 2004. http://discovery.ucl.ac.uk/1383526/.
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This thesis is about multi-period problems in which the decision-maker or players cannot see far enough ahead to solve the problem completely. The thesis considers why it might be that players reason forwards at all, let alone reasoning forwards only finitely far. It shows, using finite automata, that there is a class of problems for which forwards reasoning is more efficient than backwards reasoning. It goes on to use these finite automata to solve for an optimal foresight length. It then discusses solution concepts, and applies its preferred solution concept to two problems - one macro problem involving a central banker, and one micro problem concerning the decision whether to smoke.
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Van, de Sompel Dominique. "Limited view tomography." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515008.
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Friedlander, Mark B. "Limited Sight Distance." Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1527929.
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Limited Sight Distance is a poetry collection, written primarily between August 2012 and March 2014, while I was enrolled in the Master of Fine Arts in Creative Writing program at California State University, Long Beach. In addition to work produced during this time, it also includes poems I completed while a returning undergraduate, as well as others written outside the academic environment; all are intended to reflect both my experience and development as a poet. The subject matter of these narratives includes aging, betrayal, death, family, illness, loss, love, and work, as perceived from varying points of view. I have found that, in life, it is when we are unable to see beyond that which presents itself to us immediately, that our sight distance is limited.
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De, Villiers Mattieu. "Limited angle tomography." Doctoral thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/5271.
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Includes bibliographical references (p. 127-130).This thesis investigates the limited angle tomography problem where axial reconstructions are produced from few measured projection views covering a 100° angular range. Conventional full angle tomography requires at least a 180° range of projection views of the patient at a fine angular spacing. Inference techniques presented in the literature, such as Bayesian methods, perform inadequately on the information-starved problem of interest.
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Hui, Gan Sheuo. "The concept of selective animation : dropping the "limited" in limited animation." Kyoto University, 2008. http://hdl.handle.net/2433/136473.
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Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第13937号
人博第410号
新制||人||101(附属図書館)
19||人博||410(吉田南総合図書館)
UT51-2008-C853
京都大学大学院人間・環境学・環境学研究科共生人間学専攻
(主査)准教授 加藤 幹郎, 教授 篠原 資明, 准教授 小倉 紀蔵
学位規則第4条第1項該当
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Yang, Xuan, and 楊譞. "Budget-limited data disambiguation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196458.
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The problem of data ambiguity exists in a wide range of applications. In this thesis, we study “cost-aware" methods to alleviate the data ambiguity problems in uncertain databases and social-tagging data.
In database applications, ambiguous (or uncertain) data may originate from data integration and measurement error of devices. These ambiguous data are maintained by uncertain databases. In many situations, it is possible to “clean", or remove, ambiguities from these databases. For example, the GPS location of a user is inexact due to measurement error, but context information (e.g., what a user is doing) can be used to reduce the imprecision of the location value. In practice, a cleaning activity often involves a cost, may fail and may not remove all ambiguities. Moreover, the statistical information about how likely database entities can be cleaned may not be precisely known. We model the above aspects with the uncertain database cleaning problem, which requires us to make sensible decisions in selecting entities to clean in order to maximize the amount of ambiguous information removed under a limited budget. To solve this problem, we propose the Explore-Exploit (or EE) algorithm, which gathers valuable information during the cleaning process to determine how the remaining cleaning budget should be invested. We also study how to fine-tune the parameters of EE in order to achieve optimal cleaning effectiveness.
Social tagging data capture web users' textual annotations, called tags, for resources (e.g., webpages and photos). Since tags are given by casual users, they often contain noise (e.g., misspelled words) and may not be able to cover all the aspects of each resource. In this thesis, we design a metric to systematically measure the tagging quality of each resource based on the tags it has received. We propose an incentive-based tagging framework in order to improve the tagging quality. The main idea is to award users some incentive for giving (relevant) tags to resources. The challenge is, how should we allocate incentives to a large set of resources, so as to maximize the improvement of their tagging quality under a limited budget? To solve this problem, we propose a few efficient incentive allocation strategies. Experiments shows that our best strategy provides resources with a close-to-optimal gain in tagging quality.
To summarize, we study the problem of budget-limited data disambiguation for uncertain databases and social tagging data | given a set of objects (entities from uncertain databases or web resources), how can we make sensible decisions about which object to \disambiguate" (to perform a cleaning activity on the entity or ask a user to tag the resource), in order to maximize the amount of ambiguous information reduced under a limited budget.published_or_final_version
Computer Science
Doctoral
Doctor of Philosophy
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Vissing-Jorgensen, Annette 1971. "Limited stock market participation." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10119.
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Matos, Inês Pereira de. "Limited range coverage problems." Doctoral thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/2946.
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Doutoramento em MatemáticaTal como o título indica, esta tese estuda problemas de cobertura com alcance limitado. Dado um conjunto de antenas (ou qualquer outro dispositivo sem fios capaz de receber ou transmitir sinais), o objectivo deste trabalho é calcular o alcance mínimo das antenas de modo a que estas cubram completamente um caminho entre dois pontos numa região. Um caminho que apresente estas características é um itinerário seguro. A definição de cobertura é variável e depende da aplicação a que se destina. No caso de situações críticas como o controlo de fogos ou cenários militares, a definição de cobertura recorre à utilização de mais do que uma antena para aumentar a eficácia deste tipo de vigilância. No entanto, o alcance das antenas deverá ser minimizado de modo a manter a vigilância activa o maior tempo possível. Consequentemente, esta tese está centrada na resolução deste problema de optimização e na obtenção de uma solução particular para cada caso. Embora este problema de optimização tenha sido investigado como um problema de cobertura, é possível estabelecer um paralelismo entre problemas de cobertura e problemas de iluminação e vigilância, que são habitualmente designados como problemas da Galeria de Arte. Para converter um problema de cobertura num de iluminação basta considerar um conjunto de luzes em vez de um conjunto de antenas e submetê-lo a restrições idênticas. O principal tema do conjunto de problemas da Galeria de Arte abordado nesta tese é a 1-boa iluminação. Diz-se que um objecto está 1-bem iluminado por um conjunto de luzes se o invólucro convexo destas contém o objecto, tornando assim este conceito num tipo de iluminação de qualidade. O objectivo desta parte do trabalho é então minimizar o alcance das luzes de modo a manter uma iluminação de qualidade. São também apresentadas duas variantes da 1-boa iluminação: a iluminação ortogonal e a boa !-iluminação. Esta última tem aplicações em problemas de profundidade e visualização de dados, temas que são frequentemente abordados em estatística. A resolução destes problemas usando o diagrama de Voronoi Envolvente (uma variante do diagrama de Voronoi adaptada a problemas de boa iluminação) é também proposta nesta tese.
As the title implies, this thesis studies limited range coverage problems. Given a set of antennas (or any wireless device able to send or receive some sort of signal), the objective of the discussion that follows is to calculate the antennas’ minimum range so that a path between two points within a region is covered by the antennas, a path known as a safe route. The definition of coverage is variable and depends on the applications. In some instances, for example, when monitoring is critical as in the case of fires or military, the definition of coverage necessarily involves the use of multiple antennas to increase the effectiveness of monitoring. However, it is also desirable to extend a network’s lifespan, normally achieved by minimising the antennas’ range. Therefore the focus of this thesis will be the resolution of this dual problem and an affective solution is offered for each case. Although this question has been researched as an issue of coverage, it is also possible to establish a relation between coverage and illumination and visibility, known as Art Gallery problems. To conceptualise coverage problems as Art Gallery problems, all that is needed is to consider a set of lights instead of a set of antennas, which are subject to a similar set of restrictions. The main focus of the Art Gallery problems addressed in this thesis is 1-good illumination. An object is 1-well illuminated if it is fully contained by the convex hull of a set of lights, making this a type of quality illumination. The objective of the discussion that follows is therefore to minimise the lights’ range whilst maintaining a quality illumination. Moreover, two variants of 1-good illumination are also presented: orthogonal good illumination and good ! -illumination. The latter being related to data depth problems and data visualisation that are frequently used in statistics. The resolution of these problems using the Embracing Voronoi diagram (a variant of Voronoi diagrams adapted to good illumination) is also discussed in this thesis.
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List, Hans-Fredo. "Limited risk arbitrage investment management." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/8651.
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Hillebrenner, Torsten. "Limited als Alternative zur GmbH /." Aachen : Shaker, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015519961&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Johnson, Eric N. "Limited authority adaptive flight control." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/12953.
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Nagel, Stefan. "Limited arbitrage in equity markets." Thesis, London Business School (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406388.
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Green, Antony Dubach [Verfasser]. "Phonology limited / Antony Dubach Green." Potsdam : Universität Potsdam, 2007. http://d-nb.info/1219991279/34.
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Anderson, Christopher. "BANDWIDTH LIMITED 320 MBPS TRANSMITTER." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/607635.
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International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, CaliforniaWith every new spacecraft that is designed comes a greater density of information that will be stored once it is in operation. This, coupled with the desire to reduce the number of ground stations needed to download this information from the spacecraft, places new requirements on telemetry transmitters. These new transmitters must be capable of data rates of 320 Mbps and beyond. Although the necessary bandwidth is available for some non-bandwidth-limited transmissions in Ka-Band and above, many systems will continue to rely on more narrow allocations down to X-Band. These systems will require filtering of the modulation to meet spectral limits. The usual requirements of this filtering also include that it not introduce high levels of inter-symbol interference (ISI) to the transmission. These constraints have been addressed at CE by implementing a DSP technique that pre-filters a QPSK symbol set to achieve bandwidth-limited 320 Mbps operation. This implementation operates within the speed range of the radiation-hardened digital technologies that are currently available and consumes less power than the traditional high-speed FIR techniques.
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Luís, Sara Iolanda Ramos. "Equity research - Capri Holdings Limited." Master's thesis, Instituto Superior de Economia e Gestão, 2019. http://hdl.handle.net/10400.5/19637.
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Mestrado em FinançasComo projeto final do Mestrado em Finanças foi elaborado o presente relatório. Este, engloba uma avaliação do valor das ações com uma análise detalhada do grupo CAPRI Holdings Limited. A estrutura do relatório reflete as recomendações do instituto CFA e as normas do trabalho final de mestrado do ISEG. Em 2017, a Michael Kors adquiriu a Jimmy Choo e em 2018 a Versace dando assim origem ao grupo CAPRI. O preço-alvo é de $ 48,8 tendo sido alcançado através da avaliação pelo método Discounted Cash Flow e da avaliação pelos Múltiplos. A recomendação é reduzir estando sustentada em 5 fatores principais: a aquisição de uma empresa não cotada, a relutância do mercado de luxo e dos próprios consumidores em aceitar a união destas três marcas, a instabilidade do Reino Unido com a situação do Brexit, o aumento de impostos e a guerra comercial entre os Estados Unidos e a China. Os dados financeiros deste relatório reportam a 31 de março de 2019 não sendo qualquer evento posterior considerado.
As a final project of ISEG's Master in Finance, it was elaborated this report that includes an valuation of shares value with a detailed analysis of CAPRI Holdings Limited group. The report structure follows the CFA Institute guidelines and ISEG's Master final work project standards. In 2017, Michael Kors acquired Jimmy Choo and Versace in 2018, originating CAPRI group. The target price of $ 48,8 was achieved using valuation method of Discounted Cash Flow and a relative valuation of Multiples. The recommendation is to reduce, supported by 5 main factors: acquisition of a non-public company, some market reluctance to accept the union of the three companies, UK instability due to Brexit situation, increase of duties and trade war between US and China. Financial data of this report is dated on March 31st, 2019. Any further event has not been considered.
info:eu-repo/semantics/publishedVersion
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Tran-Thanh, Long. "Budget-limited multi-armed bandits." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/337660/.
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Decision making under uncertainty is one of the most important challenges within the research field of artificial intelligence, as they present many everyday situations that agents have to face. Within these situations, an agent has to choose from a set of options, whose payoff is uncertain (i.e. unknown and nondeterministic) to the agent. Common to such decision making problems is the need of balancing between exploration and exploitation, where the agent, in order to maximise its total payoff, must decide whether to choose the option expected to provide the best payoff (exploitation) or to try an alternative option for potential future benefit (exploration). Among many decision under uncertainty abstractions, multi–armed bandits are perhaps one of the most common and best studied, as they present one of the clearest examples of the trade–off between exploration and exploitation. Whilst the standard bandit model has a broad applicability, it does not completely describe a number of real–world decision making problems. Specifically, in many cases, pulling choice of arm (i.e. making a decision)is further constrained by several costs or limitations. In this thesis, we introduce the budget–limited bandit model, a variant of the standard bandits, in which pulling an arm is costly, and is limited by a fixed budget. This model is motivated by a number of real–world applications, such as wireless sensor networks, or online advertisement. We demonstrate that our bandit model cannot be reduced to other existing bandits, as it requires a different optimal behaviour. Given this, the main objective of this thesis is to provide novel pulling algorithms that efficiently tackle the budget–limited bandit problem. Such algorithms, however, have to meet a number of requirements from both the empirical and the theoretical perspectives. The former refers to the constraints desired by the motivations of real–world applications, whilst the latter aims to provide theoretical performance guarantees. To begin with, we propose a simple pulling algorithm, the budget–limited ε–first, that addresses the empirical requirements. In more detail, the budget–limited ε–first algorithm is an empirically efficient algorithm with low computational cost, which, however, does not fulfil the theoretical requirements. To provide theoretical guarantees, we introduce two budget–limited UCB based algorithms, namely: KUBE and fractional KUBE,iv that efficiently tackle the theoretical requirements. In particular, we prove that these algorithms achieve asymptotically optimal performance regret bounds, which only differ from the best optimal bound by a constant factor. However, we demonstrate in extensive simulations that these algorithms are typically outperformed by the budget–limited ε–first. As a result, to efficiently trade off between theoretical and empirical requirements, we develop two decreasing ε–greedy based approaches, namely: KDE and fractional KDE, that achieve good performance from both the theoretical and the empirical perspective. Specifically, we show that, similar to the budget–limited UCB based algorithms, both KDE and fractional KDE achieve asymptotically optimal performance regret bounds. In addition, we also demonstrate that these algorithms perform well, compared to the budget–limited ε first. To provide a grounding for the algorithms we develop, the second part of this thesis contains a running example of a wireless sensor network (WSN) scenario, in which we tackle the problem of long–term information collection, a key research challenge within the domain of WSNs. In more detail, we demonstrate that by using the budget–limited bandit algorithms, we advance the state–of–the–art within this domain. In so doing, we first decompose the problem of long–term information collection into two sub–problems, namely the energy management and the maximal information throughput routing problems. We then tackle the former with a budget–limited multi–armed bandit based approach, and we propose an optimal decentralised algorithm for the latter. Following this, we demonstrate that the budget–limited bandit based energy management, in conjunction with the optimal routing algorithm, outperforms the state–of–the–art information collecting algorithms in the domain of WSNs.
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Jin, Bo. "Optimal Designs with Limited Resources." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29730.
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In this dissertation we present new results regarding optimality of block designs with limited resources. The dissertation is organized as follows. The first chapter outlines the theory of optimal block design. The second chapter shows new work in optimal minimally connected block designs with spatial correlation structure. The third chapter details the discovery of the optimal incomplete designs with two blocks. The fourth chapter does the same for the optimal binary incomplete designs with three blocks. The fifth chapter summarizes the techniques used and new results found and lists possible future research topics.Ph. D.
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Key, Andrew Braxton. "Limited Revisionism and Error Theory." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/90658.
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In Joyce's Myth of Morality, Joyce proposes an error theory about morality. He then argues that, once we accept an error theory, we have three options: we can be abolitionists and jettison moral discourse, be conservationists and maintain our false moral beliefs, or be revolutionary fictionalists and assent to and act in accordance with moral discourse while believing it's false. In this paper, I argue that Joyce has ignored a fourth option—limited revisionism, or slightly changing our moral terms to avoid problematic commitments—and that this option is superior to the three aforementioned possibilities. Along the way, I show that Joyce has unfairly ignored limited revisionism because of faulty views about what makes a concept or term normative, and that limited revisionism ignores some expected pitfalls, such as overgeneralizing to legitimately error-theoretic discourses.Master of Arts
In this paper, I argue against Joyce’s assertion that if our moral terms centrally implicate falsehoods, we should act as though morality is true (because it’s useful) while also believing that it’s false (because doing otherwise would be epistemically irresponsible). I show Joyce’s position rests on a specific misunderstanding of how language operates, and argue instead that, if we accept that our current moral talk centrally implicates falsehoods, we should be open to slightly revising our moral terms to avoid implicating such falsehoods instead. I also show that my position, limited revisionism, avoids a few expected pitfalls—most importantly, it doesn’t overgeneralize and apply to terms like “witch” and “phlogiston,” which also centrally implicate falsehoods but seem like terms that shouldn’t be open to conceptual change.
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Vieira, Sérgio Filipe Gonçalves. "Object grouping in limited spaces." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/21737.
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Mestrado em Engenharia Eletrónica e TelecomunicaçõesCom a crescente necessidade de transporte de mercadoria como resultado da globalização económica, é importante o melhoramento dos processos e procedimentos das operações logísticas como o carregamento e descarregamento de mercadoria, por forma às corporações aumentarem a sua vantagem competitiva e rentabilidade. Esta dissertação explora e apresenta dois temas relacionados com processos logísticos: Posicionamento de volumes e tecnologias de deteção para monitorização de mercadorias. Uma heurística foi desenvolvida para atribuição e posicionamento 3D de volumes dentro de contentores seguindo uma estratégia de colocação que produz soluções verticalmente estáveis e com um alto grau de compactação. Desenvolveram-se dois protótipos usando tecnologia de deteção capaz de medição de volumes, varrimento por laser e visão estereoscópica por computador, como fundação para um sistema para monitorizar o carregamento e descarregamento de mercadorias. Estes sistemas pretendem providenciar assistência para os operadores logísticos na aplicação de normas e identificação de potenciais problemas. Os resultados obtidos pela heurística são promissores, mostrando que um conjunto de simples regras de posicionamento de caixas consegue obter uma boa percentagem de ocupação de volume do contentor. Ambos os protótipos de deteção apresentaram bons resultados nos testes de laboratório, com o protótipo de visão estereoscópica provando ser o mais preciso e fiável para potencial desenvolvimento em uma aplicação a ser instalada em contentores. Esta dissertação conclui com observações acerca de futuros melhoramentos e desenvolvimentos para o trabalho implementado.
With the ever necessity of cargo transportation as the results of economic globalization, it is important to improve the processes and procedures of logistic operations such as cargo loading and unloading, in order for corporations to increase their competitive advantage and profitability. This dissertation explores and presents two subjects related with logistic processes: Volume placement and sensing technologies for cargo monitoring. A heuristic was developed for 3D volume assignment and placement inside containers following a positioning strategy that produces vertically stable solutions with a high degree of compactness. Two prototypes using sensing technology capable of volume measurement, laser range finding and computer stereo vision, were developed as a foundation for a system for monitoring the loading and unloading of cargo. These systems aim to provide assistance to logistic operators on the application of standards and identification of potential issues. The obtained results on the heuristic are promising, showing that a simple set of rules for placement of boxes can achieve a good occupation percentage of the container’s volume. Both sensing prototypes showed good results on lab tests with the stereo vision prototype proving to be the most accurate and reliable for potential further developments into an application to be installed in containers. This dissertation concludes with remarks regarding future improvements and developments for the implemented work.
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Pfister, Ralph. "Die englische Gesellschaftform der Limited." [S.l. : s.n.], 2005. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB12168184.
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Austrin, Per. "Conditional Inapproximability and Limited Independence." Doctoral thesis, Stockholm : Datavetenskap och kommunikation, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9422.
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Sieglová, Marie. "Osobní společnosti v americkém právu." Master's thesis, Vysoká škola ekonomická v Praze, 2008. http://www.nusl.cz/ntk/nusl-3875.
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In this thesis the author deals with the comparision of american alternative business entities according to the law of the state Delaware with the czech "personal business societies". In the body of the thesis there are described the following 3 types of business entities: general partnership, limited partnership and limited liability limited partnership, including the description of its formation and dissolution, the rights, powers, duties and liabilities of the partners. After each section there are compared to the czech Commercial code (Seccions veřejná obchodní společnost and komanditní společnost).
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Sànchez, Martínez Olga. "Light-limited growth of Chromatium vinosum." Doctoral thesis, Universitat Autònoma de Barcelona, 1996. http://hdl.handle.net/10803/3911.
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Ferrero, Giuseppe. "Expectations, interest rate and limited commitment." Doctoral thesis, Universitat Pompeu Fabra, 2005. http://hdl.handle.net/10803/7601.
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El tema genérico de la tesis es el estudio de modelos dinámicos que departen
del supuesto tradicional de mercados perfectos y expectativas racionales.
En el primer capitulo se estudia la política monetaria en un modelo
de aprendizaje. En este modelo la producción y la inflación dependen de
las expectativas, de los shocks a la economía y del tipo de interés determinado
por el banco central. En esta economía los agentes aprenden sobre la mejor
forma de prever la inflación y la producción futuras. Se muestra que la
velocidad de aprendizajes puede ser muy lenta, es decir, que la economía
con aprendizaje tardaría mucho tiempo en llegar al equilibrio de expectativas
racionales. En particular, si el banco central siguiera las políticas económicas
que se derivarían en un modelo de expectativas racionales, la economía
podría tardar tanto en llegar al equilibrio, que estas resultarían unas
malas políticas. Mas en concreto, si se toma en cuenta el aprendizaje,
la política optima del banco central tendría que reaccionar mucho mas a
la tasa de inflación y incrementar mas el tipo de interés en periodos de
inflación alta. El segundo capitulo de la tesis aborda el
problema de impagos de deudas. En particular se estudia la estipulación
de contratos financieros de seguro y de deuda, tomando en cuenta la posibilidad
que se produzcan impagos de la deuda. Recientemente se ha empezado a estudiar
modelos de división del riesgo bajo el supuesto que, si les conviene, los
agentes pueden salir de los contratos quedando excluidos para siempre del
mercado. Este supuesto de "exclusión permanente" se ha mantenido en la
literatura por razones técnicas que simplifican el cálculo numérico del
equilibrio. Sin embargo es evidente que se trata de un supuesto poco realista.
Por lo tanto, el segundo capitulo de la tesis estudia un modelo donde el
agente que no cumple el contrato queda excluido solo temporalmente del
mercado de deuda.
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Bauducco, Sofia. "Optimal policy heterogeneity and limited commitment." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7394.
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Esta tesis contribuye a la literatura de política fiscal y monetaria óptima. Primero analizo cómo el resultado de tasas impositivas suaves, que habitualmente se obtiene en modelos de política fiscal óptima, se ve alterado en un contexto de división internacional de riesgo con compromiso parcial. Encuentro que la presencia de compromiso parcial altera significativamente la dinámica de las variables fiscales, con respecto al caso de compromiso total. La volatilidad de la tasa impositiva aumenta. En segundo lugar, estudio la política fiscal y monetaria en un modelo con shocks idiosincráticos no asegurables a la productividad laboral. Encuentro que, cuando el gobierno es utilitarista, la autoridad monetaria fija la tasa de interés nominal a cero. Los efectos agregados de bienestar son pequeños, mientras que los efectos individuales son grandes. Los beneficiarios de la inflación son agentes pobres con baja productividad, mientras que los agentes de clase media y alta siempre son perdedores.This thesis contributes to the literature on optimal fiscal and monetary policy. First, I analyze how the tax-smoothing result obtained in models of optimal fiscal policy is altered in a context of international risk sharing with limited commitment. I find that the presence of limited commitment alters substantially the dynamics of the fiscal variables with respect to the full commitment case. In particular, the volatility of the tax rate increases. Second, I study the optimal monetary and fiscal policy mix in a model in which agents are subject to idiosyncratic uninsurable shocks to their labor productivity. I find that, for a utilitarian government, the monetary policy-maker sets nominal interest rates to zero. Although the aggregate welfare costs of inflation are small, individual costs and benefits are large. Net winners from inflation are poor, less productive agents, while middle-class and rich households are always net losers.
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Senecal, Joshua G. "Length-limited data transformation and compression /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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Palmer, Martha Stone. "Driving semantics for a limited domain." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/26831.
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Hansler, Susan. "Compositional simulation of nutrient-limited bioventing." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0027/MQ50342.pdf.
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Jiang, Lianjun. "Preconditioning the limited-memory BFGS algorithm." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239445.
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Bauducco, Sofia. "Optimal policym heterogeneity and limited commitment." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7394.
Full textAbstract:
Esta tesis contribuye a la literatura de política fiscal y monetaria óptima. Primero analizo cómo el resultado de tasas impositivas suaves, que habitualmente se obtiene en modelos de política fiscal óptima, se ve alterado en un contexto de división internacional de riesgo con compromiso parcial. Encuentro que la presencia de compromiso parcial altera significativamente la dinámica de las variables fiscales, con respecto al caso de compromiso total. La volatilidad de la tasa impositiva aumenta. En segundo lugar, estudio la política fiscal y monetaria en un modelo con shocks idiosincráticos no asegurables a la productividad laboral. Encuentro que, cuando el gobierno es utilitarista, la autoridad monetaria fija la tasa de interés nominal a cero. Los efectos agregados de bienestar son pequeños, mientras que los efectos individuales son grandes. Los beneficiarios de la inflación son agentes pobres con baja productividad, mientras que los agentes de clase media y alta siempre son perdedores.This thesis contributes to the literature on optimal fiscal and monetary policy. First, I analyze how the tax-smoothing result obtained in models of optimal fiscal policy is altered in a context of international risk sharing with limited commitment. I find that the presence of limited commitment alters substantially the dynamics of the fiscal variables with respect to the full commitment case. In particular, the volatility of the tax rate increases. Second, I study the optimal monetary and fiscal policy mix in a model in which agents are subject to idiosyncratic uninsurable shocks to their labor productivity. I find that, for a utilitarian government, the monetary policy-maker sets nominal interest rates to zero. Although the aggregate welfare costs of inflation are small, individual costs and benefits are large. Net winners from inflation are poor, less productive agents, while middle-class and rich households are always net losers.
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Chang, Woojin. "Asymptotics of k-limited polling models." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/25507.
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Liatsos, Vassilios. "Scalability in planning with limited resources." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395939.
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Bell, Rebecca Jane Hesley. "Is Fuchsia excorticata (Onagraceae) seed limited?" Thesis, University of Canterbury. Biological Sciences, 2010. http://hdl.handle.net/10092/5514.
Full textAbstract:
Maintenance of native bird populations is necessary for the effective functioning of
bird-plant mutualisms such as pollination and dispersal. The New Zealand native tree
Fuchsia excorticata (Onagraceae) is declining because of possum herbivory, and is
known to be pollination limited resulting in lower seed set. However, pollination
limitation will not be of any consequence if F. excorticata is not seed limited. I tested
whether F. excorticata is seed limited. If the species is both pollen and seed limited, it
has considerable implications for one of New Zealand’s important secondary
succession forest trees, as well as the honeyeating and frugivorous birds that feed on
its flowers and fruit.
To compare whether local bird density and the pollination service affected the seed
supply, I selected two sites with high pest control, and two sites with low pest control.
Visitation rates to F. excorticata flowers and bird counts were measured at each site. I
measured the seed bank at increasing distance from parent F. excorticata trees, and
recorded the sex of parents to determine if pollination limitation was affecting seed
set according to parent gender because females are more pollen limited than
hermaphrodites. A field seed addition experiment tested for seed, microsite and
herbivore limitation. Natural seedling distribution was mapped to distinguish what
environmental conditions favoured germination and establishment.
Surprisingly, bird visitation to F. excorticata was no higher with pest control, but
abundance of honeyeating birds was higher in five minute bird counts. The F.
excorticata seed bank decreased with dispersal distance away from the parent tree,
was larger in sites with high pest control and also significantly more abundant beneath
hermaphrodite parents. On average seven times more seedlings germinated in sown
plots than unsown plots, thus proving seed limitation. Caged plots had nearly twice as
many seedlings as uncaged plots, which shows herbivore limitation. More seedlings
germinated closer to the parent tree than further away. Therefore, F. excorticata is
showing evidence of seed, microsite and herbivore limitation, and complex
interactions between each. Most importantly, the pollination limitation that F.
excorticata experiences due to lack of suitable pollinators causes a reduced seed set
which affects the soil seed bank and level of seedling regeneration. This reduced seed
supply combined with seed and microsite limitation is affecting the density of F.
excorticata seedlings, and thus perhaps ultimately the density of adult trees.
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Pople, Andrew James. "Value-based maintenance using limited data." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391958.
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Barker, Peter William Howes. "Selection mechanisms of diffusion-limited growth." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386994.
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Bhardwaj, Manish 1976. "Communications in the observation limited regime." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53191.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 141-145).
We consider the design of communications systems when the principal cost is observing the channel, as opposed to transmit energy per bit or spectral efficiency. This is motivated by energy constrained communications devices where sampling the signal, rather than transmitting or processing it, dominates energy consumption. We show that sequentially observing samples with the maximum a posteriori entropy can reduce observation costs by close to an order of magnitude using a (24,12) Golay code. This is the highest performance reported over the binary input AWGN channel, with or without feedback, for this blocklength. Sampling signal energy, rather than amplitude, lowers circuit complexity and power dissipation significantly, but makes synchronization harder. We show that while the distance function of this non-linear coding problem is intractable in general, it is Euclidean at vanishing SNRs, and root Euclidean at large SNRs. We present sequences that maximize the error exponent at low SNRs under the peak power constraint, and under all SNRs under an average power constraint. Some of our new sequences are an order of magnitude shorter than those used by the 802.15.4a standard.
(cont.) In joint work with P. Mercier and D. Daly, we demonstrate the first energy sampling wireless modem capable of synchronizing to within a ns, while sampling energy at only 32 Msamples per second, and using no high speed clocks. We show that traditional, minimum distance classifiers may be highly sensitive to parameter estimation errors, and propose robust, computationally efficient alternatives. We challenge the prevailing notion that energy samplers must accurately shift phase to synchronize with high precision.
by Manish Bhardwaj.
Ph.D.
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Hsu, Bo-June (Bo-June Paul). "Language Modeling for limited-data domains." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/52796.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 99-109).
With the increasing focus of speech recognition and natural language processing applications on domains with limited amount of in-domain training data, enhanced system performance often relies on approaches involving model adaptation and combination. In such domains, language models are often constructed by interpolating component models trained from partially matched corpora. Instead of simple linear interpolation, we introduce a generalized linear interpolation technique that computes context-dependent mixture weights from features that correlate with the component confidence and relevance for each n-gram context. Since the n-grams from partially matched corpora may not be of equal relevance to the target domain, we propose an n-gram weighting scheme to adjust the component n-gram probabilities based on features derived from readily available corpus segmentation and metadata to de-emphasize out-of-domain n-grams. In scenarios without any matched data for a development set, we examine unsupervised and active learning techniques for tuning the interpolation and weighting parameters. Results on a lecture transcription task using the proposed generalized linear interpolation and n-gram weighting techniques yield up to a 1.4% absolute word error rate reduction over a linearly interpolated baseline language model. As more sophisticated models are only as useful as they are practical, we developed the MIT Language Modeling (MITLM) toolkit, designed for efficient iterative parameter optimization, and released it to the research community.
(cont.) With a compact vector-based n-gram data structure and optimized algorithm implementations, the toolkit not only improves the running time of common tasks by up to 40x, but also enables the efficient parameter tuning for language modeling techniques that were previously deemed impractical.
by Bo-June (Paul) Hsu.
Ph.D.
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Punzo, Giuliano. "Verifiable swarm engineering with limited communication." Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=22725.
Full textAbstract:
The new paradigms of swarm engineering, distributed architectures and autonomous multi-agent systems, are foreseen to redefine the way many engineering problems are approached. The affirmation of these new concepts requires the complete understanding of complex dynamics by the designers. That is, any system whose concept departs from the monolithic architecture must deliver its tasks in a predictable way and be controlled in a safe manner, while keeping the maximum possible autonomy. This work aims to span the gap between a complete foreseeable behaviour and system autonomy using precise mathematical descriptions of the dynamics and control of multi-agent systems. Dynamical system theory, Lyapunov stability, linear algebra and graph theory are used to rigorously frame the problem and delineate the characteristics of such systems in relation to a number of applications and performance parameters. The work first considers multi-agent systems as multi-particle systems in a physics fashion to draw fundamental results about the robustness to fragmentation when the individuals do not benefit from all-to-all communications. The exploitation of limited communications together with artificial potential functions is shown to be an effective way to shape formations of agents in a range of applications for future engineering, and in particular this scheme is proved to be effective for space-based communications through the autonomous deployment of antenna arrays. In this context, application to robotics is explored through laboratory tests exploiting wheeled robots with possible applications to structural inspection or planetary exploration. A stable fractal formation is proved to emerge out of a number of agents whose interaction network presents a recursive layout whereby relative motion is driven by artificial potential functions. Finally, the fast manoeuvring problem is covered together with one of allocating resources in an efficient way to track an external signal for the benefit of the group as a whole. Through an algebraic approach, the tracking capabilities are distributed amongst the agents producing advantages at group level for the tracking of an external signal. This also translates into fast reaction to threats.
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Roux, Etienne. "A portfolio analysis of Sanlam limited." Thesis, Stellenbosch : University of Stellenbosch, 2007. http://hdl.handle.net/10019.1/4909.
Full textAbstract:
Thesis (MBA (Business Management))--University of Stellenbosch, 2007.ENGLISH ABSTRACT: The structure of Sanlam Limited is continually changing in order to align with the strategy. The aim of this research report is to determine the effectiveness of the current structure and whether it is aligned with the strategy. The current corporate strategy is to become the leader in wealth creation. This will be done through being a leader in all areas of the financial services industry and not only a provider of life insurance. The strategy is currently supported through a structure consisting of four channels, namely a life insurance cluster, investment cluster, short-term insurance cluster, and independent financial services cluster. An analysis of the life insurance cluster shows that Sanlam is currently struggling in the employee benefits sector of the industry but is a definite force in the individual life sector. In the short-term insurance industry Sanlam is represented through a shareholding in Santam. Analysis shows that Santam is currently the dominant player in this industry and should continue to be so in the future. The investment cluster consists of a number of entities with the biggest being Sanlam Investment Management. They currently have a big share of asset under management in the industry and performances are also improving after corrective measures were taken in 2004. It is difficult to compare the independent financial services cluster with other companies as they are present in so many areas of the financial services industry. Determination of the industry attractiveness has shown that all three focus areas of the clusters are fairly attractive, with the short-term insurance market being the most attractive. Competitive strength analysis indicates that the main players in each of the clusters do have competitive strength in their industry, with Santam once again being the most competitive. The results mentioned in the previous paragraphs definitely indicate that Sanlam is focussing on the correct areas and has the strengths to compete in these areas. The only concern is that growth is slowing down in the main contributor to profits, that is Sanlam Life, and they need to find areas of growth or diversification to address this risk.
AFRIKAANSE OPSOMMING: Die struktuur van Sanlam Beperk is gedurig aan die verander om met die strategie belyn te wees. Die doel van die navorsingsprojek is om te bepaal hoe effektief die strukture is en of dit wel belyn is met die strategie. Die huidige korporatiewe strategie is om die leier te wees in rykdom skepping. Dit kan alleenlik gedoen word deur die leier te wees in alle areas van die finansiele dienste sektor en nie alleenlik 'n verskaffer van lewensversekering nie. Hierdie strategie word tans ondersteun deur 'n struktuur bestaande uit vier kanale, naamlik die lewensversekeringskanaal, beleggingskanaal, korttermynversekeringskanaal, en die onafhanklike finansiele dienste-kanaal. 'n Ontleding van die lewensversekeringskanaal loon dat Sanlam tans sukkel in die werknemersvoordele area van die besigheid maar 'n definitiewe sterk verteenwoordigheid het in die individuele lewens area van die besigheid. In die korttermynversekeringskanaal word Sanlam verteenwoordig deur Santam in wie Sanlam 'n aandeelhouer is. Die analise van die industrie toon dat Santam die dominante leier in die area is en so behoort te bly in die afsienbare toekoms. Die beleggingskanaal bestaan uit 'n hele aantal besighede waarvan Sanlam Beleggingsbestuurders die grootste is. Hulle het tans 'n groot persentasie van die bates onder bestuur in die mark en vertoon ook aansienlik beter na korrektiewe stappe geneem is in 2004. Dit is moeilik om die onafhanklike finansiele dienste-kanaal met mededingers te vergelyk aangesien hulle 'n teenwoordigheid het in baie areas van die finansiele dienste sektor. Bepaling van die industrie aantreklikheidsfaktor het getoon dat al die areas waarop die kanale fokus redelik aantreklik is, met die korttermynversekering die mees aanloklikste. Die analise van die kompeterende sterkte het ook aangetoon dat die grootste eenhede in elke kanaal definitief kompeterend is, met Santam weereens die mees kompeterende. Die resultate uiteengesit in die vorige paragrawe toon aan dat Sanlam op die regte areas fokus en ook 'n sterk teenwoordigheid in die areas het. Die enigste rede tot kommer is die feit dat Sanlam Lewens, wat die grootste bydra lewer tot die groep winste, nie groei toon nie. Daar sal dus planne gemaak moet word om die besigheid te groei.
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Tarnoff, David. "Episode 3.12 – Run Length Limited Coding." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/computer-organization-design-oer/28.
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Bhargava, Nikhil(Nikhil Gaurev). "Multi-agent coordination under limited communication." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128409.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2020Cataloged from PDF of thesis.
Includes bibliographical references (pages 239-244).
In this thesis, we present a theory for constructing real-time executives that can reason about communication between agents. In multi-agent coordination problems, different agents have different beliefs about the state of the world that can eventually be reconciled if the agents are able to share sufficient information with one another. When communication is limited, this task becomes more difficult. To achieve robustness, coordination decisions need to be made, executed, and adapted in real-time by a real-time executive. Most existing real-time executives rely on perfect knowledge of the state of the world, making it difficult to use them in scenarios where agents either cannot or prefer not to communicate and share information. This thesis offers three contributions that together provide the basis for constructing a real-time executive capable of handling multi-agent coordination under limited communication.
First, we introduce delay controllability as a way to augment the input plan representation to including a communication model. Delay controllability lets us reason about multi-agent activities under limited communication in the form of communication delays and provides a guarantee that problem evaluation is tractable. Second, we provide a way to indicate by when each agent must communicate the results of their actions. Many agents have flexibility in choosing exactly when to communicate. We provide an algorithm for choosing a low-cost set of moments to communicate and present a strategy for adjusting those strategies when communication networks are unreliable causing disruptions in the original communication plan. Third, we offer a way to model noisy communication. Noisy communication offers approximate temporal information that is useful during execution but is generally difficult to incorporate.
We introduce variable-delay controllability as a way to model this kind of communication and provide the first sound and complete algorithm for incorporating noisy information that runs in polynomial time.
by Nikhil Bhargava.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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Cheng, Wu. "Optimal Denoising for Photon-limited Imaging." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1446401290.
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Jorgensen, Mark R. "Teaching the limited English proficiency student." Online version, 1999. http://www.uwstout.edu/lib/thesis/1999/1999jorgensenm.pdf.
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Baxley, Robert John. "OFDM communications over peak-limited channels." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/29631.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Zhou, G. Tong; Committee Member: Johnson, Ellis; Committee Member: Kenney, J. Stevenson; Committee Member: Li, Ye; Committee Member: Ma, Xiaoli. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Dhamdhere, Ashay. "Resource allocation in interference limited systems /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3129956.
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Akoum, Salam Walid. "Limited feedback MIMO for interference limited networks." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-12-6651.
Full textAbstract:
Managing interference is the main technical challenge in wireless networks. Multiple input multiple output (MIMO) methods are key components to overcome the interference bottleneck and deliver higher data rates. The most efficient MIMO techniques require channel state information (CSI). In practice, this information is inaccurate due to errors in CSI acquisition, as well as mobility and delay. CSI inaccuracy reduces the performance gains provided by MIMO. When compounded with uncoordinated intercell interference, the degradation in MIMO performance is accentuated. This dissertation investigates the impact of CSI inaccuracy on the performance of increasingly complex interference limited networks, starting with a single interferer scenario, continuing to a heterogeneous network with a femtocell overlay, and finishing with a clustered multicell coordination model for randomly deployed transmitting nodes.
First, this dissertation analyzes limited feedback beamforming and precoded spatial multiplexing over temporally correlated channels. Assuming uncoordinated interference from one dominant interferer, using Markov chain convergence theory, the gain in the average successful throughput at the mobile user is shown to decrease exponentially with the feedback delay. The decay rate is amplified when the user is interference limited. Interference cancellation methods at the receiver are shown to mitigate the effect of interference. This work motivates the need for practical MIMO designs to overcome the adverse effects of interference.
Second, limited feedback beamforming is analyzed on the downlink of a more realistic heterogeneous cellular network. Future generation cellular networks are expected to be heterogeneous, consisting of a mixture of macro base stations and low power nodes, to support the increasing user traffic capacity and reliability demand. Interference in heterogeneous environments cannot be coordinated using traditional interference mitigation techniques due to the on demand and random deployment of low power nodes such as femtocells. Using tools from stochastic geometry, the outage and average achievable rate of limited feedback MIMO is computed with same-tier and cross-tier interference, and feedback delay. A hybrid fixed and random network deployment model is used to analyze the performance in a fixed cell of interest. The maximum density of transmitting femtocells is derived as a function of the feedback rate and delay. The detrimental effect of same-tier interference is quantified, as the mobile user moves from the cell-center to the cell-edge.
The third part of this dissertation considers limited coordination between randomly deployed transmitters. Building on the established degrading effect of uncoordinated interference on practical MIMO methods, and the analytical tractability of random deployment models, interference coordination is analyzed. Using multiple antennas at the transmitter for interference nulling in ad hoc networks is first shown to achieve MIMO gains using single antenna receivers. Clustered coordination is then investigated for cellular systems with randomly deployed base stations. As full coordination in the network is not feasible, a random clustering model is proposed where base stations located in the same cluster coordinate. The average achievable rate can be optimized as a function of the number of antennas to maximize the coordination gains. For multicell limited feedback, adaptive partitioning of feedback bits as a function of the signal and interference strength is proposed to minimize the loss in rate due to finite rate feedback.text
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Mohapatra, Parthajit. "Fundamentals Limits Of Communication In Interference Limited Environments." Thesis, 2015. https://etd.iisc.ac.in/handle/2005/2652.
Full textAbstract:
In multiuser wireless communications, interference not only limits the performance of the system, but also allows users to eavesdrop on other users’ messages. Hence, interference management in multiuser wireless communication has received significant attention in the last decade, both in the academia and industry. The interference channel (IC) is one of the simplest information theoretic models to analyze the effect of interference on the throughput and secrecy of individual messages in a multiuser setup. In this thesis, the IC is studied under different settings with and without the secrecy constraint. The main contributions of the thesis are as follows:
• The generalized degrees of freedom (GDOF) has emerged as a useful approximate measure of the potential throughput of a multiuser wireless system. Also, multiple antennas at the transmitter and receiver can provide additional dimension for signaling, which can in turn improve the GDOF performance of the IC. In the initial part of the thesis, a K-user MIMO Gaussian IC (GIC) is studied from an achievable GDOF perspective. An inner bound on GDOF is derived using a combination of techniques such as treating interference as noise, zero-forcing receiving, interference alignment (IA), and extending the Han-Kobayashi (HK) scheme to K users. Also, outer bounds on the sum rate of the K-user MIMO GIC are derived, under different assumptions of cooperation and providing side information to the receivers. The derived outer bounds are simplified to obtain outer bounds on the GDOF. The relative performance of these bounds yields insight into the performance limits of the multiuser MIMO GIC and the relative merits of different schemes for interference management.
• Then, the problem of designing the precoding and receive filtering matrices for IA is explored for K-user MIMO (M × N) GIC. Two algorithms for designing the precoding and receive filtering matrices for IA in the block fading or constant MIMO IC with a finite number of symbol extensions are proposed. The first algorithm for IA is based on aligning a subset of the interfering signal streams at each receiver. As the first algorithm requires global channel knowledge at each node, a distributed algorithm is proposed which requires only limited channel knowledge at each node. A new performance metric is proposed, that captures the possible loss in signal dimension while designing the precoders. The performance of the algorithms are evaluated by comparing them with existing algorithms for IA precoder design.
• In the later part of the thesis, a 2-user IC with limited-rate transmitter cooperation is studied, to investigate the role of cooperation in managing interference and ensuring secrecy. First, the problem is studied in the deterministic setting, and achievable schemes are proposed, which use a combination of interference cancelation, relaying of the other user’s data bits, time sharing, and transmission of random bits, depending on the rate of the cooperative link and the relative strengths of the signal and the interference. Outer bounds on the secrecy rate are derived, under different assumptions of providing side information to receivers and partitioning the encoded message/output depending on the relative strength of the signal and the interference. The achievable schemes and outer bounds are extended to the Gaussian case. For example, while obtaining outer bounds, for the Gaussian case, it is not possible to partition the encoded message or output as performed in the deterministic case, and the novelty lies in finding the analogous quantities for the Gaussian case. The proposed achievable scheme for the Gaussian case uses a combination of cooperative and stochastic encoding along with dummy message transmission. For both the models, one of the key techniques used in the achievable scheme is interference cancelation, which has two benefits: it cancels interference and ensures secrecy simultaneously. The results show that limited-rate transmitter cooperation can greatly facilitate secure communications over 2-user ICs.