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Coding Theorem and Memory Conditions for Abstract Channels with Time StructureMittelbach, Martin 04 December 2014 (has links)
In the first part of this thesis, we generalize a coding theorem and a converse of Kadota and Wyner (1972) to abstract channels with time structure. As a main contribution we prove the coding theorem for a significantly weaker condition on the channel output memory, called total ergodicity for block-i.i.d. inputs. We achieve this result mainly by introducing an alternative characterization of information rate capacity. We show that the ψ-mixing condition (asymptotic output-memorylessness), used by Kadota and Wyner, is quite restrictive, in particular for the important class of Gaussian channels. In fact, we prove that for Gaussian channels the ψ-mixing condition is equivalent to finite output memory. Moreover, we derive a weak converse for all
stationary channels with time structure. Intersymbol interference as well as input constraints are taken into account in a flexible way. Due to the direct use of outer measures and a derivation of an adequate version of Feinstein’s lemma we are able to avoid the standard extension of the channel input σ-algebra and obtain a more transparent derivation. We aim at a presentation from an operational perspective and consider an abstract framework, which enables us to treat discrete- and continuous-time channels in a unified way.
In the second part, we systematically analyze infinite output memory conditions for abstract channels with time structure. We exploit the connections to the rich field of strongly mixing random processes to derive a hierarchy for the nonequivalent infinite channel output memory conditions in terms of a sequence of implications. The ergodic-theoretic memory condition used in the proof of the coding theorem and the ψ-mixing condition employed by Kadota and Wyner (1972) are shown to be part of this taxonomy. In addition, we specify conditions for the channel under which memory properties of a random process are invariant when the process is passed through the channel.
In the last part, we investigate cascade and integration channels with regard to mixing conditions as well as properties required in the context of the coding theorem. The results are useful to study many physically relevant channel models and allow a component-based analysis of the overall channel. We consider a number of examples including composed models and deterministic as well as random filter channels. Finally, an application of strong mixing conditions from statistical signal processing involving the Fourier transform of stationary random sequences is discussed and a list of further applications is given. / Im ersten Teil der Arbeit wird ein Kodierungstheorem und ein dazugehöriges Umkehrtheorem von Kadota und Wyner (1972) für abstrakte Kanäle mit Zeitstruktur verallgemeinert. Als wesentlichster Beitrag wird das Kodierungstheorem für eine signifikant schwächere Bedingung an das Kanalausgangsgedächtnis bewiesen, die sogenannte totale Ergodizität für block-i.i.d. Eingaben. Dieses Ergebnis wird hauptsächlich durch eine alternative Charakterisierung der Informationsratenkapazität erreicht. Es wird gezeigt, dass die von Kadota und Wyner verwendete ψ-Mischungsbedingung (asymptotische Gedächtnislosigkeit am Kanalausgang) recht einschränkend ist, insbesondere für die wichtige Klasse der Gaußkanäle. In der Tat, für Gaußkanäle wird bewiesen, dass die ψ-Mischungsbedingung äquivalent zu endlichem Gedächtnis am Kanalausgang ist. Darüber hinaus wird eine schwache Umkehrung für alle stationären Kanäle mit Zeitstruktur bewiesen. Sowohl Intersymbolinterferenz als auch Eingabebeschränkungen werden in allgemeiner und flexibler Form berücksichtigt. Aufgrund der direkten Verwendung von äußeren Maßen und der Herleitung einer angepassten Version von Feinsteins Lemma ist es möglich, auf die Standarderweiterung der σ-Algebra am Kanaleingang zu verzichten, wodurch die Darstellungen transparenter und einfacher werden. Angestrebt wird eine operationelle Perspektive. Die Verwendung eines abstrakten Modells erlaubt dabei die einheitliche Betrachtung von zeitdiskreten und zeitstetigen Kanälen.
Für abstrakte Kanäle mit Zeitstruktur werden im zweiten Teil der Arbeit Bedingungen für ein unendliches Gedächtnis am Kanalausgang systematisch analysiert. Unter Ausnutzung der Zusammenhänge zu dem umfassenden Gebiet der stark mischenden zufälligen Prozesse wird eine Hierarchie in Form einer Folge von Implikationen zwischen den verschiedenen Gedächtnisvarianten hergeleitet. Die im Beweis des Kodierungstheorems verwendete ergodentheoretische Gedächtniseigenschaft und die ψ-Mischungsbedingung von Kadota und Wyner (1972) sind dabei Bestandteil der hergeleiteten Systematik. Weiterhin werden Bedingungen für den Kanal spezifiziert, unter denen Eigenschaften von zufälligen Prozessen am Kanaleingang bei einer Transformation durch den Kanal erhalten bleiben.
Im letzten Teil der Arbeit werden sowohl Integrationskanäle als auch Hintereinanderschaltungen von Kanälen in Bezug auf Mischungsbedingungen sowie weitere für das Kodierungstheorem relevante Kanaleigenschaften analysiert. Die erzielten Ergebnisse sind nützlich bei der Untersuchung vieler physikalisch relevanter Kanalmodelle und erlauben eine komponentenbasierte Betrachtung zusammengesetzter Kanäle. Es wird eine Reihe von Beispielen untersucht, einschließlich deterministischer Kanäle, zufälliger Filter und daraus zusammengesetzter Modelle. Abschließend werden Anwendungen aus weiteren Gebieten, beispielsweise der statistischen Signalverarbeitung, diskutiert. Insbesondere die Fourier-Transformation stationärer zufälliger Prozesse wird im Zusammenhang mit starken Mischungsbedingungen betrachtet.
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Three Essays on Financial Development in Emerging MarketsDiekmann, Katharina 13 May 2013 (has links)
This dissertation collects three essays which deal with financial development in emerging markets. Owing to the appliance of different econometric methods on several data sets, insights in the behavior of and the impacts from financial markets are generated. Usually, the financial markets in emerging countries are characterized by the presence of credit constraints.
In the first chapter it is shown that the financial development in 19th century Germany generally affected the economy in a positive way. Additionally, when different economic sectors are under investigation, it is revealed that the reaction due to financial development is not homogeneously across the sectors. A structural vector autoregression (VAR) framework is applied to a new annual data set from 1870 to 1912 that was initially compiled by Walther Hoffmann (1965). With respect to the literature, the most important difference of this analysis is the focus on different sectors in the economy and the interpretation of the results in the context of a two-sector growth model. It is revealed that all sectors were affected significantly by shocks from the banking system. Interestingly, this link is the strongest in sectors with small or non-tradable-goods-producing firms, such as construction, services, transportation and agriculture. In this regard, the growth patterns in 19th century Germany are reminiscent to those in today's emerging markets.
The second chapter deals with the integration of the stock markets of mainland China with those of the United States and Hong Kong. Market integration and the resulting welfare gains as risk sharing, increasing investment and growth benefits has become a central topic in international finance research. This chapter investigates stock market integration after stock market liberalization which is assessed by spillover effects from Hong Kong and the United States to Chinese stock market indices. Dividing the sample in pre- and post-liberalization phases, causality in variance procedure is applied using four mainland China stock market indices, two indices of the stock exchange in Hong Kong and the Dow Jones Industrials index in the main part. Evidence of global and regional integration is found, but no evidence for increasing integration after the partial opening of the Chinese stock markets, neither with Hong Kong nor with the United States.
Based on the idea presented in the first chapter, the third chapter examines one of today's emerging markets. As China is experiencing remarkable economic growth in the recent decades, it is analyzed if and to what extent the ongoing deregulations in the financial system contribute to this development. Structural VARs for gross domestic product as well as for sectoral output data in conjunction with two different bank lending variables are applied. It is indicated that China is positive affected by financial development and that all sectors benefit from domestic bank lending enlargements but to different degrees. Especially in the sectors where mainly state-owned enterprises are represented - such as construction, trade and transportation - shocks in bank lending have a strong positive influence while sectors where private enterprises are prevalent, seem to be more credit constrained.
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