The past two decades have witnessed a dramatic growth in Middle Eastern satellite television. The corresponding diversification of content and restructuring of media power in the region raise many important questions for research. This dissertation is a case study of Huda TV, an English-language Islamic satellite channel broadcasting from Cairo, Egypt. The author collected participant observation data as an employee of the channel in 2005-2006. The primary research question asks how Huda TV asserts an Islamic presence in the satellite television arena. Many areas of media research, including the broad historical debates on culture and power, contemporary conceptions of hybridity, and the analysis of media institutions in the Middle East, share an overarching secular bias. Consequently, this dissertation plots out relevant bodies of theoretical and empirical research that both inform and constrain the kind of questions that can be asked about Huda TV as a Muslim institution. With a conscious effort to overcome the reductionist secularism of media studies, this work offers empirical data on the manner in which orthodox Sunni Islam operates within the global mediascape--the increasingly integrated, geographically expansive, and globally accessible media environment of which satellite television is one important component. This dissertation first examines the concrete manner in which Huda TV attempts to define Islamic satellite television as a distinct set of content and practices. Next, it turns to the channel's engagement with dominant discourses and bodies of knowledge that may compete with Islam for ultimate authority. Finally, it examines the impact of cultural and political-economic factors on the channel's work. This dissertation offers original insights into the study of contemporary Islam and contributes to significant, enduring questions of media research. / text

Ο υπολογισμός της χωρητικότητας Shannon ενός τηλεπικοινωνιακού καναλιού είναι ένα από τα κλασικά προβλήματα της θεωρίας πληροφορίας. Η τιμή της προσδιορίζει το μέγιστο δυνατό ρυθμό αξιόπιστης μετάδοσης μέσα από το κανάλι και αποτελεί ρυθμιστική παράμετρο κατά το σχεδιασμό κάθε τηλεπικοινωνιακού συστήματος. Στις πιο ενδιαφέρουσες περιπτώσεις ο υπολογισμός καταλήγει σε ένα πρόβλημα βελτιστοποίησης για το οποίο δε μπορεί να δοθεί αναλυτική λύση, οπότε καταφεύγουμε στη χρήση προσεγγιστικών μεθόδων ή στη διατύπωση φραγμάτων. Στα πλαίσια της εργασίας μελετάται η χωρητικότητα Shannon τηλεπικοινωνιακών καναλιών ενός ή πολλαπλών χρηστών. Η μελέτη ξεκινά από την απλές περιπτώσεις του διακριτού καναλιού χωρίς μνήμη (DMC) και του καναλιού AWGN και επεκτείνεται στις πιο ενδιαφέρουσες περιπτώσεις των σύμφωνων ή μη (coherence/non-coherence) καναλιών διάλειψης, σε κανάλια με μνήμη, κανάλια πολλαπλών κεραιών και κανάλια πολλαπλών χρηστών. Σε κάθε περίπτωση καταγράφονται τα σημαντικότερα ερευνητικά αποτελέσματα σχετικά με το πρόβλημα προσδιορισμού της χωρητικότητας, τη συμπεριφορά της σε σχέση με τους παράγοντες του τηλεπικοινωνιακού μοντέλου, του αλγοριθμικού υπολογισμού της και τα χαρακτηριστικά που πρέπει να έχει η είσοδος ώστε να επιτυγχάνεται η τιμή της. / Computing the Shannon Capacity of a communication channel is one of the classic problems of information theory. Its value determine the maximum possible rate of reliable transmission through the channel and constitutes a design parameter during the designing of the communication system. In most interesting cases the problem ending to an optimization problem which can’t be solved analytically, so we refuge to approximating methods and we can only state bounds for the region in which capacity belongs. In this thesis we study the Shannon Capacity of single user and multiple user communications systems. The study begins with the simple cases of Discrete Memoryless Channel (DMC) and AWGN channel and goes further to more interesting cases like coherence/non-coherence fading channels, channels with memory, multiple antenna channels and channels with multiple users. In each case, we present the most important scientific results considering the problem of capacity, its behavior in relation to the parameters of the communication model, its algorithmic computation and the characteristics of the optimal input.

Los canales múltiple-entrada-múltiple-salida (MIMO) han sido ampliamente propuestos para superar los desvanecimientos aleatorios de canal en comunicaciones inalámbricas no selectivas en frecuencia. Basados en equipar tanto transmisores como receptores con múltiple antenas, sus ventajas son dobles. Por un lado, permiten al transmisor: i) concentrar la energía transmitida en una dirección-propia determinada, o ii) codificar entre antenas con el fin de superar desvanecimientos no conocidos de canal. Por otro lado, facilitan al receptor el muestreo de la señal en el dominio espacial. Esta operación, seguida por la combinación coherente de muestras, aumenta la relación señal a ruido de entrada al receptor. De esta forma, el procesado multi-antena es capaz de incrementar la capacidad (y la fiabilidad) de la transmisión en escenarios con alta dispersión.Desafortunadamente, no siempre es posible emplazar múltiples antenas en los dispositivos inalámbricos, debido a limitaciones de espacio y/o coste. Para estos casos, la manera más apropiada de explotar el procesado multi-antena es mediante retransmisión, consistente en disponer un conjunto de repetidores inalámbricos que asistan la comunicación entre un grupo de transmisores y un grupo de receptores, todos con una única antena. Con la ayuda de los repetidores, por tanto, los canales MIMO se pueden imitar de manera distribuida. Sin embargo, la capacidad exacta de las comunicaciones con repetidores (así como la manera en que este esquema funciona con respeto al MIMO equivalente) es todavía un problema no resuelto. A dicho problema dedicamos esta tesis.En particular, la presente disertación tiene como objetivo estudiar la capacidad de canales Gaussianos asistidos por múltiples repetidores paralelos. Dos repetidores se dicen paralelos si no existe conexión directa entre ellos, si bien ambos tienen conexión directa con la fuente y el destino de la comunicación. Nos centramos en el análisis de tres canales ampliamente conocidos: el canal punto-a-punto, el canal de múltiple-acceso y el canal de broadcast, y estudiamos su mejora de funcionamiento con repetidores. A lo largo de la tesis, se tomarán las siguientes hipótesis: i) operación full-duplex en los repetidores, ii) conocimiento de canal tanto en transmisión como en recepción, y iii) desvanecimiento sin memoria, e invariante en el tiempo.En primer lugar, analizamos el canal con múltiples repetidores paralelos, en el cual una única fuente se comunica con un único destino en presencia de N repetidores paralelos. Derivamos límites inferiores de la capacidad del canal por medio de las tasas de transmisión conseguibles con distintos protocolos: decodificar-y-enviar, decodificar-parcialmente-y-enviar, comprimir-y-enviar, y repetición lineal. Asimismo, con un fin comparativo, proveemos un límite superior, obtenido a través del Teorema de max-flow-min-cut. Finalmente, para el número de repetidores tendiendo a infinito, presentamos las leyes de crecimiento de todas las tasas de transmisión, así como la del límite superior.A continuación, la tesis se centra en el canal de múltiple-acceso (MAC) con múltiples repetidores paralelos. El canal consiste en múltiples usuarios comunicándose simultáneamente con un único destino en presencia de N repetidores paralelos. Derivamos una cota superior de la región de capacidad de dicho canal utilizando, de nuevo, el Teorema de max-flow-min-cut, y encontramos regiones de tasas de transmisión conseguibles mediante: decodificar-y-enviar, comprimir-y-enviar, y repetición lineal. Asimismo, se analiza el valor asintótico de dichas tasas de transmisión conseguibles, asumiendo el número de usuarios creciendo sin límite. Dicho estudio nos permite intuir el impacto de la diversidad multiusuario en redes de acceso con repetidores.Finalmente, la disertación considera el canal de broadcast (BC) con múltiples repetidores paralelos. En él, una única fuente se comunica con múltiples destinos en presencia de N repetidores paralelos. Para dicho canal, derivamos tasas de transmisión conseguibles dado: i) codificación de canal tipo dirty paper en la fuente, ii) decodificar-y-enviar, comprimir-y-enviar, y repetición lineal, respectivamente, en los repetidores. Además, para repetición lineal, demostramos que la dualidad MAC-BC se cumple. Es decir, la región de tasas de transmisión conseguibles en el BC es igual a aquélla del MAC con una limitación de potencia suma. Utilizando este resultado, se derivan algoritmos de asignación óptima de recursos basados en teoría de optimización convexa. / Multiple-input-multiple-output (MIMO) channels are extensively proposed as a means to overcome the random channel impairments of frequency-flat wireless communications. Based upon placing multiple antennas at both the transmitter and receiver sides of the communication, their virtues are twofold. On the one hand, they allow the transmitter: i) to concentrate the transmitted power onto a desired eigen-direction, or ii) tocode across antennas to overcome unknown channel fading. On the other hand, they permit the receiver to sample the signal on the space domain. This operation, followed by the coherent combination of samples, increases the signal-to-noise ratio at the input of the detector. In fine, MIMO processing is able to provide large capacity (and reliability) gains within rich-scattered scenarios.Nevertheless, equipping wireless handsets with multiple antennas is not always possible or worthwhile. Mainly, due to size and cost constraints, respectively. For these cases, the most appropriate manner to exploit multi-antenna processing is by means of relaying. This consists of a set of wireless relay nodes assisting the communication between a set of single-antenna sources and a set of single-antenna destinations. With the aid of relays, indeed, MIMO channels can be mimicked in a distributed way. However, the exact channel capacity of single-antenna communications with relays (and how this scheme performs with respect to the equivalent MIMO channel) is a long-standing open problem. To it we have devoted this thesis.In particular, the present dissertation aims at studying the capacity of Gaussian channels when assisted by multiple, parallel, relays. Two relays are said to be parallel if there is no direct link between them, while both have direct link from the source and towards the destination. We focus on three well-known channels: the point-to-point channel, the multi-access channel and the broadcast channel, and study their performance improvement with relays. All over the dissertation, the following assumptions are taken: i) full-duplex operation at the relays, ii) transmit and receive channel state information available at all network nodes, and iii) time-invariant, memory-less fading.Firstly, we analyze the multiple-parallel relay channel, where a single source communicates to a single destination in the presence of N parallel relays. The capacity of the channel is lower bounded by means of the achievable rates with different relaying protocols, i.e. decode-and-forward, partial decode-and-forward, compress-and-forward and linear relaying. Likewise, a capacity upper bound is provided for comparison, derived using the max-flow-min-cut Theorem. Finally, for number of relays growing to infinity, the scaling laws of all achievable rates are presented, as well as the one of the upper bound.Next, the dissertation focusses on the multi-access channel (MAC) with multiple-parallel relays. The channel consists of multiple users simultaneously communicating to a single destination in the presence of N parallel relay nodes. We bound the capacity region of the channel using, again, the max-flow-min-cut Theorem and find achievable rate regions by means of decode-and-forward, linear relaying and compress-and-forward. In addition, we analyze the asymptotic performance of the obtained achievable sum-rates, given the number of users growing without bound. Such a study allows us to grasp the impact of multi-user diversity on access networks with relays.Finally, the dissertation considers the broadcast channel (BC) with multiple parallel relays. This consists of a single source communicating to multiple receivers in the presence of N parallel relays. For the channel, we derive achievable rate regions considering: i) dirty paper encoding at the source, and ii) decode-and-forward, linear relaying and compress-and-forward, respectively, at the relays. Moreover, for linear relaying, we prove that MAC-BC duality holds. That is, the achievable rate region of the BC is equal to that of the MAC with a sum-power constraint. Using this result, the computation of the channel's weighted sum-rate with linear relaying is notably simplified. Likewise, convex resource allocation algorithms can be derived.

This thesis reports the results of a study designed to investigate the influence of exposure to televised medical dramas on perceptions of medical miracles. Four hundred and eighty-one college students participated in a survey in which they responded to different questions about their medical drama viewership and their different beliefs with regard to medical miracles. Results found that heavy medical drama viewers perceived belief in medical miracles to be less normal than non-viewers. Similarly, heavy viewers perceived medical miracles to occur less often than non-viewers. Interestingly, heavy viewers perceived medical dramas to be less credible than non-viewers. In addition, this study found that personal experience with medical miracles affected responses across all three measured viewership levels. The study concludes that, when compared to no exposure to medical dramas, heavy exposure has the potential for creating a more realistic view of medical miracles. Future research should continue to study genre-specific cultivation effects with regard to health perceptions.

The demand for wireless data services has been dramatically growing over the last decade. This growth has been accompanied by a significant increase in the number of users sharing the same wireless medium, and as a result, interference management has become a hot topic of research in recent years. In this dissertation, we investigate feedback and transmitter cooperation as two closely related tools to manage the interference and achieve high data rates in several wireless networks, focusing on additive white Gaussian noise (AWGN) interference, X, and broadcast channels. We start by a one-to-many network, namely, the three-user multiple-input multiple-output (MIMO) Gaussian broadcast channel, where we assume that the transmitter obtains the channel state information (CSI) through feedback links after a finite delay. We also assume that the feedback delay is greater than the channel coherence time, and thus, the CSI expires prior to being exploited by the transmitter for its current transmission. Nevertheless, we show that this delayed CSI at the transmitter (delayed CSIT) can help the transmitter to achieve significantly higher data rates compared to having no CSI. We indeed show that delayed CSIT increases the channel degrees of freedom (DoF), which is translated to an unbounded increase in capacity with increasing signal-to-noise-ratio (SNR). For the symmetric case, i.e. with the same number of antennas at each receiver, we propose different transmission schemes whose achievable DoFs meet the upper bound for a wide range of transmit-receive antenna ratios. Also, for the general non-symmetric case, we propose transmission schemes that characterize the DoF region for certain classes of antenna configurations. Subsequently, we investigate channels with distributed transmitters, namely, Gaussian single-input single-output (SISO) K-user interference channel and 2×K X channel under the delayed CSIT assumption. In these channels, in major contrast to the broadcast channel, each transmitter has access only to its own messages. We propose novel multiphase transmission schemes wherein the transmitters collaboratively align the past interference at appropriate receivers using the knowledge of past CSI. Our achievable DoFs are greater than one (which is the channel DoF without CSIT), and strictly increasing in K. Our results are yet the best available reported DoFs for these channels with delayed CSIT. Furthermore, we consider the K-user r-cyclic interference channel, where each transmitter causes interference on only r receivers in a cyclic manner. By developing a new upper bound, we show that this channel has K/r DoF with no CSIT. Moreover, by generalizing our multiphase transmission ideas, we show that, for r=3, this channel can achieve strictly greater than K/3 DoF with delayed CSIT. Next, we add the capability of simultaneous transmission and reception, i.e. full-duplex operation, to the transmitters, and investigate its impact on the DoF of the SISO Gaussian K-user interference and M×K X channel under the delayed CSIT assumption. By proposing new cooperation/alignment techniques, we show that the full-duplex transmitter cooperation can potentially yield DoF gains in both channels with delayed CSIT. This is in sharp contrast to the previous results on these channels indicating the inability of full-duplex transmitter cooperation to increase the channel DoF with either perfect instantaneous CSIT or no CSIT. With the recent technological advances in implementation of full-duplex communication, it is expected to play a crucial role in the future wireless systems. Finally, we consider the Gaussian K-user interference and K×K X channel with output feedback, wherein each transmitter causally accesses the output of its paired receiver. First, using the output feedback and under no CSIT assumption, we show that both channels can achieve DoF values greater than one, strictly increasing in K, and approaching the limiting value of 2 as K→∞. Then, we develop transmission schemes for the same channels with both output feedback and delayed CSIT, known as Shannon feedback. Our achievable DoFs with Shannon feedback are greater than those with the output feedback for almost all values of K.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 276-285). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 276-285). Also available on the Internet.

abstract: There are many wireless communication and networking applications that require high transmission rates and reliability with only limited resources in terms of bandwidth, power, hardware complexity etc.. Real-time video streaming, gaming and social networking are a few such examples. Over the years many problems have been addressed towards the goal of enabling such applications; however, significant challenges still remain, particularly, in the context of multi-user communications. With the motivation of addressing some of these challenges, the main focus of this dissertation is the design and analysis of capacity approaching coding schemes for several (wireless) multi-user communication scenarios. Specifically, three main themes are studied: superposition coding over broadcast channels, practical coding for binary-input binary-output broadcast channels, and signalling schemes for two-way relay channels. As the first contribution, we propose an analytical tool that allows for reliable comparison of different practical codes and decoding strategies over degraded broadcast channels, even for very low error rates for which simulations are impractical. The second contribution deals with binary-input binary-output degraded broadcast channels, for which an optimal encoding scheme that achieves the capacity boundary is found, and a practical coding scheme is given by concatenation of an outer low density parity check code and an inner (non-linear) mapper that induces desired distribution of "one" in a codeword. The third contribution considers two-way relay channels where the information exchange between two nodes takes place in two transmission phases using a coding scheme called physical-layer network coding. At the relay, a near optimal decoding strategy is derived using a list decoding algorithm, and an approximation is obtained by a joint decoding approach. For the latter scheme, an analytical approximation of the word error rate based on a union bounding technique is computed under the assumption that linear codes are employed at the two nodes exchanging data. Further, when the wireless channel is frequency selective, two decoding strategies at the relay are developed, namely, a near optimal decoding scheme implemented using list decoding, and a reduced complexity detection/decoding scheme utilizing a linear minimum mean squared error based detector followed by a network coded sequence decoder. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011

Uma tendência recente em sistemas de computação é distribuir a computação entre diversos processadores físicos. Isto conduz a dois tipos de sistemas: sistemas fortemente acoplados e sistemas fracamente acoplados. Este trabalho enfoca os sistemas de computação classificados como fracamente acoplados, ou sistemas distribuídos, como são popularmente conhecidos. Um sistema distribuído, segundo [BAB 86], pode ser definido como um conjunto de processadores autônomos que não compartilham memória, não tem acesso a clocks' globais e cuja comunicação é realizada somente por troca de mensagens. As exigências intrínsecas de sistemas distribuídos compreendem a confiabilidade e a disponibilidade. Estas exigências tem levado a um crescente interesse em técnicas de tolerância a falhas, cujo objetivo é manter a consistência do sistema distribuído, mesmo na ocorrência de falhas. Uma técnica de tolerância a falhas amplamente utilizada em sistemas distribuídos é a técnica de difusão confiável. A difusão confiável é uma técnica de redundância de software, onde um processador dissemina um valor para os demais processadores em um sistema distribuído, o qual esta sujeito a falhas [BAB 85]. Por ser uma técnica básica de comunicação, diversos procedimentos de tolerância a falhas baseiam-se em difusão confiável. Este trabalho descreve a implementação de um ambiente de apoio a sistemas distribuídos intitulado Ambiente para Experimentação e Avaliação de Protocolos de Difusão Confiável (ADC). Neste ambiente são utilizados os recursos da difusão confiável para a obtenção de uma concordância entre todos os membros do sistema livres de falha. Esta concordância, conhecida como consenso, é obtida através de algoritmos de consenso, os quais visam introduzir o grau de confiabilidade exigido pelos sistemas distribuídos. O ADC (Ambiente para Experimentação e Avaliação de Protocolos de Difusão Confiável) foi desenvolvido em estações de trabalho SUN (SunOS) utilizando o sistema operacional de rede heterogêneo HetNOS [BAA 93] desenvolvido na UFRGS. O ambiente foi implementado com base em um estudo realizado sobre protocolos de difusão confiável [BAR 94]. Através da implementação do ADC e possível simular a execução de protocolos de difusão confiável aplicando modelos propostos para os mesmos. Desta execução são extraídos resultados, sobre os quais pode-se realizar uma analise. Esta análise tem sua fundamentação principalmente nos parâmetros de desempenho, confiabilidade e complexidade. Tanto a implementação do ADC como a realização da analise do modelo proposto foram realizados tendo como suporte alguns dos protocolos de difusão confiável disponíveis na literatura. O principal objetivo deste ambiente consiste na experimentação, ou seja, na verificação da relação teórico-prática dos sistemas distribuídos perante a utilização de uma técnica de redundância de software, a difusão confiável. Através deste ambiente torna-se possível a determinação de parâmetros tais como o número de mensagens de difusão trocadas entre os processos, o número de mensagens de retransmissão enviadas, o número de mensagens emitidas durante todo o processamento do modelo, etc. Estes parâmetros resultam numa analise consistente de protocolos de difusão confiável. / A recent trend in computing systems is to distribute the computation between several physical processors. This leads to two different systems: closely coupled systems and loosely coupled systems. This work focuses on computing systems classified as loosely coupled or distributed systems, as they are commonly known. According to [BAB 86], a distributed system can be defined as a set of autonomous processors with no shared memory, no global clocks and whose comunication is performed only by message exchange. The inherent requirements of distributed systems include reliability and availability. These have caused an increasing interest in fault tolerance techniques, whose goal is to keep the distributed system consistent despite failures. A fault tolerance technique largely used in distributed systems is reliable broadcast. Reliable broadcast is a software redundancy technique, where a processor disseminates a value to other processors in a distributed system, in which failures can occur [BAB85]. Because it is a basic communication technique, several fault tolerance procedures are based on reliable broadcast. This work describes the implementation of a support environment for distributed systems called Reliable Broadcast Protocols Experimentation and Evaluation Environment (ADC). Reliable broadcast resources are used in this environment to obtain an agreement among all off-failure system components. This agreement, called consensus, has been obtained through consensus algorithms, which aim to introduce the reliability degree required in distributed systems. The ADC has been developed in Sun workstation (SunOS) using the heterogeneous operating system HetNOS [BAA 93] which was developed at UFRGS. The environment has been implemented based on a research about reliable broadcast protocols [BAR 94]. Through the ADC it is possible to simulate the execution of reliable broadcast protocols applying proposed models to them. From this execution results are extracted, and over them analysis can be done. This analysis has been based essentialy in parameters such as performance, reliability and complexity. Some classical reliable broadcast protocols were used as a support to ADC implementation and model analysis. The main goal of this environment consists in validating diffusion protocols in a practical distributed systems environment, facing reliable broadcast. Through this environment it can be possible the analysis of important parameters resolution such as the number of messages exchanged between process, the number of retransmission of messages sent, the number of messages sent during the whole model processing, others. These parameters result in a consistent analysis of reliable broadcast protocols.

Within the context of debates surrounding the consumption of global media by local audiences in Third World countries, this study explores the reasons behind satellite television subscription, and consumption of international news among a sample of young professional men and women in contemporary Zimbabwe. The study seeks to uncover how the research participants respond to news broadcast on SABC Africa's '60 minutes live in Africa', a programme which they can only access via satellite television in their country. Working within the frame of audience studies which insists on understanding media consumption and reception in context, this study examines how the respondents, situated within the specific Zimbabwe context, characterised as it is by serious social, economic and political challenges, respond to both regional news and news about their country on '60 minutes live in Africa'. Within the frame of qualitative research the study employs a two-stage sampling procedure and data collection strategy to uncover the factors that underpin international media consumption and reception by professional men and women situated in a country undergoing rapid change. The findings of the study point to the various social and individual factors that underlie media consumption choices as well as to the different socially patterned reasons why local audiences are either attracted to, or reject global media. The study found that SABC Africa's '60 minutes live in Africa' is more popular and better received than Western-broadcast programmes on channels such as BBC, CNN, and Sky News among Zimbabwean professionals. I also uncovered some evidence that cultural proximity and relevance are of supreme importance in determining which media audiences chose to consume and what level of engagement they bring to their reception of global media. These and other findings directly confront media models that privilege beliefs in cultural imperialism and the dominance of Western media and their effects on Third World audiences.