On Marton's inner bound for broadcast channels

Marton's inner bound is the best known achievable region for a general discrete memoryless broadcast channel. To compute Marton's inner bound one has to solve an optimization problem over a set of joint distributions on the input and auxiliary random variables. The optimizers turn out to be structured in many cases. Finding properties of optimizers not only results in efficient evaluation of the region, but it may also help one to prove factorization of Marton's inner bound (and thus its optimality). The first part of this paper formulates this factorization approach explicitly and states some conjectures and results along this line. The second part of this paper focuses primarily on the structure of the optimizers. This section is inspired by a new binary inequality that recently resulted in a very simple characterization of the sum-rate of Marton's inner bound for binary input broadcast channels. This prompted us to investigate whether this inequality can be extended to larger cardinality input alphabets. We show that several of the results for the binary input case do carry over for higher cardinality alphabets and we present a collection of results that help restrict the search space of probability distributions to evaluate the boundary of Marton's inner bound in the general case. We also prove a new inequality for the binary skew-symmetric broadcast channel that yields a very simple characterization of the entire Marton inner bound for this channel.Comment: Submitted to ISIT 201

Euclidean network information theory

Thesis (Ph. D.)--Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 121-123).Many network information theory problems face the similar difficulty of single letterization. We argue that this is due to the lack of a geometric structure on the space of probability distributions. In this thesis, we develop such a structure by assuming that the distributions of interest are all close to each other. Under this assumption, the Kullback-Leibler (K-L) divergence is reduced to the squared Euclidean metric in an Euclidean space. In addition, we construct the notion of coordinate and inner product, which will facilitate solving communication problems. We will present the application of this approach to the point-to-point channels, general broadcast channels (BC), multiple access channels (MAC) with common sources, interference channels, and multi-hop layered communication networks without or with feedback. It can be shown that with this approach, information theory problems, such as the single-letterization, can be reduced to some linear algebra problems. Solving these linear algebra problems, we will show that for the general broadcast channels, transmitting the common message to receivers can be formulated as the trade-off between linear systems. We also provide an example to visualize this trade-off in a geometric way. For the MAC with common sources, we observe a coherent combining gain due to the cooperation between transmitters, and this gain can be obtained quantitively by applying our technique. In addition, the developments of the broadcast channels and multiple access channels suggest a trade-off relation between generating common messages for multiple users and transmitting them as the common sources to exploit the coherent combining gain, when optimizing the throughputs of communication networks. To study the structure of this trade-off and understand its role in optimizing the network throughput, we construct a deterministic model by our local approach that captures the critical channel parameters and well models the network. With this deterministic model, for multi-hop layered networks, we analyze the optimal network throughputs, and illustrate what kinds of common messages should be generated to achieve the optimal throughputs. Our results provide the insight of how users in a network should cooperate with each other to transmit information efficiently.by Shao-Lun Huang.Ph.D

Function Computation over Networks:Efficient Information Processing for Cache and Sensor Applications

This thesis looks at efficient information processing for two network applications: content delivery with caching and collecting summary statistics in wireless sensor networks. Both applications are studied under the same paradigm: function computation over networks, where distributed source nodes cooperatively communicate some functions of individual observations to one or multiple destinations. One approach that always works is to convey all observations and then let the destinations compute the desired functions by themselves. However, if the available communication resources are limited, then revealing less unwanted information becomes critical. Centered on this goal, this thesis develops new coding schemes using information-theoretic tools. The first part of this thesis focuses on content delivery with caching. Caching is a technique that facilitates reallocation of communication resources in order to avoid network congestion during peak-traffic times. An information-theoretic model, termed sequential coding for computing, is proposed to analyze the potential gains offered by the caching technique. For the single-user case, the proposed framework succeeds in verifying the optimality of some simple caching strategies and in providing guidance towards optimal caching strategies. For the two-user case, five representative subproblems are considered, which draw connections with classic source coding problems including the Gray-Wyner system, successive refinement, and the Kaspi/Heegard-Berger problem. Afterwards, the problem of distributed computing with successive refinement is considered. It is shown that if full data recovery is required in the second stage of successive refinement, then any information acquired in the first stage will be useful later in the second stage. The second part of this thesis looks at the collection of summary statistics in wireless sensor networks. Summary statistics include arithmetic mean, median, standard deviation, etc, and they belong to the class of symmetric functions. This thesis develops arithmetic computation coding in order to efficiently perform in-network computation for weighted arithmetic sums and symmetric functions. The developed arithmetic computation coding increases the achievable computation rate from $\Theta((\log L)/L)$ to $\Theta(1/\log L)$, where $L$ is the number of sensors. Finally, this thesis demonstrates that interaction among sensors is beneficial for computation of type-threshold functions, e.g., the maximum and the indicator function, and that a non-vanishing computation rate is achievable

Making domestic violence. The discursive emergence of domestic violence in the Hungarian media, 2002-2013

This thesis explores the relevance of the news media as facilitators of social change with regard to domestic violence in Hungary between 2002 and 2013. Specifically, domestic violence against women, once entirely “invisible” and “unheard of” under state socialism, and only sporadically noted in the 1990s, by the 2000s had acquired significant public visibility in the country. It is this rise in the public visibility of the issue, and the ways in which domestic violence has been progressively introduced and narrated in the Hungarian media in the 21st century, that forms the focus of the present thesis. In contrast to previous feminist literature, which tends to present the media as an institution of social control, this thesis investigates the role of the news media in discursively constructing domestic violence and engaging the emotions and moral judgements of the public, and thereby contributing to laying the foundations for social interventions against violence. It therefore understands domestic violence as discourse, and the media as both social institution and symbolic space with the power to influence our perception of the social world (including that of domestic violence); and it focuses on the agency of media texts in emotionally, morally or politically engaging publics with public issues and the suffering of others. It uses Faircloughian Critical Discourse Analysis, applied to a historically comparative casestudy design consisting of three cases from the mainstream Hungarian broadcast news media, which were selected on the basis of their data richness and relevance. The thesis seeks to illuminate the complexities and contradictions involved in the emergence of domestic violence as a mediated discourse of public interest, and to address gaps both in the Anglo-Saxon literature on domestic violence in the media, and in the Central-Eastern Europe literature on domestic violence, which currently tends to overlook the role of the media

Using visual representations to improve instructional materials for distance education computing students

Understanding how to develop instructional materials for distance education students is a challenging problem, but it is exacerbated when a domain is complex to teach, such as computer science. Visual representations have a history of use in computing as a means to alleviate the difficulties of learning abstract concepts. However, it is not clear whether improvements observed are as a result of improvements in the visual representations used in instructional materials or due to individual differences in students. This research examines the two themes of individual differences and visual representation in order to investigate how they collectively impact on improving instructional materials for distance education students studying computer science. It investigates the impact of different representations on learning while additionally investigating the relationship between individual differences and student learning.The research in this thesis shows that visual representations are important in designing instructional materials. In particular, texts with visual representations have the power to cue students to perceive instructional materials as easier to process and more engaging.Investigation into the impact of concrete high-imagery versus abstract low-imagery visual representations illustrated that concrete visual representations incurred fewer cognitive overheads for computer science students and were able to ameliorate the challenges of learning computing.The research in this thesis into individual differences demonstrated that Imagers did benefit more from studying instructional materials containing text with visual components. However the research indicates that appropriate selection of individual difference tests is dependent upon the application, i.e., whether the results are to be used to assess generalised tendencies or episodes in learning and whether the tests examine underlying approaches to cognition or practices in education.An underlying question was whether students studying instructional materials containing low-imagery visual representations would cope as well as those studying high-imagery ones. Accomplished learners demonstrated that they could perform as well as with those receiving high-imagery visual representations. However, studying and recalling these materials did incur more cognitive processing.This thesis argues that improving instructional materials by including appropriate visual representations is a useful basis for improving learning for distance education computer science students

Constructing concepts of learner autonomy in language education in the Chinese context : a narrative-based inquiry into university students' conceptions of successful English language learning

The present study aims to explore Chinese learners' conceptions of learner autonomy from learners' perspective since researchers in language education argue that concepts of learner autonomy may bear cultural imprints and recent college English language education reform in China sets learner autonomy as a prime goal. The study first presents general background and an introduction to the research context. There follows a comprehensive literature review, tracking origins of the concept of learner autonomy in the fields of philosophy, general education, and language education, with distinctive 'Western' and 'Chinese' emphases. This is followed by a review of relevant research on learner autonomy in language education, which consists of research on learner autonomy as a concept, as a means for effective learning, relationships with culture, and methodological issues. To investigate Chinese learners' conceptions of learner autonomy, the study adopted a mixed research approach to collect data: with a qualitative method as the main research method to capture in-depth understandings of learners' conceptions, and a quantitative method as a supplementary one to support qualitative data findings and at the same time reveal further diversity. Moreover, to avoid any imposition of learner autonomy theory pre-occupied in the researcher's mind, the study does not ask directly about learner autonomy to learners but instead examines whether concepts of learner autonomy are embedded in students' accounts of successful English language learning. The study involved 27 interviews and a questionnaire survey of 450 college English language learners among three different Chinese universities. The main findings of the study are as follows: 1) Both 'Western' and 'Chinese' emphases and core elements of learner autonomy are found in Chinese learners' conceptions of successful English language learning; 2) Chinese learners' conceptions of learner autonomy are found to exist in two distinctive domains: learner autonomy for academic success (LAAS) and learner autonomy for communicative competence (LACC). 3) Learners' conceptions of learner autonomy can be influenced by different sources: political, economical, social, cultural, and individual. 4) Learners' conceptions of learner autonomy are dynamic, and subject to various factors such as progress of level of education and individual language learning experiences. Based on the data findings, a reconsideration of concepts of learner autonomy drawn out from students' conceptions of successful English language learning is discussed, which combines 'Western', 'Chinese' emphases and core elements of learner autonomy, associated behaviours, and sources of influences on them. This reconstruction of the concept of learner autonomy in the Chinese context contributes to a better understanding of learner autonomy theory. The research has important implications for policy makers, teachers, parents, and students in understanding learner autonomy from learners' perspectives and for research into concepts of learner autonomy in different contexts

Teaching/Learning Physics: Integrating Research into Practice

The GIREP-MPTL International conference on Teaching/Learning Physics: Integrating Research into Practice [GIREP-MPTL 2014] was held from 7 to 12 July 2014 at the University of Palermo, Italy. The conference has been organised by the Groupe International de Recherche sur l’Enseignement de la Physique [GIREP] and the Multimedia in Physics Teaching and Learning [MPTL] group and it has been sponsored by the International Commission on Physics Education [ICPE] – Commission 14 of the International Union for Pure and Applied Physics [IUPAP], the European Physical Society – Physics Education Division [EPS-PED], the Latin American Physics Education Network [LAPEN] and the Società Italiana di Fisica [SIF]. The theme of the conference, Teaching/Learning Physics: Integrating Research into Practice, underlines aspects of great relevance in contemporary science education. In fact, during the last few years, evidence based Physics Education Research provided results concerning the ways and strategies to improve student conceptual understanding, interest in Physics, epistemological awareness and insights for the construction of a scientific citizenship. However, Physics teaching practice seems resistant to adopting adapting these findings to their own situation and new research based curricula find difficulty in affirming and spread, both at school and university levels. The conference offered an opportunity for in-depth discussions of this apparently wide-spread tension in order to find ways to do better. The purpose of the GIREP-MPTL 2014 was to bring together people working in physics education research and in physics education at schools from all over the world to allow them to share research results and exchange their experience. About 300 teachers, educators, and researchers, from all continents and 45 countries have attended the Conference contributing with 177 oral presentations, 15 workshops, 11 symposia, and around 60 poster presentations, together with 11 keynote addresses (general talks). After the conference, 147 papers have been submitted for the GIREP-MPTL 2014 International Conference proceedings. Each paper has been reviewed by at least two reviewers, from countries that are different to those of the authors and on the basis of criteria described on the Conference web site. Papers were subsequently revised by authors according to reviewers’ comments and the accepted papers are reported in this book, divided in 8 Sections on the basis of the keywords suggested by authors. The other book section (actually, the first one) contains the papers that six of the keynote talkers sent for publication in this Proceedings Book. We would like to thank all the authors that contributed with their papers to the realization of this book and all the referees that with their criticism helped authors to improve the quality of the papers