Skip to main content Accessibility help

We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.

Close cookie message
×
  1. Home
  2. Browse subjects
  3. Computer Science
  4. Communications, Information Theory and Security
  5. Content listing

Refine search

Refine search

Access:
Content type:
Publication date:
Apply   From and To filters
Subject: Show more
Journals Show more
Publishers: Show more
Societies Show more
Series: Show more
Collections: Show more

Actions for selected content:

Select all | Deselect all
  • View selected items
  • Export citations
  • Download PDF (zip)
  • Save to Kindle
  • Save to Dropbox
  • Save to Google Drive

Save Search

You can save your searches here and later view and run them again in "My saved searches".

Please provide a title, maximum of 40 characters.
Cancel
×

1325 results in Communications, Information Theory and Security

Page 20 of 67

  • 7 - Backhaul Load Constraint

  • Venugopal V. Veeravalli, University of Illinois, Urbana-Champaign, Aly El Gamal, Purdue University, Indiana
  • Book:
    Interference Management in Wireless Networks
    Published online:
    09 February 2018
    Print publication:
    22 February 2018, pp 126-147

  • Summary

    In the previous two chapters, we have considered cooperative transmission schemes that are constrained by the number of transmitters to which each message can be assigned. While meeting a backhaul capacity limit by a per-message constraint can have its analytical advantages, such as reducing a difficult information-theoretic problem to a simple combinatorial one, this approach suffers from a few important drawbacks.

    For one, the maximum transmit set size constraint may not reflect most practical scenarios for two reasons. First, because fractional reuse across different resource (e.g., frequency or time) slots can be used to achieve an equal load on the backhaul per message, it may not make sense to impose a maximum transmit set size constraint for each channel use. Secondly, the maximum transmit set size constraint may not reflect the nature of the backhaul link, as we will discuss further below.

    Also, as we have discussed in the previous chapter, the optimal solutions for the maximum transmit set size constraint may not fully utilize the constraint; i.e., for the optimal solution, some messages need not be assigned to the allowed maximum number of transmitters. We have seen in Chapter 6 that this is the case for the optimal schemes for linear interference networks, as well as for general locally connected networks where we impose the restriction of using only zero-forcing coding schemes.

    The appropriate constraint to consider for the assignment of messages to transmitters should depend on the nature of the backhaul link used in practice (see, e.g., [69, 86]). For example, in the context of heterogeneous networks, the backhaul can be a wireless network, and an overall backhaul load constraint would be a more appropriate choice. On the other hand, for the case of wireline or optical fiber backhaul links, the maximum transmit set size constraint can be useful. However, even with wireline backhaul links, an average transmit set size constraint can allow for flexible solutions that interleave the use of the backhaul links over multiple communication sessions. In general, a constraint that bounds the average transmit set size is more relevant to practice than imposing a maximum constraint on each transmit set size. We show in this chapter how the solutions for the CoMP transmission problem provided under the maximum transmit set size constraint can be used to find solutions under an average transmit set size or backhaul load constraint.

  • Preface

  • Venugopal V. Veeravalli, University of Illinois, Urbana-Champaign, Aly El Gamal, Purdue University, Indiana
  • Book:
    Interference Management in Wireless Networks
    Published online:
    09 February 2018
    Print publication:
    22 February 2018, pp ix-x

  • Summary

    Efficient interference management is the key to meeting the ever increasing demand for wireless data services in wireless networks. In this book, an information-theoretic framework for interference management is presented, along with a discussion of practically implementable schemes for interference management that approach provable bounds on performance and are applicable in large cellular networks.

    A particular focus of the book is on exploiting recent technological advancements in the wireless infrastructure that enable cooperative transmission and reception. Our theoretical framework highlights the potential of this technology to deliver the rate gains promised by interference alignment, while using simple zero-forcing schemes that are easier to implement in practice. The schemes that we present rely on local cooperation, and they are shown to be optimal in locally connected interference networks, where the path loss effect allows us to neglect connections between transmitters and receivers that are far away from each other. It is also shown that cooperative communication can be used to deliver significant rate gains using simple zero-forcing with no or minimal extra load on the backhaul, by selecting cell associations and allocation of backhaul resources based on centralized processing and knowledge of the network topology. The insights obtained are also extended to dynamic interference networks that capture the effect of deep fading conditions.

    This book is organized as follows:

  • • In Chapter 1, we provide a high-level introduction to interference management in wireless networks, including a historical perspective on wireless cellular networks, and we motivate the need for a fundamental information-theoretic understanding of this problem.

  • • In Chapter 2, we provide a detailed overview of the state of the art in determining the information-theoretic sum capacity of the interference channel. Determining the capacity even in the simplest setting with two users with one antenna at each of their transmitters and receivers is still an open problem, but exact results can be obtained in certain low-interference regimes that may arise in practice.

  • • In Chapter 3, we take an alternative approach to characterizing the rate of communication on an interference channel, based on a degrees of freedom (DoF) analysis, which is more analytically tractable. The DoF approach corresponds to analyzing the limiting normalized capacity as the signal-to-noise ratio goes to infinity, and the DoF measure emphasizes the loss in rate that results from the users interfering with each other over the effect of channel noise.

  • 10 - Recent Advances and Open Problems

  • Venugopal V. Veeravalli, University of Illinois, Urbana-Champaign, Aly El Gamal, Purdue University, Indiana
  • Book:
    Interference Management in Wireless Networks
    Published online:
    09 February 2018
    Print publication:
    22 February 2018, pp 183-192

  • Summary

    Over the years since Claude Shannon [12] introduced the subject, information theory has proven to be a powerful mathematical tool that is also practically relevant in terms of guiding the design of transmitters and receivers for communication systems and networks. From the analysis of the capacity of point-to-point communication links [12] to the more advanced analysis of network information theory [99], there is evidence that information-theoretic tools not only provide performance benchmarks but also inspire new designs for coding schemes and communication protocols. In this book, our focus has been on information-theoretic tools that are geared toward laying a framework for interference management in modern wireless networks. We started with a discussion of the information-theoretic capacity of the two-user interference channel in Chapter 2, which is a long-standing open problem. We do not yet understand how interfering signals should be handled by the decoders at the receivers except in special cases: (i) where the interference power is high and the interfering signal(s) can be decoded, and (ii) and where the interference power is low and the interfering signal(s) can be treated as noise. We then considered the degrees of freedom criterion in the rest of the book, due to its attractive simplicity and utility in providing insights for interference management. We considered general K-user interference channels in Chapter 3, and introduced the concept of asymptotic interference alignment. We then studied in Chapters 5–9 the potential gains of cooperative communication through the lens of DoF analysis in large interference networks. In these studies we assumed a centralized controller, one that has a global view of the network and can make decisions on cell associations and transmission schedules for the whole network, with the goal of maximizing the sum DoF. It is important to note that our study of models with centralized controllers does not imply that we are advocating a centralized approach in next-generation wireless networks over a distributed one that only requires local network knowledge for making decisions. Analyzing fundamental bounds on the performance for the centralized solution can also lead to good design choices for distributed schemes, as well as providing benchmarks for their performance, as we have seen in our study of distributed interference management algorithms in Chapter 4 and Section 5.7.

Interference Management in Wireless Networks
  • Fundamental Bounds and the Role of Cooperation
  • Venugopal V. Veeravalli, Aly El Gamal
  • Published online:
    09 February 2018
    Print publication:
    22 February 2018
  • Learn about an information-theoretic approach to managing interference in future generation wireless networks. Focusing on cooperative schemes motivated by Coordinated Multi-Point (CoMP) technology, the book develops a robust theoretical framework for interference management that uses recent advancements in backhaul design, and practical pre-coding schemes based on local cooperation, to deliver the increased speed and reliability promised by interference alignment. Gain insight into how simple, zero-forcing pre-coding schemes are optimal in locally connected interference networks, and discover how significant rate gains can be obtained by making cell association decisions and allocating backhaul resources based on centralized (cloud) processing and knowledge of network topology. Providing a link between information-theoretic analyses and interference management schemes that are easy to implement, this is an invaluable resource for researchers, graduate students and practicing engineers in wireless communications.

  • Chapter 9 - Ontology-based Structuring of Spectral and Spatial Recording Strategies for Cultural Heritage Assets: Background, State of Affairs, and Future Perspectives

  • Edited by Anna Bentkowska-Kafel, Lindsay MacDonald
  • Book:
    Digital Techniques for Documenting and Preserving Cultural Heritage
    Published by:
    Amsterdam University Press
    Published online:
    26 January 2021
    Print publication:
    08 January 2018, pp 159-174

  • Summary

    ABSTRACT

    The activities of COSCH community and the disciplines it represents were as diverse as they could possibly be in research into cultural heritage. To achieve common goals it was of utmost importance to have a common understanding of these diverse activities and disciplines. Work on the COSCH Knowledge Representation, or COSCHKR, was undertaken to develop a common semantic base representing different disciplines and to facilitate communication within the Action. The COSCHKR is an ontology-based inference model, guided by inference rules that provide a semantic bridge between various interdisciplinary activities involved in non-invasive technical documentation of material cultural heritage. The model is intended to support humanities experts by recommending optimal spatial and spectral techniques. The model may also be used by technology experts to compare their own solutions with the ones recommended through COSCHKR, and to understand why they may differ.

    In this chapter we present the methods adopted for designing the COSCHKR and the steps in the development of the inference model. The difficulties in maintaining a common level of understanding within the diverse disciplines during the knowledge acquisition process are discussed. We present mechanisms and methods of information collection, its structuring, and aligning, to formulate different axioms and theorems within the model. The design and development of COSCHKR was based on an iterative procedure where the gathered knowledge was first verified with the group of experts before it was processed. This verification mechanism was important for the reliability of the model, ensuring technical consistency. This chapter highlights the importance of these iterative mechanisms in the validation of knowledge gathered and then information populated inside the knowledge base.

    Keywords: COSCH ontology, knowledge representation, cultural heritage recording, Semantic Web technologies, inference system

    Introduction

    Spectral or spatial recording of material cultural heritage (CH) is an interdisciplinary task involving scientists and experts from the humanities, information technologies, and engineering. A mutual understanding and agreement about the complexities of undertaking such recoding tasks is necessary in order to deliver appropriate spectral or spatial data of physical cultural heritage objects adapted to the needs of cultural heritage experts who rely on and work with those data. The COST Action TD1201: Colour and Space in Cultural Heritage (COSCH) (Boochs 2012; Boochs et al. 2013), brought together these experts to enhance mutual understanding among the disciplines in order to better record and preserve material cultural heritage.

  • Chapter 10 - Communicating Interdisciplinary Scholarship: Conclusions from COSCH

  • Edited by Anna Bentkowska-Kafel, Lindsay MacDonald
  • Book:
    Digital Techniques for Documenting and Preserving Cultural Heritage
    Published by:
    Amsterdam University Press
    Published online:
    26 January 2021
    Print publication:
    08 January 2018, pp 175-192

  • Summary

    ABSTRACT

    The study of cultural heritage requires the expertise of many disciplines as different as history and optical science. Each discipline brings its discrete research methods and know-how. Complementary knowledge is gained, gradually, through effective collaboration, which is not always easy. The articulation and communication of respective research questions, ways of addressing these questions, and expected outcomes, are a challenge in all collaborative projects. This concluding chapter discusses how the COST Action, Colour in Space in Cultural Heritage, has addressed and managed this challenge, through the case studies described in the present book and other activities. The authors draw conclusions from COSCH research activities and note some general points that bear on the success of diffusion of interdisciplinary research and its future.

    Keywords: interdisciplinary research, communication, cultural heritage, science, optical technologies, COSCH

    It is everyone's responsibility to improve interdisciplinary communication, something that starts and ends with willingness, plenty of patience, and an open mind.

    (Darren Kocs 1993, 1060)

    The study and documentation of cultural heritage require the expertise of many disciplines as different as history and optical science. Each discipline brings its discrete research methods and know-how. Complementary knowledge is gained, gradually, through effective collaboration. The articulation and communication of respective research questions, ways of addressing these questions, and expected outcomes, are challenges common to all collaborative projects. This concluding chapter discusses how the COST Action, Colour in Space in Cultural Heritage (COSCH) has addressed and managed these challenges, through the case studies, described in the preceding chapters, and other research and training activities conducted between 2012 and 2016. We reflect on earlier projects that also shared the goal of “bridging the gap” between disciplinary approaches and mindsets, specialist research methods and tools, while showing the distinctive approach of the COSCH network. We draw conclusions from COSCH's four-year engagement in the interdisciplinary debate by noting general points that, in our view, bear on the success of future research and its diffusion.

    On the Perceived Notion of “Two Cultures”

    “The scientist has the habit of science, the artist the habit of art.”1 The concept of “two cultures” has persisted since it was forcefully proposed in the 1950s. It is not only widely understood, but also cultivated in the English-speaking academia, as evidenced by a recent, double issue of Interdisciplinary Science Reviews (James 2016) that elaborates on its legacy.

  • Chapter 3 - Beyond Photography: An Interdisciplinary, Exploratory Case Study in the Recording and Examination of Roman Silver Coins

  • Edited by Anna Bentkowska-Kafel, Lindsay MacDonald
  • Book:
    Digital Techniques for Documenting and Preserving Cultural Heritage
    Published by:
    Amsterdam University Press
    Published online:
    26 January 2021
    Print publication:
    08 January 2018, pp 35-66

  • Summary

    ABSTRACT

    A study was undertaken by an interdisciplinary group of COSCH researchers between 2014 and 2016, to record and examine silver coins believed to be ancient Roman in origin. The aim was to evaluate the suitability of various advanced, non-invasive optical and spectrometric techniques for analysing the physical characteristics and elemental composition of numismatic objects. In order to compare results, the same two silver coins were used throughout the study: two denarii portraying Empress Faustina I, wife of Antoninus Pius, believed to be posthumous deification issues of AD 141. The questions addressed included the characterization and authentication of test coins, as well as technical issues in the multimodal recording of material cultural heritage with metadata and paradata. The team investigated whether the methods chosen for this case study responded to the needs of numismatists, and whether they could feasibly be applied in museum practice, to support research and conservation of historic coins, and to enhance the documentation and dissemination of numismatic objects through heritage science.

    Keywords: numismatic studies, Roman silver coins, examination, optical techniques, multimodal recording, COSCH

    Background and Purpose of the Study

    This chapter introduces an experimental study of two silver coins, believed to be ancient Roman, and discusses some of its interdisciplinary outcomes. We undertook to investigate, in collaboration with other international researchers, how historic coins are examined and documented, and what is the role of modern, non-invasive optical and spectrometric technologies in today's numismatic research and museum practice. The network Colour and Space in Cultural Heritage (COSCH) facilitated research contacts between experts representing a wide range of interdisciplinary interests and expertise in optical, metrological and imaging technologies and material sciences. Benefiting from this combined expertise and access to specialist equipment, at a level that is rarely available to museums, this case study was designed to explore which of the advanced technologies available to us could enhance numismatic research and conservation, and museum practice in general. Therefore, our main objectives were:

    • to assess current research and documentation practice: how are historic coins in numismatic museum collections being examined and recorded, presented and disseminated in the 2010s? What is the role of digital methods?

    • to apply a wide range of optical and spectrometric techniques to measure and examine, and present the test coins;

    • to compare the results of different technologies applied for the same purpose, in particular to compare the geometric measurements achieved through several 3D techniques;

  • 3D Depth Sensing

  • Edited by Anna Bentkowska-Kafel, Lindsay MacDonald
  • Book:
    Digital Techniques for Documenting and Preserving Cultural Heritage
    Published by:
    Amsterdam University Press
    Published online:
    26 January 2021
    Print publication:
    08 January 2018, pp 195-198

  • Summary

    Definition

    Three-dimensional depth sensing can be defined as the ability or capability to tell the distances from a reference point, or observer, to all objects in a 3D scene. In technological terms, it requires a system able to take measurements, or employ computational methods, or a combination of those, to estimate distances from the system itself to all objects in its surroundings. In cultural heritage applications 3D depth sensing is at the heart of most 3D digitization systems (in some cases termed 3D optical documentation). Several restrictions apply, including the proper handling of valuable and fragile historic objects.

    Description

    Technically, 3D depth sensing is the process of acquiring the distances of all points in a 3D scene from a fixed point of reference, which in most cases is the sensing device itself. There are a number of different methods and technologies for sensing the depth in 3D space. Usually these methods are categorized into light-dependent and light-independent: a light-dependent system senses light, in any way, in order to assess the three spatial dimensions, whereas light-independent employs methods not directly sensing light, but using geometrical and topographical principles. In addition, mainly within the category of light-dependent methods, a further sub-classification is based on the principle used or the technology being applied. These are the active and passive methods: active in a sense that the measuring system formulates the conditions of the measurements in order to acquire depth, whereas passive methods rely purely on computation applied to raw “unsupervised” measurements.

    Numerous methods can be found in the literature, and here is a list of the most cited in their category:

    • 1 Light-dependent methods

    • a Active methods

    • i Laser triangulation

    • ii Time-of-flight scanning (or LiDAR, LADAR, range scanning)

    • iii Structured-light scanning

    • iv Shape from Photometry

    • v Shape from Shading

    • vi Shape from Shadow

    • vii Tomography (of any kind)

    • viii Holography

    • b Passive methods

    • i Photogrammetry

    • ii Structure from Motion

    • iii Shape from Silhouette

    • iv Shape from Stereo

    • v Shape from Texture

    • vi Shape from Focus (zooming)

    • vii Microscopy (of any kind)

    • 2 Light-independent methods

    • a Topographic methods

    • b Empirical methods

    • c Contact sensing methods.

  • Chapter 1 - An Interdisciplinary Discussion of the Terminologies Used in Cultural Heritage Research

  • Edited by Anna Bentkowska-Kafel, Lindsay MacDonald
  • Book:
    Digital Techniques for Documenting and Preserving Cultural Heritage
    Published by:
    Amsterdam University Press
    Published online:
    26 January 2021
    Print publication:
    08 January 2018, pp 3-16

  • Summary

    ABSTRACT

    Accuracy, artefact, feature, precision, reconstruction, resolution, texture, uncertainty are words central to many discussions of the documentation of cultural heritage. This terminology, whilst broadly understood across the disciplines, is often misunderstood due to its specific use in particular cases. An interdisciplinary dialogue conducted over a period of years and comprising experts in a range of fields—art history, colour science, engineering, semantics, mathematics, cultural heritage, museum studies, and others—has yielded a challenging discussion document that considers the thorny issue of a shared understanding of a set of keywords. On occasion our perceived shared language is not shared at all but reveals—at times through subtle nuance, and yet at times through gaping chasm—the disciplinary subjectivities we hold unbeknownst to ourselves. Mutual understanding of some of these key terms is central to any newly engaged, participatory transdisciplinary endeavour that seeks to develop critical methods for the documentation, analysis, preservation, and sharing of cultural heritage objects outside the traditional disciplinary silos. This chapter charts the interdisciplinary discussion towards a common understanding of terminologies used in cultural heritage. It is a discussion that recognizes critical differences or common misuse, and aims to contribute to a shared understanding that may be useful for all knowledge domains in the field. The chapter summarizes the work of a number of Think Tanks conducted by Early Career Investigators participating in the COSCH network.

    Keywords: cultural heritage, interdisciplinary research terminology, metrology, humanities, digital documentation, COSCH

    Introduction

    The digital documentation of material cultural heritage is a multidisciplinary task and often involves experts in spectral and spatial recording, and Information and Communication Technology (ICT). When generating digital representations of objects of cultural heritage, a shared understanding is necessary to develop suitable and user-oriented solutions. However, reaching a shared understanding is complex. It begins with a clear definition of the project's aim(s), including the explanation of concepts, terms, and procedures that may be unknown to some project partners. These first steps may seem obvious and should be the basis not only for multidisciplinary projects, but for all projects. However, these tasks are more multifaceted in multidisciplinary projects as, in addition to unfamiliar disciplinary terminology, each project partner might use terms that are common to various domains, but may have inherently different meanings.

Page 20 of 67