1,721,177 research outputs found
Robust Header Compression for WiMAX Femto Cells
No full textEven though WiMAX technology offers high data rates, the overall capacity over the air is shared among several WiMAX users. This is especially true for the WiMAX support of femto cells. In this scenario very small wireless cells, covered by short-range technologies such as WLAN or Bluetooth, are wirelessly connected to the Internet backbone by WiMAX links. The number of accumulated users will be high and any means to gain additional capacity are more than welcomed. An effective approach to increase capacity is to utilize header compression. In the wireless world, Robust Header Compression (ROHC), as standardized in RFC3095 (Bormann et al., 2001), is a widely applied header compression scheme. ROHC is a method to reduce the overhead of the packet header information down to 10% or less. This method is especially effective if the payload is relatively small in contrast to the header itself. In this chapter we will motivate the use of ROHC in WiMAX, as proposed in the WiMAX documents (Fitzek et al., 2004), and demonstrate the potential gain of using ROHC for WiMAX femto cells by implementation and measurements. The results presented here are the outcome of a collaborative work of acticom (acticom GmbH , 2008b) and VTT implementing acticom’s ROHC protocol stack in a commercial WiMAX system. As shown throughout this chapter, ROHC demonstrates outstanding performance over the standard system
Cellular Controlled Peer to Peer Communications:Overview and Potentials
No full textIn this chapter we present a dynamic approach to bridge cellular and peer-to-peer network architectures, referred to as Cellular Controlled Peer-to-Peer (CCP2P) communication. This approach goes beyond the concepts used in composite networks, which focus mainly on coverage extension and data relaying. In CCP2P networks, besides being connected to an outside world using cellular links, a group of mobile devices in close proximity form a cooperative cluster contributing their onboard capabilities and resources to exploit them a more efficient way. Using peerto- peer technology in combination with cellular networks, CCP2P has the potential to overcomemany important limitations of current cellular networks. The main driver behind such a concept is the short-range communication among mobile devices
Cooperative and Cognitive Networks: A Motivating Introduction:Towards the Age of Enlightenment in Wireless Communication Networks
No full textIn this introductory chapter, some key trends and emerging concepts for wireless communication networks are explored, highlighting chiefly those exploiting cooperative and cognitive principles. After discussing some key promising directions of development, a motivating overview of cooperative techniques in wireless networks in presented, followed by an overview of cognitive techniques and their use in wireless networks. The joint exploitation of these complementary principles are also considered in this chapter. Finally some visions on promising developments and possible evolutionary steps are included. The introductory discussions presented here serve as a an initial motivation to the rest of the book, where many of the concepts and techniques discussed here are explained in detail
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Analysis of Cooperative Power Saving Strategies with NetLogo
No full textAfter a detailed introduction to NetLogo programming language, given in the previous chapter, here we aim to present and discuss some results obtained with this tool. Our focus is a model for analyzing cooperative power saving strategies in a mobile wireless network. The promising outcomes of the simulation in terms of highly reduced power consumption underline both the success of cooperative strategies for a specific fundamental network application and the effectiveness of using NetLogo agent-based approach for modeling decentralized communication systems
Introduction to NetLogo
No full textNetLogo is a multi-agent modeling environment originally conceived by the complex systems community for simulating natural and social phenomena. Despite its simplicity, NetLogo is a powerful tool in many fields of research. It is especially well suited for modeling large collections of independent agents developing over time, thus being a promising solution for simulating and analyzing distributed systems such as modern wireless networks. In this chapter we illustrate the feasibility of this approach, by providing a detailed tutorial about the application of NetLogo to wireless communications
On the Energy Saving Potential in DVB-H Networks Exploiting Cooperation among Mobile Devices
No full textIn this chapter we focus on cooperative strategies for IP-services over DVB-H networks to save energy. It demonstrates the potential of non-altruistic cooperation between mobile devices. The envisioned cooperation is based on cellular reception of DVB-H data, which is then shared among mobile devices within each others’ proximity over short-range links. The short-range communication is realized by Bluetooth, where a cross-platform design approach is introduced to optimize the signalling communication in the Bluetooth system. Three different cooperative algorithms are designed for the short-range link (Bluetooth) communication. Numerical results show that a energy saving of over 50% can be achieved by cooperative networking of three mobile devices in fully cooperating mode
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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