1,720,997 research outputs found
On Efficient Topologies for Bluetooth Scatternet
No full textIn this paper we investigate the relationship between network capacity and topology for Bluetooth scatternets. We start by considering the intrinsic capacity limits of a scatternet structure, and we show that limiting capacity may be achieved for very local traffic and under specific conditions on the scatternet structure. Then, we provide a description of the performance achievable with two basic scatternet configurations, namely star and closed–loop topologies, and show the role played by inter–piconet interference in the choice of efficient configurations. Finally, we present some efficient topologies, based on Platonic solids structur
Ad hoc networks with topology-transparent scheduling schemes: scaling laws and capacity/ delay tradeoffs
No full textMathematical Analysis of the Packet Delay Statistics in Bluetooth Piconets under Round Robin Polling Regime
Full text linkPersonal Area Network technologies like Bluetooth and its subsequent derivations and evolutions (Bluetooth v1.2, v2.0+EDR) are valid candidates to realize the mobile and pervasive communication paradigm that is considered in several recent research projects. Although the delay performance of the basic Bluetooth network configuration (piconet) has been widely evaluated through numerical simulations, no satisfactory analytical framework has been yet proposed in the literature. In this paper we present an analysis of the packet delay statistic in Bluetooth piconets, for a limited–1 (round robin) polling strategy. The mathematical model proposed in this paper extends the other models presented in the literature by providing more accurate results for a wider range of traffic patterns, under the assumption of a marked Poisson arrival process. Our analysis provides a complete statistical characterization of the packet delay, by means of Laplace-Stieltjes transform, for generic traffic patterns. Furthermore, expressions for the estimation of the average packet delay for unbalanced and asymmetric traffic are derived, thus improving existing results based on the theory of M/G/1 queues with vacations. Such expressions are, however, rather complex. Therefore, we propose an approximation, based on a renewal argument, which leads to a closed–form expression for the access delay statistic. The proposed analysis permits an accurate estimation of the packet delay under a wide range of network load conditions
On efficient configurations for Bluetooth scatternets
No full textIn this paper we investigate the relationship between capacity and network topology for Bluetooth scatternets. We start by considering the intrinsic capacity limits of a scatternet structure, and we show that capacity may be approached in the presence of very local traffic only and under specific conditions on the scatternet structure. A worst case analysis is presented, addressing the performance of various network configurations in the presence of a uniform end-to-end traffic matrix. In particular, some efficient configurations, based on Platonic solids, are introduced and analyzed. Finally, we focus on the closed loop configuration, for which algorithms able to improve scatternet performance by exploiting traffic locality are presented and discussed. © 2005 Elsevier B.V. All rights reserved
Achievable Rate Regions for Bluetooth Piconets in Fading Channels
No full textWe investigate the stability of a Bluetooth piconet operating in fading (Rice, Rayleigh or Nakagami) channels. By taking into account many protocol details, such as modulation scheme and packet formats, we provide an analytical characterization of the achievable rate regions, which, for a network of N nodes, turns out to be the interior of a convex polyhedron in a (2N-2)-dimensional space. We show also that some previous analysis of Bluetooth link performance, by neglecting the impact of the multiple access scheme, may lead to erroneous conclusions in terms of optimal packet format
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
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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