1,720,980 research outputs found
Directed Diffusion Light: Low Overhead Data Dissemination in Wireless Sensor Networks
No full textIn this paper we introduce Directed Diffusion Light, a variant of the well-known protocol Directed Diffusion (DD), which results in significant savings in terms of exchanged control messages and energy consumption, and improvements in network lifetime. Directed Diffusion Light defines local rules to generate a sparse logical topology over which DD can be run. This decreases the costs associated to the required DD periodic floodings. Ns-2 based simulation results show that, when 300 sensor nodes are deployed over a squared area of side 200m Directed Diffusion Light is able to increase the network lifetime four times, to halve the average energy consumption, and to reduce the control overhead to one third the one of DD. ©2005 IEEE
A detailed simulation study of geographic random forwarding (GERAF) in wireless sensor networks
No full textThis paper provides a thorough performance evaluation of the GeRaF protocol in a multi-hop wireless sensor network scenario. The contributions of the paper are twofold. First we provide an in-depth discussion on the impact of the different protocol parameters and of network features on the protocol performance. Based on the results of the first part of our investigation we design variants of the basic GeRaF protocol which are able to significantly decrease the packet latency and to increase the packet delivery ratio. The study presented in this paper is the first attempt to thoroughly characterize the performance of GeRaF and is a necessary step toward understanding the real protocol behavior before implementing it on real devices
Localization Error-resilient Geographic Routing for Wireless Sensor Networks
No full textThis paper concerns the demonstration of the resilience to localization errors of ALBA-R, a protocol for geographic routing in wireless sensor networks (WSNs). In particular, we show that thanks to a simple yet effective nodal coloring mechanism for handling nodal connectivity holes, ALBA-R achieves the further desirable benefit of being totally resilient to localization errors, which are unavoidable in WSNs. Via ns2- based simulations we show that independently of fundamental network parameters such as network density, and also independently of errors in nodal coordinate estimations as high as the node transmission radius, ALBA-R is successful in delivering all generated packets while incurring reasonable degradation for metrics such as route-length and end-to-end latency and still remaining and energy efficient protocol. © 2008 IEEE
Demonstrating the resilience of geographical routing to localization errors
No full textNo abstract availabl
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
Geographic forwarding and adaptive load balancing in wireless sensor networks
No full textIn the future sensor nodes will either have GPS capabilities, or be able to run localization protocols in order to get an accurate estimation of their position. These features would make geographic convergecasting a feasible and promising solution for WSNs. Key for the actual implementation of WSNs is the design of cross-layer solutions which consider explicitly the resource constraints of sensor nodes, especially in terms of available energy, limited memory and processing capabilities. We present a new protocol, named ALBA (Adaptive-Load Balanced Algorithm), which uses a cross-layer approach, pursuing the following goals: i) ALBA minimizes the number of hops required to reach the sink through a geographic forwarding scheme; ii) traffic is distributed evenly in the network, favoring nodes that are experiencing low congestion, while avoiding overloaded regions; iii) channel access efficiency is optimized through an adaptive back-to-back transmission of "bursts of packets" once a relay is selected, and iv) nodes are progressively made aware of routes to redirect the packets to the sink even when a connectivity hole occurs, i.e., when some nodes are not able to deliver packets to the sink because of lack of next-hop relay nodes closer to the sink
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