1,720,957 research outputs found
Enhancements of epidemic routing in delay tolerant networks from an energy perspective
No full textIn last years, the challenge of providing end-to-end service where end-to-end forwarding paths do not exist is faced by the new emerging approach of Delay Tolerant Networks (DTNs), that support interoperability of "regional networks" by accommodating long delay between and within regional networks, such as space communications, networking in sparsely populated areas, vehicular ad-hoc networks and underwater sensor networking. The common issue of these environments consists in the absence of guarantees about the existence of continuous end-to-end paths between source and destination nodes. In this paper we consider epidemic schemes to solve this problem, proposing an extended approach aimed at the routing optimization in terms of energy consumption and message delivery probability. The performance of our idea have been evaluated through a deep campaign of simulations, verifying that the proposed extended epidemic approach leads the system to an overall enhancement. © 2013 IEEE
A bandwidth management scheme based on time multiplexing for wireless networks with predictive services
No full textNowadays, in wireless computing, guaranteeing a certain grade of Quality of Service (QoS) during wireless sessions is an important issue, especially when non-tolerant applications are running into the system. Mobility and channel quality often affect system performance, depending on the grade of mobility of hosts. In this paper, providing QoS to mobile hosts belonging to a certain service class (Mobility Independent Predictive - MIP) is the main issue and a statistical multiplexing algorithm is proposed, in order to save an enormous amount of resources; it is based on the Cell Stay Time (CST) distribution analysis for a 2-dimensional (2D) wireless environment under the Smooth Random Mobility Model (SRMM). There are many works in literature about resource pre-reservation: they offer good QoS guarantees, but a very low system utilization, because they do not care about the fact that a passive reservation can remain unused for long time. With the help of the CST statistical multiplexing introduced in this paper, better results are obtained in terms of system utilization, while the Quality of Service and prediction error are maintained at acceptable levels. The proposed idea has been validated through many simulation campaigns, with a good performance analysis in terms of some interesting parameters, like bandwidth system utilization or prediction errors. © 2009 IEEE
A Distributed Mitigation Strategy against DoS attacks in Edge Computing
Full text linkInternet of Things (IoT) is a platform where every day devices become smarter, every day processing becomes intelligent, and every day communication becomes informative. Numerous challenges prevent to secure IoT devices and their end-to-end communication in an IoT environment. In fact, the IoT security is still an open challenge. The purpose of this work is to examine a distributed strategy for mitigating Denial of Service (DoS) attacks against the fog node in an edge computing context in which the nodes exchange messages through Message Queue Telemetry Transport (MQTT) protocol. The proposed strategy is based on a dynamic message sending frequency of the lightweight nodes. It is also mitigated data tampering and eavesdropping by using Elliptic Curve Cryptography (ECC)
Novel MF-TDMA/SCPC switching algorithm for DVB-RCS/RCS2 return link in railway scenario
No full textThis work focuses on the return channel resource allocation in the DVB-RCS/RCS2 system for mobile terminals. A continuous carrier (CC) operation mode based on DVB-S2/S2X is considered and investigated. The paper focuses on the possibility of transmitting simultaneously in multifrequency-time division multiple access (MF-TDMA) or single channel per carrier (SCPC) medium access techniques, as suggested by a previous DVB-RCS+M standard. The introduction of this capability has also been analyzed for a new DVB-RCS2 standard that gives the possibility of using both return link (RL) modalities. Moreover, we propose a detailed study of the RL channel in a satellite platform in order to understand the operative range of SCPC and MF-TDMA techniques. The contribution seeks to provide some threshold indications to network operators for dynamically managing satellite resources.We considered the railway market, which is characterized by an N-LOS condition due to blockage caused by tunnels, vegetation, and buildings, as the reference scenario. Furthermore, we introduced a transparent gap filler (GF) solution to overcome this issue. Simulation campaigns are shown, in order to give satellite operators some guidelines, when they want to make use of this hybrid channel modality
Pattern Prediction and Passive Bandwidth Management for Hand-over Optimization in QoS Cellular Networks with Vehicular Mobility
No full textIn wireless networking, the main desire of end-users is to take advantage of satisfactory services, in terms of QoS, especially when they pay for a required need. Many efforts have been made to investigate how the continuity of services can be guaranteed in QoS networks, where users can move from one cell to another one. The introduction of a prediction scheme with passive reservations is the only way to face this issue; however, the deployment of in-advance bandwidth leads the system to waste resources. This work consists of two main integrated contributions: a new pattern prediction scheme based on a distributed set of Markov chains, in order to handle passive reservations, and a statistical bandwidth management algorithm for the reduction of bandwidth wastage. The result of the integration is the Distributed Prediction with Bandwidth Management Algorithm (DPBMA) that is independent from the considered technology and the vehicular environment. Several simulation campaigns were conducted in order to evaluate the effectiveness of the proposed idea. It was also compared with other prediction schemes, in terms of system utilization, accuracy, call dropping, and call blocking probabilities
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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