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Algoritmo de alocação dinâmica de largura de faixa para redes de comunicação móvel celular; Dynamic bandwidth allocation algorithm for mobile communication networks

Queiroz, Eduardo Martinelli Galvão de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/03/2008 PT
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O crescente aumento da demanda de tráfego nas redes celulares vem aumentando a necessidade de uma melhor utilização dos recursos do sistema, já que sua expansão é custosa. Nas estações rádio base (ERB), a disponibilidade de largura de faixa de freqüências é limitada e desta maneira, em uma rede de comunicação móvel celular, o controle de admissão de chamadas exerce grande influência no desempenho do sistema, pois determina a utilização de banda das ERBs e se uma determinada quantidade de recursos (banda) será alocado ou não para uma determinada chamada. O desempenho da rede pode ser atrelado a determinados parâmetros, como a probabilidade de bloqueio de novas chamadas, probabilidade de bloqueio de chamadas handoff e a utilização de banda da rede. Este trabalho propõe um controle de admissão de chamadas que, no atendimento de uma chamada, faz o empréstimo de banda de chamadas em andamento na célula no caso de banda insuficiente. O sistema adota um mecanismo heurístico que determina a banda disponível para novas chamadas conforme os valores de certos parâmetros do sistema. O empréstimo de banda é realizado em chamadas em andamento nas células até níveis mínimos estabelecidos para cada tipo de chamada...

Autoria em rede : um estudo dos processos autorais interativos de escrita nas redes de comunicação; Authorship through network : a study of the interactive authoring processes of writing in communication networks

Martins, Beatriz Cintra
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 23/03/2012 PT
Relevância na Pesquisa
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As redes de comunicação têm impulsionado um significativo deslocamento nos processos autorais de escrita, que adquirem nova dinâmica no meio digital, apresentando-se cada vez mais como uma ação interativa entre diferentes agentes criadores. Com base no pensamento de Michel Foucault sobre o tema da autoria, esta tese explora o significado desse deslizamento da posição do autor, ou da função-autor como propõe o filósofo, estruturada atualmente em uma rede de interações. A fim de construir uma reflexão sobre esse fenômeno, parte-se da pesquisa sobre a historicidade do conceito de autoria, buscando explorar as diversas constituições das práticas sociais da produção textual através da história, desde a Antiguidade até o momento atual das redes eletrônicas. Neste percurso, a Modernidade é reconhecida como o período específico no qual o processo autoral adquire uma configuração mais centrada no indivíduo, época em que também ganha espaço a noção de obra fechada e proprietária. Compreendendo a constituição da história como um processo complexo no qual se correlacionam diversas dimensões de acontecimentos, alguns aspectos que se articulam com esta questão são aprofundados na forma de intertextos. Deste modo...

Análise de desempenho de redes de comunicação industrial em acionamentos de motores elétricos trifásicos; Performance analysis of industrial communication networks in electrical motors drives

Dias, André Luís
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 09/12/2014 PT
Relevância na Pesquisa
55.94%
Este trabalho propõe analisar o desempenho de redes de comunicação industrial em aplicações de acionamentos de motores elétricos trifásicos. Compara-se o desempenho da tecnologia Profibus DP em relação à Profinet. O desempenho é verificado a partir de especificações técnicas de ambos protocolos e experimentos práticos para coleta de dados e análise dos seguintes indicadores de desempenho: tempo de ciclo, jitter e ocupação de largura de banda. Adicionalmente, é verificado o desempenho de uma aplicação de controle de posição, utilizando estes protocolos na malha de controle, através do tempo de acomodação do sistema. Conclusões mostram que a rede Profibus DPV0 é a mais rápida quando possui menos dispositivos, porém o Profinet RT consegue manter baixos valores de tempo de ciclo mesmo com grande quantidade de dispositivos e possui maior determinismo na topologia em barramento. No que diz respeito ao controle de posição estudado, as tecnologias apresentam desempenho similar para tempo de acomodação do sistema, porém o Profinet IRT foi o mais determinístico.; This work proposes a performance analysis of industrial communication networks in applications of electric AC motor drives. It compares the performance of Profibus DP technology in relation to Profinet. Performance is verified from technical specifications of both protocols and practical experiments for data collection and analysis of the following performance indicators: cycle time...

Desenvolvimento de uma metodologia baseada em redes neurais artificiais para a identificação de anomalias em redes de comunicação Profinet; Development of a methodology based on artificial neural networks to identify abnormalities in Profinet communication networks

Turcato, Afonso Celso
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/06/2015 PT
Relevância na Pesquisa
66.19%
Este trabalho propôs o desenvolvimento e a avaliação de uma metodologia com o propósito de identificar anomalias em redes de comunicação Profinet, muito utilizadas na automação de plantas industriais. A metodologia desenvolvida está fundamentada na análise das características de comunicação do protocolo Profinet e na identificação e classificação de padrões, sendo esta, uma das principais aplicações do uso de Redes Neurais Artificiais (RNA). As anomalias são identificadas por meio da análise do tráfego de rede Profinet em sua fase de operação. Tais anomalias podem ser desde defeitos comuns apresentados pelos equipamentos da rede e/ou tentativas de ataques a esta, que por sua vez, podem gerar instabilidade e mau funcionamento da unidade industrial que fazem parte. Para o desenvolvimento deste trabalho foram apresentados: o detalhamento do protocolo Profinet, os mecanismos de segurança mais utilizados atualmente, os tipos de sistemas de detecção de anomalias existentes e os principais tipos de ataques em redes de comunicação conhecidos na literatura. Alguns ensaios para a validação da metodologia foram realizados, utilizando-se uma infraestrutura de rede instalada em laboratório. Ensaios com diferentes tipos de equipamentos interligados em rede foram realizados e os resultados apresentados. Como resultado final...

A genetic algorithm for solving the first price sealed bid auction in communication networks

Portilla Figueras, José Antonio; Salcedo Sanz, Sancho; García Díaz, Pilar; Hackbarth Planeta, Klaus Dietrich
Fonte: World Scientific and Engineering Academy and Society (WSEAS) Publicador: World Scientific and Engineering Academy and Society (WSEAS)
Tipo: info:eu-repo/semantics/conferenceObject; publishedVersion
ENG
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This paper shows the first result obtained in the application of economic mechanisms for the efficient assignment of resources in communication networks. The final objective is to determine which Service Provider will carry their traffic over the network of a Network Provider, which will be the most profitable route and which price the ISPs will pay for it to the Network provider. As the price is a key driver a good approach to select the ISP may be an auction mechanism. The implementation of these kind of auction mechanisms becomes a NP complete problem which is solved in this paper using novel metaheuristics, specifically a genetic algorithm.

Distributed beamforming in man portable communication networks

Chan, Chun Man.
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xx, 95 p. : col. ill. ;
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The advancement in communication and networking technologies lead to the emergence of network centric systems adopted by military forces. Many military forces around the world are equipping their ground soldiers with "man portable" or "mobile" wireless communication devices to form a local communication network as part of the overarching communication network for information warfare. In a non-line of sight environment, the devices' communication range to the base station degrades significantly. The research objective is to examine collaborative beamforming man portable wireless communication networks in a non-ideal propagation operation environment such as in a terrain with foliage. Using distributed beamforming techniques with wireless radios, the communication range can be increased to overcome foliage attenuation and other losses. Seasonal foliage effects on the wireless network were considered in the study. Wireless beamforming strategies were devised and an analysis of system performance and tradeoffs was conducted. System synchronization of the wireless collaborative communication network is a major challenge due to the lack of fixed infrastructure and the dynamic topology of the network. Two network synchronization schemes: mutual synchronization and master-slave synchronization were investigated. Finally...

Online networks of the Italian and German extreme right

CAIANI, Manuela; WAGEMANN, Claudius
Fonte: Instituto Universitário Europeu Publicador: Instituto Universitário Europeu
Tipo: Artigo de Revista Científica
EN
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This article applies instruments of social network analysis to a study of communication networks within the Italian and German extremist right. Web links between organizational websites are used as a proxy. Indeed, extremist groups increasingly use and abuse the Internet for their propaganda and their recruitment, and also for their internal communication. The analysis includes both political parties and non-party organizations, even violent groups. In a macro-, micro-, and meso-analysis, the various specificities of the two national political sectors are demonstrated and linked to the offline reality. The Italian network appears to be very fragmented, highly diversified, and difficult to be coordinated ('policephalous network'), whereas the German network is denser and much more concentrated on a few central actors ('star structure'). These differences are mainly due to political opportunity structures in the two countries. Additionally, whereas the Italian network structure allows for the construction of a typology of sub-groups of organizations, the German communicative structure seems to be more erratic and less coordinated. The article also highlights the function of websites which are not related to any specific group. Indeed...

Attack Vulnerability of Complex Communication Networks

Xia, Yongxiang; Hill, David
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
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The Internet has been studied as a typical example of real-world complex networks. In this brief, we study the traffic performance of the Internet when it encounters a random or intentional attack. Different from previous approaches, the congestion contro

Data Gathering in Networks of Bacteria Colonies: Collective Sensing and Relaying Using Molecular Communication

Einolghozati, Arash; Sardari, Mohsen; Beirami, Ahmad; Fekri, Faramarz
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/05/2012
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The prospect of new biological and industrial applications that require communication in micro-scale, encourages research on the design of bio-compatible communication networks using networking primitives already available in nature. One of the most promising candidates for constructing such networks is to adapt and engineer specific types of bacteria that are capable of sensing, actuation, and above all, communication with each other. In this paper, we describe a new architecture for networks of bacteria to form a data collecting network, as in traditional sensor networks. The key to this architecture is the fact that the node in the network itself is a bacterial colony; as an individual bacterium (biological agent) is a tiny unreliable element with limited capabilities. We describe such a network under two different scenarios. We study the data gathering (sensing and multihop communication) scenario as in sensor networks followed by the consensus problem in a multi-node network. We will explain as to how the bacteria in the colony collectively orchestrate their actions as a node to perform sensing and relaying tasks that would not be possible (at least reliably) by an individual bacterium. Each single bacterium in the colony forms a belief by sensing external parameter (e.g....

Max-Flow Min-Cut Theorems for Multi-User Communication Networks

Riis, Soren; Gadouleau, Maximilien
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.22%
The paper presents four distinct new ideas and results for communication networks: 1) We show that relay-networks (i.e. communication networks where different nodes use the same coding functions) can be used to model dynamic networks. 2) We introduce {\em the term model}, which is a simple, graph-free symbolic approach to communication networks. 3) We state and prove variants of a theorem concerning the dispersion of information in single-receiver communications. 4) We show that the solvability of an abstract multi-user communication problem is equivalent to the solvability of a single-target communication in a suitable relay network. In the paper, we develop a number of technical ramifications of these ideas and results. One technical result is a max-flow min-cut theorem for the R\'enyi entropy with order less than one, given that the sources are equiprobably distributed; conversely, we show that the max-flow min-cut theorem fails for the R\'enyi entropy with order greater than one. We leave the status of the theorem with regards to the ordinary Shannon Entropy measure (R\'enyi entropy of order one and the limit case between validity or failure of the theorem) as an open question. In non-dynamic static communication networks with a single receiver...

Estimating inter-event time distributions from finite observation periods in communication networks

Kivelä, Mikko; Porter, Mason A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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A diverse variety of processes --- including recurrent disease episodes, neuron firing, and communication patterns among humans --- can be described using inter-event time (IET) distributions. Many such processes are ongoing, although event sequences are only available during a finite observation window. Because the observation time window is more likely to begin or end during long IETs than during short ones, the analysis of such data is susceptible to a bias induced by the finite observation period. In this paper, we illustrate how this length bias is born and how it can be corrected without assuming any particular shape for the IET distribution. To do this, we model event sequences using stationary renewal processes, and we formulate simple heuristics for determining the severity of the bias. To illustrate our results, we focus on the example of empirical communication networks, which are temporal networks that are constructed from communication events. The IET distributions of such systems guide efforts to build models of human behavior, and the variance of IETs is very important for estimating the spreading rate of information in networks of temporal interactions. We analyze several well-known data sets from the literature, and we find that the resulting bias can lead to systematic underestimates of the variance in the IET distributions and that correcting for the bias can lead to qualitatively different results for the tails of the IET distributions.; Comment: 11 pages...

Coordinated Spatial Pattern Formation in Biomolecular Communication Networks

Hori, Yutaka; Miyazako, Hiroki; Kumagai, Soichiro; Hara, Shinji
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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This paper proposes a control theoretic framework to model and analyze the self-organized pattern formation of molecular concentrations in biomolecular communication networks, emerging applications in synthetic biology. In biomolecular communication networks, bio-nanomachines, or biological cells, communicate with each other using a cell-to-cell communication mechanism mediated by a diffusible signaling molecule, thereby the dynamics of molecular concentrations are approximately modeled as a reaction-diffusion system with a single diffuser. We first introduce a feedback model representation of the reaction-diffusion system and provide a systematic local stability/instability analysis tool using the root locus of the feedback system. The instability analysis then allows us to analytically derive the conditions for the self-organized spatial pattern formation, or Turing pattern formation, of the bio-nanomachines. We propose a novel synthetic biocircuit motif called activator-repressor-diffuser system and show that it is one of the minimum biomolecular circuits that admit self-organized patterns over cell population.; Comment: 26 pages, 7 figures, 3 movies

Scaling of critical connectivity of mobile ad hoc communication networks

Wang, Li; Zhu, Chen-Ping; Gu, Zhi-Ming; Xiong, Shi-Jie; He, Da-Ren; Wang, Bing-Hong
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/06/2008
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In this paper, critical global connectivity of mobile ad hoc communication networks (MAHCN) is investigated. We model the two-dimensional plane on which nodes move randomly with a triangular lattice. Demanding the best communication of the network, we account the global connectivity $\eta$ as a function of occupancy $\sigma$ of sites in the lattice by mobile nodes. Critical phenomena of the connectivity for different transmission ranges $r$ are revealed by numerical simulations, and these results fit well to the analysis based on the assumption of homogeneous mixing . Scaling behavior of the connectivity is found as $\eta \sim f(R^{\beta}\sigma)$, where $R=(r-r_{0})/r_{0}$, $r_{0}$ is the length unit of the triangular lattice and $\beta$ is the scaling index in the universal function $f(x)$. The model serves as a sort of site percolation on dynamic complex networks relative to geometric distance. Moreover, near each critical $\sigma_c(r)$ corresponding to certain transmission range $r$, there exists a cut-off degree $k_c$ below which the clustering coefficient of such self-organized networks keeps a constant while the averaged nearest neighbor degree exhibits a unique linear variation with the degree k, which may be useful to the designation of real MAHCN.; Comment: 6 pages...

Existence of outsiders as a characteristic of online communication networks

Takaguchi, Taro; Maehara, Takanori; Toyoda, Masashi; Kawarabayashi, Ken-ichi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/11/2014
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Online social networking services (SNSs) involve communication activities between large number of individuals over the public Internet and their crawled records are often regarded as proxies of real (i.e., offline) interaction structure. However, structure observed in these records might differ from real counterparts because individuals may behave differently online and non-human accounts may even participate. To understand the difference between online and real social networks, we investigate an empirical communication network between users on Twitter, which is perhaps one of the largest SNSs. We define a network of user pairs that send reciprocal messages. Based on the mixing pattern observed in this network, we argue that this network differs from conventional understandings in the sense that there is a small number of distinctive users that we call outsiders. Outsiders do not belong to any user groups but they are connected with different groups, while not being well connected with each other. We identify outsiders by maximizing the degree assortativity coefficient of the network via node removal, thereby confirming that local structural properties of outsiders identified are consistent with our hypothesis. Our findings suggest that the existence of outsiders should be considered when using Twitter communication networks for social network analysis.; Comment: 40 pages...

Continuum percolation of wireless ad hoc communication networks

Glauche, Ingmar; Krause, Wolfram; Sollacher, Rudolf; Greiner, Martin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/04/2003
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Wireless multi-hop ad hoc communication networks represent an infrastructure-less and self-organized generalization of todays wireless cellular networks. Connectivity within such a network is an important issue. Continuum percolation and technology-driven mutations thereof allow to address this issue in the static limit and to construct a simple distributed protocol, guaranteeing strong connectivity almost surely and independently of various typical uncorrelated and correlated random spatial patterns of participating ad hoc nodes.; Comment: 30 pages, to be published in Physica A

Structural Analysis of Viral Spreading Processes in Social and Communication Networks Using Egonets

Preciado, Victor M.; Draief, Moez; Jadbabaie, Ali
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/09/2012
Relevância na Pesquisa
55.98%
We study how the behavior of viral spreading processes is influenced by local structural properties of the network over which they propagate. For a wide variety of spreading processes, the largest eigenvalue of the adjacency matrix of the network plays a key role on their global dynamical behavior. For many real-world large-scale networks, it is unfeasible to exactly retrieve the complete network structure to compute its largest eigenvalue. Instead, one usually have access to myopic, egocentric views of the network structure, also called egonets. In this paper, we propose a mathematical framework, based on algebraic graph theory and convex optimization, to study how local structural properties of the network constrain the interval of possible values in which the largest eigenvalue must lie. Based on this framework, we present a computationally efficient approach to find this interval from a collection of egonets. Our numerical simulations show that, for several social and communication networks, local structural properties of the network strongly constrain the location of the largest eigenvalue and the resulting spreading dynamics. From a practical point of view, our results can be used to dictate immunization strategies to tame the spreading of a virus...

Molecular communication networks with general molecular circuit receivers

Chou, Chun Tung
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/12/2013
Relevância na Pesquisa
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In a molecular communication network, transmitters may encode information in concentration or frequency of signalling molecules. When the signalling molecules reach the receivers, they react, via a set of chemical reactions or a molecular circuit, to produce output molecules. The counts of output molecules over time is the output signal of the receiver. The aim of this paper is to investigate the impact of different reaction types on the information transmission capacity of molecular communication networks. We realise this aim by using a general molecular circuit model. We derive general expressions of mean receiver output, and signal and noise spectra. We use these expressions to investigate the information transmission capacities of a number of molecular circuits.

Extended master equation models for molecular communication networks

Chou, Chun Tung
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We consider molecular communication networks consisting of transmitters and receivers distributed in a fluidic medium. In such networks, a transmitter sends one or more signalling molecules, which are diffused over the medium, to the receiver to realise the communication. In order to be able to engineer synthetic molecular communication networks, mathematical models for these networks are required. This paper proposes a new stochastic model for molecular communication networks called reaction-diffusion master equation with exogenous input (RDMEX). The key idea behind RDMEX is to model the transmitters as time series of signalling molecule counts, while diffusion in the medium and chemical reactions at the receivers are modelled as Markov processes using master equation. An advantage of RDMEX is that it can readily be used to model molecular communication networks with multiple transmitters and receivers. For the case where the reaction kinetics at the receivers is linear, we show how RDMEX can be used to determine the mean and covariance of the receiver output signals, and derive closed-form expressions for the mean receiver output signal of the RDMEX model. These closed-form expressions reveal that the output signal of a receiver can be affected by the presence of other receivers. Numerical examples are provided to demonstrate the properties of the model.; Comment: IEEE Transactions on Nanobioscience...

Distributive routing & congestion control in wireless multihop ad hoc communication networks

Glauche, Ingmar; Krause, Wolfram; Sollacher, Rudolf; Greiner, Martin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/04/2004
Relevância na Pesquisa
55.94%
Due to their inherent complexity, engineered wireless multihop ad hoc communication networks represent a technological challenge. Having no mastering infrastructure the nodes have to selforganize themselves in such a way that for example network connectivity, good data traffic performance and robustness are guaranteed. In this contribution the focus is on routing & congestion control. First, random data traffic along shortest path routes is studied by simulations as well as theoretical modeling. Measures of congestion like end-to-end time delay and relaxation times are given. A scaling law of the average time delay with respect to network size is revealed and found to depend on the underlying network topology. In the second step, a distributive routing & congestion control is proposed. Each node locally propagates its routing cost estimates and information about its congestion state to its neighbors, which then update their respective cost estimates. This allows for a flexible adaptation of end-to-end routes to the overall congestion state of the network. Compared to shortest-path routing, the critical network load is significantly increased.; Comment: 32 pages, to be published in Physica A

On a new concept of community: social networks, personal communities and collective intelligence

Costa,Rogério da
Fonte: Interface - Comunicação, Saúde, Educação Publicador: Interface - Comunicação, Saúde, Educação
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2006 EN
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This text essentially deals with the transmutation of the concept of "community" into "social networks". This change is due largely to the boom of virtual communities in cyberspace, a fact that has generated a number of studies not only on this new way of weaving a society, but also on the dynamic structure of communication networks. At the core of this transformation, concepts such as social capital, trust and partial sympathy are called upon, to enable us to think about the new forms of association that regulate human activity in our time.