Página 20 dos resultados de 2591 itens digitais encontrados em 0.032 segundos

## Comunicação entre MANETs com protocolo de roteamento baseado na fonte; Communication between MANETs with source based routing protocol

Dau, Maurício Leite
Tipo: Trabalho de Conclusão de Curso Formato: application/pdf
Português
Relevância na Pesquisa
35.68%
O mercado de dispositivos móveis apresenta uma grande heterogeneidade, sendo composto por smartphones, tablets, notebooks, netbooks, sensores e outros dispositivos com diferentes interfaces de comunicação sem fio. Este trabalho propõe uma alteração na estrutura do protocolo de roteamento Dynamic Source Routing (DSR) para que seja possível que esses dispositivos formem uma rede de comunicação. Essa alteração compreende a troca do modo de endereçamento IP para o endereçamento UUID. Essa alteração possibilitará a abstração dos meios de transmissão de dados, permitindo que diferentes dispositivos forme uma rede ad hoc. A comunicação entre dispositivos com diferentes tecnologias de transmissão de dados ocorre por meio de um dispositivo intermediário que possui ambas tecnologias de transmissão. A fim de analisar o comportamento do protocolo implementado são realizadas transmissões de dados em uma rede Wi-Fi operando em conjunto a uma rede emulada, que utiliza a estrutura FakeInterface. Essa rede emulada foi construída para possibilitar a execução de testes durante o desenvolvimento do trabalho e para confirmar o funcionamento do protocolo com múltiplas interfaces de rede.; The mobile market has a great heterogeneity...

## Mobile application as a tool for urban traffic data collection and generation to advanced traveler information systems using Wi-Fi networks available in urban centers

Dezani, Henrique; Damiani, Furio; Marranghello, Norian; Viudes, Ulysses; Parra, Ícaro Augusto
Tipo: Conferência ou Objeto de Conferência Formato: 288-292
Português
Relevância na Pesquisa
35.68%
This paper presents an Advanced Traveler Information System (ATIS) developed on Android platform, which is open source and free. The developed application has as its main objective the free use of a Vehicle-to- Infrastructure (V2I) communication through the wireless network access points available in urban centers. In addition to providing the necessary information for an Intelligent Transportation System (ITS) to a central server, the application also receives the traffic data close to the vehicle. Once obtained this traffic information, the application displays them to the driver in a clear and efficient way, allowing the user to make decisions about his route in real time. The application was tested in a real environment and the results are presented in the article. In conclusion we present the benefits of this application. © 2012 IEEE.

## Uma arquitetura para negociação de redes virtualizadas na internet do futuro baseada em classes de QoS; A Framework for negotiation of virtualized networks in the future internet based on QoS classes

Rafael Lopes Gomes
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
35.68%

## An unbiased Bayesian approach to functional connectomics implicates social-communication networks in autism

Venkataraman, Archana; Duncan, James S.; Yang, Daniel Y.-J.; Pelphrey, Kevin A.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.68%
Resting-state functional magnetic resonance imaging (rsfMRI) studies reveal a complex pattern of hyper- and hypo-connectivity in children with autism spectrum disorder (ASD). Whereas rsfMRI findings tend to implicate the default mode network and subcortical areas in ASD, task fMRI and behavioral experiments point to social dysfunction as a unifying impairment of the disorder. Here, we leverage a novel Bayesian framework for whole-brain functional connectomics that aggregates population differences in connectivity to localize a subset of foci that are most affected by ASD. Our approach is entirely data-driven and does not impose spatial constraints on the region foci or dictate the trajectory of altered functional pathways. We apply our method to data from the openly shared Autism Brain Imaging Data Exchange (ABIDE) and pinpoint two intrinsic functional networks that distinguish ASD patients from typically developing controls. One network involves foci in the right temporal pole, left posterior cingulate cortex, left supramarginal gyrus, and left middle temporal gyrus. Automated decoding of this network by the Neurosynth meta-analytic database suggests high-level concepts of “language” and “comprehension” as the likely functional correlates. The second network consists of the left banks of the superior temporal sulcus...

## Global Data Computation in a Dedicated Chordal Ring

Wang, Xianbing; Teo, Yong Meng
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 293646 bytes; application/pdf
Português
Relevância na Pesquisa
35.68%
Existing Global Data Computation (GDC) protocols for asynchronous systems are designed for fully connected networks. In this paper, we discuss GDC in a dedicated asynchronous chordal ring, a type of un-fully connected networks. The virtual links approach, which constructs t+1 (t

## Um estudo do aumento da capacidade de sistemas 3g WCDMA usando técnicas 3.5G de expansão do enlace reverso

Rodrigues, Eduardo Jorge Brito
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Elétrica; Automação e Sistemas; Engenharia de Computação; Telecomunicações Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Elétrica; Automação e Sistemas; Engenharia de Computação; Telecomunicações
Tipo: Dissertação Formato: application/pdf
Português
Relevância na Pesquisa
35.68%

## Efficient Resource Allocation in Multiflow Wireless Networks

Middleton, Gareth B.
Português
Relevância na Pesquisa
35.68%
We consider the problem of allocating resources in large wireless net- works in which multiple information flows must be accommodated. In particular, we seek a method for selecting schedules, routes, and power allocations for networks with terminals capable of user-cooperation at the signal level. To that end, we adopt a general information-theoretic communications model, in which the datarate of a wireless link is purely a function of transmission power, pathloss and interference. We begin by studying the case of resource allocation when only point-to-point links are available. The problem is NP-hard in this case, requiring an exponentially-complex exhaustive search to guarantee an optimal solution. This is prohibitively difficult for anything but the smallest of networks, leading us to approximate the problem using a decomposition approach. We construct the solution iteratively, developing polynomial-time algorithms to optimally allocate resources on a per-frame basis. We then update the network graph to reflect the resources consumed by the allocated frame. To manage this decomposition, we present a novel tool, termed the Network-Flow Interaction Chart. By representing the network in both space and time, our techniques trade off interference with throughput for each frame...

## Rail Electronic Data Interchange in a Border Crossing Point in South East Europe; An Assessment of Options

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Tipo: Report; Economic & Sector Work; Economic & Sector Work :: Other Infrastructure Study
Português
Relevância na Pesquisa
35.68%
Within the European Union (EU) rail transport is currently the least integrated transport mode. This leads to delays, extra costs, and insufficient use of rail freight, especially for time-sensitive cargo. This also represents a missed opportunity in terms of moving towards a greener transport modal split within the EU. Rail freight, for which international activity represents 50 percent of total activities, will not be able to develop fully if border crossing rail operations do not deliver a better service for shippers and freight operators who require seamless trans-national transport as is possible by road, air and sea. Observing that the modal split of rail in the EU is stagnating at around 16 percent after years of decline, the European Commission proposed a regulation on a European rail network for competitive freight to be based on a number of rail freight corridors which entered into force on November 9, 2010. Regulation No 913/2010 makes it mandatory to create a European rail network for competitive freight based on international freight corridors...

## Event-driven simulation scheme for spiking neural networks using lookup tables to characterize neuronal dynamics

Ros, Eduardo; Carrillo, Richard; Ortigosa, Eva M.; Barbour, Boris; Ag??s, Rodrigo
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.68%
Nearly all neuronal information processing and interneuronal communication in the brain involves action potentials, or spikes, which drive the short-term synaptic dynamics of neurons, but also their long-term dynamics, via synaptic plasticity. In many brain structures, action potential activity is considered to be sparse. This sparseness of activity has been exploited to reduce the computational cost of large-scale network simulations, through the development of event-driven simulation schemes. However, existing event-driven simulations schemes use extremely simplified neuronal models. Here, we implement and evaluate critically an event-driven algorithm (ED-LUT) that uses precalculated look-up tables to characterize synaptic and neuronal dynamics. This approach enables the use of more complex (and realistic) neuronal models or data in representing the neurons, while retaining the advantage of high-speed simulation. We demonstrate the method's application for neurons containing exponential synaptic conductances, thereby implementing shunting inhibition, a phenomenon that is critical to cellular computation. We also introduce an improved two-stage event-queue algorithm, which allows the simulations to scale efficiently to highly connected networks with arbitrary propagation delays. Finally...

## Telecommunications services for multimedia data exchange support

Gibbons, Paul C.
Tipo: Tese de Doutorado Formato: 93 p.
Português
Relevância na Pesquisa
35.68%
Approved for public release; distribution unlimited.; Multimedia holds the promise of increased knowledge, creativity and productivity for virtually any application that can be imagined. The ability to present information in both an informative and entertaining way can lead to an enhanced quality of life for an increasingly larger segment of the world's population. However, information generated in a multimedia format presents special challenges for communication networks. This thesis is an attempt to understand the impact of multimedia computing as it relates to the transmission requirements to support large volume data exchange in a distributed computing environment. With a good understanding of these requirements one will be better equipped to evaluate the various physical transmission media and communication services available to meet the high transmission demands imposed by multimedia data exchange.; http://archive.org/details/telecommunicatio00gibb; Major, United States Marine Corps

## Coordination and Interference in 802.11 Networks: Inference, Analysis and Mitigation

Magistretti, Eugenio
Tipo: Thesis; Text Formato: application/pdf
Português
Relevância na Pesquisa
35.68%
In the last decade, 802.11 wireless devices data-rates have increased by three orders of magnitude, while communications experiencing low throughput are still largely present. Such throughput loss is a fundamental problem of wireless networking that is difficult to diagnose and amend. My research addresses two key causes of throughput loss: MAC layer protocol overhead and destructive link interference. First, I design WiFi-Nano reducing the channel access overhead by an order of magnitude leveraging an innovative speculative technique to transmit preambles. This new concept is based on simultaneous preamble transmission and detection via a self-interference cancellation design, and paves the way to the realization of the collision detection paradigm in wireless networks. Next, I propose 802.11ec (Encoded Control), the first 802.11-based protocol that eliminates the overhead of control packets. Instead, 802.11ec coordinates node transmissions via a set of predefined pseudo-noise codewords, resulting in the dramatic increase of throughput and communication robustness. Finally, I design MIDAS, a model-driven network management tool that alleviates low throughput wireless links identifying key corrective actions. MIDAS' key contribution is to reveal the fundamental role of node transmission coordination in characterizing destructive interference. I implement WiFi-Nano...

## Using complex networks to quantify consistency in the use of words

Amancio, D. R.; Oliveira Junior, Osvaldo Novais de; Costa, Luciano da Fontoura
Fonte: IOP PUBLISHING LTD; BRISTOL Publicador: IOP PUBLISHING LTD; BRISTOL
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.68%
In this paper we have quantified the consistency of word usage in written texts represented by complex networks, where words were taken as nodes, by measuring the degree of preservation of the node neighborhood. Words were considered highly consistent if the authors used them with the same neighborhood. When ranked according to the consistency of use, the words obeyed a log-normal distribution, in contrast to Zipf's law that applies to the frequency of use. Consistency correlated positively with the familiarity and frequency of use, and negatively with ambiguity and age of acquisition. An inspection of some highly consistent words confirmed that they are used in very limited semantic contexts. A comparison of consistency indices for eight authors indicated that these indices may be employed for author recognition. Indeed, as expected, authors of novels could be distinguished from those who wrote scientific texts. Our analysis demonstrated the suitability of the consistency indices, which can now be applied in other tasks, such as emotion recognition.; FAPESP; FAPESP; CNPq (Brazil); CNPq (Brazil)

## Desenvolvimento de um sistema de gestão de iluminação pública através de redes de sensores e atuadores sem fio = : Development of a street lighting management system based on wireless sensors and actuators networks; Development of a street lighting management system based on wireless sensors and actuators networks

Felipe Lorenzo Della Lucia
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Relevância na Pesquisa
35.68%

## Analise comparativa entre protocolos de camada MAC para redes ad-hoc sem fio; Comparative analysis between MAC-level protocols for ad-hoc wireless networks

Carlos Eduardo Seo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Relevância na Pesquisa
35.68%

## An integrated vision for environmental monitoring and the role of acoustic communication networks

Jesus, S. M.
Tipo: Aula
Relevância na Pesquisa
35.68%
Current pace of ocean resources exploitation have set the alarm for tighter environmental monitoring. Recent European legislation requires very accurate measurements of reference values for all types of ocean pollution, including acoustic noise. For near shore or offshore construction, platforms or infrastructures extensive measurements should be carried out before during and after exploitation activities have taken place. Environmental monitoring requires the deployment of sensors with specific requirements in terms of location, spatial coverage and data access rates. In some cases, monitoring includes accessing real time information regarding detecting intruders, their localization and, eventually, their interception. A key component of any environmental monitoring network is a high performance wireless communication network capable or interconnecting both fixed and moving sensing platforms for retrieving data and transmitting commands. The Underwater Acoustic Network initiative has recently demonstrated with an at sea experiment (Trondheim, May 2011) a full functioning 3 fixed node and 2 mobile node network for collecting data and performing surveillance tasks. A summary of the results are presented and issues discussed.; FCT; FP7

## NFCU: A New Friendship-based Routing with Buffer Management in Opportunistic Networks

Qin, Yang; Li, Li; Zhang, Xiaohan; Zhong, Xiaoxiong
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.68%
Routing in opportunistic networks is a very important and challenging problem because opportunistic network utilizes the contact opportunities of mobile nodes to achieve data communication.Social-based routing uses behavior of human beings which can form a community with the same interests to deliver the message.In this paper,we analyze the drawbacks of the original friendship-based algorithm, which defined social pressure metric to determine nodes'friendship community, but the metric couldn't distinguish the distribution characterization of the connection length which has an important impact on the selection of links with better quality. Further, the existing friendship-based routing doesn't consider the buffer management, which is vital for routing design in opportunistic networks. We propose a New Friendship-based routing with buffer management based on Copy Utility, named NFCU. NFCU algorithm, which not only considers the contact periods in constructing social pressure metric to solve the drawbacks of the original friendship-based routing scheme efficiently, but also considers the buffer management, that can efficiently determine which copy of the message should be deleted timely according to the copy utility function. Our proposed strategy can reduce the network overhead significantly...

## Distributed Computation of Sparse Cuts

Sarma, Atish Das; Molla, Anisur Rahaman; Pandurangan, Gopal
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.68%
Finding sparse cuts is an important tool in analyzing large-scale distributed networks such as the Internet and Peer-to-Peer networks, as well as large-scale graphs such as the web graph, online social communities, and VLSI circuits. In distributed communication networks, they are useful for topology maintenance and for designing better search and routing algorithms. In this paper, we focus on developing fast distributed algorithms for computing sparse cuts in networks. Given an undirected $n$-node network $G$ with conductance $\phi$, the goal is to find a cut set whose conductance is close to $\phi$. We present two distributed algorithms that find a cut set with sparsity $\tilde O(\sqrt{\phi})$ ($\tilde{O}$ hides $\polylog{n}$ factors). Both our algorithms work in the CONGEST distributed computing model and output a cut of conductance at most $\tilde O(\sqrt{\phi})$ with high probability, in $\tilde O(\frac{1}{b}(\frac{1}{\phi} + n))$ rounds, where $b$ is balance of the cut of given conductance. In particular, to find a sparse cut of constant balance, our algorithms take $\tilde O(\frac{1}{\phi} + n)$ rounds. Our algorithms can also be used to output a {\em local} cluster, i.e., a subset of vertices near a given source node, and whose conductance is within a quadratic factor of the best possible cluster around the specified node. Both our distributed algorithm can work without knowledge of the optimal $\phi$ value and hence can be used to find approximate conductance values both globally and with respect to a given source node. We also give a lower bound on the time needed for any distributed algorithm to compute any non-trivial sparse cut --- any distributed approximation algorithm (for any non-trivial approximation ratio) for computing sparsest cut will take $\tilde \Omega(\sqrt{n} + D)$ rounds...

## Controlling synchronization in large laser networks using number theory

Nixon, Micha; Fridman, Moti; Ronen, Eitan; Friesem, Asher A.; Davidson, Nir; Kanter, Ido
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.68%
Synchronization in networks with delayed coupling are ubiquitous in nature and play a key role in almost all fields of science including physics, biology, ecology, climatology and sociology. In general, the published works on network synchronization are based on data analysis and simulations, with little experimental verification. Here we develop and experimentally demonstrate various multi-cluster phase synchronization scenarios within coupled laser networks. Synchronization is controlled by the network connectivity in accordance to number theory, whereby the number of synchronized clusters equals the greatest common divisor of network loops. This dependence enables remote switching mechanisms to control the optical phase coherence among distant lasers by local network connectivity adjustments. Our results serve as a benchmark for a broad range of coupled oscillators in science and technology, and offer feasible routes to achieve multi-user secure protocols in communication networks and parallel distribution of versatile complex combinatorial tasks in optical computers.; Comment: 13 pages, 4 figure and supplementary information

## Statistical Mechanics of Linear Compression Codes in Network Communication

Murayama, Tatsuto
Tipo: Artigo de Revista Científica