Página 9 dos resultados de 2591 itens digitais encontrados em 0.033 segundos

Rede serial para comunicação de dados e controle em sistema embarcado: estudo de implementação da ISO 11783; Serial control and communication data network on embedded systems: study of implementation of ISO 11783

Sakai, Rodrigo Martins Romeira
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 18/04/2008 Português
Relevância na Pesquisa
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As redes digitais demonstraram ser uma solução eficaz em automação. A conexão de diferentes módulos de diferentes fabricantes em um único barramento para a troca de dados e controle é um desafio para a indústria brasileira de máquinas agrícolas, apesar desta tecnologia estar consolidada em automóveis, aeronaves e em chão de fábrica. As vantagens obtidas com redes digitais são evidentes, porém necessitam de implementação de protocolos de redes. Na área agrícola, a norma internacional ISO 11783 apresenta forte potencial para tornar-se referência de padrão para a troca de dados entre módulos em tratores e implementos agrícolas. Esta norma, também conhecida como ISOBUS, está no estágio avançado de desenvolvimento. Contém quatorze documentos e o seu desenvolvimento está apoiado por grupos denominados "Força Tarefa", na Europa, nos EUA e recentemente no Brasil. Implementações deste padrão já estão sendo apresentadas no mercado internacional, em feiras e demonstrações de aplicação desta tecnologia. O Brasil deve investir e dominar a tecnologia, em busca de compatibilidade internacional tanto no ponto de vista tecnológico como comercial. Neste contexto, este trabalho encoraja o desenvolvimento nacional em aplicações com a norma ISOBUS...

A Network Coding Based Routing Protocol for Underwater Sensor Networks

Wu, Huayang; Chen, Min; Guan, Xin
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 10/04/2012 Português
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Due to the particularities of the underwater environment, some negative factors will seriously interfere with data transmission rates, reliability of data communication, communication range, and network throughput and energy consumption of underwater sensor networks (UWSNs). Thus, full consideration of node energy savings, while maintaining a quick, correct and effective data transmission, extending the network life cycle are essential when routing protocols for underwater sensor networks are studied. In this paper, we have proposed a novel routing algorithm for UWSNs. To increase energy consumption efficiency and extend network lifetime, we propose a time-slot based routing algorithm (TSR).We designed a probability balanced mechanism and applied it to TSR. The theory of network coding is introduced to TSBR to meet the requirement of further reducing node energy consumption and extending network lifetime. Hence, time-slot based balanced network coding (TSBNC) comes into being. We evaluated the proposed time-slot based balancing routing algorithm and compared it with other classical underwater routing protocols. The simulation results show that the proposed protocol can reduce the probability of node conflicts, shorten the process of routing construction...

Cross-layer design and optimization of short range wireless networks

Wang, Tianqi (1983 - ); Heinzelman, Wendi ; Seyedi, Alireza ; Holland, Matthew (1984 - ); Tavli, Bulent
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xvi, 235 leaves; Illustrations:ill. (some col.)
Português
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Thesis (Ph. D.)--University of Rochester. Dept. of Electrical and Computer Engineering, 2012.

"Chapter 3 of my dissertation was co-authored with Matthew Holland, Dr. Bulent Tavli, Dr. Wendi Heinzelman and Dr. Alireza Seyedi"--Foreword.; Short-range wireless networks, such as wireless sensor networks, have become an integral part of our modern lives and have been broadly applied in many fields such as industry, military and research to facilitate the gathering and distribution of information. Compared with traditional wireless networks, such as cellular networks, short-range wireless networks have the following unique characteristics. (i) Dense deployment: the network devices are often densely deployed to achieve better monitoring of the environment. (ii) Circuit power consumption: due to the short communication distances, the network devices communicate with each other using low transmit power that is comparable to the devices’ circuit power consumption. Thus, circuit power consumption is a major contributor to the energy drain of the network devices. (iii) Battery powered: the network devices are usually battery powered and may be deployed in remote areas. Thus, it is difficult or even impossible to replace the energy supplies of many of the network devices in a short-range wireless network. Therefore...

Collaborative information processing techniques for target tracking in wireless sensor networks.

Ma, Hui
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008 Português
Relevância na Pesquisa
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Target tracking is one of the typical applications of wireless sensor networks: a large number of spatially deployed sensor nodes collaboratively sense, process and estimate the target state (e.g., position, velocity and heading). This thesis aimed to develop the collaborative information processing techniques that jointly address information processing and networking for the distributive estimation of target state in the highly dynamic and resources constrained wireless sensor networks. Taking into account the interplay between information processing and networking, this thesis proposed a collaborative information processing framework. The framework integrates the information processing which is responsible for the representation, fusion and processing of data and information with networking which caters for the formation of network, the delivery of information and the management of wireless channels. Within the proposed collaborative information processing framework, this thesis developed a suite of target tracking algorithms on the basis of the recursive Bayesian estimation method. For tracking a single target in wireless sensor networks, this thesis developed the sequential extended Kalman filter (S-EKF), the sequential unscented Kalman filter (S-UKF) and the Particle filter (PF). A novel extended Kalman filter and Particle filter hybrid algorithm...

Design of Adaptive Overlays for Multi-scale Communication in Sensor Networks

PalChaudhuri, Santashil; Kumar, Rajnish; Baraniuk, Richard G.; Johnson, David B.; PalChaudhuri, Santashil; Kumar, Rajnish; Baraniuk, Richard G.; Johnson, David B.
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Conference paper
Português
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Conference Paper; In wireless sensor networks, energy and communication bandwidth are precious resources. Traditionally, layering has been used as a design principle for network stacks; hence routing protocols assume no knowledge of the application behavior in the sensor node. In resource-constrained sensor-nodes, there is simultaneously a need and an opportunity to optimize the protocol to match the application. In this paper, we design a network architecture that efficiently supports multi-scale communication and collaboration among sensors. The architecture complements the previously proposed Abstract Regions architecture for local communication and collaboration. We design a self-organizing hierarchical overlay that scales to a large number of sensors and enables multi-resolution collaboration. We design effective Network Programming Interfaces to simplify the development of applications on top of the architecture; these interfaces are efficiently implemented in the network layer. The overlay hierarchy can adapt to match the collaboration requirements of the application and data both temporally and spatially. We present an initial evaluation of our design under simulation to show that it leads to reduced communication overhead...

Cooperative Partial Detection for MIMO Relay Networks

Amiri, Kiarash
Fonte: Universidade Rice Publicador: Universidade Rice
Português
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Cooperative communication has recently re-emerged as a possible paradigm shift to realize the promises of the ever increasing wireless communication market; how- ever, there have been few, if any, studies to translate theoretical results into feasi- ble schemes with their particular practical challenges. The multiple-input multiple- output (MIMO) technique is another method that has been recently employed in different standards and protocols, often as an optional scenario, to further improve the reliability and data rate of different wireless communication applications. In this work, we look into possible methods and algorithms for combining these two tech- niques to take advantage of the benefits of both. In this thesis, we will consider methods that consider the limitations of practical solutions, which, to the best of our knowledge, are the first time to be considered in this context. We will present complexity reduction techniques for MIMO systems in cooperative systems. Furthermore, we will present architectures for flexible and configurable MIMO detectors. These architectures could support a range of data rates, modulation orders and numbers of antennas, and therefore, are crucial in the different nodes of cooperative systems. The breadth-first search employed in our realization presents a large opportunity to exploit the parallelism of the FPGA in order to achieve high data rates. Algorithmic modifications to address potential sequential bottlenecks in the traditional bread-first search-based SD are highlighted in the thesis. We will present a novel Cooperative Partial Detection (CPD) approach in MIMO relay channels...

Using Locational Data from Mobile Phones to Enhance the Science of Delivery

Haddad, Ryan; Kelly, Tim; Leinonen, Teemu; Saarinen, Vesa
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Economic & Sector Work :: Other Public Sector Study
Português
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The objective of this report is to examine the potential of locational data for the 'science of delivery' in the field of development. The 'science of delivery' is a term popularized by the World Bank President, Jim Yong Kim, and refers to using evidence-based experimentation to improve development outcomes (Walji, 2013). In this context, locational data is a new tool that is starting to be used in a variety of development fields including health, education, disaster risk management, traffic planning etc. this broad introduction to the topic in chapter one, the next chapter explores the technology behind locational data. Chapter three presents the methodology followed in this research and chapter four, which is the heart of this report, then presents a series of mini case studies of how it is actually being used in a representative sample of different development fields. This is the 'evidence-based experimentation' which can be harnessed to improve the 'science of delivery', and examples of both active and passive collection of locational data are presented. Finally...

Opportunistic computing in fully decentralized and mobile networks

BERGAMINI, LORENZO
Fonte: La Sapienza Universidade de Roma Publicador: La Sapienza Universidade de Roma
Tipo: Tese de Doutorado
Português
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The interplay of social networking platforms, information retrieval techniques and dynamic wireless communications has grown exponentially over the past few years. Together, these tools are shaping new forms of fully decentralized computation and applications. These opportunities are ampli ed by the relative simplicity to set up networks of small or tiny devices, such as wireless sensors and active or passive RFIDs, that allow to extract information from the environment, to process and to share it, expanding our data access and interaction capabilities and blurring the border between the digital and physical world. These new technologies coexist with traditional ones and entail a model of communication and computation that is decentralized and opportunistic in nature, in which new challenges arise and many standard assumptions do not hold. At the same time, more mature technologies, such as cellular telephony, have evolved to the point where we have small, portable, but relatively powerful devices, often endowed with sensing capabilities, that can run sophisticated applications and can exchange data in an ad-hoc fashion using wireless technologies such as Bluetooth. As a result, a number of potential applications arise, in which users interact across the digital and physical world...

Environmental-friendly underwater acoustic communication and networks

Jesus, S. M.
Fonte: NATO STO Centre for Maritime Research and Experimentation (CMRE) Publicador: NATO STO Centre for Maritime Research and Experimentation (CMRE)
Tipo: Aula
Publicado em //2012 Português
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Intense harvesting of ocean resources extended exploitation activities to previously unexplored open ocean areas, to greater ocean depths and to remote polar regions. Such activities include, but are not limited to, energy, geology and fisheries. In practice, not only the number of working platforms at sea has increased dramatically, but their structure is more complex with multi sites, interconnecting pipes, cables, remote sensors and mobile platforms. In many cases, each exploitation site represents a complex submerged infrastructure requiring timely maintenance, protection and monitoring. An underlying requirement for efficient protection and monitoring of such infrastructures is the existence of reliable communications which, for submerged and untethered platforms, can only be done acoustically. So, underwater acoustic communications became an enabler for many ocean activities. More, with the multiplication of agents in geographically limited areas point-to-point communications quickly evolved to the necessity of communication networks. The European Union has recently published a marine strategy directive aiming at defining the concept of "good environmental status". Among others, one of the descriptors directly addresses the amount of acoustic energy in the ocean. Acoustic energy sources combine along time and range to form what is normally termed as ocean soundscape (or ambient noise). As we know...

Effect of AWGN & Fading (Raleigh & Rician) channels on BER performance of a WiMAX communication System

Awon, Nuzhat Tasneem; Islam, Md. Ashraful; Rahman, Md. Mizanur; Islam, A. Z. M. Touhidul
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/11/2012 Português
Relevância na Pesquisa
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The emergence of WIMAX has attracted significant interests from all fields of wireless communications including students, researchers, system engineers and operators. The WIMAX can also be considered to be the main technology in the implementation of other networks like wireless sensor networks. Developing an understanding of the WIMAX system can be achieved by looking at the model of the WIMAX system. This paper discusses the model building of the WIMAX physical layer using computer MATLAB 7.5 versions. This model is a useful tool for BER (Bit error rate) performance evaluation for the real data communication by the WIMAX physical layer under different communication channels AWGN and fading channel (Rayleigh and Rician), different channel encoding rates and digital modulation schemes which is described in this paper. This paper investigates the effect of communication channels of IEEE 802.16 OFDM based WIMAX Physical Layer. The performance measures we presented in this paper are: the bit error rate (BER) versus the ratio of bit energy to noise power spectral density (Eb/No). The system parameters used in this paper are based on IEEE 802.16 standards. The simulation model built for this research work, demonstrates that AWGN channel has better performance than Rayleigh and Rician fading channels. Synthetic data is used to simulate this research work.; Comment: 7 pages...

Network Protection Codes: Providing Self-healing in Autonomic Networks Using Network Coding

Aly, Salah A.; Kamal, Ahmed E.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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Agile recovery from link failures in autonomic communication networks is essential to increase robustness, accessibility, and reliability of data transmission. However, this must be done with the least amount of protection resources, while using simple management plane functionality. Recently, network coding has been proposed as a solution to provide agile and cost efficient network self-healing against link failures, in a manner that does not require data rerouting, packet retransmission, or failure localization, hence leading to simple control and management planes. To achieve this, separate paths have to be provisioned to carry encoded packets, hence requiring either the addition of extra links, or reserving some of the resources for this purpose. In this paper we introduce autonomic self-healing strategies for autonomic networks in order to protect against link failures. The strategies are based on network coding and reduced capacity, which is a technique that we call network protection codes (NPC). In these strategies, an autonomic network is able to provide self-healing from various network failures affecting network operation. The techniques improve service and enhance reliability of autonomic communication. Network protection codes are extended to provide self-healing from multiple link failures in autonomic networks. We provide implementation aspects of the proposed strategies. We present bounds and network protection code constructions. Finally...

On the Entity Hardening Problem in Multi-layered Interdependent Networks

Banerjee, Joydeep; Das, Arun; Zhou, Chenyang; Mazumder, Anisha; Sen, Arunabha
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/12/2014 Português
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The power grid and the communication network are highly interdependent on each other for their well being. In recent times the research community has shown significant interest in modeling such interdependent networks and studying the impact of failures on these networks. Although a number of models have been proposed, many of them are simplistic in nature and fail to capture the complex interdependencies that exist between the entities of these networks. To overcome the limitations, recently an Implicative Interdependency Model that utilizes Boolean Logic, was proposed and a number of problems were studied. In this paper we study the entity hardening problem, where by entity hardening we imply the ability of the network operator to ensure that an adversary (be it Nature or human) cannot take a network entity from operative to inoperative state. Given that the network operator with a limited budget can only harden k entities, the goal of the entity hardening problem is to identify the set of k entities whose hardening will ensure maximum benefit for the operator, i.e. maximally reduce the ability of the adversary to degrade the network. We show that the problem is solvable in polynomial time for some cases, whereas for others it is NP-complete. We provide the optimal solution using ILP...

Communication-aware algorithms for target tracking in wireless sensor networks

Placzek, Bartlomiej
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/09/2014 Português
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This paper introduces algorithms for target tracking in wireless sensor networks (WSNs) that enable reduction of data communication cost. The objective of the considered problem is to control movement of a mobile sink which has to reach a moving target in the shortest possible time. Consumption of the WSN energy resources is reduced by transferring only necessary data readings (target positions) to the mobile sink. Simulations were performed to evaluate the proposed algorithms against existing methods. The experimental results confirm that the introduced tracking algorithms allow the data communication cost to be considerably reduced without significant increase in the amount of time that the sink needs to catch the target.; Comment: 11 pages, 4 figures

Visualizing Communication on Social Media: Making Big Data Accessible

McKelvey, Karissa; Rudnick, Alex; Conover, Michael D.; Menczer, Filippo
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/02/2012 Português
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The broad adoption of the web as a communication medium has made it possible to study social behavior at a new scale. With social media networks such as Twitter, we can collect large data sets of online discourse. Social science researchers and journalists, however, may not have tools available to make sense of large amounts of data or of the structure of large social networks. In this paper, we describe our recent extensions to Truthy, a system for collecting and analyzing political discourse on Twitter. We introduce several new analytical perspectives on online discourse with the goal of facilitating collaboration between individuals in the computational and social sciences. The design decisions described in this article are motivated by real-world use cases developed in collaboration with colleagues at the Indiana University School of Journalism.

The Extraction of Community Structures from Publication Networks to Support Ethnographic Observations of Field Differences in Scientific Communication

Velden, Theresa; Lagoze, Carl
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.8%
The scientific community of researchers in a research specialty is an important unit of analysis for understanding the field specific shaping of scientific communication practices. These scientific communities are, however, a challenging unit of analysis to capture and compare because they overlap, have fuzzy boundaries, and evolve over time. We describe a network analytic approach that reveals the complexities of these communities through examination of their publication networks in combination with insights from ethnographic field studies. We suggest that the structures revealed indicate overlapping sub- communities within a research specialty and we provide evidence that they differ in disciplinary orientation and research practices. By mapping the community structures of scientific fields we aim to increase confidence about the domain of validity of ethnographic observations as well as of collaborative patterns extracted from publication networks thereby enabling the systematic study of field differences. The network analytic methods presented include methods to optimize the delineation of a bibliographic data set in order to adequately represent a research specialty, and methods to extract community structures from this data. We demonstrate the application of these methods in a case study of two research specialties in the physical and chemical sciences.; Comment: Accepted for publication in JASIST

Synchronization in Small-World-Connected Computer Networks

Guclu, Hasan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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In this thesis we study synchronization phenomena in natural and artificial coupled multi-component systems, applicable to the scalability of parallel discrete-event simulation for systems with asynchronous dynamics. We analyze the properties of the virtual time horizon or synchronization landscape (corresponding to the progress of the processing elements) of these networks by using the framework of non-equilibrium surface growth. When the communication topology mimics that of the short-range interacting underlying system, the virtual time horizon exhibits Kardar-Parisi-Zhang-like kinetic roughening. Although the virtual times, on average, progress at a nonzero rate, their statistical spread diverges with the number of processing elements, hindering efficient data collection. We show that when the synchronization topology is extended to include quenched random communication links (small-world links) between the processing elements, they make a close-to-uniform progress with a nonzero rate, without global synchronization. We also provide a coarse-grained description for the small-world-synchronized virtual-time horizon and compare the findings to those obtained by simulating the simulations based on the exact algorithmic rules. We also present numerical results for the evolution of the virtual-time horizon on scale-free Barabasi-Albert networks serving as communication topology among the processing elements. Finally...

Robust Reconstruction of Complex Networks from Sparse Data

Han, Xiao; Shen, Zhesi; Wang, Wen-Xu; Di, Zengru
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/01/2015 Português
Relevância na Pesquisa
35.8%
Reconstructing complex networks from measurable data is a fundamental problem for understanding and controlling collective dynamics of complex networked systems. However, a significant challenge arises when we attempt to decode structural information hidden in limited amounts of data accompanied by noise and in the presence of inaccessible nodes. Here, we develop a general framework for robust reconstruction of complex networks from sparse and noisy data. Specifically, we decompose the task of reconstructing the whole network into recovering local structures centered at each node. Thus, the natural sparsity of complex networks ensures a conversion from the local structure reconstruction into a sparse signal reconstruction problem that can be addressed by using the lasso, a convex optimization method. We apply our method to evolutionary games, transportation and communication processes taking place in a variety of model and real complex networks, finding that universal high reconstruction accuracy can be achieved from sparse data in spite of noise in time series and missing data of partial nodes. Our approach opens new routes to the network reconstruction problem and has potential applications in a wide range of fields.; Comment: 5 pages...

The Structure of Information Pathways in a Social Communication Network

Kossinets, Gueorgi; Kleinberg, Jon; Watts, Duncan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/06/2008 Português
Relevância na Pesquisa
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Social networks are of interest to researchers in part because they are thought to mediate the flow of information in communities and organizations. Here we study the temporal dynamics of communication using on-line data, including e-mail communication among the faculty and staff of a large university over a two-year period. We formulate a temporal notion of "distance" in the underlying social network by measuring the minimum time required for information to spread from one node to another -- a concept that draws on the notion of vector-clocks from the study of distributed computing systems. We find that such temporal measures provide structural insights that are not apparent from analyses of the pure social network topology. In particular, we define the network backbone to be the subgraph consisting of edges on which information has the potential to flow the quickest. We find that the backbone is a sparse graph with a concentration of both highly embedded edges and long-range bridges -- a finding that sheds new light on the relationship between tie strength and connectivity in social networks.; Comment: 9 pages, 10 figures, to appear in Proceedings of the 14th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining (KDD'08)...

MAC/Routing design for under water sensor networks

Al-Mousa, Yamin
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
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The huge advances in communication technologies and Micro Electrical and Mechanical Systems (MEMS) have triggered a revolution in sensor networks. One major application of sensor networks is in the investigation of complex and uninhabited under water surfaces; such sensor networks are called the Underwater Wireless Sensor Networks (UWSN). UWSN comprises of a number of sensors which are submerged in water and one or several surface stations or a sinks at which the sensed data is collected. In some underwater sensor applications, autonomous underwater vehicles (AUVs) could be used. The underwater sensor nodes communicate with each other using acoustic signals. Applications for this type of networks include oceanographic data collection, pollution monitoring, offshore exploration and tactical surveillance applications. The novel networking paradigm of UWSN is facing a totally different operating environment than the ground based wireless sensor networks. This introduces new challenges such as huge propagation delays, and limited acoustic link capacity with high attenuation factors. These new challenges have their own impact on the design of most of the networking layers preventing researchers from using the same layers used for other networks. The most affected layers are the Physical...

The potential use of mobile technology: enhancing accessibility and communication in a blended learning course

Mayisela,Tabisa
Fonte: South African Journal of Education Publicador: South African Journal of Education
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2013 Português
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Mobile technology is increasingly being used to support blended learning beyond computer centres. It has been considered as a potential solution to the problem of a shortage of computers for accessing online learning materials (courseware) in a blended learning course. The purpose of the study was to establish how the use of mobile technology could enhance accessibility and communication in a blended learning course. Data were solicitedfrom a purposive convenience sample of 36 students engaged in the blended learning course. The case study utilized a mixed-methods approach. An unstructured interview was conducted with the course lecturer and these data informed the design of the students' semi-structured questionnaire. It was found that students with access to mobile technology had an increased opportunity to access the courseware of the blended learning course. Mobile technology further enhanced student-to-student and student-to-lecturer communication by means of social networks. The study concludes that mobile technology has the potential to increase accessibility and communication in a blended learning course. Recommendations, limitations of the present study, and suggestionsforfuture research were made.