Página 7 dos resultados de 2591 itens digitais encontrados em 0.030 segundos

On data-centric misbehavior detection in VANETs

Ruj, Sushmita; Cavenaghi, Marcos A.; Huang, Zhen; Nayak, Amiya; Stojmenovic, Ivan
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência
Português
Relevância na Pesquisa
35.84%
Detecting misbehavior (such as transmissions of false information) in vehicular ad hoc networks (VANETs) is a very important problem with wide range of implications, including safety related and congestion avoidance applications. We discuss several limitations of existing misbehavior detection schemes (MDS) designed for VANETs. Most MDS are concerned with detection of malicious nodes. In most situations, vehicles would send wrong information because of selfish reasons of their owners, e.g. for gaining access to a particular lane. It is therefore more important to detect false information than to identify misbehaving nodes. We introduce the concept of data-centric misbehavior detection and propose algorithms which detect false alert messages and misbehaving nodes by observing their actions after sending out the alert messages. With the data-centric MDS, each node can decide whether an information received is correct or false. The decision is based on the consistency of recent messages and new alerts with reported and estimated vehicle positions. No voting or majority decisions is needed, making our MDS resilient to Sybil attacks. After misbehavior is detected, we do not revoke all the secret credentials of misbehaving nodes, as done in most schemes. Instead...

An approach to implement data fusion techniques in wireless sensor networks using genetic machine learning algorithms

Pinto, A. R.; Montez, C.; Araújo, G.; Vasques, F.; Portugal, P.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.85%
Wireless Sensor Networks (WSNs) can be used to monitor hazardous and inaccessible areas. In these situations, the power supply (e.g. battery) of each node cannot be easily replaced. One solution to deal with the limited capacity of current power supplies is to deploy a large number of sensor nodes, since the lifetime and dependability of the network will increase through cooperation among nodes. Applications on WSN may also have other concerns, such as meeting temporal deadlines on message transmissions and maximizing the quality of information. Data fusion is a well-known technique that can be useful for the enhancement of data quality and for the maximization of WSN lifetime. In this paper, we propose an approach that allows the implementation of parallel data fusion techniques in IEEE 802.15.4 networks. One of the main advantages of the proposed approach is that it enables a trade-off between different user-defined metrics through the use of a genetic machine learning algorithm. Simulations and field experiments performed in different communication scenarios highlight significant improvements when compared with, for instance, the Gur Game approach or the implementation of conventional periodic communication techniques over IEEE 802.15.4 networks. © 2013 Elsevier B.V. All rights reserved.

Towards a network management solution for vehicular delay-tolerant networks

Ferreira, Bruno Filipe Aguiar Durães
Fonte: Universidade da Beira Interior Publicador: Universidade da Beira Interior
Tipo: Dissertação de Mestrado
Publicado em //2012 Português
Relevância na Pesquisa
35.85%
Vehicular networks appeared as a new communication solution where vehicles act as a communication infrastructure, providing data communications through vehicle-to-vehicle (V2V) or vehicle-to-infrastructure (V2I) communications. Vehicular Delay-Tolerant Networks (VDTNs) are a new disruptive network architecture assuming delay tolerant networking paradigm where there are no end-to-end connectivity. In this case the incial node transmits the data to a closed node, the data will be carried by vehicles, hop to hop until the destination. This dissertation focuses on a proposal of a network management solution, based standard protocol Simple Network Management Protocol (SNMP) to VDTN networks. The developed solution allows control a VDTN netowork through a Network Management System (NMS) with the objective to detect and, if it’s possible, anticipate, possible errors on network. The research methodology used was the prototyping. So, it was built a network management module to the laboratorial prototype, called VDTN@Lab. The system built include a MIB (Management Information Base) placed in all vehicular network nodes. The solution was built, demonstrated, validated and evaluated their performance, being ready for use.

Chain-Based Communication in Cylindrical Underwater Wireless Sensor Networks

Javaid, Nadeem; Jafri, Mohsin Raza; Khan, Zahoor Ali; Alrajeh, Nabil; Imran, Muhammad; Vasilakos, Athanasios
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 04/02/2015 Português
Relevância na Pesquisa
35.84%
Appropriate network design is very significant for Underwater Wireless Sensor Networks (UWSNs). Application-oriented UWSNs are planned to achieve certain objectives. Therefore, there is always a demand for efficient data routing schemes, which can fulfill certain requirements of application-oriented UWSNs. These networks can be of any shape, i.e., rectangular, cylindrical or square. In this paper, we propose chain-based routing schemes for application-oriented cylindrical networks and also formulate mathematical models to find a global optimum path for data transmission. In the first scheme, we devise four interconnected chains of sensor nodes to perform data communication. In the second scheme, we propose routing scheme in which two chains of sensor nodes are interconnected, whereas in third scheme single-chain based routing is done in cylindrical networks. After finding local optimum paths in separate chains, we find global optimum paths through their interconnection. Moreover, we develop a computational model for the analysis of end-to-end delay. We compare the performance of the above three proposed schemes with that of Power Efficient Gathering System in Sensor Information Systems (PEGASIS) and Congestion adjusted PEGASIS (C-PEGASIS). Simulation results show that our proposed 4-chain based scheme performs better than the other selected schemes in terms of network lifetime...

Energy Spectral Behaviors of Communication Networks of Open-Source Communities

Yang, Jianmei; Yang, Huijie; Liao, Hao; Wang, Jiangtao; Zeng, Jinqun
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 05/06/2015 Português
Relevância na Pesquisa
35.85%
Large-scale online collaborative production activities in open-source communities must be accompanied by large-scale communication activities. Nowadays, the production activities of open-source communities, especially their communication activities, have been more and more concerned. Take CodePlex C # community for example, this paper constructs the complex network models of 12 periods of communication structures of the community based on real data; then discusses the basic concepts of quantum mapping of complex networks, and points out that the purpose of the mapping is to study the structures of complex networks according to the idea of quantum mechanism in studying the structures of large molecules; finally, according to this idea, analyzes and compares the fractal features of the spectra in different quantum mappings of the networks, and concludes that there are multiple self-similarity and criticality in the communication structures of the community. In addition, this paper discusses the insights and application conditions of different quantum mappings in revealing the characteristics of the structures. The proposed quantum mapping method can also be applied to the structural studies of other large-scale organizations.

Foundations for the Development of Information and Communication Technologies in Algeria

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Português
Relevância na Pesquisa
35.84%
The rapid pace of information communication technologies (ICT) in the last ten years have transformed developed countries into "information societies". Consequently, new technologies are at the center of debate in developing countries, who also aim at profiting from its advantages. Technology transfer is unprecedented, where electronic commerce, largely due to modern semi-conductors, now allows substantial price, and operational cost reductions. Similarly, the emerging industrial enterprises, mainly small and medium scale, are competitively grouped along complementary activities. In parallel to this ICT penetration in all sectors of the economy, the information content of industrial activity, and productivity is enhanced. This paper looks at the crucial elements to develop ICTs in Algeria, suggesting its transition towards an information economy, requires an economic diversification, and competitiveness strength vis-e-vis international markets. This in turn requires the development of new sources of economic growth. To this end...

Information and Communication Technologies for Health Systems Strengthening

Otto, Kate; Shekar, Meera; Herbst, Christopher H.; Mohammed, Rianna
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Trabalho em Andamento
Português
Relevância na Pesquisa
35.85%
Information and communication technologies (ICT) for health or eHealth solutions hold great potential for generating systemic efficiencies by strengthening five critical pillars of a health system: human resources for health, supply chain management, health care financing, governance and service delivery, and infrastructure. This report describes the changing landscape of eHealth initiatives through these five pillars, with a geographic focus on Sub-Saharan Africa. This report further details seven criteria, or prerequisites, that must be considered and addressed in order to effectively establish and scale up ICT-based solutions in the health sector. These criteria include infrastructure, data and interoperability standards, local capacity, policy and regulatory environments, an appropriate business model, alignment of partnerships and priorities, and monitoring and evaluation. In order to bring specific examples of these criteria to light, this report concludes with 12 specific case studies of potentially scalable ICT-based health care solutions currently being implemented across the globe at community...

Communication performance measurement and analysis on commodity clusters.

Abdul Hamid, Nor Asilah Wati
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008 Português
Relevância na Pesquisa
35.85%
Cluster computers have become the dominant architecture in high-performance computing. Parallel programs on these computers are mostly written using the Message Passing Interface (MPI) standard, so the communication performance of the MPI library for a cluster is very important. This thesis investigates several different aspects of performance analysis for MPI libraries, on both distributed memory clusters and shared memory parallel computers. The performance evaluation was done using MPIBench, a new MPI benchmark program that provides some useful new functionality compared to existing MPI benchmarks. Since there has been only limited previous use of MPIBench, some initial work was done on comparing MPIBench with other MPI benchmarks, and improving its functionality, reliability, portability and ease of use. This work included a detailed comparison of results from the Pallas MPI Benchmark (PMB), SKaMPI, Mpptest, MPBench and MPIBench on both distributed memory and shared memory parallel computers, which has not previously been done. This comparison showed that the results for some MPI routines were significantly different between the different benchmarks, particularly for the shared memory machine. A comparison was done between Myrinet and Ethernet network performance on the same machine...

Distributed Data and Information Fusion in Visual Sensor Networks

Castanedo, Federico; Gómez Romero, Juan; Patricio Guisado, Miguel Ángel; García, Jesús; Molina, José M.
Fonte: CRC Press Publicador: CRC Press
Tipo: info:eu-repo/semantics/publishedVersion; info:eu-repo/semantics/bookPart
Publicado em //2012 Português
Relevância na Pesquisa
35.84%
Computer vision, and in particular multi-camera environments, has been widely researched over the recent years, thus leading to several proposals of multi-camera or visual sensor networks (VSNs) architectures (Valera and Velastin 2005). The aims of these systems are very different; to name some of them, there are examples in surveillance applications (Regazzoni et al. 2001), sport domains (Chen and De Vlesschouwer 2010), or ambient intelligence applications for elderly care (Zhang et al. 2010). Despite the specific goal of each system, all of them have to cope with a distributed architecture of visual sensors to acquire and process information from the environment. The obtained information must then be fused in order to generate a meaningful global picture of the environment. Since a distributed VSN can be applied to different domains/scenarios, a specific ontology provides meaning and sense of the information that the system uses for interpretation purposes. This chapter explores the use of the multi-agent paradigm and ontology-based knowledge representation formalisms to perform distributed data and information fusion (DIF) in VSNs. The multi-agent paradigm, which has been widely applied in distributed systems, provides a theoretical and practical framework to allow communication and cooperation among the components of the system. For instance...

Driving the communication channel: how Australia can better communicate with women in the APEC economies In relation to the work that Is being done by APEC groups

Dan, Dai
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Relatório
Português
Relevância na Pesquisa
35.85%
Over the last decade APEC economies have opened their markets to international trade and achieving significant gains in exports and global growth. In line with this increasing economic integration is the growing recognition by members in the APEC region, and Australia in particular, of the potential for greater patticipation of women in international trade and potentially to a greater contribution to overall economic growth. Women are often disadvantaged as a result of their under-representation in economic roles while simultaneously being burdened by traditional responsibilities. Barriers to women's full participation in trade and economic growth, including education and decision making, are costing the Asia-Pacific region up to 77 billion a year. The benefits of greater economic prosperity for women are not limited to fiscal measures. The returns from women participating in the workforce are considerable as their investment in education and healthcare exceeds that of men. This has a spill-over effect to the economy by reducing pressure on state-funded health services. The ageing population in developed APEC economies will also required more women to gain the skills and experience necessary to combat the expected demographic changes in the near future. It is important to further encourage women to take an active part in the economic growth. In recent years...

Abstractions to Support Dynamic Adaptation of Communication Frameworks for User-Centric Communication

Allen, Andrew A
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
Relevância na Pesquisa
35.84%
The convergence of data, audio and video on IP networks is changing the way individuals, groups and organizations communicate. This diversity of communication media presents opportunities for creating synergistic collaborative communications. This form of collaborative communication is however not without its challenges. The increasing number of communication service providers coupled with a combinatorial mix of offered services, varying Quality-of-Service and oscillating pricing of services increases the complexity for the user to manage and maintain `always best' priced or performance services. Consumers have to manually manage and adapt their communication in line with differences in services across devices, networks and media while ensuring that the usage remain consistent with their intended goals. This dissertation proposes a novel user-centric approach to address this problem. The proposed approach aims to reduce the aforementioned complexity to the user by (1) providing high-level abstractions and a policy based methodology for automated selection of the communication services guided by high-level user policies and (2) providing services through the seamless integration of multiple communication service providers and providing an extensible framework to support the integration of multiple communication service providers. The approach was implemented in the Communication Virtual Machine (CVM)...

Towards a network management solution for vehicular delay-tolerant networks

Ferreira, Bruno Filipe Aguiar Durães
Fonte: Universidade da Beira Interior Publicador: Universidade da Beira Interior
Tipo: Dissertação de Mestrado
Publicado em //2012 Português
Relevância na Pesquisa
35.85%
Vehicular networks appeared as a new communication solution where vehicles act as a communication infrastructure, providing data communications through vehicle-to-vehicle (V2V) or vehicle-to-infrastructure (V2I) communications. Vehicular Delay-Tolerant Networks (VDTNs) are a new disruptive network architecture assuming delay tolerant networking paradigm where there are no end-to-end connectivity. In this case the incial node transmits the data to a closed node, the data will be carried by vehicles, hop to hop until the destination. This dissertation focuses on a proposal of a network management solution, based standard protocol Simple Network Management Protocol (SNMP) to VDTN networks. The developed solution allows control a VDTN netowork through a Network Management System (NMS) with the objective to detect and, if it’s possible, anticipate, possible errors on network. The research methodology used was the prototyping. So, it was built a network management module to the laboratorial prototype, called VDTN@Lab. The system built include a MIB (Management Information Base) placed in all vehicular network nodes. The solution was built, demonstrated, validated and evaluated their performance, being ready for use.

Wide-area Wireless Communication Challenges for the Internet of Things

Dhillon, Harpreet S.; Huang, Howard; Viswanathan, Harish
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/04/2015 Português
Relevância na Pesquisa
35.85%
Aided by the ubiquitous wireless connectivity, declining communication costs, and the emergence of cloud platforms, the deployment of Internet of Things (IoT) devices and services is accelerating. Most major mobile network operators view machine-to-machine (M2M) communication networks for supporting IoT as a significant source of new revenue. In this paper, we motivate the need for wide-area M2M wireless networks, especially for short data packet communication to support a very large number of IoT devices. We first present a brief overview of current and emerging technologies for supporting wide area M2M, and then using communication theory principles, discuss the fundamental challenges and potential solutions for these networks, highlighting tradeoffs and strategies for random and scheduled access. We conclude with recommendations for how future 5G networks should be designed for efficient wide-area M2M communications.

Time as a limited resource: Communication Strategy in Mobile Phone Networks

Miritello, Giovanna; Moro, Esteban; Lara, Rubén; Martínez-López, Rocío; Roberts, Sam G. B.; Dunbar, Robin I. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/01/2013 Português
Relevância na Pesquisa
35.84%
We used a large database of 9 billion calls from 20 million mobile users to examine the relationships between aggregated time spent on the phone, personal network size, tie strength and the way in which users distributed their limited time across their network (disparity). Compared to those with smaller networks, those with large networks did not devote proportionally more time to communication and had on average weaker ties (as measured by time spent communicating). Further, there were not substantially different levels of disparity between individuals, in that mobile users tend to distribute their time very unevenly across their network, with a large proportion of calls going to a small number of individuals. Together, these results suggest that there are time constraints which limit tie strength in large personal networks, and that even high levels of mobile communication do not fundamentally alter the disparity of time allocation across networks.; Comment: 10 pages, 3 figures. Accepted for publication in Social Networks

Medians and Beyond: New Aggregation Techniques for Sensor Networks

Shrivastava, Nisheeth; Buragohain, Chiranjeeb; Agrawal, Divyakant; Suri, Subhash
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 16/08/2004 Português
Relevância na Pesquisa
35.84%
Wireless sensor networks offer the potential to span and monitor large geographical areas inexpensively. Sensors, however, have significant power constraint (battery life), making communication very expensive. Another important issue in the context of sensor-based information systems is that individual sensor readings are inherently unreliable. In order to address these two aspects, sensor database systems like TinyDB and Cougar enable in-network data aggregation to reduce the communication cost and improve reliability. The existing data aggregation techniques, however, are limited to relatively simple types of queries such as SUM, COUNT, AVG, and MIN/MAX. In this paper we propose a data aggregation scheme that significantly extends the class of queries that can be answered using sensor networks. These queries include (approximate) quantiles, such as the median, the most frequent data values, such as the consensus value, a histogram of the data distribution, as well as range queries. In our scheme, each sensor aggregates the data it has received from other sensors into a fixed (user specified) size message. We provide strict theoretical guarantees on the approximation quality of the queries in terms of the message size. We evaluate the performance of our aggregation scheme by simulation and demonstrate its accuracy...

Node similarity as a basic principle behind connectivity in complex networks

Scholz, Matthias
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
35.84%
How are people linked in a highly connected society? Since in many networks a power-law (scale-free) node-degree distribution can be observed, power-law might be seen as a universal characteristics of networks. But this study of communication in the Flickr social online network reveals that power-law node-degree distributions are restricted to only sparsely connected networks. More densely connected networks, by contrast, show an increasing divergence from power-law. This work shows that this observation is consistent with the classic idea from social sciences that similarity is the driving factor behind communication in social networks. The strong relation between communication strength and node similarity could be confirmed by analyzing the Flickr network. It also is shown that node similarity as a network formation model can reproduce the characteristics of different network densities and hence can be used as a model for describing the topological transition from weakly to strongly connected societies.; Comment: 6 pages in Journal of Data Mining & Digital Humanities (2015) jdmdh:33

Extremely low-overhead security for wireless sensor networks: Algorithms and implementation

Schab, Michael
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
35.85%
Recent advances in the development of compact microprocessors have brought forth new applications in the field of data acquisition and wireless communication. One of these applications is a compact sensor mote that has the ability to perform both data acquisition and transmission within a Wireless Sensor Network (WSN). Wireless sensor communication is susceptible to the same data security threats as traditional wireless networks. In an environment where sensors are broadcasting battlefield intelligence or patient biometrics, data confidentiality must be enforced utilizing some form of encryption. Unlike traditional wireless networks, where the communicating devices have unrestricted access to power and memory, a wireless sensor has very limited resources. A wireless sensor consists of a battery designed to last an extended amount of time, therefore it is critical that the computation and transmission overhead involved in enforcing data security be optimized to preserve battery life. The research presented in this thesis details a nesC/TinyOS implementation of the NTRUEncrypt PKCS executing on a Crossbow MICAz mote. Algorithm details regarding message encryption and decryption are analyzed along with optimization techniques that improve execution time and reduce memory size. A summary of performance metrics including execution time...

Maximizing the capability of wireless sensor networks

Cress, Cory
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
35.84%
Wireless micro-sensors introduce a new frontier in sensing devices and data acquisition capabilities. These sensors, capable of sensing, processing data, and short-range communication, can be spread over regions to form ad hoc wireless sensor networks (WSN) so as to deliver aggregate information from geographically diverse areas. This aggregate data gathering and processing induces a synergistic effect and enables a sensor network to complete sensing tasks that may never be feasible using a single, perhaps powerful, sensor. This new paradigm in sensing devices is not without many fundamental challenges, one being a constrained energy resource, which first need to be solved before the true capabilities of these networks may be realized. This thesis will discuss the models and techniques developed as an attempt to maximize the capability of a WSN. The premise used in the research is that the capability of a WSN can be maximize by developing a scheme that can duplicate the optimal energy efficient behavior of individual wireless sensors in a contention dominated, distributed decision-making, network environment. This optimal energy efficient behavior as determined by an analytically derived model and a mixed integer programming model will be presented. The analytical model enables the optimal sensor behavior to be calculated given a contention-less environment...

GPU-based implementation of real-time system for spiking neural networks

Yudanov, Dmitri
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
35.85%
Real-time simulations of biological neural networks (BNNs) provide a natural platform for applications in a variety of fields: data classification and pattern recognition, prediction and estimation, signal processing, control and robotics, prosthetics, neurological and neuroscientific modeling. BNNs possess inherently parallel architecture and operate in continuous signal domain. Spiking neural networks (SNNs) are type of BNNs with reduced signal dynamic range: communication between neurons occurs by means of time-stamped events (spikes). SNNs allow reduction of algorithmic complexity and communication data size at a price of little loss in accuracy. Simulation of SNNs using traditional sequential computer architectures results in significant time penalty. This penalty prohibits application of SNNs in real-time systems. Graphical processing units (GPUs) are cost effective devices specifically designed to exploit parallel shared memory-based floating point operations applied not only to computer graphics, but also to scientific computations. This makes them an attractive solution for SNN simulation compared to that of FPGA, ASIC and cluster message passing computing systems. Successful implementations of GPU-based SNN simulations have been already reported. The contribution of this thesis is the development of a scalable GPU-based realtime system that provides initial framework for design and application of SNNs in various domains. The system delivers an interface that establishes communication with neurons in the network as well as visualizes the outcome produced by the network. Accuracy of the simulation is emphasized due to its importance in the systems that exploit spike time dependent plasticity...

The micro-foundations of email communication networks

Engel, Ofer
Fonte: London School of Economics and Political Science Thesis Publicador: London School of Economics and Political Science Thesis
Tipo: Thesis; NonPeerReviewed Formato: application/pdf
Publicado em /06/2013 Português
Relevância na Pesquisa
35.84%
The popular and scientific literature has been discussing the advent of ‘big data’ with a measure of excitement and apprehension. For the first time in history, it seems, every breath we take, every move we make, someone’s watching us. But beyond their unprecedented volumes and the anxieties they raise, new communication data have a less obvious aspect, in so far as they are (arguably) of a fundamentally different kind, compared to traditional network datasets. Traditionally, social network data describe relationships between individuals; quasistatic social ties such as friendship, trust, kinship and employment relations. But when they are used to model digitally mediated communicative transactions, the connections are of a different nature. Instead of representing stable social ties, transactions (such as emails, text messages and phone calls) constitute sequences of shortlived events, with each transaction being a possible response to a preceding one and a potential stimulus to the next. The point of departure of this dissertation is the distinction between the topology of the tie structure and the temporal structure of sequences of communicative transactions. Theoretically, the dissertation explores mechanisms of co-evolution between these two structures at three levels of aggregation: (i) the macro-level consisting of the network itself or substructures within it...