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Um protocolo multicast bi-direcional para educação a distancia; A bidirectional multicast protocol for distance learning

Edison de Queiroz Albuquerque
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 08/09/2005 Português
Relevância na Pesquisa
39.061655%
Este trabalho está baseado em uma experiência real, vivida no dia-a-dia do nosso trabalho na Empresa Brasileira de Telecomunicações S.A, EMBRATEL, quando da busca de ferramentas capazes de viabilizar o permanente treinamento dos Consultores Técnicos da empresa, localizados em diferentes partes do nosso país, em face da escassez de recursos financeiros e de tempo. Para tanto, iniciamos com uma retrospectiva histórica da Educação a Distância no mundo, seu presente e suas tendências visíveis. Depois, apresentamos uma descrição dos protocolos multicasting existentes, seguido de nossa proposta. Apresentamos, também, uma simulação usando o Simulador ns-2 de maneira a comprovar o correto funcionamento do protocolo proposto e avaliar seu desempenho. O núcleo desta tese é a proposta de um novo protocolo multicasting, elemento essencial para a otimização da rede de suporte, um imperativo para a eficiência de seu funcionamento e, principalmente, da diminuição de seu custo, tendo em vista a situação ideal de se transmitir voz e vídeo para garantir que uma aula a distância será o mais próximo possível de uma aula presencial, conforme aponta o resultado de pesquisas referenciadas no presente texto, uma vez que vídeo é uma aplicação que demanda grande largura de banda; This work is based on a real life situation...

Security and efficiency concerns with distributed collaborative networking environments

Felker, Keith A.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xiv, 101 p. : ill. (some col.) ;
Português
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Approved for public release, distribution unlimited; The progression of technology is continuous and the technology that drives interpersonal communication is not an exception. Recent technology advancements in the areas of multicast, firewalls, encryption techniques, and bandwidth availability have made the next level of interpersonal communication possible. This thesis answers why collaborative environments are important in today's online productivity. In doing so, it gives the reader a comprehensive background in distributed collaborative environments, answers how collaborative environments are employed in the Department of Defense and industry, details the effects network security has on multicast protocols, and compares collaborative solutions with a focus on security. The thesis ends by providing a recommendation for collaborative solutions to be utilized by NPS/DoD type networks. Efficient multicast collaboration, in the framework of security is a secondary focus of this research. As such, it takes security and firewall concerns into consideration while comparing and contrasting both multicast-based and non-multicast-based collaborative solutions.

Multiplexing, scheduling, and multicasting strategies for antenna arrays in wireless networks

Lopez, Michael J. (Michael John), 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 174 p.; 639036 bytes; 638728 bytes; application/pdf; application/pdf
Português
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A transmitter antenna array has the ability to direct data simultaneously to multiple receivers within a wireless network, creating potential for a more integrated view of algorithmic system components. In this thesis, such a perspective informs the design of two system tasks: the scheduling of packets from a number of data streams into groups; and the subsequent spatial multiplexing and encoding of these groups using array processing. We demonstrate how good system designs can help these two tasks reinforce one another, or alternatively enable tradeoffs in complexity between the two. Moreover, scheduling and array processing each benefit from a further awareness of both the fading channel state and certain properties of the data, providing information about key flexibilities, constraints and goals. Our development focuses on techniques that lead to high performance even with very low-complexity receivers. We first consider spatial precoding under simple scheduling and propose several extensions for implementation, such as a unified time-domain precoder that compensates for both cross-channel and intersymbol interfer- ence. We then show how more sophisticated, channel-aware scheduling can reduce the complexity requirements of the array processing. The scheduling algorithms presented are based on the receivers' fading channel realizations and the delay tolerances of the data streams. Finally...

Coding techniques for multicasting; Coding techniques for multicasting in wireless networks

Khisti, Ashish, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 77 leaves; 3918895 bytes; 3926917 bytes; application/pdf; application/pdf
Português
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We study some fundamental limits of multicasting in wireless systems and propose practical architectures that perform close to these limits. In Chapter 2, we study the scenario in which one transmitter with multiple antennas distributes a common message to a large number of users. For a system with a fixed number (L) of transmit antennas, we show that, as the number of users (K) becomes large, the rate of the worst user decreases as O(K-(1/L)). Thus having multiple antennas provides significant gains in the performance of multicasting system with slow fading. We propose a robust architecture for multicasting over block fading channels, using rateless erasure codes at the application layer. This architecture provides new insights into the cross layer interaction between the physical layer and the application layer. For systems with rich time diversity, we observe that it is better to exploit the time diversity using erasure codes at the application layer rather than be conservative and aim for high reliability at the physical layer. It is known that the spatial diversity gains are not significantly high in systems with rich time diversity. We take a step further and show that to realize these marginal gains one has to operate very close to the optimal operating point. Next...

Online Broadcasting and Multicasting in WDM Networks with Shared Light Splitter Bank

Liang, Weifa; Liu, Yuzhen
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Português
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In this paper we deal with online broadcasting and multicasting in a WDM optical network with shared light splitter bank. Our objective is to maximize the network throughput. Since light splitting and wavelength conversion switching in WDM optical network

Approximate Minimum-Energy Multicasting in Wireless Ad Hoc Networks

Liang, Weifa
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Português
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39.000122%
A wireless ad hoc network consists of mobile nodes that are equipped with energy-limited batteries. As mobile nodes are battery-operated, an important issue in such a network is to minimize the total power consumption for each operation. Multicast is one

Online Multicasting for Network Capacity Maximization in Energy-Constrained Ad Hoc Networks

Liang, Weifa; Guo, Xiaoxing
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Português
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39.052014%
In this paper, we present new algorithms for online multicast routing in ad hoc networks where nodes are energy-constrained. The objective is to maximize the total amount of multicast message data routed successfully over the network without any knowledge

On Optimization of Network-coded Scalable Multimedia Service Multicasting

Tassi, Andrea; Chatzigeorgiou, Ioannis; Vukobratović, Dejan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 31/01/2015 Português
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39.012146%
In the near future, the delivery of multimedia multicast services over next-generation networks is likely to become one of the main pillars of future cellular networks. In this extended abstract, we address the issue of efficiently multicasting layered video services by defining a novel optimization paradigm that is based on an Unequal Error Protection implementation of Random Linear Network Coding, and aims to ensure target service coverages by using a limited amount of radio resources.; Comment: Proc. of the 6th Systems and Networks Optimization for Wireless (SNOW) Workshop 2015, to appear

Fundamental Limits and Scaling Behavior of Cooperative Multicasting in Wireless Networks

Khisti, Ashish; Erez, Uri; Wornell, Gregory
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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A framework is developed for analyzing capacity gains from user cooperation in slow fading wireless networks when the number of nodes (network size) is large. The framework is illustrated for the case of a simple multipath-rich Rayleigh fading channel model. Both unicasting (one source and one destination) and multicasting (one source and several destinations) scenarios are considered. We introduce a meaningful notion of Shannon capacity for such systems, evaluate this capacity as a function of signal-to-noise ratio (SNR), and develop a simple two-phase cooperative network protocol that achieves it. We observe that the resulting capacity is the same for both unicasting and multicasting, but show that the network size required to achieve any target error probability is smaller for unicasting than for multicasting. Finally, we introduce the notion of a network ``scaling exponent'' to quantify the rate of decay of error probability with network size as a function of the targeted fraction of the capacity. This exponent provides additional insights to system designers by enabling a finer grain comparison of candidate cooperative transmission protocols in even moderately sized networks.; Comment: The upper bound in Section (IV) has been modified so that it immediately generalizes to the multiple antenna case. The new version does not rely on Teletar's conjecture being true. Some additional typos have been corrected

Wireless Device-to-Device Caching Networks: Basic Principles and System Performance

Ji, Mingyue; Caire, Giuseppe; Molisch, Andreas F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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As wireless video transmission is the fastest-growing form of data traffic, methods for spectrally efficient video on-demand wireless streaming are essential to service providers and users alike. A key property of video on-demand is the asynchronous content reuse, such that a few dominant videos account for a large part of the traffic, but are viewed by users at different times. Caching of content on devices in conjunction with D2D communications allows to exploit this property, and provide a network throughput that is significantly in excess of both the conventional approach of unicasting from the base station and the traditional D2D networks for regular data traffic. This paper presents in a semi-tutorial concise form some recent results on the throughput scaling laws of wireless networks with caching and asynchronous content reuse, contrasting the D2D approach with a competing approach based on combinatorial cache design and network coded transmission from the base station (BS) only, referred to as coded multicasting. Interestingly, the spatial reuse gain of the former and the coded multicasting gain of the latter yield, somehow surprisingly, the same near-optimal throughput behavior in the relevant regime where the number of video files in the library is smaller than the number of streaming users. Based on our recent theoretical results...

Multicasting over Overlay Networks A Critical Review

Firdhous, Mohamed
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/11/2012 Português
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Multicasting technology uses the minimum network resources to serve multiple clients by duplicating the data packets at the closest possible point to the clients. This way at most only one data packets travels down a network link at any one time irrespective of how many clients receive this packet. Traditionally multicasting has been implemented over a specialized network built using multicast routers. This kind of network has the drawback of requiring the deployment of special routers that are more expensive than ordinary routers. Recently there is new interest in delivering multicast traffic over application layer overlay networks. Application layer overlay networks though built on top of the physical network, behave like an independent virtual network made up of only logical links between the nodes. Several authors have proposed systems, mechanisms and protocols for the implementation of multicast media streaming over overlay networks. In this paper, the author takes a critical look at these systems and mechanism with special reference to their strengths and weaknesses.; Comment: 8 pages, 1 figure, 1 table

Analysis and Optimization of Caching and Multicasting in Large-Scale Cache-Enabled Wireless Networks

Cui, Ying; Jiang, Dongdong; Wu, Yueping
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/12/2015 Português
Relevância na Pesquisa
39.182544%
Caching and multicasting at base stations are two promising approaches to support massive content delivery over wireless networks. However, existing analysis and designs do not fully explore and exploit the potential advantages of the two approaches. In this paper, we jointly consider caching and multicasting to maximize the successful transmission probability in large-scale cache-enabled wireless networks. We propose a random caching and multicasting scheme with a design parameter. Utilizing tools from stochastic geometry, we derive a tractable expression and a closed-form expression for the successful transmission probability in the general region and high signal-to-noise ratio (SNR) and user density region, respectively. Then, using optimization techniques, we develop an iterative numerical algorithm to obtain a local optimal design in the general region, and also derive a simple asymptotically optimal design in the high SNR and user density region, which provides important design insights. Finally, by numerical simulations, we show that the asymptotically optimal design has much lower computational complexity than the local optimal design and achieves a significant performance gain over some baseline schemes in the general region...

Video Contents Prior Storing Server for Optical Access Network

Tsang, Tony
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/04/2015 Português
Relevância na Pesquisa
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One of the most important multimedia applications is Internet protocol TV (IPTV) for next-generation networks. IPTV provides triple-play services that require high-speed access networks with the functions of multicasting and quality of service (QoS) guarantees. Among optical access networks, Ethernet passive optical networks (EPONs) are regarded as among the best solutions to meet higher bandwidth demands. In this paper, we propose a new architecture for multicasting live IPTV traffic in optical access network. The proposed mechanism involves assigning a unique logical link identifier to each IPTV channel. To manage multicasting, a prior storing server in the optical line terminal (OLT) and in each optical network unit (ONU) is constructed. In this work, we propose a partial prior storing strategy that considers the changes in the popularity of the video content segments over time and the access patterns of the users to compute the utility of the objects in the prior storage. We also propose to partition the prior storage to avoid the eviction of the popular objects (those not accessed frequently) by the unpopular ones which are accessed with higher frequency. The popularity distribution and ageing of popularity are measured from two online datasets and use the parameters in simulations. Simulation results show that our proposed architecture can improve the system performance and QoS parameters in terms of packet delay...

Constructing Path Efficient and Energy Aware Virtual Multicast Backbones in Static Ad Hoc Wireless Networks

Acharya, Tamaghna; Chattopadhyay, Samiran; Roy, Rajarshi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/05/2010 Português
Relevância na Pesquisa
39.229521%
For stationary wireless ad hoc networks, one of the key challenging issues in routing and multicasting is to conserve as much energy as possible without compromising path efficiency measured as end-to-end delay. In this paper, we address the problem of path efficient and energy aware multicasting in static wireless ad hoc networks. We propose a novel distributed scalable algorithm for finding a virtual multicast backbone (VMB). Based on this VMB, we have further developed a multicasting scheme that jointly improves path efficiency and energy conservation. By exploiting inherent broadcast advantage of wireless communication and employing a more realistic energy consumption model for wireless communication which not only depends on radio propagation losses but also on energy losses in transceiver circuitry, our simulation results show that the proposed VMB-based multicasting scheme outperforms existing prominent tree based energy conserving, path efficient multicasting schemes.; Comment: 17 Pages, IJWMN 2010

Rank-Two Beamforming and Power Allocation in Multicasting Relay Networks

Schad, Adrian; Law, Ka L.; Pesavento, Marius
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/02/2015 Português
Relevância na Pesquisa
48.743823%
In this paper, we propose a novel single-group multicasting relay beamforming scheme. We assume a source that transmits common messages via multiple amplify-and-forward relays to multiple destinations. To increase the number of degrees of freedom in the beamforming design, the relays process two received signals jointly and transmit the Alamouti space-time block code over two different beams. Furthermore, in contrast to the existing relay multicasting scheme of the literature, we take into account the direct links from the source to the destinations. We aim to maximize the lowest received quality-of-service by choosing the proper relay weights and the ideal distribution of the power resources in the network. To solve the corresponding optimization problem, we propose an iterative algorithm which solves sequences of convex approximations of the original non-convex optimization problem. Simulation results demonstrate significant performance improvements of the proposed methods as compared with the existing relay multicasting scheme of the literature and an algorithm based on the popular semidefinite relaxation technique.

Multicasting in Cognitive Radio Networks: Algorithms, Techniques and Protocols

Qadir, Junaid; Baig, Adeel; Ali, Asad; Shafi, Quratulain
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/06/2014 Português
Relevância na Pesquisa
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Multicasting is a fundamental networking primitive utilized by numerous applications. This also holds true for cognitive radio networks (CRNs) which have been proposed as a solution to the problems that emanate from the static non-adaptive features of classical wireless networks. A prime application of CRNs is dynamic spectrum access (DSA), which improves the efficiency of spectrum allocation by allowing a secondary network, comprising of secondary users (SUs), to share spectrum licensed to a primary licensed networks comprising of primary users (PUs). Multicasting in CRNs is a challenging problem due to the dynamic nature of spectrum opportunities available to the SUs. Various approaches, including those based in optimization theory, network coding, algorithms, have been proposed for performing efficient multicast in CRNs. In this paper, we provide a self-contained tutorial on algorithms and techniques useful for solving the multicast problem, and then provide a comprehensive survey of protocols that have been proposed for multicasting in CRNs. We conclude this paper by identifying open research questions and future research directions.

Introduction to IP multicast in production networks; IP multicast in production networks

Vidyadharan Girija, Ganesh
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Masters Project
Português
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59.39549%
The objective of this paper is to introduce the reader to the world of IP multicasting. I intend to achieve this goal by providing an introduction that bridges the gap between the existing unicast networks and the developing multicast network. The basics of multicast that is covered in the earlier chapter includes the multicast addressing scheme, different protocols used for multicast transmission, various distribution trees that are formed by these protocols and various aspects of multicast forwarding. We take a look at IGMP which is the protocol that runs between the host devices and their first hop multicast routers, enabling the host to join/leave a multicast group. The protocols used for running IP multicast over networks are discussed in detail with additional emphasis on PIM-SM which is the most common among the available selection. The paper concludes with a general overlook on the avenues where multicasting could play a major role benefitting the Internet Service Providers and eve large corporate networks, and a glance on the pros and cons of multicasting.; Includes bibliographical references.

Performance evaluation of multicast routing on IPv4 and IPv6 networks

Hari, Suneetha
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
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Even though the transition from IPv4 to IPv6 has not been realized at the pace that it was anticipated, eventually with the depletion of IPv4 address space and the ever-growing demands of the Internet, the transition is inevitable. In the rapidly evolving world of technology, multimedia applications and voice/video conferencing are fast finding their ways into the Internet and corporate networks. Multicast routing protocols run over unicast routing protocols to provide efficient routing of such applications. This thesis was aimed at understanding how the transition from IPv4 to IPv6 would impact multicast routing. The multicast routing protocol Protocol Independent Multicast-Sparse Mode (PIM-SM) was used over both IPv4 and IPv6 networks and a mixed IPv4-IPv6 network. Parameters such as protocol overheads, throughput and jitter were evaluated in a lab environment using jperf.

RODMRP - resilient on demand multicast routing protocol

Pathirana, Dhammika
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
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ODMRP (On-Demand Multicast Routing Protocol) [6] [8] [2] is a popular multicast protocol for wireless ad hoc networks. The strengths of ODMRP are simplicity, high packet delivery ratio, and non-dependency on a specific unicast protocol. ODMRP floods a route request over the entire network to select a set of forwarding nodes for packet delivery. However, a single forwarding path is vulnerable to node failures, which are common due to the dynamic nature of mobile ad hoc networks. Furthermore, a set of misbehaving or malicious nodes can create network partitions and mount Denial-of-Service (DoS) attacks. This thesis proposes a ODMRP-based wireless multicast protocol named RODMRP that offers more reliable forwarding paths in face of node and network failures. A subset of the nodes that are not on forwarding paths rebroadcast received packets to nodes in their neighborhoods to overcome perceived node failures. This rebroadcasting creates redundant forwarding paths to circumvent failed areas in the network. Each node makes this forwarding decision probabilistically. Our simulation results indicate that RODMRP improves packet delivery ratio with minimal overheads, while retaining the original strengths of ODMRP.

Minimizing Energy and Maximizing Network Lifetime Multicasting in Wireless Ad Hoc Networks

Liang, Weifa
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Português
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48.703687%
Most mobile nodes in a wireless ad hoc network are powered by energy limited batteries, the limited battery lifetime imposes a constraint on the network performance. Therefore, energy efficiency is paramount of importance in the design of routing protocols for the applications in such a network, and efficient operations are critical to enhance the network lifetime. In this paper we consider energy-efficient routing for the minimizing energy and maximizing network lifetime multicast problem in ad hoc networks. We aim to construct a multicast tree rooted at the source and spanning the destination nodes such that the minimum residual battery energy (also referred to the network lifetime) among the nodes in the network is maximized and the total transmission energy consumption is minimized. Due to the NP-hardness of the concerned problem, all previously proposed algorithms for it are heuristic algorithms, and there is little known about the analytical performance of these algorithms in terms of approximation ratios. We here focus on devising approximation algorithms for the problem with provably guaranteed approximation ratios. Specifically, we present an approximation algorithm for finding a multicast tree such that the total transmission energy consumption is no more than γ times of the optimum...