Página 1 dos resultados de 5436 itens digitais encontrados em 0.020 segundos

Planejamento de capacidade em redes corporativas para implementação de serviços VoIP; Corporate network capacity planning to voip services implementation

Monks, Eduardo Maronas
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
46.03%
Este trabalho tem como objetivo o estudo da tecnologia VoIP (Voz sobre IP) e a sua aplicação em redes corporativas, enfocando o planejamento de capacidade da rede de dados para absorver serviços VoIP. Serão apresentados tópicos sobre a fundamentação teórica de VoIP (Voz sobre IP), os requisitos de arquitetura de rede e QoS (Qualidade de Serviço) exigidos pelo serviço. Mostra-se também como a metodologia para planejamento de capacidade usado em telefonia convencional pode ser adaptada aos serviços VoIP em uma rede corporativa. Foi aplicada a metodologia adaptada através de um estudo de caso em uma rede corporativa real.; This work has as objective the study of capacity planning in corporate networks for the implementation of VoIP (Voice over IP) services. We will presents topics about the theorical background of VoIP, the requirements of architecture of network and QoS (Quality of Service) demanded by the service. It will also reveal how the methodology used for planning capacity in conventional telephony, could be adjusted to the VoIP services in a corporate network. The adjusted methodology was applied in a real corporate network.

Modelo de avaliação da capacidade da rede de acesso metálica para o provimento de serviços suportados pela tecnologia ADSL; Model of evaluation of the metallic access network capacity for the provisions of services supported for ADSL technology

Monteiro, Sandro de Castro
Fonte: Universidade de Brasília Publicador: Universidade de Brasília
Tipo: Dissertação
PT_BR
Relevância na Pesquisa
46.07%
Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2007.; A tecnologia das linhas digitais de assinantes – DSL (Digital Subscriber Line) tem sido uma boa solução para atender a demanda de serviços de dados, permitindo a transmissão em altas taxas sobre a mesma rede de acesso utilizada pelo sistema de telefonia convencional, que opera em freqüências abaixo de 4 kHz. Mas os sinais DSL trabalham com freqüências superiores e sua transmissão sobre os pares de cobre sofre altas perdas e provoca fortes induções nos demais pares do cabo, reduzindo a taxa de bits transmitidos e impondo limites sobre o comprimento da rede. Dessa forma, é importante que as operadoras de telecomunicações conheçam esses limites para utilizar ao máximo a rede para os serviços DSL, garantindo os níveis de qualidade do serviço. Este trabalho propõe um modelo para avaliar a capacidade da rede de pares metálicos para os serviços que utilizam o sistema ADSL (Asymmetric Digital Subscriber Line), sendo esse o tipo de DSL mais popular por oferecer acesso à internet e sinais de TV para clientes residenciais a baixo custo. A avaliação é feita em cima da taxa máxima transmitida pelo ADSL no sentido estação-cliente...

Virtual Network Capacity Expansion through Service Outsourcing

Ozianyi, Vitalis; Jesus, Vitor; Sargento, Susana; Aguiar, Rui L; Ventura, Neco
Fonte: IEEE Publicador: IEEE
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
46.11%
Roaming agreements in 3G and beyond 3G networks can greatly enhance the delivery of services to end users. The cost of service delivery to the user depends on the price charged on networks traversed by user traffic. In a QoS DiffServ environment, network resources may be sold in aggregate blocks at wholesale prices to competing ISPs. This can influence the cost of delivering services between two points using access networks owned by competing operators. Demand for network services by users varies over time and network capacities are finite; thus a fully loaded network would reject new service requests and an underutilized network will become less productive. In this paper we explore a service outsourcing scheme between competing operators that allows a custodian network operating at full capacity to outsource service provision to a candidate network. Outsourcing would be price-influenced enabling the home (custodian) operator to levy local predictable charges to the end users for services offered on the visited network. This will virtually expand the capacity of the custodian network and boost incomes for both operators.

Storage of Phase-Coded Patterns via STDP in Fully-Connected and Sparse Network: A Study of the Network Capacity

Scarpetta, Silvia; de Candia, Antonio; Giacco, Ferdinando
Fonte: Frontiers Research Foundation Publicador: Frontiers Research Foundation
Tipo: Artigo de Revista Científica
Publicado em 23/08/2010 EN
Relevância na Pesquisa
46.16%
We study the storage and retrieval of phase-coded patterns as stable dynamical attractors in recurrent neural networks, for both an analog and a integrate and fire spiking model. The synaptic strength is determined by a learning rule based on spike-time-dependent plasticity, with an asymmetric time window depending on the relative timing between pre and postsynaptic activity. We store multiple patterns and study the network capacity. For the analog model, we find that the network capacity scales linearly with the network size, and that both capacity and the oscillation frequency of the retrieval state depend on the asymmetry of the learning time window. In addition to fully connected networks, we study sparse networks, where each neuron is connected only to a small number z ≪ N of other neurons. Connections can be short range, between neighboring neurons placed on a regular lattice, or long range, between randomly chosen pairs of neurons. We find that a small fraction of long range connections is able to amplify the capacity of the network. This imply that a small-world-network topology is optimal, as a compromise between the cost of long range connections and the capacity increase. Also in the spiking integrate and fire model the crucial result of storing and retrieval of multiple phase-coded patterns is observed. The capacity of the fully-connected spiking network is investigated...

Dynamic Cooperative Clustering Based Power Assignment: Network Capacity and Lifetime Efficient Topology Control in Cooperative Ad Hoc Networks

Li, Xiao-Hong; Xiao, Ling; Wang, Dong
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em 16/03/2014 EN
Relevância na Pesquisa
46.12%
Cooperative communication (CC) is used in topology control as it can reduce the transmission power and expand the transmission range. However, all previous research on topology control under the CC model focused on maintaining network connectivity and minimizing the total energy consumption, which would lead to low network capacity, transmission interruption, or even network paralysis. Meanwhile, without considering the balance of energy consumption in the network, it would reduce the network lifetime and greatly affect the network performance. This paper tries to solve the above problems existing in the research on topology control under the CC model by proposing a power assignment (DCCPA) algorithm based on dynamic cooperative clustering in cooperative ad hoc networks. The new algorithm clusters the network to maximize network capacity and makes the clusters communicate with each other by CC. To reduce the number of redundant links between clusters, we design a static clustering method by using Kruskal algorithm. To maximize the network lifetime, we also propose a cluster head rotating method which can reach a good tradeoff between residual energy and distance for the cluster head reselection. Experimental results show that DCCPA can improve 80% network capacity with Cooperative Bridges algorithm; meanwhile...

On optimising the capacity and power efficiency of a wireless network

Hunjet, R.; Coyle, A.
Fonte: IEEE; USA Publicador: IEEE; USA
Tipo: Conference paper
Publicado em //2012 EN
Relevância na Pesquisa
56.16%
With wireless networking becoming more prevalent, the capacity and power efficiency of these networks is of concern to both users and network designers. Wireless network capacity is difficult to define, with current research providing upper bounds and throughput results for given traffic profiles. However, these measures are not suitable as optimisation metrics. This paper first outlines a novel method to measure the average capacity metric of a network. Then we compare the optimisation of power efficiency to that of average capacity and investigate the effect each metric has on the other. Finally, a new approach to network optimisation is presented in the form of a multi-objective cross entropy optimisation. This optimisation simultaneously improves the capacity and power efficiency of the networks indicating that superior solutions can be found when considering the power and capacity problem in unison. When conducting the aforementioned optimisations, the impact that the insertion of additional nodes has upon the metrics is also investigated. The current literature suggests that the additional nodes would reduce the network capacity. Our results, however, show that this is not the case when appropriate transmission powers are utilised in conjunction with the node addition.; Robert Hunjet...

Design and capacity performance analysis of wireless mesh network

Ting, A.; Chieng, David
Fonte: ACM Publicador: ACM
Tipo: Conferência ou Objeto de Conferência Formato: application/pdf
Publicado em //2008
Relevância na Pesquisa
46.13%
From the network operator’s point of view, the high CAPEX/OPEX cost resulting from fixed/wired backhaul links can be inhibitive to successful deployment of broadband wireless services. The emerging wireless mesh network (WMN) technology is seen as one of the potential solutions which may reduce wired backhaul dependency through multihop transmission. Despite the advantages, many remain sceptical on WMN’s network capacity and scalability performances particularly when the user density is high. This paper provides an insight on the best possible upper-bound capacity performance of WMN, taking into consideration three key design parameters namely 1) Percentage of wired backhaul points per network, 2) Mesh-to-Access Link-Rate Ratio (R) and 3) Number of radio interfaces per mesh node including hybrid radio options. These design options are compared and contrasted with different deployment densities. The results generally show that the higher the number of backhaul points, the higher the effective access capacity available to mesh node and hence user domain. Increasing the R and the number of radio per mesh node are two alternative means to push up the effective access capacity per mesh node without increasing the number of wired backhaul points. This is most significant in multi radio system where about 80% of the backhaul points can be eliminated with R= 3 in order to maintain effective access capacity close to full rate (Capacity...

On-line disjoint path routing for network capacity maximization in energy-constrained ad hoc networks

Liang, Weifa; Liu, Yuzhen
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.1%
In this paper we consider on-line disjoint path routing in energy-constrained ad hoc networks. The objective is to maximize the network capacity, i.e. maximize the number of messages routed successfully by the network without any knowledge of future disjo

Network Capacity Region and Minimum Energy Function for a Delay-Tolerant Mobile Ad Hoc Network

Urgaonkar, Rahul; Neely, Michael J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/01/2011
Relevância na Pesquisa
46.1%
We investigate two quantities of interest in a delay-tolerant mobile ad hoc network: the network capacity region and the minimum energy function. The network capacity region is defined as the set of all input rates that the network can stably support considering all possible scheduling and routing algorithms. Given any input rate vector in this region, the minimum energy function establishes the minimum time average power required to support it. In this work, we consider a cell-partitioned model of a delay-tolerant mobile ad hoc network with general Markovian mobility. This simple model incorporates the essential features of locality of wireless transmissions as well as node mobility and enables us to exactly compute the corresponding network capacity and minimum energy function. Further, we propose simple schemes that offer performance guarantees that are arbitrarily close to these bounds at the cost of an increased delay.; Comment: Extended version of IEEE/ACM Transactions on Networking article

On Network Coding Capacity - Matroidal Networks and Network Capacity Regions

Kim, Anthony
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/03/2011
Relevância na Pesquisa
46.19%
One fundamental problem in the field of network coding is to determine the network coding capacity of networks under various network coding schemes. In this thesis, we address the problem with two approaches: matroidal networks and capacity regions. In our matroidal approach, we prove the converse of the theorem which states that, if a network is scalar-linearly solvable then it is a matroidal network associated with a representable matroid over a finite field. As a consequence, we obtain a correspondence between scalar-linearly solvable networks and representable matroids over finite fields in the framework of matroidal networks. We prove a theorem about the scalar-linear solvability of networks and field characteristics. We provide a method for generating scalar-linearly solvable networks that are potentially different from the networks that we already know are scalar-linearly solvable. In our capacity region approach, we define a multi-dimensional object, called the network capacity region, associated with networks that is analogous to the rate regions in information theory. For the network routing capacity region, we show that the region is a computable rational polytope and provide exact algorithms and approximation heuristics for computing the region. For the network linear coding capacity region...

Computing Bounds on Network Capacity Regions as a Polytope Reconstruction Problem

Kim, Anthony; Medard, Muriel
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.12%
We define a notion of network capacity region of networks that generalizes the notion of network capacity defined by Cannons et al. and prove its notable properties such as closedness, boundedness and convexity when the finite field is fixed. We show that the network routing capacity region is a computable rational polytope and provide exact algorithms and approximation heuristics for computing the region. We define the semi-network linear coding capacity region, with respect to a fixed finite field, that inner bounds the corresponding network linear coding capacity region, show that it is a computable rational polytope, and provide exact algorithms and approximation heuristics. We show connections between computing these regions and a polytope reconstruction problem and some combinatorial optimization problems, such as the minimum cost directed Steiner tree problem. We provide an example to illustrate our results. The algorithms are not necessarily polynomial-time.; Comment: Appeared in the 2011 IEEE International Symposium on Information Theory, 5 pages, 1 figure

Scalability and Dimensioning of Network-Capacity Measurement System using Reflecting Servers

Ekelin, Svante; Johnsson, Andreas; Flinta, Christofer
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/05/2015
Relevância na Pesquisa
46.11%
In a class of methods for measurement of available path capacity and other capacity-related metrics in a network, trains of probe packets are transmitted from a sender to a receiver across a network path, and the sequences of time stamps at sending and reception are analyzed. In large-scale implementations there may potentially be interference between the probe-packet trains corresponding to several concurrent measurement sessions, due to congestion in the network and common measurement end points. This paper outlines principles for large-scale deployments of network capacity measurement methods using standardized network functionality. Further, the paper provides an in-depth study of dimensioning and scalability challenges related to the measurement end-points of such systems. The main result is a framework for dimensioning of large-scale network capacity measurement systems based on TWAMP. The framework is based on a method for explicit calculation of queuelength and waiting-time distributions, where results from M/G/1 queuing theory are combined with Monte Carlo integration.

The Case for Structured Random Codes in Network Capacity Theorems

Nazer, Bobak; Gastpar, Michael
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/02/2008
Relevância na Pesquisa
46.03%
Random coding arguments are the backbone of most channel capacity achievability proofs. In this paper, we show that in their standard form, such arguments are insufficient for proving some network capacity theorems: structured coding arguments, such as random linear or lattice codes, attain higher rates. Historically, structured codes have been studied as a stepping stone to practical constructions. However, K\"{o}rner and Marton demonstrated their usefulness for capacity theorems through the derivation of the optimal rate region of a distributed functional source coding problem. Here, we use multicasting over finite field and Gaussian multiple-access networks as canonical examples to demonstrate that even if we want to send bits over a network, structured codes succeed where simple random codes fail. Beyond network coding, we also consider distributed computation over noisy channels and a special relay-type problem.; Comment: 23 pages, 7 figures, To appear in European Transactions on Telecommunication: Special Issue on New Directions in Information Theory

Storage of phase-coded patterns via STDP in fully-connected and sparse network: a study of the network capacity

Scarpetta, S.; de Candia, A.; Giacco, F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 07/09/2010
Relevância na Pesquisa
46.16%
We study the storage and retrieval of phase-coded patterns as stable dynamical attractors in recurrent neural networks, for both an analog and a integrate-and-fire spiking model. The synaptic strength is determined by a learning rule based on spike-time-dependent plasticity, with an asymmetric time window depending on the relative timing between pre- and post-synaptic activity. We store multiple patterns and study the network capacity. For the analog model, we find that the network capacity scales linearly with the network size, and that both capacity and the oscillation frequency of the retrieval state depend on the asymmetry of the learning time window. In addition to fully-connected networks, we study sparse networks, where each neuron is connected only to a small number z << N of other neurons. Connections can be short range, between neighboring neurons placed on a regular lattice, or long range, between randomly chosen pairs of neurons. We find that a small fraction of long range connections is able to amplify the capacity of the network. This imply that a small-world-network topology is optimal, as a compromise between the cost of long range connections and the capacity increase. Also in the spiking integrate and fire model the crucial result of storing and retrieval of multiple phase-coded patterns is observed. The capacity of the fully-connected spiking network is investigated...

Beamsteering on Mobile Devices: Network Capacity and Client Efficiency

Yu, Hang; Zhong, Lin; Sabharwal, Ashutosh
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/12/2010
Relevância na Pesquisa
46.06%
Current and emerging mobile devices are omni directional in wireless communication. Such omni directionality not only limits device energy efficiency but also poses a significant challenge toward the capacity of wireless networks through inter-link interference. In this work, we seek to make mobile clients directional with beamsteering. We first demonstrate that beamsteering is already feasible to mobile devices such as Netbooks and eBook readers in terms of form factor, power efficiency, and device mobility. We further reveal that beamsteering mobile clients face a unique challenge to balance client efficiency and network capacity. There is an optimal operating point for a beamsteering mobile client in terms of the number of antennas and transmit power that achieve the required capacity with lowest power. Finally, we provide a distributed algorithm called BeamAdapt that allows each client to closely approach its optimal point iteratively without central coordination. We also offer a cellular system realization of BeamAdapt. Using Qualnet-based simulation, we show that BeamAdapt with four antennas can reduce client power consumption by 55% while maintaining a required network throughput for a large-scale network, compared to the same network with omni directional mobile clients.

Towards a System Theoretic Approach to Wireless Network Capacity in Finite Time and Space

Ciucu, Florin; Khalili, Ramin; Jiang, Yuming; Yang, Liu; Cui, Yong
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46%
In asymptotic regimes, both in time and space (network size), the derivation of network capacity results is grossly simplified by brushing aside queueing behavior in non-Jackson networks. This simplifying double-limit model, however, lends itself to conservative numerical results in finite regimes. To properly account for queueing behavior beyond a simple calculus based on average rates, we advocate a system theoretic methodology for the capacity problem in finite time and space regimes. This methodology also accounts for spatial correlations arising in networks with CSMA/CA scheduling and it delivers rigorous closed-form capacity results in terms of probability distributions. Unlike numerous existing asymptotic results, subject to anecdotal practical concerns, our transient one can be used in practical settings: for example, to compute the time scales at which multi-hop routing is more advantageous than single-hop routing.

Neural Network Capacity for Multilevel Inputs

Stowe, Matt; Kak, Subhash
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 30/07/2013
Relevância na Pesquisa
46.04%
This paper examines the memory capacity of generalized neural networks. Hopfield networks trained with a variety of learning techniques are investigated for their capacity both for binary and non-binary alphabets. It is shown that the capacity can be much increased when multilevel inputs are used. New learning strategies are proposed to increase Hopfield network capacity, and the scalability of these methods is also examined in respect to size of the network. The ability to recall entire patterns from stimulation of a single neuron is examined for the increased capacity networks.; Comment: 24 pages,17 figures

Broadcasting for Network Lifetime Maximization in Wireless Sensor Networks

Guo, Xiaoxing
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Relevância na Pesquisa
45.97%
Networks that are dynamically formed by hundreds or thousands of inexpensive sensors are widely used in environmental monitoring, disaster recovery and the other domains. In this paper we present a protocol, LM-PB, for on-line broadcast routing in wireless sensor networks where the sensors are energy-constrained. Our protocol is aiming at maximizing the duration before the network becomes inoperative due to the lack of battery energy at sensors. An appropriate selection of transmitting sensors, which cover the rest in the network, is an efficient technique for broadcasting. LM-PB makes such selections by utilizing a novel timing heuristic, called FDL. It does not need any explicit control message and is free of exploring the network topology. Our experimental results demonstrate that LM-PB provides longer network lifetime compared with the existing passive protocols. Meanwhile we notice that the total number of successfully routed messages, termed as the network capacity, is also maximized by LM-PB. Particularly, the results indicate that the additional delay incurred by LM-PB is much less than the worst case analyzed value, and is acceptable.

On-Line Disjoint Path Routing for Network Capacity Maximization in Ad Hoc Networks

Liang, Weifa; Liu, Yuzhen; Guo, Xiaoxing
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Relevância na Pesquisa
66.09%
In this paper we consider on-line disjoint path routing in energy-constrained ad hoc networks. The objective is to maximize the network capacity, i.e., maximize the number of messages routed successfully by the network without any knowledge of future disjoint path connection request arrivals and generation rates. We first present two on-line algorithms for the problem. One is based on maximizing the network lifetime and another is based on an exponential function of energy utilization at nodes. We then conduct extensive experiments by simulations to analyze the performance of the proposed algorithms. The experimental results show that the proposed algorithms outperform those existing algorithms that do not take into account the power load balancing among the nodes.

Optimizing the Cellular Network Planning Process for In-Building Coverage using Simulation

Huerta-Barrientos,A.; Elizondo-Cortés,M.
Fonte: UNAM, Centro de Ciencias Aplicadas y Desarrollo Tecnológico Publicador: UNAM, Centro de Ciencias Aplicadas y Desarrollo Tecnológico
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2013 EN
Relevância na Pesquisa
46.01%
The global scenario of mobile telecommunications networks suggests that the next years the number of mobile users will continue growing as well as the services demand. The biggest growth is expected mainly in Asiatic and developing countries. Particularly, the Mexican telecommunications market suggests that if the number of mobile users will continue growing in Mexico as in the last years, then the mobile networks operators should increment the network capacity and the in-building coverage in order to maximize the quality of service. Also, network operators should offer attractive plans to users in order to maximize their economic benefits. Therefore, this research study aims to develop a simulation model to analyze the services transmission in a Third Generation mobile network and maximize the network coverage and the theoretical economic benefit of network operators. The delivered services included are voice, data and video. Using this simulation model we obtained the optimal cost-effective network design in a scenario of a Mexican airport. This design consisted of six cells, each one configured with an Omni-directional antenna and capacity of seven traffic channels. Through the traffic channels were delivered the services: sound...