Página 1 dos resultados de 75 itens digitais encontrados em 0.004 segundos

Alocação dinâmica de largura de banda em redes EPON; Dynamic bandwidth allocation for EPON networks

Carrasco Arbieto, Carmen Orencia
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
Relevância na Pesquisa
76.54%
As redes de telecomunicações se dividem em redes de longa distância, redes metropolitanas e redes de acesso. As redes de longa distância e metropolitana usufruem a alta capacidade de largura de banda da fibra óptica, enquanto nas redes de acesso há um gargalo de largura de banda por causa do uso de pares de fios e cabo coaxial. Para solucionar este problema e oferecer aos usuários acesso banda larga de baixo custo foram propostas as redes ópticas passivas (passive optical network - PON). A PON é formada por dois elementos básicos, a unidade de rede óptica (optical network unit - ONU), localizada perto dos assinantes, e o terminal de linha óptica (optical line terminal - OLT), localizado próximo ao provedor de serviços. Dentre os padrões disponíveis para redes PON, o Ethernet (EPON), padronizado pelo grupo IEEE 802.3ah, é opção atraente porque ele é bastante difundido nas redes locais. O protocolo de controle multiponto (multipoint control protocol - MPCP), já especificado, é responsável pelo controle de acesso ao meio, fornecendo infra-estrutura de sinalização para transmissão entre OLT e ONUs. Entretanto, o algoritmo de alocação de largura de banda, que realiza o controle de acesso ao meio com base no MPCP...

Algoritmo de alocação dinâmica de largura de faixa para redes de comunicação móvel celular; Dynamic bandwidth allocation algorithm for mobile communication networks

Queiroz, Eduardo Martinelli Galvão de
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
Relevância na Pesquisa
66.28%

Algoritmos para alocação de banda em redes de acesso GPON; Algorithms for bandwidth allocation in GPON access networks

Santos, Alex Ferreira dos
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
Relevância na Pesquisa
66.53%

Differential bandwidth allocation with multiplexed TCP connections

Iwashima, Hiroyoshi, 1980-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 66 p.; 3876583 bytes; 3882882 bytes; application/pdf; application/pdf
EN_US
Relevância na Pesquisa
46.09%
This thesis presents and evaluates the design and implementation of a user-level library that performs bandwidth allocation among multiple application flows using multiple TCP connections. This work is motivated by emerging trends in network overlay applications to send multiple flows of data between machines. Existing approaches to manage the network either do not offer the control over network resources that these applications need, or are difficult to adopt. We present a novel user-level approach to this problem that uses multiple TCP connections, and we also present an evaluation of multiplexing strategies for the scheduler that multiplexes the multiple application flows onto the multiple TCP connections. We implemented and designed two scheduling algorithms, striping and pinning, to perform the multiplexing and evaluated them for various application behavior and various link characteristics through emulation. We describe how striping is preferred for applications that are not delay dependent, as well as applications that are not order dependent, while pinning is preferred for applications that are heavily memory constrained. Our results show that, for delay-constrained applications, links with low loss and low number of cross traffic favor the striping scheduler...

Efficient asynchronous scheduling algorithms for cost-effective buffered crossbar switches

Karimi, Masoumeh
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.35%
Buffered crossbar switches have recently attracted considerable attention as the next generation of high speed interconnects. They are a special type of crossbar switches with an exclusive buffer at each crosspoint of the crossbar. They demonstrate unique advantages over traditional unbuffered crossbar switches, such as high throughput, low latency, and asynchronous packet scheduling. However, since crosspoint buffers are expensive on-chip memories, it is desired that each crosspoint has only a small buffer.^ This dissertation proposes a series of practical algorithms and techniques for efficient packet scheduling for buffered crossbar switches. To reduce the hardware cost of such switches and make them scalable, we considered partially buffered crossbars, whose crosspoint buffers can be of an arbitrarily small size. Firstly, we introduced a hybrid scheme called Packet-mode Asynchronous Scheduling Algorithm (PASA) to schedule best effort traffic. PASA combines the features of both distributed and centralized scheduling algorithms and can directly handle variable length packets without Segmentation And Reassembly (SAR). We showed by theoretical analysis that it achieves 100% throughput for any admissible traffic in a crossbar with a speedup of two. Moreover...

Bandwidth allocation for quality of service provision in IEEE 802.16 systems.

Tang, Tze Wei
Relevância na Pesquisa
46.09%
This thesis investigates various aspects of bandwidth allocation and scheduling in the Medium Access Control (MAC) layer of IEEE 802.16 systems. We highlight the important aspects of designing a scheduler and describe the scheduler design problem from a general perspective. That is, we provide a scheduler design framework driven by a set of objectives defined for the systems. In addition, we include Subscriber Station differentiation into our scheduler design. This approach is comprehensive, as it covers the requirements of both the network provider and the end users. In developing the framework, we discuss the importance of achieving customer satisfaction. This leads to an interesting objective that maximises the number of satisfied customers, rather than network centric objectives, such as fairness. We contend that providing fairness to customers does not necessarily achieve the best outcome for customer satisfaction and artificially limits the choices available to service providers. In order to maximise the number of satisfied customers, we analyse in detail the Dual-Queue (DQ) scheduling discipline proposed by Hayes et al. [2]. The DQ algorithms of Hayes’ work are focused on wireline networks, and are not directly deployable in an 802.16 environment...

Dynamic Bit Allocation for Object Tracking in Bandwidth Limited Sensor Networks

Masazade, Engin; Niu, Ruixin; Varshney, Pramod K.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.36%
In this paper, we study the target tracking problem in wireless sensor networks (WSNs) using quantized sensor measurements under limited bandwidth availability. At each time step of tracking, the available bandwidth $R$ needs to be distributed among the $N$ sensors in the WSN for the next time step. The optimal solution for the bandwidth allocation problem can be obtained by using a combinatorial search which may become computationally prohibitive for large $N$ and $R$. Therefore, we develop two new computationally efficient suboptimal bandwidth distribution algorithms which are based on convex relaxation and approximate dynamic programming (A-DP). We compare the mean squared error (MSE) and computational complexity performances of convex relaxation and A-DP with other existing suboptimal bandwidth distribution schemes based on generalized Breiman, Friedman, Olshen, and Stone (GBFOS) algorithm and greedy search. Simulation results show that, A-DP, convex optimization and GBFOS yield similar MSE performance, which is very close to that based on the optimal exhaustive search approach and they outperform greedy search and nearest neighbor based bandwidth allocation approaches significantly. Computationally, A-DP is more efficient than the bandwidth allocation schemes based on convex relaxation and GBFOS...

Joint Downlink Cell Association and Bandwidth Allocation for Wireless Backhauling in Two-Tier HetNets with Large-Scale Antenna Arrays

Wang, Ning; Hossain, Ekram; Bhargava, Vijay K.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.29%
The problem of joint downlink cell association (CA) and wireless backhaul bandwidth allocation (WBBA) in two-tier cellular heterogeneous networks (HetNets) is considered. Large-scale antenna array is implemented at the macro base station (BS), while the small cells within the macro cell range are single-antenna BSs and they rely on over-the-air links to the macro BS for backhauling. A sum logarithmic user rate maximization problem is investigated considering wireless backhauling constraints. A duplex and spectrum sharing scheme based on co-channel reverse time-division duplex (TDD) and dynamic soft frequency reuse (SFR) is proposed for interference management in two-tier HetNets with large-scale antenna arrays at the macro BS and wireless backhauling for small cells. Two in-band WBBA scenarios, namely, unified bandwidth allocation and per-small-cell bandwidth allocation scenarios, are investigated for joint CA-WBBA in the HetNet. A two-level hierarchical decomposition method for relaxed optimization is employed to solve the mixed-integer nonlinear program (MINLP). Solutions based on the General Algorithm Modeling System (GAMS) optimization solver and fast heuristics are also proposed for cell association in the per-small-cell WBBA scenario. It is shown that when all small cells have to use in-band wireless backhaul...

A Study on Impacts of RTT Inaccuracy on Dynamic Bandwidth Allocation in PON and Solution

Hong, Son Nguyen; Anh, Hao Nguyen; Trong, Thua Huynh
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.47%
The circle travelling delay between OLT (Optical Line Terminal) and ONU (Optical Network Unit) is one of most important items in dynamic bandwidth allocation (DBA) algorithms in PON, called RTT (Round Trip Time). The RTT is taken into account when OLT assigns the start times for upstream bandwidth grants. In most case, RTT is estimated before making bandwidth allocation decisions in dynamic bandwidth allocation algorithms. If the estimated RTT is incorrect, the bandwidth allocation decisions are not matched with bandwidth requests of channels. Thus, performance of PON can get worse by deviation of RTT. There are several reasons that cause the RTT to be varying, such as processing delay, distance of OLT and ONU, changing in fiber refractive index resulting from temperature drift, and degree of accuracy of RTT estimation methods. In this paper, we evaluate the impacts of RTT inaccuracy on performance of DBA and identify levels of collision and waste of bandwidth. By this way, we propose a method to remedy the performance degradation encountered by the situation; Comment: 10 pages, 4 figures, IJCNC

Efficient Upload Bandwidth Estimation and Communication Resource Allocation Techniques

Andreica, Mugurel Ionut; Tapus, Nicolae
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.09%
In this paper we address two problems, for which we present novel, efficient, algorithmic solutions. The first problem is motivated by practical situations and is concerned with the efficient estimation of the upload bandwidth of a machine, particularly in the context of a peer-to-peer content sharing and distribution application. The second problem is more of a theoretical nature and considers a constrained communication resource allocation situation.; Comment: Proceedings of the 9th WSEAS International Conference on Multimedia, Internet & Video Technologies (MIV), Budapest, Hungary, 3-5 September, 2009; ISBN: 978-960-474-114-4 / ISSN: 1790-5109

Gotsis, Antonis G.; Komnakos, Dimitris I.; Vouyioukas, Demosthenes D.; Constantinou, Philip
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.23%
Adaptive Radio Resource Allocation is essential for guaranteeing high bandwidth and power utilization as well as satisfying heterogeneous Quality-of-Service requests regarding next generation broadband multicarrier wireless access networks like LTE and Mobile WiMAX. A downlink OFDMA single-cell scenario is considered where heterogeneous Constant-Bit-Rate and Best-Effort QoS profiles coexist and the power is uniformly spread over the system bandwidth utilizing a Uniform Power Loading (UPL) scenario. We express this particular QoS provision scenario in mathematical terms, as a variation of the well-known generalized assignment problem answered in the combinatorial optimization field. Based on this concept, we propose two heuristic search algorithms for dynamically allocating subchannels to the competing QoS classes and users which are executed under polynomially-bounded cost. We also propose an Integer Linear Programming model for optimally solving and acquiring a performance upper bound for the same problem at reasonable yet high execution times. Through extensive simulation results we show that the proposed algorithms exhibit high close-to-optimal performance, thus comprising attractive candidates for implementation in modern OFDMA-based systems.; Comment: accepted for publication at the Springer Telecommunication Systems Journal (TSMJ)

Multiuser Joint Energy-Bandwidth Allocation with Energy Harvesting - Part I: Optimum Algorithm & Multiple Point-to-Point Channels

Wang, Zhe; Aggarwal, Vaneet; Wang, Xiaodong
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.4%
In this paper, we develop optimal energy-bandwidth allocation algorithms in fading channels for multiple energy harvesting transmitters, each may communicate with multiple receivers via orthogonal channels. We first assume that the side information of both the channel states and the energy harvesting states is known for $K$ time slots {\em a priori}, and the battery capacity and the maximum transmission power in each time slot are bounded. The objective is to maximize the weighted sum-rate of all transmitters over the $K$ time slots by assigning the transmission power and bandwidth for each transmitter in each slot. The problem is formulated as a convex optimization problem with ${\cal O}(MK)$ constraints, where $M$ is the number of the receivers, making it hard to solve with a generic convex solver. An iterative algorithm is proposed that alternatively solves two subproblems in each iteration. The convergence and the optimality of this algorithm are also shown. We then consider the special case that each transmitter only communicates with one receiver and the objective is to maximize the total throughput. We develop efficient algorithms for solving the two subproblems and the optimal energy-bandwidth allocation can be obtained with an overall complexity of ${\cal O}(MK^2)$. Moreover...

Multiuser Joint Energy-Bandwidth Allocation with Energy Harvesting - Part II: Multiple Broadcast Channels & Proportional Fairness

Wang, Zhe; Aggarwal, Vaneet; Wang, Xiaodong
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.36%
In this paper, we consider the energy-bandwidth allocation for a network with multiple broadcast channels, where the transmitters access the network orthogonally on the assigned frequency band and each transmitter communicates with multiple receivers orthogonally or non-orthogonally. We assume that the energy harvesting state and channel gain of each transmitter can be predicted for $K$ slots {\em a priori}. To maximize the weighted throughput, we formulate an optimization problem with $O(MK)$ constraints, where $M$ is the number of the receivers, and decompose it into the energy and bandwidth allocation subproblems. In order to use the iterative algorithm proposed in [1] to solve the problem, we propose efficient algorithms to solve the two subproblems, so that the optimal energy-bandwidth allocation can be obtained with an overall complexity of ${\cal O}(MK^2)$, even though the problem is non-convex when the broadcast channel is non-orthogonal. For the orthogonal broadcast channel, we further formulate a proportionally-fair (PF) throughput maximization problem and derive the equivalence conditions such that the optimal solution can be obtained by solving a weighted throughput maximization problem. Further, the algorithm to obtain the proper weights is proposed. Simulation results show that the proposed algorithm can make efficient use of the harvested energy and the available bandwidth...

A Distributed Cluster Scheme For Bandwidth Management In Multi-hop MANETs

Pattanayak, Binod Kumar; Jagadev, Alok Kumar; Mishra, Manoj Kumar; Nayak, Manoj Ranjan
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.19%
Electronic collaboration among devices in a geographically localized environment is made possible with the implementation of IEEE 802.11 based wireless ad hoc networks. Dynamic nature of mobile ad hoc networks(MANETs) may lead to unpredictable intervention of attacks or fault occurrence, which consequently may partition the network, degrade its performance, violate the QoS requirements and most importantly, affect bandwidth allocation to mobile nodes in the network. In this paper, we propose a new distributed cluster scheme for MANETs, especially in harsh environments, based on the concept of survivability to support QoS requirements and to protect bandwidth efficiently. With the incorporation of clustering algorithms in survivability technology, we employ a simple network configuration and expect to reduce occurrences of faults in MANETs. At the same time, we address the scalability problem, which represents a great challenge to network configuration. We do expect a simplification of accessing bandwidth allocation with required QoS support for different applications.; Comment: 7 pages, 5 figures

Online Bandwidth Allocation

Forišek, Michal; Katreniak, Branislav; Katreniaková, Jana; Královič, Rastislav; Královič, Richard; Koutný, Vladimír; Pardubská, Dana; Plachetka, Tomáš; Rovan, Branislav
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.97%
The paper investigates a version of the resource allocation problem arising in the wireless networking, namely in the OVSF code reallocation process. In this setting a complete binary tree of a given height $n$ is considered, together with a sequence of requests which have to be served in an online manner. The requests are of two types: an insertion request requires to allocate a complete subtree of a given height, and a deletion request frees a given allocated subtree. In order to serve an insertion request it might be necessary to move some already allocated subtrees to other locations in order to free a large enough subtree. We are interested in the worst case average number of such reallocations needed to serve a request. It was proved in previous work that the competitive ratio of the optimal online algorithm solving this problem is between 1.5 and O(n). We partially answer the question about its exact value by giving an O(1)-competitive online algorithm. Same model has been used in the context of memory management systems, and analyzed for the number of reallocations needed to serve a request in the worst case. In this setting, our result is a corresponding amortized analysis.

Self-Stabilizing TDMA Algorithms for Dynamic Wireless Ad-hoc Networks

Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.98%
In dynamic wireless ad-hoc networks (DynWANs), autonomous computing devices set up a network for the communication needs of the moment. These networks require the implementation of a medium access control (MAC) layer. We consider MAC protocols for DynWANs that need to be autonomous and robust as well as have high bandwidth utilization, high predictability degree of bandwidth allocation, and low communication delay in the presence of frequent topological changes to the communication network. Recent studies have shown that existing implementations cannot guarantee the necessary satisfaction of these timing requirements. We propose a self-stabilizing MAC algorithm for DynWANs that guarantees a short convergence period, and by that, it can facilitate the satisfaction of severe timing requirements, such as the above. Besides the contribution in the algorithmic front of research, we expect that our proposal can enable quicker adoption by practitioners and faster deployment of DynWANs that are subject changes in the network topology.

Fairness for ABR multipoint-to-point connections

Fahmy, Sonia; Jain, Raj; Goyal, Rohit; Vandalore, Bobby
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.06%
In multipoint-to-point connections, the traffic at the root (destination) is the combination of all traffic originating at the leaves. A crucial concern in the case of multiple senders is how to define fairness within a multicast group and among groups and point-to-point connections. Fairness definition can be complicated since the multipoint connection can have the same identifier (VPI/VCI) on each link, and senders might not be distinguishable in this case. Many rate allocation algorithms implicitly assume that there is only one sender in each VC, which does not hold for multipoint-to-point cases. We give various possibilities for defining fairness for multipoint connections, and show the tradeoffs involved. In addition, we show that ATM bandwidth allocation algorithms need to be adapted to give fair allocations for multipoint-to-point connections.; Comment: Proceedings of SPIE 98, November 1998

Optimal Bandwidth and Power Allocation for Sum Ergodic Capacity under Fading Channels in Cognitive Radio Networks

Gong, Xiaowen; Vorobyov, Sergiy A.; Tellambura, Chintha
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.29%
This paper studies optimal bandwidth and power allocation in a cognitive radio network where multiple secondary users (SUs) share the licensed spectrum of a primary user (PU) under fading channels using the frequency division multiple access scheme. The sum ergodic capacity of all the SUs is taken as the performance metric of the network. Besides all combinations of the peak/average transmit power constraints at the SUs and the peak/average interference power constraint imposed by the PU, total bandwidth constraint of the licensed spectrum is also taken into account. Optimal bandwidth allocation is derived in closed-form for any given power allocation. The structures of optimal power allocations are also derived under all possible combinations of the aforementioned power constraints. These structures indicate the possible numbers of users that transmit at nonzero power but below their corresponding peak powers, and show that other users do not transmit or transmit at their corresponding peak power. Based on these structures, efficient algorithms are developed for finding the optimal power allocations.; Comment: 28 pages, 6 figures, submitted to the IEEE Trans. Signal Processing in June 2010

A note on the data-driven capacity of P2P networks

Chakareski, Jacob; Frossard, Pascal; Kerivin, Hervé; Leblet, Jimmy; Simon, Gwendal
Tipo: Artigo de Revista Científica