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On delay-sensitive communication over wireless systemsLiu, Lingjia 15 May 2009 (has links)
This dissertation addresses some of the most important issues in delay-sensitive
communication over wireless systems and networks. Traditionally, the design of communication
networks adopts a layered framework where each layer serves as a “black
box” abstraction for higher layers. However, in the context of wireless networks with
delay-sensitive applications such as Voice over Internet Protocol (VoIP), on-line gaming,
and video conferencing, this layered architecture does not offer a complete picture.
For example, an information theoretic perspective on the physical layer typically ignores
the bursty nature of practical sources and often overlooks the role of delay in
service quality. The purpose of this dissertation is to take on a cross-disciplinary
approach to derive new fundamental limits on the performance, in terms of capacity
and delay, of wireless systems and to apply these limits to the design of practical
wireless systems that support delay-sensitive applications. To realize this goal, we
consider a number of objectives.
1. Develop an integrated methodology for the analysis of wireless systems that
support delay-sensitive applications based, in part, on large deviation theory.
2. Use this methodology to identify fundamental performance limits and to design
systems which allocate resources efficiently under stringent service requirements.
3. Analyze the performance of wireless communication networks that takes advantage of novel paradigms such as user cooperation, and multi-antenna systems.
Based on the proposed framework, we find that delay constraints significantly
influence how system resources should be allocated. Channel correlation has a major
impact on the performance of wireless communication systems. Sophisticated power
control based on the joint space of channel and buffer states are essential for delaysensitive
communications.
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Contribuições ao calculo de banda e de probabilidade de perda para trafego multifractal de redes / Contributions to the effective bandwidth and loss probability computing for multifractal network trafficVieira, Flavio Henrique Teles 19 December 2006 (has links)
Orientador: Lee Luan Ling / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-08T01:26:33Z (GMT). No. of bitstreams: 1
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Previous issue date: 2006 / Resumo: A modelagem multifractal generaliza os modelos de tráfego existentes na literatura e se mostra apropriada para descrever as características encontradas nos fluxos de tráfego das redes atuais. A presente tese investiga abordagens para alocação de banda, predição de tráfego e estimação de probabilidade de perda de bytes considerando as características multifractais de tráfego. Primeiramente, um Modelo Multifractal baseado em Wavelets (MMW) é proposto. Levando em consideração as propriedades deste modelo, são derivados o parâmetro de escala global, a função de autocorrelação e a banda efetiva para processos multifractais. A capacidade de atualização em tempo real do MMW aliada à banda efetiva proposta permite o desenvolvimento de um algoritmo de estimação adaptativa de banda efetiva. Através deste algoritmo é introduzido um esquema de provisão adaptativo de banda efetiva. Estuda-se também a alocação de banda baseada em predição de tráfego. Para este fim, propõe-se um preditor adaptativo fuzzy de tráfego, o qual é aplicado em uma nova estratégia de alocação de banda. O preditor fuzzy adaptativo proposto utiliza funções de base ortonormais baseadas nas propriedades do MMW. Com relação à probabilidade de perda para tráfego multifractal, derivase uma expressão analítica para a estimação da probabilidade de perda de bytes considerando que o tráfego obedece ao MMW. Além disso, uma caracterização mais completa do comportamento de fila é efetuada pela obtenção de limitantes para a probabilidade de perda e para a ocupação média do buffer em termos da banda efetiva do MMW. Por fim, é apresentado um esquema de controle de admissão usando o envelope efetivo proposto para o MMW oriundo do cálculo de rede estatístico, que garante que os fluxos admitidos obedeçam simultaneamente aos requisitos de perda e de retardo. As simulações realizadas evidenciam a relevância das propostas apresentadas / Abstract: Multifractal modeling generalizes the existing traffic models and is believed to be appropriate to describe the characteristics of traffic flows of modern communication networks. This thesis investigates some novel approaches for bandwidth allocation, traffic prediction and byte loss probability estimation, by considering the multifractal characteristics of the network traffic. Firstly, a Wavelet based Multifractal Model (WMM) is proposed. Taking into account the properties of this multifractal model, we derive the global scaling parameter, the autocorrelation function and the effective bandwidth for multifractal processes. The real time updating capacity of the WMM in connection with our effective bandwidth proposal allows us to develop an algorithm for adaptive effective bandwidth estimation. Then, through this algorithm, an adaptive bandwidth provisioning scheme is introduced. In this work, we also study a prediction-based bandwidth allocation case. For this end, we develop an adaptive fuzzy predictor, which is incorporated into a novel bandwidth allocation scheme. The proposed adaptive fuzzy predictor makes use of orthonormal basis functions based on the properties of the WMM. Additionally, we derive an analytical expression for the byte loss probability estimation assuming that the traffic obeys the MMW. Besides, a more complete characterization of the queuing behavior is carried out through the estimation of the bounds for the loss probability and mean queue length in buffer in terms of the WMM based effective bandwidth. Finally, an admission control scheme is presented that uses the WMM based effective envelope derived through the statistical network calculus, guaranteeing that the admitted flows simultaneously attend the loss and delay requirements. The computer simulation results confirm the relevance of the presented proposals / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica
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Alocação dinâmica de recursos em redes OFDM multiusuários baseada em banda efetivaGonçalves, Bruno Henrique Pereira 19 December 2013 (has links)
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Previous issue date: 2013-12-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This paper proposes adaptive resource allocation in multiuser wireless networks based on
OFDM. Two allocation schemes are proposed: for TDMA networks and LTE networks.
The resource allocation schemes that provide QoS are developed from the union of OFDM
wireless networks, the proposal of adaptive modeling of traffic flows and the proposal of
adaptive estimation of effective bandwidth. The performances of the proposed schemes
are verified through simulation. Concepts and studies on traffic modeling, multifractal
traffic modeling, theory of effective bandwidth, OFDM, are addressed in order to support
the understanding and development of the proposed schemes. An algorithm for adaptive
parameter estimation of the multifractal model bMWM is proposed, and studies to
estimate the effective bandwidth are presented. Some methods of estimating effective
bandwidth are proposed using traffic flow models. / Este trabalho propõe esquemas de alocação adaptativa de recursos em redes sem fio
multiusuário OFDM. Dois esquemas de alocação são propostos: para redes TDMA e
para redes LTE. Os esquemas de alocação de recursos foram elaborados a partir da
união de tecnologia de redes sem fio OFDM, proposta de modelagem adaptativa de
fluxos de tráfego e proposta de estimação adaptativa de banda efetiva, de maneira a
garantir requisitos de QoS em redesmultiusuário. Simulações são realizadas para validar o
desempenho dos esquemas de alocação propostos. Conceitos e estudos sobre modelagem
de tráfego, modelagem de tráfego multifractal, teoria de banda efetiva e OFDM são
tratados de maneira a subsidiar o entendimento e a elaboração dos esquemas propostos. É
proposto um algoritmo para estimação adaptativa de parâmetros do modelo multifractal
bMWM, e são apresentados estudos realizados para estimação de banda efetiva. Alguns
métodos de estimação de banda efetiva são propostos utilizando modelos de fluxo de
tráfego.
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Analytical Modelling and Optimization of Congestion Control for Prioritized Multi-Class Self-Similar TrafficMin, Geyong, Jin, X. January 2013 (has links)
No / Traffic congestion in communication networks can dramatically deteriorate user-perceived Quality-of-Service (QoS). The integration of the Random Early Detection (RED) and priority scheduling mechanisms is a promising scheme for congestion control and provisioning of differentiated QoS required by multimedia applications. Although analytical modelling of RED congestion control has received significant research efforts, the performance models reported in the current literature were primarily restricted to the RED algorithm only without consideration of traffic scheduling scheme for QoS differentiation. Moreover, for analytical tractability, these models were developed under the simplified assumption that the traffic follows Short-Range-Dependent (SRD) arrival processes (e.g., Poisson or Markov processes), which are unable to capture the self-similar nature (i.e., scale-invariant burstiness) of multimedia traffic in modern communication networks. To fill these gaps, this paper presents a new analytical model of RED congestion control for prioritized multi-class self-similar traffic. The closed-form expressions for the loss probability of individual traffic classes are derived. The effectiveness and accuracy of the model are validated through extensive comparison between analytical and simulation results. To illustrate its application, the model is adopted as a cost-effective tool to investigate the optimal threshold configuration and minimize the required buffer space with congestion control.
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