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CSMA with Implicit Scheduling through State-keeping: A Distributed MAC Framework for QoS in Broadcast LANsKangude, Shantanu 13 May 2004 (has links)
Channel access fairness and efficiency in capacity utilization are the two main objectives for Quality of Service (QoS) specific to Medium Access Control (MAC) protocols in computer networks. For bursty and unpredictable traffic in networks, fairness and efficiency involve a mutual tradeoff with the currently popular QoS mechanisms. We propose a QoS MAC framework for carrier sensing multiple access (CSMA) networks, that achieves fairness with improved efficiency through extensive state-keeping based on the MAC evolution. This CSMA with Implicit Scheduling through State-keeping (CSMA/ISS) framework involves the tracking of traffic arrival at active nodes, the nodes that need channel access frequently. It also involves implicit channel access grants to different active nodes according to their estimated queue backlogs and the fair scheduling requirements. These methods save channel capacity that may otherwise be required for disseminating the access requirements of various nodes, and their access rights according to fairness rules. A static, hierarchical, and weighted fair access scheme is designed in CSMA/ISS by allowing repeated rounds of access that are weighted fairly according to requirements. Weighted fairness across classes is achieved by invoking channel access for each traffic class in a round as many times as its weight. Within each class, all active nodes are allowed equal access through in-order channel access based on a looped list of active nodes. Although CSMA/ISS is proposed as a distributed control framework for efficiency, it may also be employed in central control protocols. It may also be adapted to different types of CSMA networks, both wireless and wired, by an appropriate choice of the underlying classical access mechanism. The CSMA/ISS framework was modeled and simulated as a QoS capable MAC protocol for a wired fully connected local network environment. We present the CSMA/ISS framework, the example implementation, and the results of performance evaluation of the example implementation. Significant performance improvements were observed, and the memory and processing trade-off was found to be low to moderate.
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[en] A FRAMEWORK FOR SIMULATION OF MOBILE AD HOC NETWORKS / [pt] UM FRAMEWORK PARA SIMULAÇÃO DE REDES MÓVEIS AD HOCALEXANDRE MELE 28 August 2003 (has links)
[pt] Uma rede móvel ad hoc consiste de uma coleção de
dispositivos computacionais portáteis, equipados com uma
interface de comunicação sem fio, com uma distribuição
arbitrária e dinâmica no espaço, e onde cada host também
serve de roteador para os demais hosts, descobrindo e
mantendo rotas multi-hop entre os hosts. De uma forma
geral, os protocolos para redes móveis ad hoc são mais
complexos do que os protocolos para as redes fixas, devido
à várias características destas redes, como por exemplo, a
topologia dinâmica, a interferência mútua, o acesso
compartilhado e a largura de banda restrita dos enlaces sem
fio, bem como a operação com energia restrita e menor
quantidade de recursos disponíveis nos hosts móveis.
Um grande foco da pesquisa em redes móveis ad hoc tem sido o
desenvolvimento, a análise e a comparação de protocolos de
roteamento. Por isto, existe a demanda por ambientes para a
prototipação rápida, a simulação e a depuração de
protocolos de roteamento (e de outras camadas) para este
tipo de redes. Preferencialmente estes ambientes devem ser
flexíveis, ser simples de usar, e permitir definir vários
níveis de abstrações para descrever as características
físicas da rede móvel, tais como o padrão de mobilidade, os
enlaces sem fio, consumo de energia, etc. Esta dissertação
trata do projeto e implementação de um framework para a
simulação de redes móveis ad hoc que visa facilitar a
criação de ambientes para prototipação, teste, análise de
desempenho e complexidade de protocolos para este tipo de
redes. / [en] A mobile ad hoc network consists of a set of portable
computational devices, equipped with a wireless
communication interface, that are randomly and
dynamically distributed in space, and where each host
serves as a router for the other hosts by discovering and
maintaining multi-hop routes among the hosts. In general,
protocols for mobile ad hoc networks are more complex than
equivalent protocols for static networks, due to several
properties of such networks, such as its dynamic topology,
the mutual interference, concurrent access and smaller
communication bandwidth of the wireless links, as well as,
operation with restricted amount of energy, and scarce
resources of the mobile devices. A main focus of research
in mobile ad hoc networks has been the development,
analysis and comparison of routing protocols for such
networks. Therefore, there is some demand for environments
that facilitate the rapid prototyping, the simulation and
the debugging of protocols at the network and other layers
for such networks. These environments should preferably be
flexible, easy to use, and allow for the definition of
different levels of abstractions for modeling the main
characteristics of the mobile network, such as the pattern
of mobility, the wireless links, the energy consumption,
etc. This thesis describes the design and implementation of
a framework for the simulation of mobile ad hoc networks,
which aims at supporting the development of concrete
simulation environments for prototyping, testing and doing
the complexity and performance analysis of protocols for
such networks.
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