An analytical packet/flow-level modelling approach for wireless LANs with Quality-of-Service support

We present an analytical packet/flow-level modelling approach for the performance analysis of IEEE 802.11e WLAN, where we explicitly take into account QoS differentiation mechanisms based on minimum contention window size values and Arbitration InterFrame Space (AIFS) values, as included in the Enhanced Distributed Channel Access (EDCA) protocol of the 802.11e standard. We first enhance the packet-level approach previously used for best-effort WLANs to include traffic classes with different QoS requirements. The packet-level model approach yields service weights that discriminate among traffic classes. From these observations, the packet/flow-level model for 802.11e is the \textit{generalized} discriminatory processor-sharing (GDPS) queueing model where the state-dependent system capacity is distributed among active traffic classes according to state-dependent priority weights. Extensive simulations show that the discriminatory processor-sharing model closely represents the flow behavior of 802.11e

Throughput quantitative analysis of EDCA 802.11e in different scenarios

This document presents a quantitative analysis of the direct and relative throughput of IEEE 802.11e. The global throughput of an 802.11e WLAN is determined by EDCA (Enhanced Distributed Channel Access) parameters, among other aspects, that are usually configured with predetermined and static values. This study carefully evaluates the Quality of Service (QoS) of Wi-Fi with EDCA in several realistic scenarios with noise and a blend of wireless traffic (e.g., voice, video, and best effort, with Pareto distribution). The metrics of the benefits obtained in each case are compared, and the differentiated impact of network dynamics on each case is quantified. The results obtained show that the default settings are not optimal, and that with an appropriate selection, can be achieved improvements of the order of 25 %, according to the type of traffic. In addition, it could be shown the quantitative impact of each parameter EDCA on the overall performance. This study proposes a new experimental scenario based on the relative proportion of traffic present in the network. Stations have been simulated using the Möbius tool, which supports an extension of SPN (Stochastic Petri Networks), known as HSAN (Hierarchical Stochastic Activity Networks).Facultad de Informátic

Providing proportional differentiation in end-to-end quality of service for wireless multi-hop ad hoc network

Master'sMASTER OF ENGINEERIN

Uma proposta de escalonamento confiável para redes sem fio baseadas no padrão IEEE 802.11/11e

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia ElétricaEste trabalho investiga o problema de escalonamento de recursos de rede no contexto de sistemas móveis cooperativos que trocam mensagens com requisitos de tempo real firmes utilizando uma rede sem fio compatível com o adendo IEEEE 802.11e. Assim, devido a aspectos físicos da comunicação sem fio, a retransmissão de mensagens é um problema crucial, especialmente em uma aplicação de tempo real. Experimentos realizados neste contexto mostraram que a abordagem regular para retransmissões proposta pelo adendo IEEE 802.11e não é suficiente para aplicações de tempo real que necessitam um certo nível de confiabilidade. Para tratar este problema, este trabalho propõe uma nova abordagem que integra retransmissão e escalonamento de mensagens de forma combinada na camada de acesso ao meio. De acordo com a abordagem proposta, o algoritmo de escalonamento é capaz de lidar com os erros de transmissão residuais e aumentar o grau de confiabilidade para as mensagens de tempo real. Assim, a solução proposta é flexível para lidar com falhas inesperadas e suportar requisitos adicionais de qualidade de serviço aumentando a robustez e a adaptabilidade do sistema. A abordagem proposta é avaliada através de simulações em diferentes cenários de carga de tráfego. Os resultados obtidos são analisados comparativamente com a abordagem padrão para escalonamento e retransmissão do adendo IEEE 802.11e. Estes resultados confirmam os benefícios da proposta

Quality of Service Support in IEEE 802.11 Wireless LAN

Wireless Local Area Networks (WLANs) are gaining popularity at an unprecedented rate, at home, at work, and in public hot spot locations. As these networks become ubiquitous and an integral part of the infrastructure, they will be increasingly used for multi-media applications. The heart of the current 802.11 WLANs mechanism is the Distributed Coordination Function (DCF) which does not have any Quality of Service (QoS) support. The emergence of multimedia applications, such as the local services in WLANs hotspots and distributions of entertainment in residential WLANs, has prompted research in QoS support for WLANs. The absence of QoS support results in applications with drastically different requirements receiving the same (yet potentially unsatisfactory) service. Without absolute throughput support, the performance of applications with stringent throughput requirements will not be met. Without relative throughput support, heterogeneous types of applications will be treated unfairly and their performance will be poor. Without delay constraint support, time-sensitive applications will not even be possible. The objective of this dissertation is, therefore, to develop a comprehensive and integrated solution to provide effective and efficient QoS support in WLANs in a distributed, fair, scalable, and robust manner.In this dissertation, we present a novel distributed QoS mechanism called Distributed Relative/Absolute Fair Throughput with Delay Support (DRAFT+D). DRAFT+D is de- signed specifically to provide integrated QoS support in IEEE 802.11 WLANs. Unlike any other distributed QoS mechanism, DRAFT+D supports two QoS metrics (throughput and delay) with two QoS models (absolute and relative) under two fairness constraints (utilitarian and temporal fairness) in the same mechanism at the same time a fully distributed manner. DRAFT+D is also equipped with safeguards against excessive traffic injection DRAFT+D operates as a fair-queuing mechanism that controls packet transmissions (a) by using a distributed deficit round robin mechanism and (b) by modifying the way Backoff Interval (BI) are calculated for packets of different traffic classes. Fair relative throughput support is achieved by calculating BI based on the throughput requirements. Absolute throughput and delay support are achieved by allocating sufficient shares of bandwidth to these types of traffic