Quality of service in WiMAX networks

Mestrado em Engenharia Electrónica e TelecomunicaçõesO acesso à banda larga é um requisito importante na actualidade para satisfazer os utilizadores em termos de novas aplicações e serviços em tempo real. O WiMAX, como tecnologia sem fios para áreas metropolitanas, prometendo cobrir uma maior superfície e com maior débito, é uma tecnologia promissora para as redes de próxima geração. No entanto um requisito importante para a instalação e massificação desta tecnologia é o seu comportamento a nível de qualidade de serviços e garantia aos utilizadores do cumprimento eficiente dos requisitos de QoS. Esta tese aborda e estuda o suporte de qualidade de serviços para redes WiMAX presente em diferentes modelos de simulação, implementados na ferramenta de simulação ns-2. Para além da validação e comparação entre os modelos existentes, também é efectuada a especificação e implementação de uma solução de QoS composta por um classificador e escalonador, e é proposto e avaliado um algoritmo de escalonamento que utiliza prioritização de classes de serviço e informação física dinâmica “cross layer” para decisões de escalonamento no simulador. Para validar e avaliar as soluções propostas e desenvolvidas, um conjunto de cenários orientados para a utilização de vários serviços e aferição de métricas de QoS foram simulados. Os resultados obtidos mostram a diferenciação entre distintas classes de tráfego. O mecanismo proposto apresenta um pequeno ganho em débito e latência comparativamente às soluções previamente analisadas/implementadas. ABSTRACT: Broadband access is an important requirement to satisfy user demands and support a new set of real time services and applications. WiMAX, as a Broadband Wireless Access solution for Wireless Metropolitan Area Networks, covering large distances with high throughputs, is a promising technology for Next Generation Networks. Nevertheless, for the successful deployment and massification of WiMAX based solutions, Quality of Service (QoS) is a mandatory feature that must be supported. In this thesis , the QoS support for WiMAX in ns-2 simulation software is addressed. A QoS framework, composed by a packet classification mechanism and a scheduler, has been specified and implemented on the simulator, providing service differentiation over WiMAX networks. Furthermore, validation and comparison of different IEEE 802.16 simulation models is provided. Finally a scheduling solution is proposed and evaluated that uses prioritization and dynamic cross layer information for schedulling decisions in WiMAX networks. In order to validate the developed solutions, a set of QoS oriented scenarios have been simulated and the obtained results show that the implemented schedullers are able to efficiently differentiate between the different traffic classes and achieve gains in throughput and delay

Qualidade de serviço em redes de acesso IEEE 802.16

Mestrado em Engenharia Electrónica e TelecomunicaçõesA procura de serviços e de aplicações com elevadas exigências de largura de banda, e a vontade crescente para aceder a este tipo de serviços em qualquer lugar, torna necessária a integração da Internet actual com as redes móveis de próxima geração. No entanto, existirão sempre àreas remotas onde o acesso à Internet, e nomeadamente a serviços de banda larga, será difícil de conseguir. O protocolo IEEE 802.16 é uma tecnologia de banda larga sem fios que pode ser usada neste tipo de cenários. Esta dissertação apresenta uma arquitectura de rede capaz de suportar serviços de tempo real com integração de QoS em ambientes IPv6 através da utilização de redes IEEE 802.16. Nomeadamente, a arquitectura definida suporta o acesso dinâmico e rápido por parte dos terminais móveis aos serviços de rede, tal como reservas e modificações dinâmicas de serviços de tempo real, característica essencial para o suporte de alta mobilidade. Para além disto, a solução proposta fornece também suporte IPv6 e diferenciação de serviços direccionados para o mesmo terminal móvel. Esta dissertação apresenta a arquitectura desenvolvida, os módulos necessários para a integração da tecnologia IEEE 802.16 num ambiente de próxima geração, a implementação desses módulos para a construção de uma rede real, e testes para avaliar o desempenho da rede em termos de QoS num ambiente de rede de acesso mista, composta por IEEE 802.16 e IEEE 802.11. São também efectuados testes de mobilidade para avaliar o desempenho da solução descrita neste tipo de ambientes. Os resultados obtidos com a arquitectura desenvolvida mostram que a arquitectura pode fornecer QoS fima- fim sobre a concatenação de redes metropolitanas e locais, com suporte de mobilidade.The growing demand of high bandwidth services and applications, and the increasing will of access to these services anywhere, is motivating the requirement to integrate the current Internet with the future mobile networks. However, there will always be remote areas where Internet access will be difficult to achieve. The IEEE 802.16 is an attractive broadband wireless technology for these scenarios, non-withstanding its limitations for dynamic environments. This Thesis discusses a network architecture able to support IPv6 QoS aware real time services using 802.16 networks. Specifically, this solution supports dynamic and fast access from the Mobile Nodes to the network services, as well as dynamic reservations and modifications of services. These fast and dynamic reservations are crucial to the support of fast mobility approaches. Moreover, the proposed solution is also able to provide IPv6 support and efficient traffic differentiation for services running on the same MN. This Thesis presents the envisioned architecture, the modules required to provide the integrated QoS approach over the 802.16 network, the implementation of the modules to build a real network, and address main implementation results in terms of QoS performance, and in terms of mobility with QoS support for converged networks comprising WiMAX and Wi-Fi technologies. The obtained results show that our architecture is able to provide end-to-end QoS over the concatenation of metro and local area networks, and that seamless mobility is achieved with high performance measures, thus being able to support real-time services

Channel Aware Uplink Scheduler for a Mobile Subscriber Station of IEEE 802.16e

The scheduling part of the IEEE 802.16 (WiMAX) standards is kept as an open issue to provide differentiation among equipment manufacturers and operators. The uplink scheduling is very significant and more complex compared to downlink scheduling. Uplink scheduling is divided into two parts; one is scheduling the resources among many users from a base station (BS) and the other is sharing the resources among its services in a single user. BS uplink scheduling has been given more attention compared to subscriber station (SS) uplink scheduling. SS scheduler plays a significant role in providing the quality of service (QoS) among its services. The channel status awareness is vital in designing the SS scheduler as the channel conditions vary for a mobile user. This work proposes a scheduling algorithm for SS, which utilizes the channel information and queue length variation for the reallocation of received aggregated bandwidth grant to optimize the QoS parameters. The performance of the proposed algorithm is studied by conducting simulations using QualNet 5.0.2 simulation tool. Simulation results demonstrate the effectiveness of the proposed algorithm to improve the QoS

Interoperability of wireless communication technologies in hybrid networks: Evaluation of end-to-end interoperability issues and quality of service requirements

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Hybrid Networks employing wireless communication technologies have nowadays brought closer the vision of communication “anywhere, any time with anyone”. Such communication technologies consist of various standards, protocols, architectures, characteristics, models, devices, modulation and coding techniques. All these different technologies naturally may share some common characteristics, but there are also many important differences. New advances in these technologies are emerging very rapidly, with the advent of new models, characteristics, protocols and architectures. This rapid evolution imposes many challenges and issues to be addressed, and of particular importance are the interoperability issues of the following wireless technologies: Wireless Fidelity (Wi-Fi) IEEE802.11, Worldwide Interoperability for Microwave Access (WiMAX) IEEE 802.16, Single Channel per Carrier (SCPC), Digital Video Broadcasting of Satellite (DVB-S/DVB-S2), and Digital Video Broadcasting Return Channel through Satellite (DVB-RCS). Due to the differences amongst wireless technologies, these technologies do not generally interoperate easily with each other because of various interoperability and Quality of Service (QoS) issues. The aim of this study is to assess and investigate end-to-end interoperability issues and QoS requirements, such as bandwidth, delays, jitter, latency, packet loss, throughput, TCP performance, UDP performance, unicast and multicast services and availability, on hybrid wireless communication networks (employing both satellite broadband and terrestrial wireless technologies). The thesis provides an introduction to wireless communication technologies followed by a review of previous research studies on Hybrid Networks (both satellite and terrestrial wireless technologies, particularly Wi-Fi, WiMAX, DVB-RCS, and SCPC). Previous studies have discussed Wi-Fi, WiMAX, DVB-RCS, SCPC and 3G technologies and their standards as well as their properties and characteristics, such as operating frequency, bandwidth, data rate, basic configuration, coverage, power, interference, social issues, security problems, physical and MAC layer design and development issues. Although some previous studies provide valuable contributions to this area of research, they are limited to link layer characteristics, TCP performance, delay, bandwidth, capacity, data rate, and throughput. None of the studies cover all aspects of end-to-end interoperability issues and QoS requirements; such as bandwidth, delay, jitter, latency, packet loss, link performance, TCP and UDP performance, unicast and multicast performance, at end-to-end level, on Hybrid wireless networks. Interoperability issues are discussed in detail and a comparison of the different technologies and protocols was done using appropriate testing tools, assessing various performance measures including: bandwidth, delay, jitter, latency, packet loss, throughput and availability testing. The standards, protocol suite/ models and architectures for Wi-Fi, WiMAX, DVB-RCS, SCPC, alongside with different platforms and applications, are discussed and compared. Using a robust approach, which includes a new testing methodology and a generic test plan, the testing was conducted using various realistic test scenarios on real networks, comprising variable numbers and types of nodes. The data, traces, packets, and files were captured from various live scenarios and sites. The test results were analysed in order to measure and compare the characteristics of wireless technologies, devices, protocols and applications. The motivation of this research is to study all the end-to-end interoperability issues and Quality of Service requirements for rapidly growing Hybrid Networks in a comprehensive and systematic way. The significance of this research is that it is based on a comprehensive and systematic investigation of issues and facts, instead of hypothetical ideas/scenarios or simulations, which informed the design of a test methodology for empirical data gathering by real network testing, suitable for the measurement of hybrid network single-link or end-to-end issues using proven test tools. This systematic investigation of the issues encompasses an extensive series of tests measuring delay, jitter, packet loss, bandwidth, throughput, availability, performance of audio and video session, multicast and unicast performance, and stress testing. This testing covers most common test scenarios in hybrid networks and gives recommendations in achieving good end-to-end interoperability and QoS in hybrid networks. Contributions of study include the identification of gaps in the research, a description of interoperability issues, a comparison of most common test tools, the development of a generic test plan, a new testing process and methodology, analysis and network design recommendations for end-to-end interoperability issues and QoS requirements. This covers the complete cycle of this research. It is found that UDP is more suitable for hybrid wireless network as compared to TCP, particularly for the demanding applications considered, since TCP presents significant problems for multimedia and live traffic which requires strict QoS requirements on delay, jitter, packet loss and bandwidth. The main bottleneck for satellite communication is the delay of approximately 600 to 680 ms due to the long distance factor (and the finite speed of light) when communicating over geostationary satellites. The delay and packet loss can be controlled using various methods, such as traffic classification, traffic prioritization, congestion control, buffer management, using delay compensator, protocol compensator, developing automatic request technique, flow scheduling, and bandwidth allocation