25 research outputs found
Handover in Mobile WiMAX Networks: The State of Art and Research Issues
The next-generation Wireless Metropolitan Area
Networks, using the Worldwide Interoperability for Microwave
Access (WiMAX) as the core technology based on the IEEE
802.16 family of standards, is evolving as a Fourth-Generation
(4G) technology. With the recent introduction of mobility management
frameworks in the IEEE 802.16e standard, WiMAX
is now placed in competition to the existing and forthcoming
generations of wireless technologies for providing ubiquitous
computing solutions. However, the success of a good mobility
framework largely depends on the capability of performing fast
and seamless handovers irrespective of the deployed architectural
scenario. Now that the IEEE has defined the Mobile WiMAX
(IEEE 802.16e) MAC-layer handover management framework,
the Network Working Group (NWG) of the WiMAX Forum
is working on the development of the upper layers. However,
the path to commercialization of a full-fledged WiMAX mobility
framework is full of research challenges. This article focuses on
potential handover-related research issues in the existing and
future WiMAX mobility framework. A survey of these issues in
the MAC, Network and Cross-Layer scenarios is presented along
with discussion of the different solutions to those challenges. A
comparative study of the proposed solutions, coupled with some
insights to the relevant issues, is also included
Handover management in mobile WiMAX using adaptive cross-layer technique
The protocol type and the base station (BS) technology are the main communication media between the Vehicle to Infrastructure (V2I) communication in vehicular networks. During high speed vehicle movement, the best communication would be with a seamless handover (HO) delay in terms of lower packet loss and throughput. Many studies have focused on how to reduce the HO delay during lower speeds of the vehicle with data link (L2) and network (L3) layers protocol. However, this research studied the Transport Layer (L4) protocol mobile Stream Control Transmission Protocol (mSCTP) used as an optimal protocol in collaboration with the Location Manager (LM) and Domain Name Server (DNS). In addition, the BS technology that performs smooth HO employing an adaptive algorithm in L2 to perform the HO according to current vehicle speed was also included in the research. The methods derived from the combination of L4 and the BS technology methods produced an Adaptive Cross-Layer (ACL) design which is a mobility oriented handover management scheme that adapts the HO procedure among the protocol layers. The optimization has a better performance during HO as it is reduces scanning delay and diversity level as well as support transparent mobility among layers in terms of low packet loss and higher throughput. All of these metrics are capable of offering maximum flexibility and efficiency while allowing applications to refine the behaviour of the HO procedure. Besides that, evaluations were performed in various scenarios including different vehicle speeds and background traffic. The performance evaluation of the proposed ACL had approximately 30% improvement making it better than the other handover solutions
Performance study of FMIPv6-based cross-layer WiMAX handover scheme for supporting VoIP service
This report presents performance study of the FMIPv6-based cross-layer handover scheme for VoIP supports over mobile WiMAX network. For this performance validation and evaluation, the handover delays for four different handover mechanisms are formulated and ns2 based simulation module has been developed. The handover delay, the total delay, and the R factor representing VoIP quality are measured to evaluate the VoIP support characteristics of the FMIPv6-based cross-layer scheme. Simulation results verified that the proposed FMIPv6-based cross-layer handover scheme, compared to the non-cross-layer scheme, successfully reduces total handover delay by almost 50% for the case of layer-3 handover. Further, simulation was also evaluated in terms of R factor indicating voice quality level, of which 70 is a minimum value of a traditional PSTN call to be considered as the lower limit of a VoIP call quality [6]. Through the simulation in this study, the result revealed that the proposed scheme effectively improves VoIP call quality from unacceptable quality to acceptable quality (R factor of 75). Based on these simulation results, it was found that the proposed FMIPv6-based cross-layer handover scheme is an adequate protocol for supporting VoIP services in mobile WiMAX environment
Mobility and Handoff Management in Wireless Networks
With the increasing demands for new data and real-time services, wireless
networks should support calls with different traffic characteristics and
different Quality of Service (QoS)guarantees. In addition, various wireless
technologies and networks exist currently that can satisfy different needs and
requirements of mobile users. Since these different wireless networks act as
complementary to each other in terms of their capabilities and suitability for
different applications, integration of these networks will enable the mobile
users to be always connected to the best available access network depending on
their requirements. This integration of heterogeneous networks will, however,
lead to heterogeneities in access technologies and network protocols. To meet
the requirements of mobile users under this heterogeneous environment, a common
infrastructure to interconnect multiple access networks will be needed. In this
chapter, the design issues of a number of mobility management schemes have been
presented. Each of these schemes utilizes IP-based technologies to enable
efficient roaming in heterogeneous network. Efficient handoff mechanisms are
essential for ensuring seamless connectivity and uninterrupted service
delivery. A number of handoff schemes in a heterogeneous networking environment
are also presented in this chapter.Comment: 28 pages, 11 figure
Securing Handover in Wireless IP Networks
In wireless and mobile networks, handover is a complex process that involves multiple layers of protocol and security executions. With the growing popularity of real time communication services such as Voice of IP, a great challenge faced by handover nowadays comes from the impact of security implementations that can cause performance degradation especially for mobile devices with limited resources.
Given the existing networks with heterogeneous wireless access technologies, one essential research question that needs be addressed is how to achieve a balance between security and performance during the handover. The variations of security policy and agreement among different services and network vendors make the topic challenging even more, due to the involvement of commercial and social factors.
In order to understand the problems and challenges in this field, we study the properties of handover as well as state of the art security schemes to assist handover in wireless IP networks. Based on our analysis, we define a two-phase model to identify the key procedures of handover security in wireless and mobile networks. Through the model we analyze the performance impact from existing security schemes in terms of handover completion time, throughput, and Quality of Services (QoS). As our endeavor of seeking a balance between handover security and performance, we propose the local administrative domain as a security enhanced localized domain to promote the handover performance. To evaluate the performance improvement in local administrative domain, we implement the security protocols adopted by our proposal in the ns-2 simulation environment and analyze the measurement results based on our simulation test
Acesso banda larga sem fios em ambientes heterogéneos de próxima geração
Doutoramento em Engenharia InformáticaO acesso ubíquo à Internet é um dos principais desafios para os operadores
de telecomunicações na próxima década. O número de utilizadores da Internet
está a crescer exponencialmente e o paradigma de acesso "always connected,
anytime, anywhere" é um requisito fundamental para as redes móveis de
próxima geração. A tecnologia WiMAX, juntamente com o LTE, foi
recentemente reconhecida pelo ITU como uma das tecnologias de acesso
compatíveis com os requisitos do 4G. Ainda assim, esta tecnologia de acesso
não está completamente preparada para ambientes de próxima geração,
principalmente devido à falta de mecanismos de cross-layer para integração de
QoS e mobilidade. Adicionalmente, para além das tecnologias WiMAX e LTE,
as tecnologias de acesso rádio UMTS/HSPA e Wi-Fi continuarão a ter um
impacto significativo nas comunicações móveis durante os próximos anos.
Deste modo, é fundamental garantir a coexistência das várias tecnologias de
acesso rádio em termos de QoS e mobilidade, permitindo assim a entrega de
serviços multimédia de tempo real em redes móveis.
Para garantir a entrega de serviços multimédia a utilizadores WiMAX, esta
Tese propõe um gestor cross-layer WiMAX integrado com uma arquitectura de
QoS fim-a-fim. A arquitectura apresentada permite o controlo de QoS e a
comunicação bidireccional entre o sistema WiMAX e as entidades das
camadas superiores. Para além disso, o gestor de cross-layer proposto é
estendido com eventos e comandos genéricos e independentes da tecnologia
para optimizar os procedimentos de mobilidade em ambientes WiMAX. Foram
realizados testes para avaliar o desempenho dos procedimentos de QoS e
mobilidade da arquitectura WiMAX definida, demonstrando que esta é
perfeitamente capaz de entregar serviços de tempo real sem introduzir custos
excessivos na rede.
No seguimento das extensões de QoS e mobilidade apresentadas para a
tecnologia WiMAX, o âmbito desta Tese foi alargado para ambientes de
acesso sem-fios heterogéneos. Neste sentido, é proposta uma arquitectura de
mobilidade transparente com suporte de QoS para redes de acesso multitecnologia.
A arquitectura apresentada integra uma versão estendida do IEEE
802.21 com suporte de QoS, bem como um gestor de mobilidade avançado
integrado com os protocolos de gestão de mobilidade do nível IP. Finalmente,
para completar o trabalho desenvolvido no âmbito desta Tese, é proposta uma
extensão aos procedimentos de decisão de mobilidade em ambientes
heterogéneos para incorporar a informação de contexto da rede e do terminal.
Para validar e avaliar as optimizações propostas, foram desenvolvidos testes
de desempenho num demonstrador inter-tecnologia, composta pelas redes de
acesso WiMAX, Wi-Fi e UMTS/HSPA.Ubiquitous Internet access is one of the main challenges for the
telecommunications industry in the next decade. The number of users
accessing the Internet is growing exponentially and the network access
paradigm of “always connected, anytime, anywhere” is a central requirement
for the so-called Next Generation Mobile Networks (NGMN). WiMAX, together
with LTE, was recently recognized by ITU as one of the compliant access
technologies for 4G. Nevertheless, WiMAX is not yet fully prepared for next
generation environments, mainly due to the lack of QoS and mobility crosslayer
procedures to support real-time multimedia services delivery.
Furthermore, besides the 4G compliant WiMAX and LTE radio access
technologies, UMTS/HSPA and Wi-Fi will also have a significant impact in the
mobile communications during the next years. Therefore, it is fundamental to
ensure the coexistence of multiple radio access technologies in what QoS and
mobility procedures are concerned, thereby allowing the delivery of real-time
services in mobile networks.
In order to provide the WiMAX mobile users with the demanded multimedia
services, it is proposed in this Thesis a WiMAX cross-layer manager integrated
in an end-to-end all-IP QoS enabled architecture. The presented framework
enables the QoS control and bidirectional communication between WiMAX and
the upper layer network entities. Furthermore, the proposed cross-layer
framework is extended with media independent events and commands to
optimize the mobility procedures in WiMAX environments. Tests were made to
evaluate the QoS and mobility performance of the defined architecture,
demonstrating that it is perfectly capable of handling and supporting real time
services without introducing an excessive cost in the network.
Following the QoS and mobility extensions provided for WiMAX, the scope of
this Thesis is broaden and a seamless mobility architecture with QoS support in
heterogeneous wireless access environments is proposed. The presented
architecture integrates an extended version of the IEEE 802.21 framework with
QoS support, as well as an advanced mobility manager integrated with the IP
level mobility management protocols. Finally, to complete the work within the
framework of this Thesis, it is proposed an extension to the handover decisionmaking
processes in heterogeneous access environments through the
integration of context information from both the network entities and the enduser.
Performance tests were developed in a real testbed to validate the
proposed optimizations in an inter-technology handover scenario involving
WiMAX, Wi-Fi and UMTS/HSPA
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
SCALABLE AND EFFICIENT VERTICAL HANDOVER DECISION ALGORITHMS IN VEHICULAR NETWORK CONTEXTS
A finales de los años noventa, y al comienzo del nuevo milenio, las redes inalámbricas han evolucionado bastante, pasando de ser sólo una tecnología prometedora para convertirse en un requisito para las actividades cotidianas en las sociedades desarrolladas. La infraestructura de transporte también ha evolucionado, ofreciendo comunicación a bordo para mejorar la seguridad vial y el acceso a contenidos de información y entretenimiento.
Los requisitos de los usuarios finales se han hecho dependientes de la tecnología, lo que significa que sus necesidades de conectividad han aumentado debido a los diversos requisitos de las aplicaciones que se ejecutan en sus dispositivos móviles, tales como tabletas, teléfonos inteligentes, ordenadores portátiles o incluso ordenadores de abordo (On-Board Units (OBUs)) dentro de los vehículos. Para cumplir con dichos requisitos de conectividad, y teniendo en cuenta las diferentes redes inalámbricas disponibles, es necesario adoptar técnicas de Vertical Handover (VHO) para cambiar de red de forma transparente y sin necesidad de intervención del usuario.
El objetivo de esta tesis es desarrollar algoritmos de decisión (Vertical Handover Decision Algorithms (VHDAs)) eficientes y escalables, optimizados para el contexto de las redes vehiculares. En ese sentido se ha propuesto, desarrollado y probado diferentes algoritmos de decisión basados en la infraestructura disponible en las actuales, y probablemente en las futuras, redes inalámbricas y redes vehiculares. Para ello se han combinado diferentes técnicas, métodos computacionales y modelos matemáticos, con el fin de garantizar una conectividad apropiada, y realizando el handover hacia las redes más adecuadas de manera a cumplir tanto con los requisitos de los usuarios como los requisitos de las aplicaciones.
Con el fin de evaluar el contexto, se han utilizado diferentes herramientas para obtener información variada, como la disponibilidad de la red, el estado de la red, la geolocalizaciónMárquez Barja, JM. (2012). SCALABLE AND EFFICIENT VERTICAL HANDOVER DECISION ALGORITHMS IN VEHICULAR NETWORK CONTEXTS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17869Palanci