33 research outputs found
Flexible Macroblock Ordering for Context-Aware Ultrasound Video Transmission over Mobile WiMAX
The most recent network technologies are enabling
a variety of new applications, thanks to the provision of increased bandwidth and better management of Quality of Service.
Nevertheless, telemedical services involving multimedia data are still lagging behind, due to the concern of the end users, that is,
clinicians and also patients, about the low quality provided. Indeed, emerging network technologies should be appropriately
exploited by designing the transmission strategy focusing on quality provision for end users. Stemming from this principle, we
propose here a context-aware transmission strategy for medical video transmission over WiMAX systems. Context, in terms of
regions of interest (ROI) in a specific session, is taken into account for the identification of multiple regions of interest,
and compression/transmission strategies are tailored to such context information. We present a methodology based on H.264
medical video compression and Flexible Macroblock Ordering (FMO) for ROI identification. Two different unequal error
protection methodologies, providing higher protection to the most diagnostically relevant data, are presented
Acesso banda larga sem fios em ambientes heterogéneos de próxima geração
Doutoramento em Engenharia InformĂĄticaO acesso ubĂquo Ă Internet Ă© um dos principais desafios para os operadores
de telecomunicaçÔes na prĂłxima dĂ©cada. O nĂșmero de utilizadores da Internet
estĂĄ a crescer exponencialmente e o paradigma de acesso "always connected,
anytime, anywhere" Ă© um requisito fundamental para as redes mĂłveis de
próxima geração. A tecnologia WiMAX, juntamente com o LTE, foi
recentemente reconhecida pelo ITU como uma das tecnologias de acesso
compatĂveis com os requisitos do 4G. Ainda assim, esta tecnologia de acesso
não estå 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 rĂĄdio UMTS/HSPA e Wi-Fi continuarĂŁo a ter um
impacto significativo nas comunicaçÔes móveis durante os próximos anos.
Deste modo, Ă© fundamental garantir a coexistĂȘncia das vĂĄrias tecnologias de
acesso rĂĄdio 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 propÔe 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 Ă©
perfeitamente capaz de entregar serviços de tempo real sem introduzir custos
excessivos na rede.
No seguimento das extensÔes de QoS e mobilidade apresentadas para a
tecnologia WiMAX, o Ăąmbito 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 versĂŁo estendida do IEEE
802.21 com suporte de QoS, bem como um gestor de mobilidade avançado
integrado com os protocolos de gestĂŁo de mobilidade do nĂvel IP. Finalmente,
para completar o trabalho desenvolvido no Ăąmbito desta Tese, Ă© proposta uma
extensĂŁo aos procedimentos de decisĂŁo de mobilidade em ambientes
heterogéneos para incorporar a informação de contexto da rede e do terminal.
Para validar e avaliar as optimizaçÔes 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 âalways connected, anytime, anywhereâ 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
Adaptive load balancing routing algorithms for the next generation wireless telecommunications networks
This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel UniversityWith the rapid development of wireless networks, mesh networks are evolving as a new important technology, presenting a high research and commercial interest. Additionally, wireless mesh networks have a wide variety of applications, offering the ability to provide network access in both rural and urban areas with low cost of maintenance. One of the main functionalities of a wireless mesh network is load balancing routing, which is the procedure of finding the best, according to some criteria, routes that data need to follow to transfer from one node to another. Routing is one of the state-of-the-art areas of research because the current algorithms and protocols are not efficient and effective due to the diversity of the characteristics of these networks. In this thesis, two new routing algorithms have been developed for No Intra-Cell Interference (NICI) and Limited Intra-Cell Interference (LICI) networks based on WiMAX, the most advanced wireless technology ready for deployment. The algorithms created are based on the classical Dijkstra and Ford-Fulkerson algorithms and can be implemented in the cases of unicast and multicast transmission respectively.State scholarships foundation of Greece
Comparison of vertical handover decision-based techniques in heterogeneous networks
Industry leaders are currently setting out standards for 5G Networks projected for 2020 or even sooner. Future generation networks will be heterogeneous in nature because no single network type is capable of optimally meeting all the rapid changes in customer demands. Heterogeneous networks are typically characterized by some network architecture, base stations of varying transmission power, transmission solutions and the deployment of a mix of technologies (multiple radio access technologies). In heterogeneous networks, the processes involved when a mobile node successfully switches from one radio access technology to the other for the purpose of quality of service continuity is termed vertical handover or vertical handoff. Active calls that get dropped, or cases where there is discontinuity of service experienced by mobile users can be attributed to the phenomenon of delayed handover or an outright case of an unsuccessful handover procedure. This dissertation analyses the performance of a fuzzy-based VHO algorithm scheme in a Wi-Fi, WiMAX, UMTS and LTE integrated network using the OMNeT++ discrete event simulator. The loose coupling type network architecture is adopted and results of the simulation are analysed and compared for the two major categories of handover basis; multiple and single criteria based handover methods. The key performance indices from the simulations showed better overall throughput, better call dropped rate and shorter handover time duration for the multiple criteria based decision method compared to the single criteria based technique. This work also touches on current trends, challenges in area of seamless handover and initiatives for future Networks (Next Generation Heterogeneous Networks)
An optimal admission control protocol for heterogeneous multicast streaming services
We investigate optimal call admission control (CAC)
policy for multicast streaming services (MSS) in 3rd generation
(3G) and beyond wireless mobile networks. Several MSS sessions
are supported simultaneously in a bandwidth-limited network.
Active sessions are those that are currently serving some users,
and inactive sessions are those that are currently not serving any
users. An admission decision in MSS is required only when an
inactive session is requested, unlike in unicasting. For this reason,
if a user request for an inactive MSS session arrives, we should
make an admission decision in anticipation of (i) the possible
reward earned based on users served during a session active time
generated by accepting it, and (ii) the influence of the session active
time upon the future status of network bandwidth and admission
decisions. Our objective is to determine when to admit or block a
user asking an inactive MSS session to achieve the optimality in
rewards. We formulate this problem as a semi-Markov decision
process (SMDP), and a value iteration algorithm is used to obtain
an optimal stationary deterministic policy. We also derive the
user blocking probability of the optimal policy by analyzing an
embedded Markov chain induced by it.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=26hb201
Radio Communications
In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modiïŹed our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the ïŹeld of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks