43 research outputs found
Multicast resource management for next generation mobile communication systems
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
MOBILITY SUPPORT ARCHITECTURES FOR NEXT-GENERATION WIRELESS NETWORKS
With the convergence of the wireless networks and the Internet and the booming
demand for multimedia applications, the next-generation (beyond the third generation, or
B3G) wireless systems are expected to be all IP-based and provide real-time and non-real-time
mobile services anywhere and anytime. Powerful and efficient mobility support is
thus the key enabler to fulfil such an attractive vision by supporting various mobility
scenarios. This thesis contributes to this interesting while challenging topic.
After a literature review on mobility support architectures and protocols, the thesis
starts presenting our contributions with a generic multi-layer mobility support framework,
which provides a general approach to meet the challenges of handling comprehensive
mobility issues. The cross-layer design methodology is introduced to coordinate the
protocol layers for optimised system design. Particularly, a flexible and efficient cross-layer
signalling scheme is proposed for interlayer interactions. The proposed generic
framework is then narrowed down with several fundamental building blocks identified to
be focused on as follows.
As widely adopted, we assume that the IP-based access networks are organised into
administrative domains, which are inter-connected through a global IP-based wired core
network. For a mobile user who roams from one domain to another, macro (inter-domain)
mobility management should be in place for global location tracking and effective handoff
support for both real-time and non-real-lime applications. Mobile IP (MIP) and the Session
Initiation Protocol (SIP) are being adopted as the two dominant standard-based macro-mobility
architectures, each of which has mobility entities and messages in its own right.
The work explores the joint optimisations and interactions of MIP and SIP when utilising
the complementary power of both protocols. Two distinctive integrated MIP-SIP
architectures are designed and evaluated, compared with their hybrid alternatives and other
approaches. The overall analytical and simulation results shown significant performance
improvements in terms of cost-efficiency, among other metrics.
Subsequently, for the micro (intra-domain) mobility scenario where a mobile user
moves across IP subnets within a domain, a micro mobility management architecture is
needed to support fast handoffs and constrain signalling messaging loads incurred by intra-domain
movements within the domain. The Hierarchical MIPv6 (HMIPv6) and the Fast
Handovers for MIPv6 (FMIPv6) protocols are selected to fulfil the design requirements.
The work proposes enhancements to these protocols and combines them in an optimised
way. resulting in notably improved performances in contrast to a number of alternative
approaches
Piezoelectric Materials
The science and technology in the area of piezoelectric ceramics are extremely progressing, especially the materials research, measurement technique, theory and applications, and furthermore, demanded to fit social technical requests such as environmental problems. While they had been concentrated on piezoelectric ceramics composed of lead-containing compositions, such as lead zirconate titanate (PZT) and lead titanate, at the beginning because of the high piezoelectricity, recently lead water pollution by soluble PZT of our environment must be considered. Therefore, different new compositions of lead-free ceramics in order to replace PZT are needed. Until now, there have been many studies on lead-free ceramics looking for new morphotropic phase boundaries, ceramic microstructure control to realize high ceramic density, including composites and texture developments, and applications to new evaluation techniques to search for high piezoelectricity. The purpose of this book is focused on the latest reports in piezoelectric materials such as lead-free ceramics, single crystals, and thin films from viewpoints of piezoelectric materials, piezoelectric science, and piezoelectric applications
Performance study of air interface for broadband wireless packet access
Ph.DDOCTOR OF PHILOSOPH
Contribution to resource management in cellular access networks with limited backhaul capacity
La interfaz radio de los sistemas de comunicaciones móviles es normalmente considerada como
la única limitación de capacidad en la red de acceso radio. Sin embargo, a medida que se van
desplegando nuevas y más eficientes interfaces radio, y de que el tráfico de datos y multimedia va
en aumento, existe la creciente preocupación de que la infraestructura de transporte (backhaul) de
la red celular pueda convertirse en el cuello de botella en algunos escenarios. En este contexto, la
tesis se centra en el desarrollo de técnicas de gestión de recursos que consideran de manera
conjunta la gestión de recursos en la interfaz radio y el backhaul. Esto conduce a un nuevo
paradigma donde los recursos del backhaul se consideran no sólo en la etapa de dimensionamiento,
sino que además son incluidos en la problemática de gestión de recursos.
Sobre esta base, el primer objetivo de la tesis consiste en evaluar los requerimientos de
capacidad en las redes de acceso radio que usan IP como tecnología de transporte, de acuerdo a las
recientes tendencias de la arquitectura de red. En particular, se analiza el impacto que tiene una
solución de transporte basada en IP sobre la capacidad de transporte necesaria para satisfacer los
requisitos de calidad de servicio en la red de acceso. La evaluación se realiza en el contexto de la
red de acceso radio de UMTS, donde se proporciona una caracterización detallada de la interfaz
Iub. El análisis de requerimientos de capacidad se lleva a cabo para dos diferentes escenarios:
canales dedicados y canales de alta velocidad. Posteriormente, con el objetivo de aprovechar
totalmente los recursos disponibles en el acceso radio y el backhaul, esta tesis propone un marco de
gestión conjunta de recursos donde la idea principal consiste en incorporar las métricas de la red de
transporte dentro del problema de gestión de recursos. A fin de evaluar los beneficios del marco de
gestión de recursos propuesto, esta tesis se centra en la evaluación del problema de asignación de
base, como estrategia para distribuir el tráfico entre las estaciones base en función de los niveles de
carga tanto en la interfaz radio como en el backhaul. Este problema se analiza inicialmente
considerando una red de acceso radio genérica, mediante la definición de un modelo analítico
basado en cadenas de Markov. Dicho modelo permite calcular la ganancia de capacidad que puede
alcanzar la estrategia de asignación de base propuesta. Posteriormente, el análisis de la estrategia
propuesta se extiende considerando tecnologías específicas de acceso radio. En particular, en el
contexto de redes WCDMA se desarrolla un algoritmo de asignación de base basado en simulatedannealing
cuyo objetivo es maximizar una función de utilidad que refleja el grado de satisfacción
de las asignaciones respecto los recursos radio y transporte. Finalmente, esta tesis aborda el diseño
y evaluación de un algoritmo de asignación de base para los futuros sistemas de banda ancha
basados en OFDMA. En este caso, el problema de asignación de base se modela como un problema
de optimización mediante el uso de un marco de funciones de utilidad y funciones de coste de
recursos. El problema planteado, que considera que existen restricciones de recursos tanto en la
interfaz radio como en el backhaul, es mapeado a un problema de optimización conocido como
Multiple-Choice Multidimensional Knapsack Problem (MMKP). Posteriormente, se desarrolla un
algoritmo de asignación de base heurístico, el cual es evaluado y comparado con esquemas de
asignación basados exclusivamente en criterios radio. El algoritmo concebido se basa en el uso de
los multiplicadores de Lagrange y está diseñado para aprovechar de manera simultánea el balanceo
de carga en la intefaz radio y el backhaul.Postprint (published version
Formulation, implementation considerations, and first performance evaluation of algorithmic solutions - D4.1
Deliverable D4.1 del projecte Europeu OneFIT (ICT-2009-257385)This deliverable contains a first version of the algorithmic solutions for enabling opportunistic networks. The presented algorithms cover the full range of identified management tasks: suitability, creation, QoS control, reconfiguration and forced terminations. Preliminary evaluations complement the proposed algorithms. Implementation considerations towards the practicality of the considered algorithms are also included.Preprin
A General Framework for Analyzing, Characterizing, and Implementing Spectrally Modulated, Spectrally Encoded Signals
Fourth generation (4G) communications will support many capabilities while providing universal, high speed access. One potential enabler for these capabilities is software defined radio (SDR). When controlled by cognitive radio (CR) principles, the required waveform diversity is achieved via a synergistic union called CR-based SDR. Research is rapidly progressing in SDR hardware and software venues, but current CR-based SDR research lacks the theoretical foundation and analytic framework to permit efficient implementation. This limitation is addressed here by introducing a general framework for analyzing, characterizing, and implementing spectrally modulated, spectrally encoded (SMSE) signals within CR-based SDR architectures. Given orthogonal frequency division multiplexing (OFDM) is a 4G candidate signal, OFDM-based signals are collectively classified as SMSE since modulation and encoding are spectrally applied. The proposed framework provides analytic commonality and unification of SMSE signals. Applicability is first shown for candidate 4G signals, and resultant analytic expressions agree with published results. Implementability is then demonstrated in multiple coexistence scenarios via modeling and simulation to reinforce practical utility