No description available.

Yes / The pre-emption procedure is an important part of the Radio Resource Management (RRM) when dealing with the emergency traffic. It allows resources to be allocated to higher priority connections by pre-empting lower priority connections. The provision of the pre-emption mechanism becomes much more important in the case of satellite systems such as the Inmarsat Broadband Global Area Network (BGAN) system which aids in providing the communication during a catastrophe. This paper focuses on the preemption framework for a UMTS based satellite systems. Three algorithms have been proposed, Greedy, SubSetSum and Fuzzy pre-emption algorithm. Extensive simulations are carried out for the three algorithms and their performances are compared against each other. Simulation results show that the Fuzzy pre-emption algorithm performs better than the other two algorithms. / European Space Agency/Inmarsat

Wireless mesh networking has emerged as a promising technology for future broadband wireless access, providing a viable and economical solution for both peer-to-peer applications and Internet access. The success of wireless mesh networks (WMNs) is highly contingent on effective radio resource management. In conventional wireless networks, system throughput is usually a common performance metric. However, next-generation broadband wireless access networks including WMNs are anticipated to support multimedia traffic (e.g., voice, video, and data traffic). With heterogeneous traffic, quality-of-service (QoS) provisioning and fairness support are also imperative. Recently, wireless mesh networking for suburban/rural residential areas has been attracting a plethora of attentions from industry and academia. With austere suburban and rural networking environments, multi-hop communications with decentralized resource allocation are preferred. In WMNs without powerful centralized control, simple yet effective resource allocation approaches are desired for the sake of system performance melioration. In this dissertation, we conduct a comprehensive research study on the topic of radio resource management for WMNs supporting multimedia traffic. In specific, this dissertation is intended to shed light on how to effectively and efficiently manage a WMN for suburban/rural residential areas, provide users with high-speed wireless access, support the QoS of multimedia applications, and improve spectrum utilization by means of novel radio resource allocation. As such, five important resource allocation problems for WMNs are addressed, and our research accomplishments are briefly outlined as follows: Firstly, we propose a novel node clustering algorithm with effective subcarrier allocation for WMNs. The proposed node clustering algorithm is QoS-aware, and the subcarrier allocation is optimality-driven and can be performed in a decentralized manner. Simulation results show that, compared to a conventional conflict-graph approach, our proposed approach effectively fosters frequency reuse, thereby improving system performance; Secondly, we propose three approaches for joint power-frequency-time resource allocation. Simulation results show that all of the proposed approaches are effective in provisioning packet-level QoS over their conventional resource allocation counterparts. Our proposed approaches are of low complexity, leading to preferred candidates for practical implementation; Thirdly, to further enhance system performance, we propose two low-complexity node cooperative resource allocation approaches for WMNs with partner selection/allocation. Simulation results show that, with beneficial node cooperation, both proposed approaches are promising in supporting QoS and elevating system throughput over their non-cooperative counterparts; Fourthly, to further utilize the temporarily available radio spectrum, we propose a simple channel sensing order for unlicensed secondary users. By sensing the channels according to the descending order of their achievable rates, we prove that a secondary user should stop at the first sensed free channel for the sake of optimality; and Lastly, we derive a unified optimization framework to effectively attain different degrees of performance tradeoff between throughput and fairness with QoS support. By introducing a bargaining floor, the optimal tradeoff curve between system throughput and fairness can be obtained by solving the proposed optimization problem iteratively.

Wireless mesh networking has emerged as a promising technology for future broadband wireless access, providing a viable and economical solution for both peer-to-peer applications and Internet access. The success of wireless mesh networks (WMNs) is highly contingent on effective radio resource management. In conventional wireless networks, system throughput is usually a common performance metric. However, next-generation broadband wireless access networks including WMNs are anticipated to support multimedia traffic (e.g., voice, video, and data traffic). With heterogeneous traffic, quality-of-service (QoS) provisioning and fairness support are also imperative. Recently, wireless mesh networking for suburban/rural residential areas has been attracting a plethora of attentions from industry and academia. With austere suburban and rural networking environments, multi-hop communications with decentralized resource allocation are preferred. In WMNs without powerful centralized control, simple yet effective resource allocation approaches are desired for the sake of system performance melioration. In this dissertation, we conduct a comprehensive research study on the topic of radio resource management for WMNs supporting multimedia traffic. In specific, this dissertation is intended to shed light on how to effectively and efficiently manage a WMN for suburban/rural residential areas, provide users with high-speed wireless access, support the QoS of multimedia applications, and improve spectrum utilization by means of novel radio resource allocation. As such, five important resource allocation problems for WMNs are addressed, and our research accomplishments are briefly outlined as follows: Firstly, we propose a novel node clustering algorithm with effective subcarrier allocation for WMNs. The proposed node clustering algorithm is QoS-aware, and the subcarrier allocation is optimality-driven and can be performed in a decentralized manner. Simulation results show that, compared to a conventional conflict-graph approach, our proposed approach effectively fosters frequency reuse, thereby improving system performance; Secondly, we propose three approaches for joint power-frequency-time resource allocation. Simulation results show that all of the proposed approaches are effective in provisioning packet-level QoS over their conventional resource allocation counterparts. Our proposed approaches are of low complexity, leading to preferred candidates for practical implementation; Thirdly, to further enhance system performance, we propose two low-complexity node cooperative resource allocation approaches for WMNs with partner selection/allocation. Simulation results show that, with beneficial node cooperation, both proposed approaches are promising in supporting QoS and elevating system throughput over their non-cooperative counterparts; Fourthly, to further utilize the temporarily available radio spectrum, we propose a simple channel sensing order for unlicensed secondary users. By sensing the channels according to the descending order of their achievable rates, we prove that a secondary user should stop at the first sensed free channel for the sake of optimality; and Lastly, we derive a unified optimization framework to effectively attain different degrees of performance tradeoff between throughput and fairness with QoS support. By introducing a bargaining floor, the optimal tradeoff curve between system throughput and fairness can be obtained by solving the proposed optimization problem iteratively.

The promising development of wireless technologies has brought in an increasing demand of multimedia traffic. Since various types of traffic are inherently distinct in bandwidth requirements, delay sensitivities, and error tolerances, an adequate bandwidth allocation scheme is essential for the limited radio resource to fulfill different QoS (quality of service) requirements in mobile wireless networks. In this dissertation, we present a generalized channel preemption scheme (the GCPM) and a jamming-based medium access control with dynamic priority adjustment (the JMDPA) for the two different medium access models of a mobile wireless network, grant/request-based and contention-based, respectively. In the proposed GCPM, a mobile call is identified by four parameters, call type, traffic class, channel requirement, and preemption ratio. To effectively reduce dropping probability, high-priority handoff calls are allowed to fully or partially preempt low-priority ongoing calls when the mobile network becomes congested. An analytical model with multi-dimensional Markov chains is introduced to simultaneously investigate the effect of full and partial preemptions on the performance of a mobile wireless network. On the other hand, the proposed JMDPA scheme prioritizes a mobile node with two priorities, local and global; both of the local and global priorities can be dynamically changed based on the outcome in every contention round. Thus, any possible starvation of low-priority traffic or any ineffective contention of high-priority traffic can be avoided. A multi-dimensional Markov model, together with the scalability analysis, is introduced to evaluate the performance of the proposed JMDPA. The analytical results provide very useful guidelines to tune the QoS parameters for supporting prioritized multimedia traffic.

no / This paper is focused on the design of an adaptive Connection Admission Control (CAC) algorithm for a Universal Mobile Telecommunication System (UMTS) based satellite system with variable link capacity. The main feature of the proposed algorithm is to maximize the resource utilization by adapting to the link conditions and the antenna gain of the users. The link quality of the user may vary depending on the weather condition, user mobility and any other propagation factors. The algorithm is compared against a non-adaptive admission control algorithm under different test cases. The proposed CAC algorithm is simulated using MATLAB and the performance results are obtained for a mix of multimedia traffic classes such as video streaming, web browsing, netted voice and email. The simulation results indicate a higher system performance in terms of the blocking ratio and the number of admitted connections.

No / The traffic pattern has significant impact on the performance of network-on-chip. Many recent studies have shown that multimedia applications can be supported in on-chip interconnects. Driven by the motivation of evaluating on-chip interconnects in multimedia embedded systems, a new analytical model is proposed to investigate the performance of the fat-tree based on-chip interconnection network under bursty multimedia traffic and nonuniform message destinations. Extensive simulation experiments are conducted to validate the accuracy of the model, which is then adopted as a cost-efficient tool to investigate the effects of bursty multimedia traffic with nonuniform destinations on the network performance.

Wireless operators adopting third-generation (3G) technologies and those migrating from second-generation (2G) to 3G face a number of challenges related to traffic modeling, demand characterization, and performance analysis, which are key elements in the processes of designing, dimensioning and optimizing their network infrastructure. Traditional traffic modeling assumptions used for circuit-switched voice traffic no longer hold true with the convergence of voice and data over packet-switched infrastructures. Self-similar models need to be explored to appropriately account for the burstiness that packet traffic is expected to exhibit in all time scales. The task of demand characterization must include an accurate description of the multiple user profiles and service classes the network is expected to support, with their distinct geographical distributions, as well as forecasts of how the market should evolve over near and medium terms. The appropriate assessment of the quality of service becomes a more complex issue as new metrics and more intricate dependencies have to be considered when providing a varying range of services and applications that include voice, real-time, and non-real time data. All those points have to be considered by the operator to obtain a proper dimensioning, resource allocation, and rollout plan for system deployment. Additionally, any practical optimization strategy has to rely on accurate estimates of expected demand and growth in demand. In this research, we propose a practical framework to characterize the traffic offered to multimedia wireless systems that allows proper dimensioning and optimization of the system for a particular demand scenario. The framework proposed includes a methodology to quantitatively and qualitatively describe the traffic offered to multimedia wireless systems, solutions to model that traffic as practical inputs for simulation analysis, and investigation of demand-sensitive techniques for system dimensioning and performance optimization. We consider both theoretical and practical aspects related to the dimensioning of hybrid traffic (voice and data) for mobile wireless networks. We start by discussing wireless systems and traffic theory, with characterization of the main metrics and models that describe the users’ voice and data demand, presenting a review of the most recent developments in the area. The concept of service class is used to specify parameters that depend on the application type, performance requirements and traffic characteristics for a given service. Then we present the concept of “user profile,“ which ties together a given combination of service class, propagation environment and terminal type. Next, we propose a practical approach to explore the dynamics of user geographical distribution in creating multi-service, multi-class traffic layers that serve as input for network traffic simulation algorithms. The concept of quality-of-service (QoS) is also discussed, focusing on the physical layer for 3G systems. We explore system simulation as a way to dimension a system given its traffic demand characterization. In that context, we propose techniques to translate geographical distributions of user profiles into the actual number of active users of each layer, which is the key parameter to be used as input in simulations. System level simulations are executed for UMTS systems, with the purpose of validating the methodology proposed here. We complete the proposed framework by applying all elements together in the process of dimensioning and optimization of 3G wireless networks using the demand characterization for the system as input. We investigate the effects of modifying some elements in the system configuration such as network topology, radio-frequency (RF) configuration, and radio resource management (RRM) parameters, using strategies that are sensitive to traffic geographical distribution. Case study simulations are performed for Universal Mobile Telecommunications System (UMTS) networks, and multiple system variables (such as antenna tilts, pilot powers, and RRM parameters) are optimized using traffic sensitive strategies, which result in significant improvements in the overall system capacity and performance. Results obtained in the case studies, allied to a generic discussion of the trade-offs involved in the proposed framework, demonstrate the close dependence between the processes of system dimensioning and optimization with the accurate modeling of traffic demand offered to the system. / Ph. D.

Made available in DSpace on 2014-06-12T15:51:44Z (GMT). No. of bitstreams: 2 arquivo2806_1.pdf: 3483412 bytes, checksum: cab776dc5a3fdf07c8cda900906f6a98 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Aires Moreira, Josilene; Fawzi Hadj Sadok, Djamel. Cache strategies for internet-based video on-demand distribution. 2011. Tese (Doutorado). Programa de Pós-Graduação em Ciência da Computação, Universidade Federal de Pernambuco, Recife, 2011.

This thesis dissertation addresses the problem of energy constraints in ad hoc wireless networks. In this sort of networks nodes are generally powered by means of batteries, which involves significant limitations regarding the time of operation of devices. The nodes whose battery level describes important energy depletion represent potential elements for loss of connectivity, which results in an increase of packet loss rate. Therefore, the management of energy expenditure is one of the main research challenges to face in ad hoc networks, especially when developing applications in real scenarios. However, energy management is not a trivial task due to the inherent features of this kind of networks, such as the distributed operation as well as the access medium mechanism. In that sense, traditional solutions of energy optimization based on the definition of power-saving intervals (sleep mode) are not suitable considering the operational characteristics of an ad hoc network, due to the substantial deterioration of network connectivity. In addition, the exponential growth of applications focused on the transmission of multimedia contents (especially video) available on mobile devices involves specific quality of service levels. Consequently, the design of solutions for the optimization of energy resources should be carried out without degrading the Quality of Experience perceived by the users. The contributions of this thesis are focused, in the first place, on the analysis of those factors which generate an increase of the energy consumption in the wireless medium and are related to the principle of operation of the radio interface. In particular, the intense operation in reception mode on the interference areas, as a result of the overhearing effect, as well as the high number of transmission retries due to channel access contention, are defined as the main aspects that increase energy demand in the network. On the other hand, with the aim of optimizing energy resources in the nodes without causing damage on the Quality of Service, this thesis proposes meaningful improvements to the routing protocol by means of a cross-layer scheme. Specifically, the designed mechanism carries out an evaluation of both the energy capacity available in the nodes and the distribution of devices along the wireless medium. To that end, this proposal introduces a new metric in the routing computation process, called strategic value, which reports the importance of a node in the network in terms of connectivity (i.e. number of neighbor nodes). This scheme aims to reduce the energy expenditure caused by the overhearing effect along the areas with higher node density as well as to extend the lifetime for those nodes with higher number of neighbors which are strategic to preserve network connectivity. Additionally, considering the current pragmatic approach in ad hoc networks focused on the design of specific applications, the evaluation hereby presented has been performed by means of a simulation environment and also through the implementation of a testbed. Specifically, the operation of the proposed scheme has been analyzed on a set of ad hoc nodes which has been implemented through development platforms. Also, a software tool has been developed in order to control and configure the experiments. Results prove that the proposal allows to extend the lifetime of the network as well as to increase packet reception rate as a consequence of the prevention in the route breakages due to energy depletion. Finally, it is worth mentioning that the knowledge acquired by the design, configuration and analysis of experiments by means of hardware devices, has motivated the development of proposals and application studies of ad hoc networks in real environments, which represent an additional contribution of this thesis dissertation. / El presente trabajo de tesis doctoral aborda la problemática de las limitaciones de energía en redes inalámbricas ad hoc. En este tipo de redes, los nodos generalmente emplean baterías como fuente de alimentación, lo que limita de forma dramática la autonomía de funcionamiento. Los nodos con mayor agotamiento de energía constituyen potenciales elementos para la pérdida de conectividad parcial o total de la red ocasionando el incremento de la pérdida de paquetes. Por tanto, la gestión eficiente del gasto es uno de los principales desafíos a enfrentar en el ámbito de investigación de redes ad hoc, en especial para el desarrollo de aplicaciones en escenarios reales de operación. Sin embargo, dicha gestión no es una tarea trivial debido a las características inherentes de este tipo de redes, como por ejemplo la operación distribuida, así como el acceso compartido al medio inalámbrico. En tal sentido, los mecanismos usuales de optimización del gasto de energía basados en el establecimiento de períodos de bajo consumo (modo sleep), no se ajustan a las características operativas de una red ad hoc, debido al impacto notable que ocasionan sobre la conectividad en la red. Además, el crecimiento significativo de las aplicaciones y servicios de distribución de contenidos multimedia, especialmente tráfico de vídeo, demandan niveles específicos de calidad de servicio. Por consiguiente, el diseño de soluciones de optimización de los recursos de energía disponible en los nodos no debe implicar la degradación de la calidad de experiencia percibida por los usuarios finales. Las contribuciones del trabajo de tesis se centran, en primer lugar, en el análisis de los factores que incrementan el gasto de energía en el medio inalámbrico y que están relacionados con el principio de operación de la interfaz de radio. En particular, el incremento dramático del funcionamiento en modo recepción ocasionado sobre las zonas de interferencia por el efecto overhearing así como el mayor número de intentos de transmisión debido a la contienda por el acceso al canal, se definen como las principales causas que incrementan la demanda de energía en la red. Por otra parte, con el objetivo de optimizar los recursos de energía disponibles en los nodos sin ocasionar un perjuicio sobre la calidad de servicio, en el presente trabajo de tesis se proponen mejoras al protocolo de encaminamiento mediante un esquema cross-layer. En concreto, el mecanismo diseñado realiza una evaluación de la capacidad de energía disponible en los nodos, así como de la distribución de los dispositivos en el medio inalámbrico. Con tal fin, la propuesta introduce en el cómputo de enrutamiento una métrica nueva denominada valor estratégico, la cual reporta la importancia de un nodo en la red en términos de conectividad (número de dispositivos vecinos). El esquema apunta a reducir el gasto de energía ocasionado por el efecto overhearing en las zonas con mayor densidad de dispositivos, así como extender la autonomía de operación sobre aquellos nodos con mayor número de vecinos, que resultan estratégicos para conservar la conectividad en la red. Además, de forma consecuente con el actual enfoque pragmático en redes ad hoc orientado al diseño de soluciones para escenarios específicos de aplicación, la evaluación de la propuesta se ha realizado tanto en un entorno de simulación, así como mediante la implementación de un testbed. Específicamente, se ha analizado la operación del mecanismo de enrutamiento propuesto sobre un conjunto de nodos ad hoc implementados mediante plataformas de desarrollo. Adicionalmente, se ha desarrollado una herramienta para el control y configuración de los experimentos. Los resultados demuestran que la propuesta permite extender el tiempo de operación de la red, así como incrementar la tasa de paquetes en recepción como consecuencia de la prevención en la ruptura de los enlaces por agotamiento / El present treball de tesi doctoral aborda la problemàtica de les limitacions d'energia en xarxes sense fil ad hoc. En este tipus de xarxes, els nodes generalment empren bateries com a font d'alimentació, la qual cosa limita de forma dramàtica l'autonomia de funcionament. Els nodes amb major esgotament d'energia constituïxen potencials elements per a la pèrdua de connectivitat parcial o total de la xarxa, ocasionant l'increment de la pèrdua de paquets. Per tant, la gestió eficient de la despesa és un dels principals desafiaments a enfrontar en l'àmbit d'investigació de xarxes ad hoc, en especial per al desenvolupament d'aplicacions en escenaris reals d'operació. No obstant això, aquesta gestió no és una tasca trivial a causa de les característiques inherents d'este tipus de xarxes, com per exemple l'operació distribuïda així com l'accés compartit al mitjà sense fil. En este sentit, els mecanismes usuals d'optimització de la despesa d'energia basats en l'establiment de períodes de baix consum (mode sleep), no s'ajusten a les característiques operatives d'una xarxa ad hoc, a causa de l'impacte notable que ocasionen sobre la connectivitat a la xarxa. A més, el creixement significatiu de les aplicacions i serveis de distribució de continguts multimèdia, especialment tràfic de vídeo, demanden nivells específics de qualitat de servei. Per tant, el disseny de solucions d'optimització dels recursos d'energia disponible en els nodes no ha d'implicar la degradació de la qualitat d'experiència percebuda pels usuaris finals. Les contribucions del treball de tesi se centren, en primer lloc, en l'anàlisi dels factors que incrementen la despesa d'energia en el mitjà sense fil i que estan relacionats amb el principi d'operació de la interfície de ràdio. En particular, l'increment dramàtic del funcionament en mode recepció, ocasionat sobre les zones d'interferència per l'efecte overhearing, així com el major nombre d'intents de transmissió a causa de la contesa per l'accés al canal, es definixen com les principals causes que incrementen la demanda d'energia a la xarxa. D'altra banda, amb l'objectiu d'optimitzar els recursos d'energia disponibles en els nodes sense ocasionar un perjudici sobre la qualitat de servici, en el present treball de tesi es proposen millores al protocol d'encaminament mitjançant un esquema cross-layer. En concret, el mecanisme dissenyat realitza una avaluació de la capacitat d'energia disponible en els nodes així com de la distribució dels dispositius en el mitjà sense fil. Amb tal fi, la proposta introduïx en el còmput d'encaminament una nova mètrica denominada valor estratègic, la qual reporta la importància d'un node en la xarxa en termes de connectivitat (nombre de dispositius veïns). L'esquema reduix la despesa ocasionada per l'efecte overhearing a les zones amb major densitat de dispositius i estén l'autonomia d'operació sobre aquells nodes amb major nombre de veïns, que resulten estratègics per conservar la connectivitat a la xarxa. A més, de forma conseqüent amb l'actual enfocament pragmàtic en xarxes ad hoc orientat al disseny de solucions per a escenaris específics d'aplicació, l'avaluació de la proposta s'ha realitzat tant en un entorn de simulació així com per mitjà de la implementació d'un testbed. Específicament, s'ha analitzat l'operació del mecanisme d'encaminament proposat sobre un conjunt de nodes ad hoc implementats mitjançant plataformes de desenvolupament. Addicionalment, s'ha desenvolupat una eina per al control i configuració dels experiments. Els resultats demostren que la proposta permet estendre el temps d'operació de la xarxa així com incrementar la taxa de paquets en recepció com a conseqüència de la prevenció en la ruptura dels enllaços per esgotament d'energia. / González Martínez, SR. (2017). Diseño de un Esquema Cross-Layer para el Balance entre Eficiencia Energética y Calidad de Servicio en la Transmisión de Tráfico Multimedia en Redes Ad-Hoc [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/84284 / TESIS