We design, implement and evaluate statistical methods for managing uncertainty when consuming and provisioning resources in a federated computational market. To enable efficient allocation of resources in this environment, providers need to know consumers' risk preferences, and the expected future demand. The guarantee levels to offer thus depend on techniques to forecast future usage and to accurately capture and model uncertainties. Our main contribution in this thesis is threefold; first, we evaluate a set of techniques to forecast demand in computational markets; second, we design a scalable method which captures a succinct summary of usage statistics and allows consumers to express risk preferences; and finally we propose a method for providers to set resource prices and determine guarantee levels to offer. The methods employed are based on fundamental concepts in probability theory, and are thus easy to implement, as well as to analyze and evaluate. The key component of our solution is a predictor that dynamically constructs approximations of the price probability density and quantile functions for arbitrary resources in a computational market. Because highly fluctuating and skewed demand is common in these markets, it is difficult to accurately and automatically construct representations of arbitrary demand distributions. We discovered that a technique based on the Chebyshev inequality and empirical prediction bounds, which estimates worst case bounds on deviations from the mean given a variance, provided the most reliable forecasts for a set of representative high performance and shared cluster workload traces. We further show how these forecasts can help the consumers determine how much to spend given a risk preference and how providers can offer admission control services with different guarantee levels given a recent history of resource prices. / QC 20100909

The main objective of this thesis focuses on the design of an adaptive algorithm for admission control and content-aware load balancing for Web traffic. In order to set the context of this work, several reviews are included to introduce the reader in the background concepts of Web load balancing, admission control and the Internet traffic characteristics that may affect the good performance of a Web site. The admission control and load balancing algorithm described in this thesis manages the distribution of traffic to a Web cluster based on QoS requirements. The goal of the proposed scheduling algorithm is to avoid situations in which the system provides a lower performance than desired due to servers' congestion. This is achieved through the implementation of forecasting calculations. Obviously, the increase of the computational cost of the algorithm results in some overhead. This is the reason for designing an adaptive time slot scheduling that sets the execution times of the algorithm depending on the burstiness that is arriving to the system. Therefore, the predictive scheduling algorithm proposed includes an adaptive overhead control.Once defined the scheduling of the algorithm, we design the admission control module based on throughput predictions. The results obtained by several throughput predictors are compared and one of them is selected to be included in our algorithm. The utilisation level that the Web servers will have in the near future is also forecasted and reserved for each service depending on the Service Level Agreement (SLA). Our load balancing strategy is based on a classical policy. Hence, a comparison of several classical load balancing policies is also included in order to know which of them better fits our algorithm. A simulation model has been designed to obtain the results presented in this thesis.

In the last decade, the world has witnessed rapid increasing applications of wireless networks. However, with the fixed spectrum allocation policy that has been used since the beginning of the spectrum regulation to assign different spectrum bands to different wireless applications, it has been observed that most of the allocated spectrum bands are underutilized. Therefore, if these bands can be opportunistically used by new emerging wireless networks, the spectrum scarcity can be resolved. Cognitive Radio (CR) is a revolutionary and promising technology that can identify and then exploit the spectrum opportunities. In Cognitive Radio Networks (CRNs), the spectrum can be utilized by two kinds of users: Primary Users (PUs) having exclusive licenses to use certain spectrum bands for specific wireless applications, and Secondary Users (SUs) having no spectrum licenses but seeking for any spectrum opportunities. The SUs can make use of the licensed unused spectrum if they do not make any harmful interference to the PUs. However, the variation of the spectrum availability over the time and locations, due to the coexistence with the PUs, and the spread of the spectrum opportunities over wide spectrum bands create a unique trait of the CRNs. This key trait poses great challenges in different aspects of the radio resource management in CRNs such as the spectrum sensing, spectrum access, admission control, channel allocation, Quality-of-Service (QoS) provisioning, etc. In this thesis, we study the resource management of both single-hop and multi-hop CRNs. Since most of the new challenges in CRNs can be tackled by designing an efficient Medium Access Control (MAC) framework, where the solutions of these challenges can be integrated for efficient resource management, we firstly propose a novel MAC framework that integrates a kind of cooperative spectrum sensing method at the physical layer into a cooperative MAC protocol considering the requirements of both the SUs and PUs. For spectrum identification, a computationally simple but efficient sensing algorithm is developed, based on an innovative deterministic sensing policy, to assist each sensing user for identifying the optimum number of channels to sense and the optimum sensing duration. We then develop an admission control scheme and channel allocation policy that can be integrated in the proposed MAC framework to regulate the number of sensing users and number of access users; therefore, the spectrum identification and exploitation can be efficiently balanced. Moreover, we propose a QoS-based spectrum allocation framework that jointly considers the QoS provisioning for heterogeneous secondary Real-Time (RT) and Non-Real Time (NRT) users with the spectrum sensing, spectrum access decision, and call admission control. We analyze the proposed QoS-based spectrum allocation framework and find the optimum numbers of the RT and NRT users that the network can support. Finally, we introduce an innovative user clustering scheme to efficiently manage the spectrum identification and exploitation in multi-hop ad hoc CRNs. We group the SUs into clusters based on their geographical locations and occurring times and use spread spectrum techniques to facilitate using one frequency for the Common Control Channels (CCCs) of the whole secondary network and to reduce the co-channel interference between adjacent clusters by assigning different spreading codes for different clusters. The research results presented in this thesis contribute to realize the concept of the CRNs by developing a practical MAC framework, spectrum sensing, spectrum allocation, user admission control, and QoS provisioning for efficient resource management in these promising networks.

A Web-server farm is a specialized facility designed specifically for housing Web servers catering to one or more Internet facing Web sites. In this dissertation, stochastic dynamic programming technique is used to obtain the optimal admission control policy with different classes of customers, and stochastic uid- ow models are used to compute the performance measures in the network. The two types of network traffic considered in this research are streaming (guaranteed bandwidth per connection) and elastic (shares available bandwidth equally among connections). We first obtain the optimal admission control policy using stochastic dynamic programming, in which, based on the number of requests of each type being served, a decision is made whether to allow or deny service to an incoming request. In this subproblem, we consider a xed bandwidth capacity server, which allocates the requested bandwidth to the streaming requests and divides all of the remaining bandwidth equally among all of the elastic requests. The performance metric of interest in this case will be the blocking probability of streaming traffic, which will be computed in order to be able to provide Quality of Service (QoS) guarantees. Next, we obtain bounds on the expected waiting time in the system for elastic requests that enter the system. This will be done at the server level in such a way that the total available bandwidth for the requests is constant. Trace data will be converted to an ON-OFF source and fluid- flow models will be used for this analysis. The results are compared with both the mean waiting time obtained by simulating real data, and the expected waiting time obtained using traditional queueing models. Finally, we consider the network of servers and routers within the Web farm where data from servers flows and merges before getting transmitted to the requesting users via the Internet. We compute the waiting time of the elastic requests at intermediate and edge nodes by obtaining the distribution of the out ow of the upstream node. This out ow distribution is obtained by using a methodology based on minimizing the deviations from the constituent in flows. This analysis also helps us to compute waiting times at different bandwidth capacities, and hence obtain a suitable bandwidth to promise or satisfy the QoS guarantees. This research helps in obtaining performance measures for different traffic classes at a Web-server farm so as to be able to promise or provide QoS guarantees; while at the same time helping in utilizing the resources of the server farms efficiently, thereby reducing the operational costs and increasing energy savings.

Today, telecommunication is improving rapidly. People are online anywhere anytime. Due to increasing demand in communication, wireless technologies are progressing quickly trying to provide more services in a wide range. In order to address mobility and connectivity requirements of users in wide areas, Worldwide Interoperability for Microwave Access (Wimax) has been introduced as a forth generation telecommunication technology. Wimax, which is also called Metropolitan Area Network (MAN), is based on IEEE 802.16 standard where a Base Station (BS) provides last mile broadband wireless access to the end users known as Mobile Stations (MS). However, in places where high constructions exist, the signal rate between MS and BS decreases or even the signal can be lost completely due to shadow fading. As a response to this issue, recently an intermediate node specification, namely Relay Station, has been defined in IEEE 802.16j standard for relaying, which provides both throughput enhancement and coverage extension. However, this update has introduced a new problem / call admission control in non-transparent relay networks that support coverage extension. In this thesis, a Quality of Service (QoS) aware dynamic admission control algorithm for IEEE 802.16j non-transparent relay networks is introduced. Our objectives are admitting more service flows, utilizing the bandwidth, giving individual control to each relay station (RS) on call acceptance and rejection, and finally not affecting ongoing service flow quality in an RS due to the dense population of service flows in other RSs. The simulation results show that the proposed algorithm outperforms the other existing call admission control algorithms. Moreover, this algorithm can be interpreted as pioneer call admission control algorithm in IEEE 802.16j non-transparent networks.

In the last decade, the world has witnessed rapid increasing applications of wireless networks. However, with the fixed spectrum allocation policy that has been used since the beginning of the spectrum regulation to assign different spectrum bands to different wireless applications, it has been observed that most of the allocated spectrum bands are underutilized. Therefore, if these bands can be opportunistically used by new emerging wireless networks, the spectrum scarcity can be resolved. Cognitive Radio (CR) is a revolutionary and promising technology that can identify and then exploit the spectrum opportunities. In Cognitive Radio Networks (CRNs), the spectrum can be utilized by two kinds of users: Primary Users (PUs) having exclusive licenses to use certain spectrum bands for specific wireless applications, and Secondary Users (SUs) having no spectrum licenses but seeking for any spectrum opportunities. The SUs can make use of the licensed unused spectrum if they do not make any harmful interference to the PUs. However, the variation of the spectrum availability over the time and locations, due to the coexistence with the PUs, and the spread of the spectrum opportunities over wide spectrum bands create a unique trait of the CRNs. This key trait poses great challenges in different aspects of the radio resource management in CRNs such as the spectrum sensing, spectrum access, admission control, channel allocation, Quality-of-Service (QoS) provisioning, etc. In this thesis, we study the resource management of both single-hop and multi-hop CRNs. Since most of the new challenges in CRNs can be tackled by designing an efficient Medium Access Control (MAC) framework, where the solutions of these challenges can be integrated for efficient resource management, we firstly propose a novel MAC framework that integrates a kind of cooperative spectrum sensing method at the physical layer into a cooperative MAC protocol considering the requirements of both the SUs and PUs. For spectrum identification, a computationally simple but efficient sensing algorithm is developed, based on an innovative deterministic sensing policy, to assist each sensing user for identifying the optimum number of channels to sense and the optimum sensing duration. We then develop an admission control scheme and channel allocation policy that can be integrated in the proposed MAC framework to regulate the number of sensing users and number of access users; therefore, the spectrum identification and exploitation can be efficiently balanced. Moreover, we propose a QoS-based spectrum allocation framework that jointly considers the QoS provisioning for heterogeneous secondary Real-Time (RT) and Non-Real Time (NRT) users with the spectrum sensing, spectrum access decision, and call admission control. We analyze the proposed QoS-based spectrum allocation framework and find the optimum numbers of the RT and NRT users that the network can support. Finally, we introduce an innovative user clustering scheme to efficiently manage the spectrum identification and exploitation in multi-hop ad hoc CRNs. We group the SUs into clusters based on their geographical locations and occurring times and use spread spectrum techniques to facilitate using one frequency for the Common Control Channels (CCCs) of the whole secondary network and to reduce the co-channel interference between adjacent clusters by assigning different spreading codes for different clusters. The research results presented in this thesis contribute to realize the concept of the CRNs by developing a practical MAC framework, spectrum sensing, spectrum allocation, user admission control, and QoS provisioning for efficient resource management in these promising networks.

This dissertation argues that admission control should be applied as early as possible within a system. To that end, this dissertation examines the benefits and trade-offs involved in applying admission control to a networked computer system at the level of the network interface hardware. Admission control has traditionally been applied in software, after significant resources have already been expended on processing a request. This design decision leads to systems whose algorithmic cost is a function of the load applied to the system, rather than the load admitted to the system. By performing admission control at the network interface, it is possible to develop systems whose algorithmic cost is a function of load admitted to the system, rather than load applied to the system. Such systems are able to deal with excessive applied loads without exhibiting performance degradation. This dissertation first examines existing admission control approaches, focussing on the cost of admission control within those systems. It then goes on to develop a model of system behaviour under overload, and the impact of admission control on that behaviour. A new class of admission control mechanisms which are able to perform load rejection using the network interface hardware are then described, along with a prototype implementation using commodity hardware. A prototype implementation in the FreeBSD operating system is evaluated for a variety of network protocols and performance is compared to the standard FreeBSD implementation. Performance and scalability under overload is significantly improved.

There is a prolific increase in the penetration of user devices such as smartphones and tablets. In addition, user expectations for higher Quality of Service (QoS), enhanced data rates and lower latencies are relentless. In this context, network densification through the dense deployment of small cell networks, underlaying the currently existing macrocell networks, is the most appealing approach to handle the aforementioned requirements. Small cell networks are capable of reusing the spectrum locally and providing most of the capacity while macrocell networks provide a blanket coverage for mobile user equipment (UEs). However, such setup imposes a lot of issues, among which, co-tier and cross-tier interference are the most challenging. To handle co-tier interference, I have proposed a semi-distributed (hierarchical) interference management scheme based on joint clustering and resource allocation (RA) for small cells. I have formulated the problem as a Mixed Integer Non-Linear Program (MINLP), whose solution was obtained by dividing the problem into two sub-problems, where the related tasks were shared between the Femto Gateway (FGW) and small cells. As for cross-tier interference, I have formulated RA problems for both the macrocell and small cells as optimization problems. In particular, I have introduced the idea of ``Tier-Awareness'' and studied the impact of the different RA policies in the macrocell tier on the small cells performance. I have shown that the RA policy in one tier should be carefully selected. In addition, I have formulated the RA problem for small cells as an optimization problem with an objective function that accounts for both RA and admission control (AC). Finally, I have studied cloud radio access network (C-RAN) of small cells which has been considered as a typical realization of a mobile network which is capable of supporting soft and green technologies in Fifth Generation (5G) networks, as well as a platform for the practical implementation of network multiple-input multiple-output (MIMO) and coordinated multi-point (CoMP) transmission concepts. / February 2016

Depuis quelques années, il y a un réel changement dans les usages des réseaux en termes d'applications véhiculées ainsi que dans leur nombre. On voit apparaître de plus en plus d'applications contraintes en termes de délai, comme par exemple la téléphonie sur IP, ainsi que d'applications gourmandes en ressources comme par exemple le Srteaming Video. La croissance en volume de ces applications copmmence à poser des problèmes de congestion dasn les réseaux filiares et sans fil. Les opérateurs réseaux doivent être capables d'absorber ces changements de trafic, de faire face à cette demande de plus en plus intensive en bande passante et de fournir une bonne qualité (QoS) aux applications. Cela nécessite des mécanismes intellignets en termes d'ordonnancement et de gestion des files d'attente, de contrôle d'admission, de contrôle de débit et/ou de routage. L'objectif initial de cette thèse étati d'aboutir à la conception d'une nouvelle architecture de traitement et de gestion du trafic et de la qualité de service pour le contrôle d'admission. Plus précisément nous présentons une nouvelle solution pour le contrôle d'admission qui repose sur l'élaboration en continu d'un plan de connaissance et sur la modélisatio automatique du comportement d'un lien réseau par une file d'attente monoserveur. Norte solution doit permettre d'offrir une garantie probabiliste d'un paramètre de performance QoS qui peut être le délai d'attente moyen des paquets dans le buffer du lien ou le taux de perte. Nous avons évalué les performances de notre nouveau contro^le d'admission par simulation en considérant diverses conditions possibles de trafic. Lers résultats obtenus indiquent que la solution proposée permet d'atteindre un contrôle d'admission ni trop conservateur, ni trop permissif. En outre, notre solution offre l'avantage de se baser uniquement sur une connaisssance acquise au cours du temps et permet ainsi de s'affranchir d'un paramétrage compliqué des paramètres comme c'est le cas pour les solutions classiques de contrôle d'admission / Over the las few years, new ussages such as streaming or live video watching are increasingly representing a significant part of Internet traffic. Network operators face the challenge of satisfying the quality of experience expected by end-users while, in the same time, avoiding the over-provisioning of transmission links. Bandwidth management offers a wide spectrum of policies to overcome this issue. Possible options include congestion control, scheduling algorithms, traffic shaping and admission control. The initial objective of this thesis was to design of a new architecture of traffic management and quality of service for admission control. More precisely, we introduce a novel data-driven method based on a time-varying model that we refer to as Knowledge-Based Admission Control solutions (KBAC). Our KBAC solution consists of three main stages : (i) collect leasurments on the on-going traffic over the communication link ; (ii) maintain an up-to-date broad view of the link behavior, and feed it to a Knowledge Plane ; (iii) model the observed link behavior by a mono-server queue whose parameters are set auutomatically and which predicts the expected QoS if a flow requesting admission were to be accepted. our KBAC solution provides a probalistic guarantee whose admission thresold is either expressed, as a bounded dealy or as a bounded loss rate. We run extensive siçmulations using various traffic conditions to assess the behavior of our KBAC solution in the case of a delay thresold. The results show that our KBAC solution leads to a good trade-off between flow performance and resource utilization. This ability stems from the quick and autoamtic adjustment of its admission policy according to the actual variations on the traffic conditions. On the other hand, our KBAC solution avoids the critical step of precisely calibrating key parameters.

Made available in DSpace on 2015-04-11T14:03:17Z (GMT). No. of bitstreams: 1 DISSERTACAO CLAUDIA SUZANY.pdf: 727638 bytes, checksum: 99ca8c710111acef29c2891b5586f81b (MD5) Previous issue date: 2008-11-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This thesis presents a prototype of admission control for VoIP calls in wireless mesh networks, called CAC-RM, using the IEEE 802.11g protocol. This admission control goal is to avoid that incoming VoIP data flows consume excessive resources and cause degradation in the established ones. The admission control proposed in our approach only accepts new VoIP calls if the inprogress calls quality do not become degraded. The main features of our approach are: (i) an estimated ocupation time at the channel with VoIP traffic and with traffic without quality requirements, so called BE (Best effort); (ii) the resources reservation for VoIP traffic; (iii) an integration of our prototype to the OLSR proactive routing protocol (sending control messages with information about the occupancy node time with BE and VoIP traffic); (iv) an intra-flow interference estimate with admission control integrated; (v) regulation for BE traffic; and (vi) prioritization to sending and receiving VoIP traffic. The prototype was initially evaluated by simulations of a wireless mesh network in a scenario where all nodes are neighbours, considering two variations: the first one has only VoIP data flows and the second has VoIP and BE data flows. We measured the packet loss and the delays of VoIP calls and evaluated the MOS (Mean Opinion Score) measure indicating the user s satisfaction. In the first scenario, without CAC-RM, when the number of VOIP calls increases, their quality are decreased (indicated by the MOS value measured). Using the proposed calls admission control some calls were rejected and the gains is about 70% in the MOS value measured. Besides there was a reduction up to 82% and 96%, respectively, in packets losses and delays. In the second variation the proposed CAC to avoid reduction to about 29% of VoIP with quality over 3.5, and reduces too the damagethe packet VoIP losses uppon 86 %. In other scenario using multiple hops, we used VoIP traffic and hop count, ETX and ML metrics. When the network is saturated, there are no calls with enough VoIP quality. But it s possible to get satisfatory VoIP calls rejecting some calls as done by the proposed CAC. This gives a gain of MOS and reduces to 75 % the packet loss. In both scenarios, the proposed VoIP call admission control has provem efficient avoiding admission of new VoIP calls would degrade the quality of already established connections and ensuring that BE traffic does not damage VoIP packets on the wireless mesh network. / Esta dissertação apresenta um controle de admissão para chamadas VoIP em Rede Mesh sem fio, denominado CAC-RM,que utiliza o protocolo IEEE 802.11g. Seu uso visa prevenir que a chegada de novas chamadas VoIP na rede consuma excessivamente recursos dos nós e causem degradação nos fluxos já estabelecidos, devido ao congestionamento do meio sem fio. Em nossa pesquisa, o controle de admissão proposto só aceitará novas chamadas VoIP caso a qualidade das chamadas em andamento não se torne insatisafatória. As principais características de nossa proposta são: (i) a estimativa do tempo de ocupação do meio com tráfego VoIP e tráfego que não necessita de requisitos de qualidade, denominado BE (Best effort); (ii) a reserva de recursos para tráfego VoIP; (iii) a integração do controle de admissão ao protocolo de roteamento pró-ativo OLSR (usando o envio de mensagens de controle com informações sobre o tempo de ocupação do nó com tráfego BE e VoIP); (iv) a estimativa sobre a interferência intra-fluxo integrada ao controle de admissão; (v) regulagem do tráfego BE; e (vi) a priorização do envio e recebimento do tráfego VoIP. Inicialmente, o controle de admissão proposto foi avaliado a partir de simulações de uma rede mesh sem fio em um cenário em que todos os nós são vizinhos e considerando duas variações: na primeira há somente tráfego VoIP e na segunda, tráfego VoIP e BE. Foram medidos e avaliados a perda e atrasos de pacotes das chamadas VoIP, assim como os valores do MOS (Mean Opinion Score), que indica a satisfação do usuário. No cenário em que os nós vizinhos só trafegam VoIP e não é utilizado o CAC-RM, à medida que a quantidade de chamadas VoIP cresce, sua qualidade é reduzida até que se torna inviável o uso do VoIP na rede. Com o uso do CAC-RM, obteve-se ganhos de até 70% no valor do MOS medido a partir da rejeição de algumas chamadas. Além disso, houve redução de até 82% e 96%, respectivamente, nas perdas de pacotes e atrasos. Já no cenário em que há tráfego VoIP e BE, o CAC proposto conseguiu evitar redução de, aproximadamenre, 29% das chamadas com qualidade, além de conseguir reduzir em até 86% as perdas de pacotes VoIP. No cenário com múltiplos saltos foram transmitidas chamadas VoIP na presença das métricas de roteamento Contagem de salto, ETX e ML. Sem o uso do CAC-RM e com tráfego intenso de dados, não há chamadas VoIP com qualidade satisfatória quando são necessários 02 saltos. A partir da rejeição de algumas chamadas feitas pelo CAC proposto, é possível obter chamadas VoIP com qualidade, contabilizando ganho no MOS, com redução de até 75% nas perdas de pacote. Em ambos os cenários simulados, o controle de admissão de chamadas proposto, mostrou-se eficiente ao evitar que a entrada de novas chamadas VoIP comprometesse o desempenho de chamadas já estabelecidas e que a existência de tráfego BE inviabilizasse o uso do VoIP na rede mesh sem fio.