No / This paper proposes a novel call admission control (CAC) algorithm and develops a two-dimensional markov chain processes (MCP) analytical model to evaluate its performance for heterogeneous wireless network. Within the context of this paper, a hybrid UMTS-WLAN network is investigated. The designed threshold-based CAC algorithm is launched basing on the user’s classification and channel allocation policy. In this approach, channels are assigned dynamically in accordance with user class differentiation. The two-dimensional MCP mathematical analytic method reflects the system performance by appraising the dropping likelihood of handover traffics. The results show that the new CAC algorithm increases the admission probability of handover traffics, while guarantees the system quality of service (QoS) requirement.

We develop and analyze a class of CAC algorithms for resource management in wireless networks with the goal not only to satisfy QoS constraints, but also to maximize a value or reward objective function specified by the system. We demonstrate through analytical modeling and simulation validation that the CAC algorithms developed in this research for resource management can greatly improve the system reward obtainable with QoS guarantees, when compared with existing CAC algorithms designed for QoS satisfaction only. We design hybrid partitioning-threshold, spillover and elastic CAC algorithms based on the design techniques of partitioning, setting thresholds and probabilistic call acceptance to use channel resources for servicing distinct QoS classes. For each CAC algorithm developed, we identify optimal resource management policies in terms of partitioning or threshold settings to use channel resources. By comparing these CAC algorithms head-to-head under identical conditions, we determine the best algorithm to be used at runtime to maximize system reward with QoS guarantees for servicing multiple service classes in wireless networks. We study solution correctness, solution optimality and solution efficiency of the class of CAC algorithms developed. We ensure solution optimality by comparing optimal solutions achieved with those obtained by ideal CAC algorithms via exhaustive search. We study solution efficiency properties by performing complexity analyses and ensure solution correctness by simulation validation based on real human mobility data. Further, we analyze the tradeoff between solution optimality vs. solution efficiency and suggest the best CAC algorithm used to best tradeoff solution optimality for solution efficiency, or vice versa, to satisfy the system's solution requirements. Moreover, we develop design principles that remain applicable despite rapidly evolving wireless network technologies since they can be generalized to deal with management of 'resources' (e.g., wireless channel bandwidth), 'cells' (e.g., cellular networks), "connections" (e.g., service calls with QoS constraints), and "reward optimization" (e.g., revenue optimization in optimal pricing determination) for future wireless service networks. To apply the CAC algorithms developed, we propose an application framework consisting of three stages: workload characterization, call admission control, and application deployment. We demonstrate the applicability with the optimal pricing determination application and the intelligent switch routing application. / Ph. D.

[pt] As disciplinas de Controle de Admissão constituem um recurso importante para a obtenção de Qualidade de Serviço em redes de comunicação. Nesse trabalho, é feito um estudo a respeito da aplicação do Controle de Admissão à Internet. Utilizando- se o software ns-2, é avaliado o desempenho de alguns desses mecanismos em cenários distintos e sob diversas condições de tráfego. / [en] Admission control disciplines are un important resource in the search for Quality of Service on communications networks. In this work, we studt the Admission control applications on the Internet. Using the ns-2 networks simulation software, we evaluate the performance of some of these mechanisms on distinct scenarios, and under several circunstances and traffic conditions.

Este trabalho propõe políticas para servidores Web baseados em sessões, visando ao oferecimento de garantias de qualidade de serviço (Quality of Service - QoS) a seus usuários. Para o fornecimento de QoS, dois tipos de políticas são consideradas: as responsáveis pela diferenciação de serviços e as responsáveis pelo controle de admissão. Alguns algoritmos de escalonamento foram desenvolvidos com o objetivo de oferecer melhores serviços para as sessões prioritárias: o algoritmo de escalonamento baseado em sessão (SBSA) e o algoritmo de escalonamento baseado em sessão com diferenciação de serviços (SBSA-DS). Quanto ao controle de admissão, foram consideradas duas novas políticas, as quais utilizam diferentes parâmetros para a tomada de decisão e têm como objetivo garantir a finalização do maior número de sessões prioritárias. A partir dos resultados obtidos nos experimentos realizados por meio de simulação, constatou-se que o emprego dos algoritmos e das políticas desenvolvidos melhora o atendimento das sessões para as quais deve ser oferecido um serviço preferencial. Portanto, em servidores Web preocupados com a garantia de QoS para seus usuários, os quais interagem com o sistema por meio de sessões, o uso dessas novas técnicas se mostra adequado / This work considers policies for Web servers based on sessions, aiming at the guarantees of Quality of Service (QoS) to the systems users. Two types of policies are considered: the responsible for the differentiation of services and the responsible for the admission control. Some scheduling algorithms had been developed to offer better services for the priority sessions: the Session Based Scheduling Algorithm (SBSA) and the Session Based Scheduling Algorithm with Differentiation of Services (SBSA-DS). In relation to the admission control, two new policies had been considered, which use different parameters to help the decisions and have as objective guarantee the finalization of as many priority sessions as possible. From the obtained results of the experiments realized by mean of simulation, it is evidenced that the use of the developed algorithms and policies improves the attendance of the sessions that deserve preferential service. Therefore, in Web servers worried in the guarantee the QoS for their users, which interact with the system by sessions, the use of these new techniques reveals adequate

Esta dissertação de mestrado apresenta o projeto, implementação e teste de um gerador de carga de trabalho para servidores Web que permite a caracterização de sessões e que representa uma carga real. O gerador desenvolvido gera carga visando à alimentar programas que simulam o comportamento de servidores Web. Para a definição dos parâmetros utilizados no gerador de carga sintética desenvolvido, diversos estudos sobre a carga em servidores Web encontrados na literatura, logs de servidores Web reais e benchmarks para servidores Web, foram utilizados. Vários algoritmos de controle de admissão e de escalonamento de requisições descritos na literatura foram implementados para teste e validação do gerador desenvolvido. Visando a utilização de sessões, é proposto nesta dissertação um algoritmo de controle de admissão, RED-SB (Random Early Detection - Session Based) que se baseia em um algoritmo (RED) que não considera sessão. Esses algoritmos foram executados utilizando-se um modelo de simulação de servidor Web com suporte a diferenciação de serviços, chamado SWDS (Servidor Web com Diferenciação de Serviços) / This MSc dissertation presents the design, implementation and tests of a workload generator for Web servers that allows the characterization of sessions and represents a real workload. The generator developed generates a workload to be used as an input to programs that simulate the behavior of Web servers. For the definition of the parameters used in the synthetic workload generator developed, several studies about the web server load described in the literature, actual web server logs and benchmarks for Web servers were used. Several algorithms for admission control and scheduling of requests described in the literature were implemented for testing and validation of the generator developed. Aiming at the utilization of sessions, this dissertation proposes an admission control algorithm RED-SB (Random Early Detection - Session based) which is based on an algorithm (RED) that does not consider session. These algorithms were implemented using a simulation model ofWeb server that supports service differentiation, called SWDS (Web Server with Service Differentiation)

Software Defined Networking (SDN) provides centralized control by separating the control plane from the data plane on network devices. Subareas of networking such as Quality of Service (QoS) can greatly benefit from this separation as QoS policies can be provided globally for the network. One way of providing QoS is to reserve and monitor network resources to guarantee a specific data rate for a requested transmission end-to-end. The presented thesis looks into possible ways of controlling the wireless medium using SDN to provide QoS. A method for providing QoS in a multihop SDN network supporting wired and wireless communication was implemented. The method was evaluated using network performance metrics such as throughput and packet jitter. The results of the experiments showed that the implemented method could limit bandwidth utilization and prioritize bandwidth usage for higher priority nodes. The performance of the network was concluded to have severe issues with dropped packets and irregular packet jitter spikes.

nÃo hà / O crescimento do nÃmero dos usuÃrios do serviÃo de Voice over IP(VoIP) faz dele o serviÃo com o maior interesse de ser provido por operadoras de telefonia celular. Por outro lado, este demanda um controle de Quality of Service (QoS) bastante rÃgido, o que torna-se mais complicado em redes sem fio, porque alÃm de congestionamentos na rede, os pacotes podem ser perdidos devido à erros nas transmissÃes no enlace de rÃdio. Dentro deste paradigma, estratÃgias de controle de congestionamento aparecem como uma boa soluÃÃo para lidar com as garantias de QoS em situaÃÃes de sobrecarga do sistema, onde os recursos se encontram exauridos e os requerimentos de qualidade se encontram ameaÃados. Este trabalho consiste na avaliaÃÃo de algoritmos de controle de congestionamento objetivando um aumento de capacidade e das garantias de QoS para serviÃos de voz. Os algoritmos avaliados neste trabalho sÃo os escalonamentos de pacotes e os controles de admissÃo. A anÃlise em cenÃrios de serviÃos mistos composto por usuÃrios VoIP e Web tambÃm està contida neste trabalho. O maior foco està no controle do atraso de pacote, jà que este à um requerimento crucial para serviÃos de tempo-real, como o VoIP. Os resultados mostram que um arcabouÃo de controle de congestionamento projetado para este serviÃo à capaz de melhorar o desempenho do sistema e mitigar os efeitos de congestionamento da rede. No cenÃrio de serviÃos mistos, os algoritmos sÃo capazes de efetuar reserva de recursos dependendo da prioridade definida para cada serviÃo, levando a um aumento na qualidade percebida pelo serviÃo mais sensÃvel atravÃs de uma leve degradaÃÃo no serviÃo mais robusto. / The growth in the number of Voice over IP(VoIP) users on the internet makes it the service with the highest interest to be provided by cellular operators. On the other hand, it demands very strict Quality of Service (QoS) control, which becomes even more complicated in wireless networks, because packets can be lost due to radio link transmission erros, as well as networks congestion. Within this paradigm, congestion control strategies appear as a good solution to cope with QoS guarantees under high loads, where the resources are exhausted and the service quality is threatened. This works comprises the evaluation of congestion control algorithms aiming to improve system capacity and QoS guarantees for speech users. The evaluated alagorithms within this work are packet scheduling and admission control. The analysys in mixed services scenarios composed of VoIP and Web users is also provid in this works. The main focus of the framework is to control the packet delay, since it is a crucial requirement for real-time services. The results show thata suitable congestion control framework is able to provid perfomace improvements and mitigation of the the effects from overloaded conditions. In the mixed services scenario, the algorithms are capable to perform resource reservation depending on the priority defined to each service, leanding to an increase in the quality of more sensitive service by degrading the more robust service

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.

<p>Revenue maximization for network operators is considered as a criterion for resource allocation in wireless cellular networks. A business model encompassing service level agreements between network operators and service providers is presented. Admission control, through price model aware admission policing and service level control, is critical for the provisioning of useful services over a general purpose wireless network. A technical solution consisting of a fast resource scheduler taking into account service requirements and wireless channel properties, a service level controller that provides the scheduler with a reasonable load, and an admission policy to uphold the service level agreements and maximize revenue, is presented.</p><p>Two different types of service level controllers are presented and implemented. One is based on a scalar PID controller, that adjusts the admitted data rates for all active clients. The other one is obtained with linear programming methods, that optimally assign data rates to clients, given their channel qualities and price models.</p><p>Two new scheduling criteria, and algorithms based on them, are presented and evaluated in a simulated wireless environment. One is based on a quadratic criterion, and is implemented through approximative algorithms, encompassing a search based algorithm and two different linearizations of the criterion. The second one is based on statistical measures of the service rates and channel states, and is implemented as an approximation of the joint probability of achieving the delay limits while utilizing the available resources efficiently.</p><p>Two scheduling algorithms, one based on each criterion, are tested in combination with each of the service level controllers, and evaluated in terms of throughput, delay, and computational complexity, using a target test system. Results show that both schedulers can, when feasible, meet explicit throughput and delay requirements, while at the same time allowing the service level controller to maximize revenue by allocating the surplus resources to less demanding services.</p>

Revenue maximization for network operators is considered as a criterion for resource allocation in wireless cellular networks. A business model encompassing service level agreements between network operators and service providers is presented. Admission control, through price model aware admission policing and service level control, is critical for the provisioning of useful services over a general purpose wireless network. A technical solution consisting of a fast resource scheduler taking into account service requirements and wireless channel properties, a service level controller that provides the scheduler with a reasonable load, and an admission policy to uphold the service level agreements and maximize revenue, is presented. Two different types of service level controllers are presented and implemented. One is based on a scalar PID controller, that adjusts the admitted data rates for all active clients. The other one is obtained with linear programming methods, that optimally assign data rates to clients, given their channel qualities and price models. Two new scheduling criteria, and algorithms based on them, are presented and evaluated in a simulated wireless environment. One is based on a quadratic criterion, and is implemented through approximative algorithms, encompassing a search based algorithm and two different linearizations of the criterion. The second one is based on statistical measures of the service rates and channel states, and is implemented as an approximation of the joint probability of achieving the delay limits while utilizing the available resources efficiently. Two scheduling algorithms, one based on each criterion, are tested in combination with each of the service level controllers, and evaluated in terms of throughput, delay, and computational complexity, using a target test system. Results show that both schedulers can, when feasible, meet explicit throughput and delay requirements, while at the same time allowing the service level controller to maximize revenue by allocating the surplus resources to less demanding services.