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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

QoS-CARE : a reliable system for preserving QoS contracts through dynamic reconfiguration / QoS-CARE : un système fiable pour préserver les contrats de qualité de service dans une reconfiguration dynamique

Tamura, Gabriel 28 May 2012 (has links)
Le principal défi de cette thèse est de préserver de façon fiable la qualité de service (QoS) définie par contrats dans des systèmes logiciels à base de composants, ceci dans des conditions changeantes d'exécution du système. En réponse à ce défi, nous présentons deux contributions. La première est un modèle pour les applications logicielles à base de composants avec contrats de qualité de service et règles de reconfiguration définies par des graphes attribués typés. Ainsi, nous utilisons des modèles formels à l'exécution pour reconfigurer de manière fiable des applications logicielles de façon à préserver les contrats de QoS. Plus précisément, nous montrons la faisabilité d'exploiter des patrons de conception à l'exécution dans des boucles de reconfiguration tout en garantissant les niveaux de QoS attendues. Nous mettons en œuvre ce modèle formel par le biais d'une architecture à base de composants qui peut être utilisée comme une couche supplémentaire de la plateforme SCA, ceci afin de préserver les contrats de QoS.La seconde contribution est la caractérisation des propriétés d'adaptation pour évaluer les systèmes logiciels auto-adaptatifs de manière standardisée et comparable. De par leur nature, les mécanismes d'adaptation des systèmes logiciels auto-adaptatifs sont essentiellement des boucles de rétroaction telles que définies par la théorie du contrôle. Ainsi, pour les évaluer, il est nécessaire de ré-interpréter ces proprétés dans le domaine du logiciel. Nous définissons la fiabilité de la réalisation de notre modèle formel en termes de sous-ensemble des propriétés d'adaptation caractérisées, et nous montrons que ces propriétés sont garanties dans cette réalisation. / The main challenge of this Thesis is to reliably preserve quality of service (QoS) contracts in component-based software systems under changing conditions of system execution. In response to this challenge, the presented contribution is twofold. The first is a model for component-based software applications, QoS contracts and reconfiguration rules as typed attributed graphs, and the definition of QoS-contracts semantics as state machines in which transitions are performed as software reconfigurations. Thus, we effectively use (formal) models at runtime to reliably reconfigure software applications for preserving its QoS contracts. More specifically, we show the feasibility of exploiting design patterns at runtime in reconfiguration loops to fulfill expected QoS levels associated to specific context conditions. We realize this formal model through a component-based architecture and implementation that can be used as an additional layer of SCA middleware stacks to preserve the QoS contracts of executed applications.The second contribution is the characterization of adaptation properties to evaluate self-adaptive software systems in a standardized and comparable way. By its own nature, the adaptation mechanisms of self-adaptive software systems are essentially feedback loops as defined in control theory. Thus, it results reasonable to evaluate them using the standard properties used to evaluate feedback loops, re-interpreting these properties for the software domain. We define the relibility of our formal model realization in terms of a subset of the characterized adaptation properties, and we show that these properties are guaranteed in this realization.
2

QoS Representation, Negotiation and Assurance in Cloud Services

Zheng, Xianrong 20 February 2014 (has links)
Cloud services are Internet-based IT services. Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS) are three representative examples. As the cloud market becomes more open and competitive, Quality of Service (QoS) will be more important. However, cloud providers and cloud consumers have different and sometimes opposite preferences. If such a conflict occurs, a Service Level Agreement (SLA) cannot be established without negotiation. To allow service consumers to express their QoS requirements, and negotiate them with service providers, we argue for cloud service negotiation. It aims to establish and enforce SLAs for cloud services. Specifically, we study how to measure, negotiate, and enforce QoS requirements for cloud services, and so formulate three research problems, i.e., QoS measurement, QoS negotiation, and QoS assurance. In terms of its scope, the topic covers business side automated negotiation and technical side resource allocation techniques. As a result, it has a potential impact on cloud service adoption. To address QoS measurement, we initiate a quality model named CLOUDQUAL for cloud services. It is a model with quality dimensions and metrics that targets general cloud services. CLOUDQUAL contains six quality dimensions, i.e., usability, availability, reliability, responsiveness, security, and elasticity, of which usability is subjective, whereas the others are objective. To address QoS negotiation, we present a mixed negotiation approach for cloud services, which is based on the “game of chicken”. In particular, if a party is uncertain about the strategy of its counterpart, it is best to mix concession and tradeoff strategies in negotiation. In fact, the mixed approach, which exhibits a certain degree of intelligence, can achieve a higher utility than a concession approach, while incurring fewer failures than a tradeoff approach. To address QoS assurance, we propose a QoS-driven resource allocation method for cloud services. It can meet users’ QoS requirements while minimizing resources consumed. Especially, to honor a QoS specified in a SLA, we develop QoS assurance mechanisms, and determine the minimum resources that should be allocated. As a result, the method makes both technical and economic sense for cloud providers. / Thesis (Ph.D, Computing) -- Queen's University, 2014-02-20 14:26:06.616
3

TCP EXTENSIONS FOR A SATELLITE CHANNEL

Hu, Xuenan, Zhou, Tingxian 10 1900 (has links)
International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The usage of Internet is explosively growing. Satellite has become a choice solution breaking through the bandwidth bottleneck and the terrain limit. TCP, which is well suited to terrestrial networks, performs poorly on a satellite channel. The reduced efficiency and QoS(Quality of Service) mainly result from three characteristics of a satellite link: higher bit error rate, the high latency, asymmetry. For this issue, the paper presents connection-subsection network architecture, and brings forward S-TCP based on the architecture.
4

PROPOSAL OF POLLED-CSMA PROTOCOL FOR AN AD HOC SCADA SYSTEM

Yuxiang, Yang, Xiaoyu, Dang, Tingxian, Zhou 10 1900 (has links)
International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / In this paper we introduce an ad hoc distributed supervisory control and data acquisition (SCADA) system, which covers two types of traffic, a small number of slave stations with stream traffic and much larger number of slave stations with burst traffic. To improve the system’s real-time transmission and channel allocation efficiency, a MAC scheme, named Polled-CSMA, is designed by integrating the merits of polling and CSMA protocols. Extensive analysis shows that this MAC protocol meets the system’s QOS requirements.
5

Scheduling Algorithms and QoS in HSDPA / Scheduling Algorithms and QoS in HSDPA

Iqbal, Javed, Mustafa, Basit January 2009 (has links)
High Speed Downlink Packet Access (HSDPA) is the extension to the Universal Mobile Telecommunication System (UMTS). HSDPA allows for higher data rates due to new adaptive Modulation and Coding (AMC) techniques, Hybrid Automatic Repeat reQuest (H-ARQ) and fast scheduling algorithm. One of the key features of HSDPA technology is to handle UMTS traffic classes with different Quality of Service (QoS) requirements. In order to provide QoS several scheduling algorithms, QoS control constraints, and different other schemes have been proposed in literature. In the thesis, a simple matlab based model for HSDPA is presented in order to simulate various algorithms. The QoS controls in terms of guaranteed bit rate (GBR) have been implemented by means of barrier functions which perform barrier around the feasible region. The results illustrate the trade-off between the cell throughput and the minimum guaranteed bit rate. Traffic classes are prioritized by means of QoS parameters. The priority is given to RT traffic streams over interactive services. Real-Time (RT) algorithms have been simulated to prioritize traffic classes based on delays. / QoS is the ability to provide resources and prioritize different applications. As mentioned before, the 3GPP standard defines four categories of service (Conversation, streaming, interactive and background) for UMTS. Strategies in traffic management, priority GBR allowances and bandwidth are important strategies for traffic differentiation and quality of service (QoS). Providing QoS over HSDPA is one of the challenging tasks for researchers. The significant results and findings of our thesis are as follows • In this thesis various algorithms were implemented with their duties barrier to provide guarantees of quality, in terms of speed guaranteed (GBR). The emphasis was to ensure the flow and priority categories of traffic. First the performance of algorithms were studied alone and then along with the barrier functions. It is concluded that barrier functions play an important role by means of providing QoS guarantee in HSDPA, considering channel conditions. Traffic classes were prioritized on QoS parameters defined for barrier functions. It was found that minimum bit rates were maintained by barrier functions but the cell throughput decreases with their barrier functions depending upon QoS parameters. The streaming aware scheduler has been evaluated by means of simulations in mixed scenarios and it is concluded that this algorithm protects streaming QoS in high overload conditions. It is therefore concluded that barrier functions and streaming aware schedulers are the best option for QoS control. These schedulers are very simple and consider diversity gains as well.
6

預算法全IP核心網路服務品質管理之路徑規劃

李宗勳 Unknown Date (has links)
面對通訊與資訊科技的大幅進步、網際網路的蓬勃發展、以及電信自由化帶來的激烈競爭,通訊網路正在進行一個巨大的變革,企圖將原有Circuit Switching 與 Packet Switching 網路整合成一個單一整合型網路-All-IP網路以支援所有的應用服務。All-IP網路受限於封包交換網路原有的特性,有服務品質問題(QoS)有待克服,因此有必要在All-IP網路上提供服務品質管理機制以實現整合型網路的目標。而要提供適當的QoS 管理,其成功之關鍵主要在於是否能提供一個簡單易行之架構。本論文先提出BBQ(Budget-Based QoS)採用以預算為基礎之服務品質管理,BBQ提供一個高適用性的管理架構和相關的管理工具,可適用於不同的下層網路架構和不同營運目標的網管政策。 而在本文中提出以路徑規劃(Path Planning)的方式作為此架構的路由方法。路徑規劃係以過去的歷史訊務資料為基礎,為未來可能進入網路中的訊務規劃出一組具有品質要求的路徑,而在系統運作時,只需根據訊務的需求,指定一條符合其品質要求的路徑即可。此方法不但可以給予進入網路的訊務絕對的服務品質保證,而且事前的運算可以免除在系統運作時大量的計算負擔。在本論文中,我們設計了一套路徑規劃的演算法,來驗證我們的方法之效能。而經過反覆的模擬測試,發現本路徑規劃方法的確較傳統OSPF演算法擁有較佳的網路效能,且可以提供進入網路的訊務較佳的服務品質保證。 / The advance in information technology and impact of telecommunications liberalization cause a revolution in commucation world. It attempt to merge circuit-switching and packet-switching network into one standlone perform. All-IP is one of those candidates. But All-IP also inherits the characteristics of packet-switching network, the problem of transmission quality. So, we need some management system of quality on All-IP network to achieve the ambition of converged network. In this thesis, we propose BBQ management system. BBQ offers a highly adaptive management architecture and some management tools for operators. Those tools can be used in different underly network layer and can be tuned by different network policy. We propose the path planning as routing approach in BBQ architecture. Path-planning is doing path calculation for the traffic may happen in future using the historic traffic statistic. In run-time, admission control component will assign a planned path that satisfy the requirements of admitted traffic. In this method, absolute transmission quality is guaranteed to admitted traffic. And pre-planning can reduce heavy calculation overhead in run-time. In this thesis, we design a path-planning algorithm, the GPPA algorithm, which takes pre-defined profit as its maximize objective under bandwidth and quality constraints. Through an performance evaluation using simulation method, we demonstrate that the path-planning might outperform the traditional OSPF algorithm.
7

Qos Aware Service Oriented Architecture

Adepu, Sagarika 08 1900 (has links)
Service-oriented architecture enables web services to operate in a loosely-coupled setting and provides an environment for dynamic discovery and use of services over a network using standards such as WSDL, SOAP, and UDDI. Web service has both functional and non-functional characteristics. This thesis work proposes to add QoS descriptions (non-functional properties) to WSDL and compose various services to form a business process. This composition of web services also considers QoS properties along with functional properties and the composed services can again be published as a new Web Service and can be part of any other composition using Composed WSDL.
8

A QoS framework for connection services in Parlay

Bata, Yusuf 29 February 2008 (has links)
Abstract Most applications using network connection services require information to be transferred within specific constraints (or Quality of Service). Parlay enables applications to access functionality of underlying networks while preserving network integrity. Connection service functionality of underlying networks is currently provided to applications by Parlay in the Call Control and Data Session Control SCFs. Parlay does not however provide access to the QoS functionality of connection services although this functionality may be provided by networks. This report presents the design, specification and simulation of a QoS framework for connection services provided by Parlay. The QoS framework provides applications with access to the QoS functionality of connection services in the underlying networks. The design is divided into 3 parts (or models): the object model (defines the objects that make up the QoS framework), the information model (deals with how objects specify QoS and mappings between different QoS specifications), and the interaction model (defines how objects interact). A formal, technology-independent specification of the QoS framework is presented using UML. The specification is composed using the three parts of the design. A simulation of the QoS framework presented in this report is also described to validate the framework. The simulation is a multi-threaded, distributed CORBA application implemented in JAVA (Java SDK version 1.5) and is based on the UML specification of the QoS framework. Details about the simulation design and implementation are summarised in this report. The QoS framework provides per-application, per-connection QoS support for Parlay’s connection services, supports existing and future Parlay connection services, follows existing Parlay design paradigms, and co-exists with and makes use of existing and future Parlay infrastructure. Parlay guidelines relating to permitted changes are followed strictly in the design of the QoS framework, which ensures the backward compatibility of Parlay if the QoS framework is added to the Parlay API. All Parlay design guidelines are also followed to allow for the easy integration of the QoS framework into the Parlay API. The simulation validates that the design of the QoS framework is: complete (in terms of specification), realistic, compatible with a standard Parlay implementation (JAVA and CORBA), and scalable (easy integration of new connection services).
9

QoS management in DSL services of an ISP in Iran

HASSANI, SEYED RASHIDALDIN January 2010 (has links)
<p>Quality of Service is a set of mechanisms created for differentiating users and data flows. Provisioning the QoS in service provider networks is always interesting for their business departments for they can offer and sell diverse services and to make more money. This thesis QoS for DSL subscribers of Pardis Online - the private ISP in Iran. The size of the network, the certain network connectivity limitations the ISP has in addition to the complexity of the services it provides, necessitate a comprehensive study to elucidate the different service types and requirements and then choosing a specific implementation of QoS in order to meet the ISP’s need. The internet bandwidth in the region that ISP operates is very expensive and the users suffer from the lack of bandwidth so the limited internet links are usually congested in the network. This document concludes with proposing a layered QoS that guarantees that the total bandwidth of an area in congested times is distributed to the users in that area proportionate to the subscribed band width. The resulting proposals are tested in the Lab and their performance under the simulated traffic is monitored and analyzed.</p>
10

Enhanced QoS in Wireless Certified USB

Al-Dalati, Issam 09 May 2011 (has links)
Our study investigates the performance of the WUSB standards and compares it to the Wimedia Standard. To the best of our knowledge, no technical contributions exist in the open literature at present simulating WUSB and its performance. The study showed that WUSB can achieve better throughput when bursting is enabled at the maximum burst size and it provides more accurate timing control of device activity than using the standard facilities of the WiMedia MAC. Our study also addresses protocol extensions and improvement to the original WUSB standard to support better Quality of Service (QoS). First improvement enables a di erent reservation mechanism along with contention based access to support higher priority security and medical system monitoring applications. Second improvement enables the host device to use an adaptive packet loss technique to change the packet size dynamically during the data transmission to achieve packet loss less than 10%. Third improvement enables redundancy in the cluster by adding a backup host to prevent mobility failures and changes. This backup host is chosen by a prede ned cost weighting function.

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