Browsing by Subject "quality of service"

Now showing 1 - 8 of 8

Access status: Open Access ,
An analysis of IEEE 802.11 EDCA ad-hoc networks in the presence of hidden nodes
(2008-07-01) (Data obrony: 2011-05-25) Kosek-Szott, Katarzyna
Wydział Elektrotechniki, Automatyki, Informatyki i Elektroniki
This dissertation deals with quality of service (QoS) provisioning in IEEE 802.11 ad-hoc networks with hidden nodes. In particular, it focuses on the Enhanced Distributed Channel Access (EDCA) function of the Medium Access Control (MAC) layer of the IEEE 802.11 standard. The following thesis was formulated and proved: It is possible to improve the performance of the EDCA (Enhanced Distributed Channel Access) function by modifying the IEEE 802.11 standard in order to improve the efficiency of ad-hoc networks with hidden nodes. Furthermore, in such networks, it is possible to improve the fairness of traffic prioritising for the access categories defined in the IEEE 802.11 standard. The thesis is proved by the proposed BusySiMOn mechanism, which implements an intelligent two-step reservation procedure combined with the advantages of EDCA service differentiation. It is shown that when BusySiMOn is applied, the overall throughput, fairness and maximum frame delay are improved in comparison* to the four-way handshake mechanism. Additionally, a novel mathematical model of the IEEE 802.11 EDCA function is proposed. The proposed model can be used for rapid estimation of throughput of ad-hoc networks for the basic and the four-way handshake based channel access. It is kept reasonably simple to make it attractive to network designers.
Access status: Open Access ,
Congestion control in flow-aware networks
(2007-05-31) (Data obrony: 2009-06-29) Domżał, Jerzy
Wydział Elektrotechniki, Automatyki, Informatyki i Elektroniki
The congestion control mechanisms for Flow-Aware Networks are presented in the dissertation. The research was performed for four proposals, the EFM (Enhanced Flushing Mechanism), the RAEF (Remove Active Elastic Flows), the RBAEF (Remove and Block Active Elastic Flows) and the RPAEF (Remove and Prioritize in access Active Elastic Flows) mechanisms. The idea of all presented congestion control mechanisms is similar and relies on total or partial cleaning of the PFL (Protected Flow List) content in the MBAC (Measurement Based Admission Control) block in congestion. The main goal of the proposed solutions is to minimize the acceptance time of new streaming flows in FAN routers. The streaming transmission in FAN is proposed for low traffic consuming applications with demands on low packet delays and loss. The congestion control mechanisms for FAN, proposed in the dissertation are described in details and analyzed by simulation experiments run on the ns-2 simulator. The obtained results show the advantages of the new solutions. The second part of the dissertation presents the new proposal of realizing the FAN concept. In this solution, the algorithm for random dropping of packets from the queue in congestion is used. It is implemented based on the AFD(Approximate Fair Dropping) mechanism. The new proposal is less complex than two well known FAN versions.
Access status: Open Access ,
Management methods in SLA-aware distributed storage systems
(Wydawnictwa AGH, 2012) Nikolow, Darin; Słota, Renata; Lakovic, Danilo; Winiarczyk, Paweł; Pogoda, Marek; Kitowski, Jacek
Traditional data storage systems provide access to user’s data on the “best effort” basis. While this paradigm is sufficient in many use cases it becomes an obstacle for applications with Quality of Service (QoS) constraints. Service Level Agreement (SLA) is a part of the contract agreed between the service provider and the client and contains a set of well defined QoS requirements regarding the provided service and the penalties applied in case of violations. In the paper we propose a set of SLA parameters and QoS metrics relevant to data storage processes and the management methods necessary for avoiding SLA violations. A key assumption in the proposed approach is that the underlying distributed storage system does not provide functionality for resource or bandwidth reservation for a given client request.
Access status: Open Access ,
Net neutral quality of service differentiation in flow-aware networks
(2008-09-25) (Data obrony: 2011) Wójcik, Robert
Wydział Elektrotechniki, Automatyki, Informatyki i Elektroniki
Flow-Aware Networking (FAN) architecture is evaluated in this dissertation with regard to its service differentiation and quality of service (QoS) assurance capabilities. The network neutrality debate is presented first, and it is shown that the potential resolutions will have a strong impact on QoS architectures. Secondly, the detailed concept of FAN is presented and compared with other flow-based QoS architectures designed for IP networks. It is argued that all the solutions have their advantages and disadvantages, however, in FAN, the pros outnumber the cons in comparison with other architectures. The main goal of the dissertation is to propose and evaluate new mechanisms to enhance service differentiation capabilities of FAN architecture. The waiting times phenomenon as a result of admission control functionality is documented. Next, differentiated blocking and differentiated queuing mechanisms are proposed. Finally, Class of Service on Demand is shown as the ultimate method of providing rich service differentiation without violating the network neutrality principle. The static limitation and automatic intelligent limitation mechanisms are proposed as a simple, yet efficient way of improving service assurance. It is shown that limitation mechanisms significantly contributes to FAN's scalability and yields great performance benefits. Finally, the predictive approach is presented, which changes the functioning of the admission control block in FAN. Instead of waiting for congestion to appear and only then blocking new connections, the mechanism takes a pro-active approach and starts to act on the basis of the predicted values of the congestion indicators.
Access status: Restricted ,
Ocena jakości usług uzdrowiskowych na przykładzie Sanatorium „Energetyk” w Krynicy-Zdroju
(Data obrony: 2017-07-19) Mączyńska, Gabriela
Wydział Geologii, Geofizyki i Ochrony Środowiska
W pracy podjęto ocenę jakości usług uzdrowiskowych świadczonych przez Sanatorium „Energetyk” w Krynicy-Zdroju. Przedstawiony został dokładny opis występujących na tym obszarze leczniczych wód mineralnych i ich korzystnego wpływu na zdrowie człowieka. Dokonana została również analiza oferty Sanatorium „Energetyk” pod względem usług leczniczych i pozaleczniczych. Wśród kuracjuszy przeprowadzono sondaż diagnostyczny oraz ankietę metodą Servqual. Otrzymane wyniki pozwoliły na określenie poziomu jakości usług i zadowolenia kuracjuszy. Posłużyły również w opracowaniu zmian i uzupełnieniu aktualnej oferty.
Access status: Open Access ,
Policy-based sla storagemanagement model fordistributeddata storage services
(Wydawnictwa AGH, 2018) Nikolow, Darin; Słota, Renata; Polak, Stanisław; Pogoda, Marek; Kitowski, Jacek
There is high demand for storage related services supporting scientists in their research activities. Those services are expected to provide not only capacity but also features allowing for more exible and cost ecient usage. Such features include easy multiplatform data access, long term data retention, support for performance and cost dierentiating of SLA restricted data access. The paper presents a policy-based SLA storage management model for distributed data storage services. The model allows for automated management of distributed data aimed at QoS provisioning with no strict resource reservation. The problem of providing users with the required QoS requirements is complex, and therefore the model implements heuristic approach for solving it. The corresponding system architecture, metrics and methods for SLA focused storage management are developed and tested in a real, nationwide environment. Keywords distributed storage systems, quality of service, service level agreement, management model, heuristics.
Access status: Restricted ,
Quality of service in wireless access for vehicular networks (WAVE)
(Data obrony: 2016-07-13) Okehie, Chima
Wydział Informatyki, Elektroniki i Telekomunikacji
Access status: Open Access ,
Quality of the logistic customer service in service area
(AGH University of Science and Technology Press, 2008) Radziejowska, Grażyna
The paper presents the issue of customer logistics. Particular attention is given to the quality of customer service. It was assumed that this subject range includes three fundamental decision areas: logistic service provider - customer, logistic services system and the range of logistic services. Theoretical considerations are supported by an estimation of logistic customer services conducted on the basis of a logistics company.