Informatik-Kolloquium
Montag, 10. März 2008
Ort: Geb. 41/500, Raum 1503
Uhrzeit: 16:00 Uhr (c.t.)
Prof. Boudewijn Haverkort
University of Twente
7500 AE Enschede
The Netherlands
Zusammenfassung
"Recently, a quality-of-service (QoS) extension of the IEEE 802.11 standard (known as IEEE 802.11e) for wireless LANs has been proposed. We present a versatile and accurate performance model to study how these new QoS enhancements can be used to improve the performance of wireless nodes competing for bandwidth in a multi-hop ad hoc network. The paper presents the three QoS enhancements, and shows how they can be modeled using a simple, yet effective, parameterized quasi-birth-death model. The model is developed hierarchically, in that known results at packet level (e.g., as developed by Bianchi and others) are used in our flow-level model, in which a single bottleneck station interacts with a time-varying number of traffic sources. Thus, we are able to study the impact of the QoS enhancements on the flow-level performance. This has not been done before. The results of our analysis are compared with extensive simulations (using Opnet), and show excellent agreement for throughput, number of active sources and buffer length at the bottleneck station. An important asset of our model is that it allows for very quick evaluations: where simulations require up to an hour per scenario, our model is solved in seconds."
Freitag, 14. März 2008
Ort: Geb. 33, Raum 0231
Uhrzeit: 13:30 Uhr (s.t.)
Prof. Bernard Zeigler
University of Twente
7500 AE Enschede
The Netherlands
Zusammenfassung
Ontologies are models of the world relating to specific aspects or applications that are typically represented in frame-based languages and form the knowledge components for logical agents on the Semantic Web. A convergence is underway that re-enforces the commonality of the object-based origins of artificial intelligence, knowledge representation, and software engineering. The Unified Modeling Language (UML) is being extended to incorporate ontology representations so that software systems in general will have more explicit models of their domains of operation. However, such a framework lacks several fundamental features that are particularly relevant to Modeling and Simulation (M&S) methodology. In this talk, we point out these limitations and then go on to discuss recent extensions to the System Entity Structure, (SES) a knowledge representation formalism that focuses on elements and relationships that are fundamental to model composition, validation, reuse, and interoperability. We show how the SES specifies a family of hierarchical, modular simulation models and can be viewed as an ontology for M&S with the set of all simulation models as its domain of discourse. Since simulation models include both static and dynamic elements with application to numerous real-world domains, the SES represents an advanced ontology framework. In particular, we discuss applications to automated model-driven development and testing of command, control and information systems.
Freitag, 11. April 2008
Ort: Universitäts - Casino
Uhrzeit: 15:00 Uhr (s.t.)
Programm
Begrüßung
Prof. Dr. Ulf Schmerl
Dekan der Fakultät für Informatik
Grußwort
Prof. Dr. Merith Niehuss
Präsidentin der Universität der Bundeswehr München
Jahresbericht 2007
Prof. Dr. Ulf Schmerl
Dekan der Fakultät für Informatik
Eingeladener Vortrag
Primzahlen und Primzahl-Algorithmen
Prof. Dr. Otto Forster
Ludwig-Maximilians-Universität München
Bayerische Akademie der Wissenschaften
Ort: Geb. 41/500, Raum 1503
Uhrzeit: 16:00 Uhr (c.t.)
Prof. Boudewijn Haverkort
University of Twente
7500 AE Enschede
The Netherlands
Bottleneck Analysis for Multi-Hop IEEE 802.11e Ad Hoc Networks
Zusammenfassung
"Recently, a quality-of-service (QoS) extension of the IEEE 802.11 standard (known as IEEE 802.11e) for wireless LANs has been proposed. We present a versatile and accurate performance model to study how these new QoS enhancements can be used to improve the performance of wireless nodes competing for bandwidth in a multi-hop ad hoc network. The paper presents the three QoS enhancements, and shows how they can be modeled using a simple, yet effective, parameterized quasi-birth-death model. The model is developed hierarchically, in that known results at packet level (e.g., as developed by Bianchi and others) are used in our flow-level model, in which a single bottleneck station interacts with a time-varying number of traffic sources. Thus, we are able to study the impact of the QoS enhancements on the flow-level performance. This has not been done before. The results of our analysis are compared with extensive simulations (using Opnet), and show excellent agreement for throughput, number of active sources and buffer length at the bottleneck station. An important asset of our model is that it allows for very quick evaluations: where simulations require up to an hour per scenario, our model is solved in seconds."
Freitag, 14. März 2008
Ort: Geb. 33, Raum 0231
Uhrzeit: 13:30 Uhr (s.t.)
Prof. Bernard Zeigler
University of Twente
7500 AE Enschede
The Netherlands
Ontology Framework for Modeling and Simulation in Complex System Development
Zusammenfassung
Ontologies are models of the world relating to specific aspects or applications that are typically represented in frame-based languages and form the knowledge components for logical agents on the Semantic Web. A convergence is underway that re-enforces the commonality of the object-based origins of artificial intelligence, knowledge representation, and software engineering. The Unified Modeling Language (UML) is being extended to incorporate ontology representations so that software systems in general will have more explicit models of their domains of operation. However, such a framework lacks several fundamental features that are particularly relevant to Modeling and Simulation (M&S) methodology. In this talk, we point out these limitations and then go on to discuss recent extensions to the System Entity Structure, (SES) a knowledge representation formalism that focuses on elements and relationships that are fundamental to model composition, validation, reuse, and interoperability. We show how the SES specifies a family of hierarchical, modular simulation models and can be viewed as an ontology for M&S with the set of all simulation models as its domain of discourse. Since simulation models include both static and dynamic elements with application to numerous real-world domains, the SES represents an advanced ontology framework. In particular, we discuss applications to automated model-driven development and testing of command, control and information systems.
Ort: Universitäts - Casino
Uhrzeit: 15:00 Uhr (s.t.)
Programm
Begrüßung
Prof. Dr. Ulf Schmerl
Dekan der Fakultät für Informatik
Grußwort
Prof. Dr. Merith Niehuss
Präsidentin der Universität der Bundeswehr München
Jahresbericht 2007
Prof. Dr. Ulf Schmerl
Dekan der Fakultät für Informatik
Eingeladener Vortrag
Primzahlen und Primzahl-Algorithmen
Prof. Dr. Otto Forster
Ludwig-Maximilians-Universität München
Bayerische Akademie der Wissenschaften
