Chair of Computer Networks and Computer Communications
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Publication database

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2009

Journal articles:

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Patrick Wuechner, Janos Sztrik and Hermann De Meer
Investigating the mean response time in finite-source retrial queues using the algorithm by Gaver, Jacobs, and Latouche
Annales Mathematicae et Informaticae (AMI), 36:143--160
2009
ISSN: 1787-5021 (Print); 1787-6117 (Online)

Keywords: Performance evaluation; Finite-source retrial queues; Closed-form solutions; Orbital search; Block-structured Markov chain; MOSEL-2

Tags: AutoI, DFG_MathMod, EuroNF, ResumeNet, MOSEL2

Abstract: In this paper, we discuss the maximum of the mean response time that appears in finite-source retrial queues with orbital search when the arrival rate is varied. We show that explicit closed-form equations of the mean response time can be derived by exploiting the block-structure of the finite Markov chain underlying the model and using an efficient computational algorithm proposedby Gaver, Jacobs, and Latouche. However, we also show that already for the discussed relatively simple model, the resulting equation is rather complex which hampers further evaluation.

Books and journal issues (Ed.):

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Performance Modeling of Computer Networks - Special Issue in Memory of Dr. Gunter Bolch
Hermann De Meer and Patrick Wuechner, editor, Volume 53 of Computer Networks (ComNet)
Publisher: Elsevier B.V.,
2009

Tags: EuroNF, MOSEL2

Abstract: I am grateful for this opportunity to pay tribute to my dear friend and life-long mentor Dr. Gunter Bolch as a co-editor of this special issue in his memory. We were not only sharing common academic interests and writing scholarly books together but we were also sharing passions for such diverse activities as travelling and foreign cultures, cross-country skiing, or Jazz music. Gunter was very open minded, a beautifully moderate person, and a friend in its truest meaning. This special issue, however, is devoted to his academic passion of Performance Modeling, in general, and Queueing Networks, in particular. He has not only co-authored scholarly written books that have widely been cited and have gained world-wide acknowledgement, but many colleagues have taken pride in cooperation and joint publications with him during his overly productive life. Likewise, many of his students were motivated by his academic and personal spirit and followed up contributing in similar research areas. This special issue provides a collection of original contributions by former students of his and colleagues who have cooperated with him. While the contributions were solicited by invitation based on the relationship at least one author had with Gunter, all papers were thoroughly reviewed by at least three international reviewers each and subsequently carefully revised by the authors. As a result, we have been able to collect ten quality-assured papers as a witness to Gunter?s productive academic life and in memory of his achievements.

Conference and workshop papers:

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Christopher Auer, Patrick Wuechner and Hermann De Meer
Target-Oriented Self-Structuring in Classifying Cellular Automata
In Pedro P. B. de Oliveira and Jarkko Kari, editor, Proc. of the 15th Int'l Workshop on Cellular Automata and Discrete Complex Systems (Automata 2009) , page 260--271.
Publisher: Mackenzie,
2009
ISBN: 978-1-905986-21-7

Tags: AutoI, EuroNF, ResumeNet, Socionical

Abstract: Some cellular automata are able to solve classification problems on their initial configuration by building globally visible structures. However, no formal measures exist yet for describing or detecting this behavior in general. The lack of such formal methods often leads to quite observer-dependent discussions of emergent computation. In this paper, we propose the measures of target orientation and self-structuring that allow to formally evaluate a cellular automaton's ability to solve a classification problem by emergent computation. By the means of these measures, globally emerging patterns can be recognized and their contribution to the solution of the classification problem can be judged in an observer-independent way.

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Christopher Auer, Patrick Wuechner and Hermann De Meer
The Degree of Global-State Awareness in Self-Organizing Systems
Proc. of the 4th Int'l Workshop on Self-Organizing Systems (IWSOS 2009) Volume 5918 of Lecture Notes in Computer Science (LNCS) , page 125--136.
Publisher: Springer-Verlag,
2009
ISBN: 978-3-642-10864-8

Tags: AutoI, EuroNF, ResumeNet, Socionical

Abstract: Since the entities composing self-organizing systems have direct access only to information provided by their vicinity, it is a nontrivial task for them to determine properties of the global system state. However, this ability appears to be mandatory for certain self-organizing systems in order to achieve an intended functionality. Based on Shannon's information entropy, we introduce a formal measure that allows to determine the entities' degree of global-state awareness. Using this measure, self-organizing systems and suitable system settings can be identified that provide the necessary information to the entities for achieving the intended system functionality. Hence, the proposed degree supports the evaluation of functional properties during the design and management of self-organizing systems. We show this by applying the measure exemplarily to a self-organizing sensor network designed for intrusion detection. This allows us to find preferable system parameter settings.

Note: The original publication is available at www.springerlink.com (2009)

2008

Journal articles:

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Matthias Hollick, Hermann De Meer, Jens B. Schmitt and Patrick Wuechner
Modeling of Self-Organizing Systems (Guest Editorial)
Praxis der Informationsverarbeitung und Kommunikation (PIK), 31(1):2--3
2008
ISSN: 0930-5157

Tags: DFG_MathMod, EuroNF, EuroFGI, EuroFGI_MMSOS

Abstract: In the last decade, we witnessed the unparalleled success of communication networks such as the Internet or wireless mobile communication networks. The unprecedented scale of the aforementioned networks does not mark the end of the growth, but the emergence of wireless sensor networks and the ,,Internet of Things" are going to further add to the complexity of today's communication networks. For providers and network operators to be able to plan, build, and maintain next generation networks, it is necessary to push the envelope of traditional means to control the network. From a user's perspective, the organic growth of autonomously operated (community) networks and of application-level overlay networks presents further challenges.

Note: Editorial

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Patrick Wuechner, Janos Sztrik and Hermann De Meer
The Impact of Retrials on the Performance of Self-Organizing Systems
Praxis der Informationsverarbeitung und Kommunikation (PIK), 31(1):29--33
2008
ISSN: 0930-5157

Tags: AutoI, DFG_MathMod, EuroFGI, EuroFGI_MMSOS, EuroNF, ResumeNet, MOSEL2

Abstract: This article describes the application of the theory of retrial queues in capturing certain aspects of self-organizing behavior that arises, for example, in Peer-to-Peer networks. It can be shown that retrials have a fair effect on the performance of such self-organizing systems, and thus, should be taken into account adequately during the design and evaluation of these systems. Moreover, it can be shown that there is a notable difference between finite-source and infinite-source retrial queueing models. The main goal of this paper is to show the practical applicability of retrial queues and some of their varieties.

Books and journal issues (Ed.):

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Modeling of Self-Organizing Systems
Matthias Hollick, Hermann De Meer, Jens B. Schmitt and Patrick Wuechner, editor, Volume 31 of Praxis der Informationsverarbeitung und Kommunikation (PIK)
Publisher: K. G. Saur Verlag,
2008

Tags: EuroFGI, EuroFGI_MMSOS, EuroNF

Abstract: In the last decade, we witnessed the unparalleled success of communication networks such as the Internet or wireless mobile communication networks. The unprecedented scale of the aforementioned networks does not mark the end of the growth, but the emergence of wireless sensor networks and the ,,Internet of Things" are going to further add to the complexity of today's communication networks. For providers and network operators to be able to plan, build, and maintain next generation networks, it is necessary to push the envelope of traditional means to control the network. From a user's perspective, the organic growth of autonomously operated (community) networks and of application-level overlay networks presents further challenges.

Booklets:

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Patrick Wuechner, Christopher Auer, Gunter Bolch and Hermann De Meer
Queueing Networks and Markov Chains - 2nd Edition: Problems and Solutions
distributed by John Wiley & Sons
2008

Tags: MOSEL2

Abstract: In 2006, the second edition of our textbook on ?Queueing Networks and Markov Chains ? Modeling and Performance Evaluation with Computer Science Applications? was published. With completion of this solution manual, we are now pleased to offer additional support to lecturers who want to use the book for course work and assignments. In order to reserve the full benefit of the solution manual to lecturers, it may be worthwhile noting that access to the solution manual has been limited to lecturers only and access can only be gained through presentation of sufficient credentials to the publisher.

Conference and workshop papers:

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Christopher Auer, Patrick Wuechner and Hermann De Meer
A Method to Derive Local Interaction Strategies for Improving Cooperation in Self-Organizing Systems
Proc. of the 3rd Int'l Workshop on Self-Organizing Systems (IWSOS 2008) Volume 5343 of Lecture Notes in Computer Science (LNCS) , page 170--181.
Publisher: Springer-Verlag,
2008
ISBN: 978-3-540-92156-1

Tags: AutoI, EuroNF, ResumeNet

Abstract: To achieve a preferred global behavior of self-organizing systems, suitable local interaction strategies have to be found. In general, this is a non-trivial task. In this paper, a general method is proposed that allows to systematically derive local interaction strategies by specifying the preferred global behavior. In addition, the resulting strategies can be evaluated using Markovian analysis. Then, by applying the proposed method exemplarily to the iterated prisoner?s dilemma, we are able to systematically generate a cooperation-fostering strategy which can be shown to behave similar to the ,,tit for tat with forgiveness" strategy that, under certain circumstances, outperforms the well-known ,,tit for tat" strategy used, for instance, in BitTorrent peer-to-peer file-sharing networks.

Note: The original publication is available at www.springerlink.com (2008); received best-paper award

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Patrick Wuechner, Janos Sztrik and Hermann De Meer
Homogeneous Finite-Source Retrial Queues with Search of Customers from the Orbit
Proc. of the 14th GI/ITG Conf. on Measurement, Modelling and Evaluation of Computer and Communication Systems (MMB 2008) , page 109--124.
Publisher: VDE Verlag,
2008
ISBN: 978-3-8007-3090-2

Keywords: Retrial queueing systems; Finite number of sources; Orbital search; Performance tool; Performance measures

Tags: DFG_MathMod, EuroNF, MOSEL2

Abstract: We consider a retrial queueing system with a finite number of homogeneous sources of calls and a single server. Each source generates a request after an exponentially distributed time. An arriving customer finding the server idle enters into service immediately; otherwise the customer enters into an orbit. The service times are supposed to be exponentially distributed random variables. An orbiting customer competes for service, the inter-retrial times are exponentially distributed. Upon completion of a service, with a certain probability the server searches for an orbiting customer. Assuming the search time to be negligible, the source, service, and retrial times to be independent random variables, we perform the steady-state analysis of the model computing various steady-state performance measures and illustrative numerical examples are presented. The novelty of the investigation is the introduction of orbital search by the server for customers in finite-source retrial queues. The MOSEL-2 tool is used to formulate and solve the problem.

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