@inproceedings {INPROC-2007-84, author = {Dominique Dudkowski and Pedro Jos{\'e} Marr{\'o}n and Kurt Rothermel}, title = {{Migration Policies for Location-Centric Data Storage in Mobile Ad-Hoc Networks}}, booktitle = {Proceedings of the 3rd International Conference on Mobile Ad-hoc and Sensor Networks (MSN'07); Beijing, China, December, 2007}, publisher = {Springer}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {197--208}, type = {Conference Paper}, month = {December}, year = {2007}, keywords = {location-centric; MANET; migration}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Location-centric data storage is a fundamental paradigm for data management in wireless ad-hoc networks. It guarantees that data is stored at network nodes near specific geometric reference locations in the region where the network is deployed. In mobile ad-hoc networks, maintaining spatial proximity between data and its associated location requires explicit migration mechanisms in order to ``keep the data in place''. In this paper we propose comprehensive policies for data migration that effectively maintain the spatial coherence of data given the particular characteristics of mobile ad-hoc networks. Using extensive simulations we show how the proposed policies outperform related migration approaches over a wide range of system parameter settings, in particular, node density, network dynamics, and migratable data size.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-84&engl=1} } @inproceedings {INPROC-2007-83, author = {J{\"o}rg H{\"a}hner and Dominique Dudkowski and Pedro Jos{\'e} Marr{\'o}n and Kurt Rothermel}, title = {{Quantifying Network Partitioning in Mobile Ad Hoc Networks.}}, booktitle = {Proceedings of the 8th International Conference on Mobile Data Management (MDM 2007), Mannheim, Germany, May 2007}, publisher = {IEEE}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {174--181}, type = {Conference Paper}, month = {May}, year = {2007}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The performance of distributed algorithms in mobile ad hoc networks is strongly influenced by the connectivity of the network. In cases where the connectivity is low, network partitioning occurs. The mobility and the density of network nodes as well as the communication technology are fundamental properties that have a large impact on partitioning. A detailed characterization of this behavior helps to improve the performance of distributed algorithms. In this paper we introduce a set of metrics that characterize partitioning in mobile ad hoc networks. Based on an extensive simulation study we show the impact of node mobility, density and transmission range on the proposed metrics for a wide range of network scenarios.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-83&engl=1} } @inproceedings {INPROC-2007-73, author = {Sebastien Baehni and Rachid Guerraoui and Boris Koldehofe and Maxime Monod}, title = {{Towards Fair Event Dissemination}}, booktitle = {Proceedings of the 27th IEEE International Conference on Distributed Computing Systems Workshops (ICDCSW'07)}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, type = {Conference Paper}, month = {June}, year = {2007}, doi = {10.1109/ICDCSW.2007.83}, language = {English}, cr-category = {C.2.2 Network Protocols, C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-73/INPROC-2007-73.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Event dissemination in large scale dynamic systems is typically claimed to be best achieved using decentralized peer-to-peer architectures. The rationale is to have every participant in the system act both as a client (information consumer) and as a server (information dissemination enabler), thus, precluding specific brokers which would prevent scalability and fault-tolerance. We argue that, for such decentralized architectures to be really meaningful, participants should serve the system as much as they benefit from it. That is, the system should be fair in the sense that the extend to which a participant acts as a server should depend on the extend to which it has the opportunity to act as a client. This is particularly crucial in selective information dissemination schemes where clients are not all interested in the same information. In this position paper, we discuss what a notion of fairness could look like, explain why current architectures are not fair, and raise several challenges towards achieving fairness.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-73&engl=1} } @inproceedings {INPROC-2007-57, author = {The SpoVNet Consortium and Boris Koldehofe and Gerald Georg Koch}, title = {{SpoVNet: An Architecture for Supporting Future Internet Applications}}, booktitle = {Proc. 7th W{\"u}rzburg Workshop on IP: Joint EuroFGI and ITG Workshop on ``Visions of Future Generation Networks''}, address = {W{\"u}rzburg, Germany}, publisher = {-}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, type = {Workshop Paper}, month = {July}, year = {2007}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-57/INPROC-2007-57.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {This talk presents an approach for providing Spontaneous Virtual Networks (SpoVNets) that enable flexible, adaptive, and spontaneous provisioning of application-oriented and network-oriented services on top of heterogeneous networks. SpoVNets supply new and uniform communication abstractions for future Internet applications so applications can make use of advanced services not supported by today's Internet. We expect that many functions, which are currently provided by SpoVNet on the application layer will become an integral part of future networks. Thus, SpoVNet will transparently use advanced services from the underlying network infrastructure as they become available (e.g., QoS-support in access networks or multicast in certain ISPs), enabling a seamless transition from current to future genera-tion networks without modifying the applications.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-57&engl=1} } @inproceedings {INPROC-2007-55, author = {Klaus Herrmann}, title = {{Group Anti-Entropy - Achieving Eventual Consistency in Mobile Service Environments}}, booktitle = {Proceedings of the 8th IEEE International Conference on Mobile Data Management (MDM'07)}, publisher = {IEEE Computer Society Press}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, type = {Conference Paper}, month = {January}, year = {2007}, keywords = {mobility, ambient services, data consistency, optimistic replication}, language = {English}, cr-category = {C.2.4 Distributed Systems, H.2 Database Management}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-55/INPROC-2007-55.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Data consistency protocols are vital ingredients of mobile data management systems. Notable research efforts have been spent to find adequate consistency models for allowing mobile and nomadic users to share mutable data. Recently, mobile Ambient Service infrastructures that pose somewhat different requirements have entered the focus of attention. Such services are not as loosely coupled as the afore-mentioned systems, but they still need flexible consistency protocols that may adapt to the current dynamics in the system. We propose an extension to the well-known anti-entropy protocol that makes use of the nature of Ambient Service environments to allow for a flexible consistency management among arbitrary groups of mobile service replicas. We will show that our protocol can exploit the concept of group updates to increase its efficiency in terms of bandwidth usage. Furthermore, we prove that it avoids costly state transfers by means of a simple rule that limits the divergence within the overall set of replicas. Finally, we introduce two simple tunable parameters, and we present experimental results that show how they may be used to shape the characteristics of the protocol.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-55&engl=1} } @inproceedings {INPROC-2007-54, author = {Gero M{\"u}hl and Matthias Werner and Michael A. Jaeger and Klaus Herrmann and Helge Parzyjegla}, title = {{On the Definitions of Self-Managing and Self-Organizing Systems}}, booktitle = {KiVS 2007 Workshop: Selbstorganisierende, Adaptive, Kontextsensitive verteilte Systeme (SAKS 2007)}, address = {Bern, Switzerland}, publisher = {Springer-Verlag}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {Informatik aktuell}, type = {Conference Paper}, month = {March}, year = {2007}, keywords = {self-organization, self-management, adaptivity, classification, formal model}, language = {English}, cr-category = {C.2.4 Distributed Systems, F.1.1 Models of Computation}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-54/INPROC-2007-54.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The management costs of software systems are becoming the dominating cost factor in running IT infrastructures. The main driving force behind this development is the ever-increasing system complexity which is becoming the limiting factor for further development. The fact that human administrators get more and more overstrained by management tasks has led to the idea of systems that manage themselves, i.e., self-managing systems. Another concept that is closely related to selfmanagement is self-organization. Self-organizing software systems often build on bio- and nature-inspired approaches. However, most publications on self-managing or self-organizing systems miss a clear definition of these terms. Even worse, although self-management and self-organization aim at similar goals, their relation still has not been defined properly. In this paper, we approach these problems by introducing a classification of systems that models self-organizing systems as a subclass of selfmanaging systems. The classification builds upon a definition of adaptive systems and introduces self-manageable, self-managing, and selforganizing systems. Our proposal serves as a starting point for further discussions, eventually leading to a better understanding of the terms self-organization and self-management and their interrelationship.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-54&engl=1} } @inproceedings {INPROC-2007-53, author = {Michael A. Jaeger and Helge Parzyjegla and Gero M{\"u}hl and Klaus Herrmann}, title = {{Self-Organizing Broker Topologies for Publish/Subscribe Systems}}, booktitle = {The 22nd Annual ACM Symposium on Applied Computing}, address = {Seoul, Korea}, publisher = {ACM Press}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {543--550}, type = {Conference Paper}, month = {March}, year = {2007}, keywords = {publish/subscribe, adaptable middleware, self-organization, overlay networks}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-53/INPROC-2007-53.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Distributed publish/subscribe systems are usually deployed on top of an overlay network that enables complex routing strategies implemented in the application layer. Up to now, only little effort has been spent on the design of the broker overlay network assuming that it is either static or manually administered. As publish/subscribe systems are increasingly targeted at dynamic environments where client behavior and network characteristics vary over time, static overlay networks lead to suboptimal performance. In this paper, we present a self-organizing broker overlay infrastructure that adapts dynamically to achieve a better efficiency on both, the application and the network layer. This is obtained by taking network metrics as well as notification traffic into account.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-53&engl=1} } @inproceedings {INPROC-2007-51, author = {Klaus Herrmann}, title = {{Self-Organizing Replica Placement - A Case Study on Emergence}}, booktitle = {Proceedings of the first IEEE International Conference on Self-Adaptive and Self-Organizing Systems}, publisher = {IEEE Computer Society Press}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {13--22}, type = {Conference Paper}, month = {July}, year = {2007}, keywords = {self-organization, emergence, replica placement, case study}, language = {English}, cr-category = {C.2.4 Distributed Systems, H Information Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-51/INPROC-2007-51.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The concept of self-organization is rapidly gaining importance in the area of distributed computing systems. However, we still lack the necessary means for engineering such system in a standardized way since their common properties are rather abstract, and the mechanisms from which self-organization emerges are too diverse. Therefore, it has become common practice to engineer computing systems by taking inspirations from well-known case studies of biological systems. However, the concepts found in such systems are in many cases only partially transferable to the domain of distributed computing systems since biological systems are subject to vastly different constraints compared to those in a computing system. Our contributions in this paper are the following: (i) We present a case study of a self-organizing software system that originates from the domain of distributed computing systems. Therefore, its concepts can be exploited in other distributed computing systems much more directly. (ii) We give a detailed analysis of the emergent properties of the system and the mechanisms by which they arise. (iii) We generalize the mechanisms by which self-organization emerges in this system and present a catalog of design questions that may help engineers in creating arbitrary self-organizing systems.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-51&engl=1} } @inproceedings {INPROC-2007-50, author = {Klaus Herrmann}, title = {{Self-Organizing Infrastructures for Ambient Services}}, booktitle = {Kommunikation in Verteilten Systemen (KiVS), 15. ITG/GI Fachtagung Kommunikation in Verteilten Systemen (KiVS 2007)}, publisher = {Springer-Verlag}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {Informatik aktuell}, pages = {299--306}, type = {Conference Paper}, month = {January}, year = {2007}, isbn = {3-540-69961-9}, keywords = {self-organization, middleware, data consistency, lookup service, mobile ad hoc networks, replica placement, wireless mesh networks}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-50/INPROC-2007-50.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The vision of Ambient Intelligence (AmI) as a new paradigm for supporting the mobile user in his daily activities is currently entering the focus of European research efforts. A high degree of autonomy on the part of the supporting software system is inherent to this vision of omnipresent and continuously running services. However, adequate concepts for creating respective infrastructures that may operate autonomously and in a self-organized fashion are still largely unexplored. We propose the Ad hoc Service Grid (ASG) as a dedicated AmI infrastructure that may be deployed in an ad hoc fashion at arbitrary medium-sized locations (shopping malls, construction sites, trade fairs, etc.). In this paper, we give an overview over our results thus far. We focus on the problems of service placement, discovery and lookup, and data consistency within an ASG environment and show how we have solved these problems with new self-organizing and adaptive algorithms. These vital functions are the basis for the realization of ASG systems and represent an essential contribution to AmI research in general.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-50&engl=1} } @inproceedings {INPROC-2007-48, author = {Marcus Handte and Klaus Herrmann and Gregor Schiele and Christian Becker and Kurt Rothermel}, title = {{Automatic Reactive Adaptation of Pervasive Applications}}, booktitle = {Proceedings of ICPS'07: IEEE International Conference on Pervasive Services}, publisher = {IEEE Computer Society Press}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {214--222}, type = {Conference Paper}, month = {July}, year = {2007}, keywords = {adaptivity, components, mobility, optimization}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-48/INPROC-2007-48.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Pervasive Computing envisions seamless and distraction-free support for everyday tasks through distributedapplications that leverage the resources of the users' environment. Due to the mobility of users and devices, applications need to adapt continuously to their changing execution environment. Therefore, developers need a suitable framework in order to efficiently create adaptive applications. In this paper, we present and evaluate our approach to adapting a pervasive computing application to changes during its execution. This work is based on the minimal component system PCOM and on an algorithm to fully automate the initial configuration of a componentbased application which we have presented in earlier work. The contribution of this paper is threefold. First, we describe a number of modifications to the component model that are required to enable fully automatic adaptation. Secondly, we propose a simple yet powerful cost model to capture the complexity of specific adaptations. Thirdly, we describe an online optimization heuristic that extends our distributed configuration algorithm in order to choose to a low-cost configuration whenever the current configuration of a pervasive application requires adaptation.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-48&engl=1} } @inproceedings {INPROC-2007-46, author = {Matthias Gauger and Pedro Jos{\'e} Marr{\'o}n and Daniel Kauker and Kurt Rothermel}, title = {{Low Overhead Assignment of Symbolic Coordinates in Sensor Networks}}, booktitle = {Proceedings of the IFIP First International Conference on Wireless Sensor and Actor Networks, WSAN'07}, editor = {Luis Orozco-Barbosa and Teresa Olivares and Rafael Casado and Aurelio Berm{\'u}dez}, publisher = {Springer}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {181--192}, type = {Conference Paper}, month = {September}, year = {2007}, isbn = {978-0-387-74898-6}, language = {English}, cr-category = {C.3 Special-Purpose and Application-Based Systems}, contact = {gauger@cs.uni-bonn.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Approximate information on the location of nodes in a sensor network is essential to many types of sensor network applications and algorithms. In many cases, using symbolic coordinates is an attractive alternative to the use of geographic coordinates due to lower costs and lower requirements on the available location information during coordinate assignment. In this paper, we investigate different possible methods of assigning symbolic coordinates to sensor nodes. We present a method based on broadcasting coordinate messaging and filtering using sensor events. We show in the evaluation that this method allows a reliable assignment of symbolic coordinates while only generating a low overhead.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-46&engl=1} } @inproceedings {INPROC-2007-45, author = {Daniel Minder and Pedro Jos{\'e} Marr{\'o}n and Andreas Lachenmann and Kurt Rothermel}, title = {{Coordinated group adaptation in sensor networks}}, booktitle = {6. Fachgespr{\"a}ch Sensornetzwerke}, publisher = {RWTH Aachen}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {Technischer Bericht}, volume = {AIB 2007-11}, pages = {43--46}, type = {Conference Paper}, month = {July}, year = {2007}, issn = {0935-3232}, keywords = {wireless sensor network; group adaptation; coordination}, language = {English}, cr-category = {D.4.7 Operating Systems Organization and Design, C.2.1 Network Architecture and Design, C.2.3 Network Operations}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-45/INPROC-2007-45.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {In Wireless Sensor Networks, several algorithms are used to perform different functionality, e.g. routing or clock synchronization. Each algorithm is intended for specific network characteristics and user requirements. But the acutal characteristics and requirements may change during system runtime. TinyCubus and particularly its Tiny Data Managment Framework use adaptation to solve this problem. In this paper, we first explain the centralized adaptation process. Then, we examine how this can be done localized in the network. Since coordination between local adaptation decisions is found to be necessary, metrics for this coordination and their dependencies are shown.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-45&engl=1} } @inproceedings {INPROC-2007-38, author = {Lars Geiger and Frank D{\"u}rr}, title = {{Kontextbezogene Kommunikation}}, booktitle = {4. GI/ITG KuVS Fachgespr{\"a}ch Ortsbezogene Anwendungen und Dienste}, editor = {J{\"o}rg Roth and Axel K{\"u}pper and Claudia Linnhoff-Popien}, address = {M{\"u}nchen}, publisher = {Verlag Dr. Hut}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {22--26}, type = {Conference Paper}, month = {September}, year = {2007}, isbn = {978-3-89963-591-1}, keywords = {Kontext; Kommunikation; Multicast; Nexus}, language = {German}, cr-category = {C.2.1 Network Architecture and Design, C.2.2 Network Protocols, C.2.4 Distributed Systems, C.2.6 Internetworking}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-38/INPROC-2007-38.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Verbindet man die Position eines Benutzers mit weiteren Attributen wie beispielsweise Typ, Alter oder Status zu seinem Kontext, so ergeben sich daraus interessante neue Anwendungsm{\"o}glichkeiten. In diesem Artikel soll ein Verfahren vorgestellt werden, wie ein solcher Kontext benutzt werden kann, um Nachrichten an bestimmte Gruppen von Benutzern --- bestimmt durch ihren Kontext --- zu versenden. Ein solcher Kommunikationsmechanismus k{\"o}nnte beispielsweise eingesetzt werden, um Verkehrsnachrichten gezielt an alle Fahrzeuge innerhalb eines bestimmten Gebietes und mit einer bestimmten Fahrtrichtung zu {\"u}bermitteln.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-38&engl=1} } @inproceedings {INPROC-2007-35, author = {Tobias Farrell and Reynold Cheng and Kurt Rothermel}, title = {{Energy-Efficient Monitoring of Mobile Objects with Uncertainty-Aware Tolerances}}, booktitle = {Proceedings of the 11th International Database Engineering and Applications Symposium (IDEAS 2007); Banff, Canada, September 6-8, 2007}, editor = {Bipin C. Desai and Ken Barker}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {129--140}, type = {Conference Paper}, month = {September}, year = {2007}, isbn = {0-7695-2947-X}, doi = {10.1109/IDEAS.2007.4318097}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, ee = {http://ieeexplore.ieee.org/xpls/abs_all.jsp?isnumber=4318075&arnumber=4318097}, contact = {Tobias.Farrell@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {In location-based services, continuous queries are often employed to monitor the locations of mobile ob-jects that are determined by sensing devices like GPS receivers. Due to limited battery resources, it is impor-tant for these objects to acquire and report location data only if necessary. We study how these energy-consuming operations can be reduced with a con-trolled impact on query accuracy of continuous range queries (CRQs). Specifically, we develop uncertainty-aware tolerances, which are user-defined error bounds that provide correctness guarantees, with considera-tion of different sources of data uncertainty: sensing uncertainty, sampling uncertainty, and communication delay. Novel algorithms are developed to control carefully when an object should acquire and update a location, while satisfying these tolerances. Extensive simulations validate the effectiveness of our methods.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-35&engl=1} } @inproceedings {INPROC-2007-34, author = {Tobias Farrell and Ralph Lange and Kurt Rothermel}, title = {{Energy-efficient Tracking of Mobile Objects with Early Distance-based Reporting}}, booktitle = {Proceedings of the Fourth Annual International Conference on Mobile and Ubiquitous Systems: Networking and Services (MobiQuitous 2007); Philadelphia, PA, USA, August 6-10, 2007}, publisher = {IEEE Press}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, type = {Conference Paper}, month = {August}, year = {2007}, isbn = {1-4244-1025-8}, doi = {10.1109/MOBIQ.2007.4450984}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-34/INPROC-2007-34.pdf, http://www.ieeexplore.ieee.org/xpls/abs_all.jsp?isnumber=4450969&arnumber=4450984}, contact = {Tobias.Farrell@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Many location-based systems rely on fine-grained tracking of mobile objects that determine their own locations with sensing devices like GPS receivers. For these objects, energy is a very valuable and limited resource. A distance-based reporting protocol can be employed to reduce the energy they consume by sending position updates. However, the energy required for position sensing has not been considered in the past. In this paper, we study how the resulting energy consumption from both sensing and update operations can be reduced for distance-based reporting. We show that significant savings are achieved by sending position updates earlier than actually required. For uniform movement, we derive the minimal power consumption analytically. Subsequently, two novel online heuristics are proposed that control the sending of position updates at runtime. Their effectiveness is validated by extensive simulations.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-34&engl=1} } @inproceedings {INPROC-2007-15, author = {Martin Saternus and Mirko Knoll and Frank D{\"u}rr and Torben Weis}, title = {{Symstry: Ein P2P-System f{\"u}r Ortsbezogene Anwendungen}}, booktitle = {Proceedings of 15. ITG/GI - Fachtagung (KiVS 2007)}, publisher = {VDE-Verlag}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {99--104}, type = {Conference Paper}, month = {February}, year = {2007}, isbn = {ISBN 978-3-8007-2980-7}, keywords = {peer-to-peer; context-aware system}, language = {German}, cr-category = {H.3.3 Information Search and Retrieval}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-15&engl=1} } @inproceedings {INPROC-2007-14, author = {Martin Saternus and Torben Weis and Mirko Knoll and Frank D{\"u}rr}, title = {{A Middleware for Context-Aware Applications and Services Based on Messenger Protocols}}, booktitle = {Proceedings of the Fifth Annual IEEE International Conference on Pervasive Computing and Communications Workshops (PerComW'07)}, publisher = {IEEE}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {467--471}, type = {Conference Paper}, month = {March}, year = {2007}, keywords = {context-aware application; middleware; user interface; messenger}, language = {English}, cr-category = {D.2.6 Software Engineering Programming Environments, H.5.0 Information Interfaces and Presentation General}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Nowadays most context-aware applications are independent proprietary pieces of software. A general framework or middleware deployed in the field does not exist; therefore the implementation of context-aware applications and services assumes the development of the whole application stack for each application. Along these development issues, deployment and privacy problems are to be solved. This imposes the following challenges concerning a middleware for context-aware applications: (1) We need an architecture that allows to implement and deploy services easily on the network. (2) We need a user interface that is widespread, well known to users and allows to mange one’s privacy settings for every single service transparently. In this paper we describe our middleware’s architecture for context-aware applications, based on messenger protocols.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-14&engl=1} } @inproceedings {INPROC-2007-133, author = {Andreas Lachenmann and Pedro Jos{\'e} Marr{\'o}n and Daniel Minder and Kurt Rothermel}, title = {{Meeting Lifetime Goals with Energy Levels}}, booktitle = {Proceedings of the 5th ACM Conference on Embedded Networked Sensor Systems (SenSys 2007)}, publisher = {ACM}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {131--144}, type = {Conference Paper}, month = {November}, year = {2007}, doi = {10.1145/1322263.1322277}, keywords = {wireless sensor network; energy; lifetime goal; programming abstraction}, language = {English}, cr-category = {D.3.3 Programming Language Constructs and Features, D.4.8 Operating Systems Performance}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-133/INPROC-2007-133.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {In this paper we present Levels, a programming abstraction for energy-aware sensor network applications. Unlike most previous work it does not try to maximize network lifetime but rather helps to meet user-defined lifetime goals while maximizing application quality. Levels is targeted to applications where there is no redundancy and no node should fail early. With our programming abstraction the application developer defines so-called energy levels. These energy levels form a stack and can be deactivated from top to bottom if the lifetime goal cannot be met otherwise. Each code block within an energy level contains information about its energy consumption, which can be obtained from simulation tools without much effort. The runtime system then uses the data about the energy consumption of the different levels to compute an optimal level assignment for the time remaining. As we show in the evaluation, applications using Levels can accurately meet given lifetime goals and offer good application quality. In addition, the runtime overhead of our system is almost negligible.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-133&engl=1} } @inproceedings {INPROC-2007-132, author = {Daniel Minder and Andreas Grau and Pedro Jos{\'e} Marr{\'o}n}, title = {{On Group Formation for Self-Adaptation in Pervasive Systems}}, booktitle = {Proceedings of the First International Conference on Autonomic Computing and Communication Systems}, publisher = {ACM}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {1--10}, type = {Conference Paper}, month = {October}, year = {2007}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-132/INPROC-2007-132.pdf, http://portal.acm.org/citation.cfm?doid=1365562.1365584}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Adaptation in Pervasive Computing normally focuses on services or on application behaviour, but the consideration of lower level algorithms in this process can lead to significant performance increase. To perform adaptation of algorithms the concept of context normally used in Pervasive Computing has to be extended. Based on the same context, group formation models are established to group devices with similar relevant context to optimise the adaptation process. In this paper, such group formation models are developed and evaluated. We also draw general conclusions for adaptation.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-132&engl=1} } @inproceedings {INPROC-2007-13, author = {Marcus Handte and Klaus Herrmann and Gregor Schiele and Christian Becker}, title = {{Supporting Pluggable Configuration Algorithms in PCOM}}, booktitle = {Perware Workshop at 5th IEEE International Conference on Pervasive Computing and Communications (PerCom)}, address = {New York, USA}, publisher = {IEEE}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {472--476}, type = {Conference Paper}, month = {March}, year = {2007}, language = {English}, cr-category = {D.2.11 Software Engineering Software Architectures, D.1.2 Automatic Programming}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-13/INPROC-2007-13.pdf, http://dx.doi.org/10.1109/PERCOMW.2007.111}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Pervasive Computing envisions distributed applications that optimally leverage the resources present in their ever-changing execution environment. To ease the development of pervasive applications, we have created a pervasive component system (PCOM). PCOM automates the configuration and runtime adaptation of a component-based application using a builtin distributed configuration algorithm. In this paper, we present an architectural extension that allows switching between different algorithms. This enables PCOM to dynamically select an algorithm that suits the computational resources present in an environment. To validate the extended architecture, we compare the overheads of a distributed and a centralized configuration algorithm in two different environments.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-13&engl=1} } @inproceedings {INPROC-2007-12, author = {Gregor Schiele and Marcus Handte and Christian Becker}, title = {{Good Manners for Pervasive Computing - An Approach Based on the Ambient Calculus}}, booktitle = {WIP Track at 5th IEEE International Conference on Pervasive Computing and Communications (PerCom)}, address = {New York, USA}, publisher = {IEEE}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {589--593}, type = {Conference Paper}, month = {March}, year = {2007}, language = {English}, cr-category = {D.2.7 Software Engineering Distribution, Maintenance, and Enhancement}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {When people interact, they follow distinct rules that coordinate the order of speech, who opens doors, whom and how to greet, and many things more. Such a social codex depends on the milieu -- or ambience -- people are acting in. People breaking the codex are either considered badly educated or foreigners to the ambience -- sometimes even both. In Pervasive Computing a multitude of applications is expected to populate our environment and to follow objects and users throughout their daily journey. Consequently, we will need a new codex -- or manners -- for Pervasive Computing applications that controls the interaction between applications. Such a codex will have to incorporate our existing codices as well as technical aspects. In this work in progress paper we present an approach to extend our prior work on Pervasive Computing system support by specifying interdependencies of applications based on the ambient calculus. This allows specifying and technically enforcing ``manners'' for Pervasive Computing applications.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-12&engl=1} } @inproceedings {INPROC-2007-05, author = {Steffen Maier and Andreas Grau and Harald Weinschrott and Kurt Rothermel}, title = {{Scalable Network Emulation: A Comparison of Virtual Routing and Virtual Machines}}, booktitle = {Proceedings of the IEEE Symposium on Computers and Communications (ISCC'07), Aveiro, Portugal, July 1-4}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {395--402}, type = {Conference Paper}, month = {July}, year = {2007}, keywords = {network emulation; performance measurement; virtual machine; virtual routing}, language = {English}, cr-category = {C.4 Performance of Systems, D.4.4 Operating Systems Communications Management, D.4.8 Operating Systems Performance, I.6.3 Simulation and Modeling Applications}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-05/INPROC-2007-05.pdf, http://dx.doi.org/10.1109/ISCC.2007.4381529}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Performance analysis is a necessary step during the development of distributed applications and communication protocols. Network emulation testbeds provide synthetic, configurable environments for comparative performance measurements of real implementations. However, realistic scenarios require more communicating nodes than usual testbeds are able to provide. In order to enable scalable network emulation, various concepts for the virtualization of nodes have been proposed. The overhead of virtualization strongly impacts the total size of a scenario, that can be emulated on a given testbed. However, the overhead of different virtualization approaches in the context of network emulation has not been compared directly so far. In this paper, we present a comparison of different virtual machine implementations (Xen, User Mode Linux) and our own virtual routing approach (NET). We discuss qualitative evaluation criteria and present a quantitative evaluation showing the efficiency of each approach in a traditional wired infrastructure-based and in a wireless ad hoc network emulation scenario. Our results give insights on which virtualization approach is best suited for which kind of network emulation.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-05&engl=1} } @inproceedings {INPROC-2007-02, author = {Andreas Lachenmann and Pedro Jos{\'e} Marr{\'o}n and Matthias Gauger and Daniel Minder and Olga Saukh and Kurt Rothermel}, title = {{Removing the Memory Limitations of Sensor Networks with Flash-Based Virtual Memory}}, booktitle = {Proceedings of the European Conference on Computer Systems (EuroSys 2007)}, publisher = {EuroSys}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {Also published in ACM SIGOPS Operating Systems Review, vol. 41(3), 2007}, pages = {131--144}, type = {Conference Paper}, month = {March}, year = {2007}, language = {English}, cr-category = {D.4.2 Storage Management, D.3.4 Programming Languages Processors}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-02/INPROC-2007-02.pdf, http://www.ipvs.uni-stuttgart.de/abteilungen/vs/forschung/projekte/tinycubus/start}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Virtual memory has been successfully used in different domains to extend the amount of memory available to applications. We have adapted this mechanism to sensor networks, where, traditionally, RAM is a severely constrained resource. In this paper we show that the overhead of virtual memory can be significantly reduced with compile-time optimizations to make it usable in practice, even with the resource limitations present in sensor networks. Our approach, ViMem, creates an efficient memory layout based on variable access traces obtained from simulation tools. This layout is optimized to the memory access patterns of the application and to the specific properties of the sensor network hardware. Our implementation is based on TinyOS. It includes a pre-compiler for nesC code that translates virtual memory accesses into calls of ViMem’s runtime component. ViMem uses flash memory as secondary storage. In order to evaluate our system we have modified nontrivial existing applications to make use of virtual memory. We show that its runtime overhead is small even for large data sizes.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-02&engl=1} } @inproceedings {INPROC-2007-01, author = {Andreas Lachenmann and Pedro Jos{\'e} Marr{\'o}n and Daniel Minder and Olga Saukh and Matthias Gauger and Kurt Rothermel}, title = {{Versatile Support for Efficient Neighborhood Data Sharing}}, booktitle = {Proceedings of the 4th European Conference on Wireless Sensor Networks (EWSN 2007)}, editor = {Koen Langendoen and Thiemo Voigt}, publisher = {Springer-Verlag}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {Lecture Notes in Computer Science}, volume = {4373}, pages = {1--16}, type = {Conference Paper}, month = {January}, year = {2007}, keywords = {wireless sensor networks; neighborhood data sharing; polite gossiping}, language = {English}, cr-category = {C.2.2 Network Protocols, C.3 Special-Purpose and Application-Based Systems, D.3.3 Programming Language Constructs and Features}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2007-01/INPROC-2007-01.pdf, http://www.ipvs.uni-stuttgart.de/abteilungen/vs/forschung/projekte/tinycubus/start, http://dx.doi.org/10.1007/978-3-540-69830-2_1}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Many applications in wireless sensor networks rely on data from neighboring nodes. However, the effort for developing efficient solutions for sharing data in the neighborhood is often substantial. Therefore, we present a general-purpose algorithm for this task that makes use of the broadcast nature of radio transmission to reduce the number of packets. We have integrated this algorithm into TinyXXL, a programming language extension for data exchange. This combined system offers seamless support both for data exchange among the components of a single node and for efficient neighborhood data sharing. We show that compared to existing solutions, such as Hood, our approach further reduces the work of the application developer and provides greater efficiency.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2007-01&engl=1} } @article {ART-2007-17, author = {Klaus Herrmann and Gero M{\"u}hl and Michael Jaeger}, title = {{MESHMdl Event Spaces -- A Coordination Middleware for Self-Organizing Applications in Ad hoc Networks}}, journal = {Journal on Pervasive and Mobile Computing - Special Issue on Middleware for Pervasive Computing}, publisher = {Elsevier Science Publishers B. V.}, volume = {3}, number = {4}, pages = {467--487}, type = {Article in Journal}, month = {August}, year = {2007}, issn = {1574-1192}, doi = {http://dx.doi.org/10.1016/j.pmcj.2007.04.003}, language = {English}, cr-category = {C.2.4 Distributed Systems}, contact = {Please contact me by a href=``mailto:klaus.herrmann@ipvs.uni-stuttgart.de?subject=Paper\%20inquiry''email if you need a copy of this article.}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Mobile ad hoc networks (MANETs) are gaining importance as a promising technology for flexible, proximity-based, mobile communication. However, the inherent dynamics of MANETs imposes strong limitations on the design of distributed applications. They need to be able to adapt to changing conditions quickly and organize themselves in terms of component placement and communication habits. In this paper, we present MESHMdl, a middleware that provides a high level of awareness and decoupling for application components to make them more flexible and adaptable. We focus on the Event Space as the central communication medium of MESHMdl. The Event Space offers a simple, unified communication interface for inter-agent communication as well as for communication with the middleware and resource access. Furthermore, it serves as a means for flexibly extending a MESHMdl daemon. We investigate the performance of the Event Space on different mobile devices and show that it is superior to comparable systems.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2007-17&engl=1} } @article {ART-2007-11, author = {Lorenzo Alvisi and Jeroen Doumen and Rachid Guerraoui and Boris Koldehofe and Harry Li and Robbert van Renesse and Gilles Tredan}, title = {{How robust are gossip-based communication protocols?}}, journal = {ACM SIGOPS Operating Systems Review}, address = {New York, NY, USA}, publisher = {ACM Press}, volume = {41}, number = {5}, pages = {14--18}, type = {Article in Journal}, month = {October}, year = {2007}, doi = {10.1145/1317379.1317383}, issn = {0163-5980}, language = {English}, cr-category = {C.2.4 Distributed Systems, D.2.4 Software Engineering Software/Program Verification}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Gossip-based communication protocols are often touted as being robust. Not surprisingly, such a claim relies on assumptions under which gossip protocols are supposed to operate. In this paper, we discuss and in some cases expose some of these assumptions and discuss how sensitive the robustness of gossip is to these assumptions. This analysis gives rise to a collection of new research challenges.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2007-11&engl=1} } @article {ART-2007-02, author = {Illya Stepanov and Kurt Rothermel}, title = {{Simulating mobile ad hoc networks in city scenarios}}, journal = {Computer Communications}, publisher = {Elsevier}, volume = {30}, number = {7}, pages = {1466--1475}, type = {Article in Journal}, month = {April}, year = {2007}, keywords = {Communication systems; Geographic information systems; Mobile communication; Modeling; Simulation}, language = {English}, cr-category = {C.2.1 Network Architecture and Design, C.4 Performance of Systems, I.6.3 Simulation and Modeling Applications}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Simulation tools are frequently used for the performance evaluations of mobile ad hoc networks. Currently the tools do not take a spatial environment into account, thus providing a poor support for urban scenarios. In this paper, we describe a platform for the modeling of city scenarios. We extend the mostly used MANET simulator ns-2 by the corresponding mobility and wireless transmission models. These models have been evaluated against real-world measurements. By using the tool’s emulation facility, we integrate unmodified applications and real implementations of network protocols. We demonstrate the usefulness of the platform by modeling a mobile application in a simulated environment of Stuttgart downtown. We show that obtained simulation results differ extensively from those with simpler models.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2007-02&engl=1} } @article {ART-2007-01, author = {Steffen Maier and Daniel Herrscher and Kurt Rothermel}, title = {{Experiences with node virtualization for scalable network emulation}}, journal = {Computer Communications}, publisher = {Elsevier}, volume = {30}, number = {5}, pages = {943--956}, type = {Article in Journal}, month = {March}, year = {2007}, keywords = {software performance evaluation; network emulation; mobile ad hoc network; scalability; virtual routing}, language = {English}, cr-category = {C.4 Performance of Systems, D.4.4 Operating Systems Communications Management, D.4.8 Operating Systems Performance, I.6.3 Simulation and Modeling Applications}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/ART-2007-01/ART-2007-01.pdf, http://dx.doi.org/10.1016/j.comcom.2006.08.018}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {During the development of network protocols and distributed applications, their performance has to be analyzed in appropriate environments. Network emulation testbeds provide a synthetic, configurable network environment for comparative performance measurements of real implementations. Realistic scenarios have to consider hundreds of communicating nodes. Common network emulation approaches limit the number of nodes in a scenario to the number of computers in an emulation testbed. To overcome this limitation, we introduce a virtual node concept for network emulation. The key problem for node virtualization is a transparent, yet efficient separation of node resources. In this paper, we provide a brief survey of candidate node virtualization approaches to facilitate scalable network emulation. Based on the gathered insights, we propose a lightweight virtualization solution to achieve maximum scalability and discuss the main points regarding its implementation. We present extensive evaluations that show the scalability and transparency of our approach in both a traditional wired infrastructure-based, and in two wireless ad hoc network emulation scenarios. The measurements indicate that our solution can push the upper limit of emulation scenario sizes by a factor of 10--28. Given our emulation testbed consisting of 64 computers, this translates to possible scenario sizes of up to 1792 nodes. In addition to the evaluation of our virtualization approach, we discuss key concepts for controlling comprehensive emulation scenarios to support scalability of our system as a whole.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2007-01&engl=1} } @inbook {INBOOK-2007-04, author = {Klaus Herrmann}, title = {{Selbstorganisierende Infrastrukturen f{\"u}r Ambient Services}}, series = {GI-Edition Lecture Notes in Informatics (LNI) - Ausgezeichnete Informatikdissertationen 2006}, publisher = {K{\"o}llen Verlag}, series = {GI-Edition Lecture Notes in Informatics (LNI)}, volume = {D-7}, pages = {109--118}, type = {Article in Book}, month = {January}, year = {2007}, keywords = {self-organization, replica placement, ambient intelligence, ambient services}, language = {German}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INBOOK-2007-04/INBOOK-2007-04.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Die Vision von intelligenten Umgebungen (Ambient Intelligence - AmI) als neues Paradigma f{\"u}r die Unterst{\"u}tzung mobiler Benutzer bei allt{\"a}glichen T{\"a}tigkeiten r{\"u}ckt derzeit zunehmend in den Fokus Europ{\"a}ischer Forschungsaktivit{\"a}ten. Ein hoher Grad an Autonomie auf Seiten der unterst{\"u}tzenden Software-Systeme ist hierf{\"u}r eine unabdingbare Voraussetzung. Derartige Systeme m{\"u}ssen in der Lage sein, sich selbst ohne steuernde Eingriffe von Benutzern an deren Aktivit{\"a}ten und Verhalten anzupassen. Entsprechende Systeme sind derzeit jedoch weitgehend unerforscht. Diese Arbeit stellt den ersten umfassenden Ansatz f{\"u}r eine selbstorganisierende Plattform zur Unterst{\"u}tzung von so genannten Ambient Services dar - Diensten, die es dem mobilen Benutzer gestatten, mit seiner unmittelbaren Umgebung zu interagieren. Diese als Ad hoc Service Grid (ASG) bezeichnete Plattform kann spontan in beliebigen Umgebungen (z.B. Einkaufszentren, Baustellen, Messen, etc.) eingesetzt werden, um dort entsprechende Dienste anzubieten. In der Arbeit schlagen wir zun{\"a}chst ein Modell f{\"u}r eine entsprechende Infrastruktur aus spontan vernetzten Rechnerknoten vor. Diese ist modular aufgebaut und im Einsatz flexibel erweiterbar. Der eigentliche Fokus liegt jedoch auf der Entwicklung und Evaluierung einer Reihe von Basis-Algorithmen und Protokollen f{\"u}r das selbstorganisierte Betreiben dieser Infrastruktur. Hier konzentrieren wir uns auf die Platzierung von Ambient Service-Instanzen, deren Auffinden (Discovery und Lookup), und auf die Erhaltung der Konsistenz einer Gruppe verteilt laufender Replikate eines solchen Dienstes. Diese Mechanismen legen zusammen eine essenzielle Grundlage f{\"u}r die Weiterentwicklung intelligenter Umgebungen.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INBOOK-2007-04&engl=1} } @inbook {INBOOK-2007-01, author = {J{\"o}rg H{\"a}hner and Christian Becker and Pedro Jos{\'e} Marr{\'o}n and Kurt Rothermel}, title = {{Drahtlose Sensornetze - Fenster zur Realwelt}}, series = {Die Informatisierung des Alltags}, address = {Berlin, Heidelberg}, publisher = {Springer-Verlag}, pages = {41--60}, type = {Article in Book}, month = {July}, year = {2007}, isbn = {978-3-540-71454-5}, keywords = {Sensornetze; Datenverwaltung; Konsistenz}, language = {German}, cr-category = {C.2 Computer-Communication Networks, H.2 Database Management}, ee = {http://dx.doi.org/10.1007/978-3-540-71455-2_4}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Sensornetze stellen eine technische L{\"o}sung f{\"u}r die Erfassung und Verarbeitung von Informationen der physischen Welt dar. Dabei handelt es sich um eine Menge sogenannter Sensorknoten, die — meist drahtlos — miteinander kommunizieren k{\"o}nnen. Sensorknoten sind miniaturisierte Computer, die — neben einem Mikroprozessor und einer Kommunikationsschnittstelle — mit Sensoren ausgestattet sind. Diese Sensoren erlauben es, physikalische Gr{\"o}{\ss}en in der Umgebung des Knotens zu messen. Mit Hilfe des Mikroprozessors k{\"o}nnen diese Messwerte verarbeitet und {\"u}ber die Kommunikationsschnittstelle an andere Sensorknoten verschickt werden. In diesem Beitrag werden zun{\"a}chst verschiedene Einsatz-gebiete von Sensornetzen vorgestellt. Danach werden technische Eigenschaften von Sensornetzen anhand exemplarischer Sensorknoten diskutiert. Neue wissen-schaftliche Herausforderungen werden beispielhaft anhand des Gebiets der Daten-verwaltung in Sensornetzen vorgestellt.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INBOOK-2007-01&engl=1} }