@inproceedings {INPROC-2008-98, author = {Jos{\'e} Mocito and Briones-Garc{\'\i}a J. Alfonso and Boris Koldehofe and Hugo Miranda and Lu{\'\i}s Rodrigues}, title = {{Geographical distribution of subscriptions for Content-based Publish/Subscribe in MANETs}}, booktitle = {Proceedings of the Middleware'08 Companion}, address = {Leuven, Belgium}, publisher = {ACM}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, type = {Conference Paper}, month = {December}, year = {2008}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Establishing content-based publish/subscribe in the resource constrained and failure prone environment of Mobile Ad-Hoc Networks (MANETs) is a highly challenging task. Movement of nodes and network partitioning can require frequent and possibly expensive reorganizations of the publish/subscribe system. Many approaches towards publish/subscribe in MANETs either rely explicitly on location information, or are characterized by a high subscription and publication overhead. In this paper we present preliminary research on how geographical distribution of subscriptions may help to overcome some shortcomings of both approaches.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-98&engl=1} } @inproceedings {INPROC-2008-90, author = {Stephan Schuhmann and Lars V{\"o}lker}, title = {{Combining Passive Autoconfiguration and Anomaly-based Intrusion Detection in Ad-hoc Networks}}, booktitle = {Proceedings of the 8th International Workshop on Applications and Services in Wireless Networks (ASWN 2008); Kassel, Germany, October 9-10, 2008}, publisher = {IEEE}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {87--95}, type = {Workshop Paper}, month = {October}, year = {2008}, keywords = {MANET; Intrusion Detection; Anomalies; OLSR}, language = {English}, cr-category = {C.2.0 Computer-Communication Networks, General, C.2.2 Network Protocols}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-90/INPROC-2008-90.pdf, http://dx.doi.org/10.1109/ASWN.2008.14}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Two essential services of Ad-hoc networks are IP address autoconfiguration and intrusion detection systems. Since both autoconfiguration and intrusion detection may base their decisions on routing protocol anomalies, their interdependencies can cause problems. In this paper, we present our approach to efficiently combine autoconfiguration and intrusion detection, and present our enhancements in attack detection for an autoconfiguration system. We have identified anomalies indicating specific attacks, implemented suitable anomaly detectors, and evaluated our system. The results show that it is possible to detect both the attacks and IP address conflicts in an efficient way.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-90&engl=1} } @inproceedings {INPROC-2008-84, author = {Ralph Lange and Frank D{\"u}rr and Kurt Rothermel}, title = {{Scalable Processing of Trajectory-Based Queries in Space-Partitioned Moving Objects Databases}}, booktitle = {Proceedings of the 16th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems (ACM GIS 2008)}, address = {Irvine, CA, USA}, 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 = {November}, year = {2008}, keywords = {spatio-temporal indexing; moving objects database; MOD; trajectory-based query; distributed query processing}, language = {English}, cr-category = {H.2.8 Database Applications}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-84/INPROC-2008-84.pdf, http://doi.acm.org/10.1145/1463434.1463474}, contact = {ralph.lange@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Space-partitioned Moving Objects Databases (SP-MODs) allow for the scalable, distributed management of large sets of mobile objects' trajectories by partitioning the trajectory data to a network of database servers. Processing a spatio-temporal query q therefore requires efficiently routing q to the servers storing the affected trajectory segments. With a coordinate-based query - like a spatio-temporal range query - the relevant servers are directly determined by the queried range. However, with trajectory-based queries - like retrieving the distance covered by a certain object during a given time interval - the relevant servers depend on actual movement of the queried object. Therefore, efficient routing mechanisms for trajectory-based queries are an important challenge in SP-MODs. In this paper, we present the Distributed Trajectory Index (DTI) that allows for such efficient query routing by creating an overlay network for each trajectory. We further present an enhanced index called DTI+S. It accelerates the processing of queries on aggregates of dynamic attributes, like the maximum speed during a time interval, by augmenting DTI with summaries of trajectory segments. Our simulations with a network of 1000 database servers show that DTI+S can reduce the overall processing time by more than 98\%.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-84&engl=1} } @inproceedings {INPROC-2008-83, author = {Faraz Memon and Daniel Tiebler and Frank D{\"u}rr and Kurt Rothermel and Marco Tomsu and Peter Domschitz}, title = {{OID: Optimized Information Discovery using Space Filling Curves in P2P Overlay Networks}}, booktitle = {Proceedings of 14th International Conference on Parallel and Distributed Systems (ICPADS'08)}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {311--319}, type = {Conference Paper}, month = {December}, year = {2008}, isbn = {978-0-7695-3434-3}, language = {English}, cr-category = {C.2.2 Network Protocols, C.2.3 Network Operations, C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-83/INPROC-2008-83.pdf, http://dx.doi.org/10.1109/ICPADS.2008.57}, contact = {faraz.memon@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {In this paper, we present the system design and evaluation of a Space-Filling Curve (SFC)-based P2P information discovery system OID. The OID system uses multiple SFCs to significantly optimize the performance of multi-attribute range queries, particularly for applications with a large number of data attributes where a single big SFC-based index is inefficient. The basic idea is to have multiple SFCbased indices and select the best one to perform a query. We also introduce two tree-based query optimizations that increase the scalability of the system.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-83&engl=1} } @inproceedings {INPROC-2008-70, author = {Stephan Schuhmann and Klaus Herrmann and Kurt Rothermel}, title = {{A Framework for Adapting the Distribution of Automatic Application Configuration}}, booktitle = {Proceedings of the 2008 ACM International Conference on Pervasive Services (ICPS 2008), Sorrento, Italy, July 6-10, 2008}, publisher = {ACM}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {163--172}, type = {Conference Paper}, month = {July}, year = {2008}, keywords = {Adaptivity; Components; Middleware; Pervasive Computing; Application Configuration}, language = {English}, cr-category = {C.2.4 Distributed Systems, D.2.11 Software Engineering Software Architectures}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-70/INPROC-2008-70.pdf, http://doi.acm.org/10.1145/1387269.1387297}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Numerous current research projects deal with the issue of automatic application configuration in pervasive computing scenarios. While completely distributed configuration is inevitable in infrastructure-less ad hoc scenarios, many realistic pervasive application scenarios are located in heterogeneous environments where additional computation power of resource-rich devices can be utilized. However, most of the current projects either focus solely on smart environments which rely on additional infrastructure devices, or they address ad hoc environments and treat all involved devices as equal. This leads to suboptimal results in case of present resource-rich devices, as their additional computation power is not exploited. In this paper, we present a framework that is based on clustering and allows the efficient and flexible support of automatic application configuration both in infrastructure-based and ad hoc environments. This is realized by a new concept called Virtual Container that enables the local emulation of remote devices’ functionalities and resources. In our evaluation results, we prove that this concept considerably reduces configuration delays noticeable by the user.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-70&engl=1} } @inproceedings {INPROC-2008-69, author = {Stephan Schuhmann and Klaus Herrmann and Kurt Rothermel and Jan Blumenthal and Dirk Timmermann}, title = {{Improved Weighted Centroid Localization in Smart Ubiquitous Environments}}, booktitle = {Proceedings of the Fifth International Conference on Ubiquitous Intelligence and Computing (UIC 2008), Oslo, Norway, June 23-25, 2008}, publisher = {Springer-Verlag}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {Lecture Notes in Computer Science}, volume = {5061}, pages = {20--34}, type = {Conference Paper}, month = {June}, year = {2008}, keywords = {Weighted Centroid Localization; WLAN; Ubiquitous Computing}, language = {English}, cr-category = {C.2.1 Network Architecture and Design, C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-69/INPROC-2008-69.pdf, http://www.springerlink.com/content/l3l121u67r12445u}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Location-awareness is highly relevant subject in ubiquitous computing, as many applications exploit location information to provide adequate services or adapt to a changing physical environment. While GPS provides reliable outdoor localization, indoor positioning systems present a bigger challenge. Many indoor localization systems have been proposed. However, most of them rely on customized hardware or presume some dedicated infrastructure. In this paper, we focus on WLAN-based localization in smart ubiquitous environments. We propose an improved scheme of the Weighted Centroid Localization (WCL) algorithm that is robust and provides higher location accuracy than the original WCL algorithm. The improvements are based on the use of dynamic weighting factors that are solely dependent on the correlation of the Received Signal Strength Indicators of the received beacon signals. Compared to the original WCL scheme, our approach does not increase requirements to the environment. Real-world experiments in a typical environment that we report on in this paper confirm that the increased location accuracy determined in previous calculations is reproducible in a realistic noisy environment. This provides a simple, cost-efficient, and battery-conserving, but yet adequate technique for getting the accurate location information of mobile devices.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-69&engl=1} } @inproceedings {INPROC-2008-68, author = {Saukh Olga and Robert Sauter and Matthias Gauger and Pedro Jos{\'e} Marr{\'o}n and Kurt Rothermel}, title = {{On Boundary Recognition without Location Information in Wireless Sensor Networks}}, booktitle = {Proceedings of the 2008 International Conference on Information Processing in Sensor Networks (IPSN 2008)}, address = {Washington, DC, USA}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {207--218}, type = {Conference Paper}, month = {April}, year = {2008}, isbn = {978-0-7695-3157-1}, doi = {http://dx.doi.org/10.1109/IPSN.2008.11}, language = {English}, cr-category = {C.2.4 Distributed Systems}, 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-2008-68&engl=1} } @inproceedings {INPROC-2008-67, author = {Matthias Gauger and Olga Saukh and Marcus Handte and Pedro Jos{$\backslash$'e} Marr{$\backslash$'o}n and Andreas Heydlauff and Kurt Rothermel}, title = {{Sensor-based Clustering for Indoor Applications}}, booktitle = {Proceedings of the 5th IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks (SECON 2008)}, publisher = {IEEE Computer Society Press}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, type = {Conference Paper}, month = {June}, year = {2008}, language = {English}, cr-category = {C.2.4 Distributed Systems}, contact = {gauger@cs.uni-bonn.de}, 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-2008-67&engl=1} } @inproceedings {INPROC-2008-39, author = {Jorge A. Briones and Boris Koldehofe and Kurt Rothermel}, title = {{SPINE: Publish/Subscribe for Wireless Mesh Networks through Self-Managed Intersecting Paths}}, booktitle = {Proceedings of the 8th International Conference on Innovative Internet Community Systems (I2CS 2008); Schoelcher, Martinique, June 16-18, 2008}, address = {Schoelcher, Martinique}, publisher = {online proceedings}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, type = {Conference Paper}, month = {June}, year = {2008}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-39/INPROC-2008-39.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Application deployment on Wireless Mesh Networks (WMNs) is a challenging issue. First it requires communication abstractions that allow for interoperation with Internet applications and second the offered solution should be sensitive to the available resources in the underlying network. Loosely coupled communication abstractions, like publish/subscribe, promote interoperability, but unfortunately are typically implemented at the application layer without considering the available resources at the underlay imposing a significant degradation of application performance in the setting of Wireless Mesh Networks. In this paper we present SPINE, a content-based publish/subscribe system,   which considers the particular challenges of deploying application-level services in Wireless Mesh Networks. SPINE is designed to reduce the overhead which stems from both publications and reconfigurations, to cope with the inherent capacity limitations on communication links as well as with mobility of the wireless mesh-clients. We demonstrate the effectiveness of SPINE by comparison with traditional approaches in implementing content-based publish/subscribe.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-39&engl=1} } @inproceedings {INPROC-2008-37, author = {Ralph Lange and Frank D{\"u}rr and Kurt Rothermel}, title = {{Online Trajectory Data Reduction using Connection-preserving Dead Reckoning}}, booktitle = {Proceedings of the Fifth Annual International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services: MobiQuitous '08; Dublin, Ireland, July 21-25, 2008}, publisher = {ICST}, 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 = {July}, year = {2008}, isbn = {978-963-9799-21-9}, keywords = {Online trajectory reduction; dead reckoning; MOD}, language = {English}, cr-category = {H.2.8 Database Applications}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-37/INPROC-2008-37.pdf, http://portal.acm.org/citation.cfm?id=1595044}, contact = {ralph.lange@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Moving objects databases (MODs) store objects’ trajectories by spatiotemporal polylines that approximate the actual movements given by sequences of sensed positions. Determining such a polyline with as few vertices as possible under the constraint that it does not deviate by more than a certain accuracy bound epsilon from the sensed positions is an algorithmic problem known as trajectory reduction. A specific challenge is online trajectory reduction, i.e. continuous reduction with position sensing in realtime. This particularly is required for moving objects with embedded position sensors whose movements are tracked and stored by a remote MOD. In this paper, we present Connection-preserving Dead Reckoning (CDR), a new approach for online trajectory reduction. It outperforms the existing approaches by 30 to 50\%. CDR requires the moving objects to temporally store some of the previously sensed positions. Although the storage consumption of CDR generally is small, it is not bounded. We therefore further present CDRM whose storage allocation and execution time per position fix can be adjusted and limited. Even with very limited storage allocations of less than 1 kB CDRM outperforms the existing approach by 20 to 40\%.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-37&engl=1} } @inproceedings {INPROC-2008-28, author = {Paolo Costa and Daniela Gavidia and Boris Koldehofe and Hugo Miranda and Mirco Musolesi and Orian Riva}, title = {{When Cars Start Gossiping}}, booktitle = {Proceedings of the ACM EuroSys 2008 Affilated Workshops}, publisher = {ACM Press}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {1--4}, type = {Workshop Paper}, month = {April}, year = {2008}, language = {English}, cr-category = {C.2.4 Distributed Systems}, 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-2008-28&engl=1} } @inproceedings {INPROC-2008-15, author = {Dominique Dudkowski and Harald Weinschrott and Pedro Jos{\'e} Marr{\'o}n}, title = {{Design and Implementation of a Reference Model for Context Management in Mobile Ad-Hoc Networks}}, booktitle = {Proceedings of the International Workshop on Data Management for Wireless and Pervasive Communications (DMWPC2008); Gino-wan, Okinawa, Japan, March, 2008}, publisher = {IEEE}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {832--837}, type = {Conference Paper}, month = {March}, year = {2008}, keywords = {context; data management; MANET; reference model; hybrid system}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-15/INPROC-2008-15.pdf, http://www.computer.org/portal/web/csdl/doi/10.1109/WAINA.2008.72}, contact = {harald.weinschrott@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The fundamental paradigm of context-aware computing has lead to a diversity of conceivable context-based applications. In order to support these applications, efficient and scalable context management platforms have become utterly important. In this paper we propose a layered reference model that encapsulates suitable abstractions to tackle the complexity of context management in mobile ad-hoc networks. For each layer, we outline strategies and mechanisms we have developed to manage context information efficiently so that it can readily be used by context-based services and applications in these networks. In addition, we discuss refinements of the current model that we currently investigate, which are related to data semantics such as context quality and expressive location models, performance enhancement by adaptation, and aspects regarding the integration of ad-hoc context management with infrastructure-based systems leading to a hybrid system structure.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-15&engl=1} } @inproceedings {INPROC-2008-145, author = {Matthias Gauger and Pedro Jos{\'e} Marr{\'o}n and Marcus Handte and Olga Saukh and Daniel Minder and Andreas Lachenmann and Kurt Rothermel}, title = {{Integrating Sensor Networks in Pervasive Computing Environments Using Symbolic Coordinates}}, booktitle = {Proceedings of the Third International Conference on Communication System Software and Middleware (COMSWARE 2008)}, publisher = {IEEE}, 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 = {January}, year = {2008}, keywords = {wireless sensor network; pervasive computing; routing; symbolic coordinates}, language = {English}, cr-category = {C.3 Special-Purpose and Application-Based Systems, C.2.2 Network Protocols}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-145/INPROC-2008-145.pdf, http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4554476}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Wireless sensor networks can monitor different types of physical phenomena and are able to provide a diverse set of context data to interested clients. Allowing mobile pervasive computing devices to access such data requires solutions for routing messages between mobile devices and the static sensor network. This paper presents a novel approach that addresses this problem with the help of symbolic coordinates. It requires only a small amount of topology information distributed in the network and allows mobile devices to send messages to arbitrary areas. The routing task is split among the client nodes, which specify a symbolic source route, and the sensor nodes that handle node-to-node routing. The paper describes the algorithm, specific challenges associated with its design and gives an extensive evaluation of the approach and its properties, showing that the use of symbolic coordinates in these environments is a viable alternative to more traditional types of routing.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-145&engl=1} } @inproceedings {INPROC-2008-14, author = {Matthias Gauger and Daniel Minder and Pedro Jos{\'e} Marr{\'o}n and Arno Wacker and Andreas Lachenmann}, title = {{Prototyping Sensor-Actuator Networks for Home Automation}}, booktitle = {Proceedings of the 3rd Workshop on Real-World Wireless Sensor Networks (REALWSN 2008)}, publisher = {ACM}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, type = {Conference Paper}, month = {April}, year = {2008}, keywords = {sensor-actuator networks; home automation; prototyping}, language = {English}, cr-category = {C.2.4 Distributed Systems, B.4.1 Data Communications Devices}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Integrating actuators into sensor networks is often considered to be the next logical step in the evolution of wireless sensor networks. However, few practical examples of such sensor and actuator networks have been demonstrated so far. In this paper, we present a prototype system that supports the easy prototyping of such applications in the area of home automation. We demonstrate the utility of this system with a simple light control application built on top of it. We also report first experiences and insights gained with the help of real-world experiments.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-14&engl=1} } @inproceedings {INPROC-2008-123, author = {Matthias Gauger and Olga Saukh and Marcus Handte and Pedro Jos{\'e} Marr{\'o}n and Andreas Heydlauff and Kurt Rothermel}, title = {{Sensor-based Clustering for Indoor Applications}}, booktitle = {Proceedings of the European Conference on Wireless Sensor Networks (EWSN 2008), Poster/Demo session}, publisher = {Springer}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, type = {Workshop Paper}, month = {September}, year = {2008}, language = {English}, cr-category = {C.2.4 Distributed Systems}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The lifetime requirements on wireless sensor networks often require the redundant deployment of sensor nodes with appropriate management mechanisms based on node clustering. Yet, existing clustering approaches do not take the primary task of sensor networks into account: performing relevant measurements. They usually form 'arbitrary' clusters, e.g., using connectivity information, and thus, the resulting measurements are often of only limited use to the applications. This problem can be avoided by considering application-specific semantics. For indoor applications, the notion of a room provides a natural unit of clustering since walls are constructed deliberately to ensure locality. This paper shows that it is feasible to automatically create clusters that reflect boundaries between rooms by analyzing the measurements of inexpensive, broadly available sensors. The paper first analyzes the applicability of statistical clustering methods and based on this analysis, it proposes and evaluates a lightweight approach to determine clusters in real deployments.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-123&engl=1} } @inproceedings {INPROC-2008-122, author = {Matthias Gauger and Olga Saukh and Marcus Handte and Pedro Jos{\'e} Marr{\'o}n and Andreas Heydlauff and Kurt Rothermel}, title = {{Sensor-based Clustering for Indoor Applications}}, booktitle = {Proceedings of the 5th IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks (SECON 2008)}, publisher = {IEEE Communications Society}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {478--486}, type = {Conference Paper}, month = {June}, year = {2008}, isbn = {978-1-4244-1777-3}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-122/INPROC-2008-122.pdf, http://ieeexplore.ieee.org/search/srchabstract.jsp?arnumber=4557787}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The lifetime requirements on wireless sensor networks often require the redundant deployment of sensor nodes with appropriate management mechanisms based on node clustering. Yet, existing clustering approaches do not take the primary task of sensor networks into account: performing relevant measurements. They usually form 'arbitrary' clusters, e.g., using connectivity information, and thus, the resulting measurements are often of only limited use to the applications. This problem can be avoided by considering application-specific semantics. For indoor applications, the notion of a room provides a natural unit of clustering since walls are constructed deliberately to ensure locality. This paper shows that it is feasible to automatically create clusters that reflect boundaries between rooms by analyzing the measurements of inexpensive, broadly available sensors. The paper first analyzes the applicability of statistical clustering methods and based on this analysis, it proposes and evaluates a lightweight approach to determine clusters in real deployments.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-122&engl=1} } @inproceedings {INPROC-2008-113, author = {Frank D{\"u}rr and Kurt Rothermel}, title = {{Kommunikationsprotokolle zur Vermittlung kontextbezogener Informationen auf Basis r{\"a}umlicher Umgebungsmodelle}}, booktitle = {Proceedings of VDE-Kongress 2008 -- Zukunftstechnologien: Innovationen - M{\"a}rkte - Nachwuchs}, address = {Munich, Germany}, publisher = {VDE Verlag GmbH}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {1--6}, type = {Conference Paper}, month = {November}, year = {2008}, isbn = {978-3-8007-3126-8}, keywords = {contextcast; geocast; Protokoll; protocol; kommunikation; communication; location-based; context-aware; ortsbezogen; kontextbezogen; Ort; Kontext; lokationsbasiert; service; Dienst}, language = {German}, cr-category = {C.2 Computer-Communication Networks}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-113/INPROC-2008-113.pdf, http://www.vde-verlag.de/proceedings-en/453126101.html}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {In diesem Artikel stellen wir ein neuartiges kontextbezogenes Kommunikationsparadigma namens Contextcast vor. Contextcast erm{\"o}glicht das selektive Senden von Nachrichten an Teilnehmer mit einem bestimmten Kontext, wobei der Kontext eines Teilnehmers beispielsweise durch seinen Aufenthaltsort, seine Interessen oder seine Situation bestimmt ist. Typische Anwendungen f{\"u}r Contextcast sind die gezielte Verteilung von Warnmeldungen, Touristeninformationen oder Veranstaltungshinweise. Wir pr{\"a}sentieren zun{\"a}chst Konzepte zur effizienten Vermittlung von ortsbezogenen Informationen (Geocast) und diskutieren anschlie{\ss}end notwendige Erweiterungen f{\"u}r die effiziente Realisierung der Contextcast-Kommunikation.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-113&engl=1} } @inproceedings {INPROC-2008-110, author = {Frank D{\"u}rr and Jonas Palauro and Lars Geiger and Ralph Lange and Kurt Rothermel}, title = {{Ein kontextbezogener Instant-Messaging-Dienst auf Basis des XMPP-Protokolls}}, booktitle = {5. GI/ITG KuVS Fachgespr{\"a}ch Ortsbezogene Anwendungen und Dienste. N{\"u}rnberg. September 2008}, address = {N{\"u}rnberg}, publisher = {Georg-Simon-Ohm-Hochschule N{\"u}rnberg}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, series = {Sonderdruck Schriftenreihe der Georg-Simon-Ohm-Hochschule N{\"u}rnberg}, volume = {42}, pages = {23--28}, type = {Workshop Paper}, month = {September}, year = {2008}, issn = {1867-5433}, keywords = {Nexus; Instant-Messaging; Kontextbezug; context-awareness; Contextcast; XMPP}, language = {German}, cr-category = {H.4.3 Information Systems Applications Communications Applications}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-110/INPROC-2008-110.pdf, http://www.nexus.uni-stuttgart.de/, http://www.wireless-earth.de/fg_lbs/meeting_5/meeting_5.html}, contact = {frank.duerr@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Dieser Beitrag beschreibt die Verteilung kontextbezogener Informationen mittels eines erweiterten Instant-Messaging-Dienstes. Dieser Dienst erm{\"o}glicht das Senden von Nachrichten an alle Teilnehmer, die einen bestimmten Kontext besitzen und sich z.B. an einem bestimmten Ort aufhalten oder bestimmte Interessen besitzen. Als Basis dient das Extensible Messaging and Presence Protokoll (XMPP) sowie ein XMPP-basierter Instant-Messaging-Dienst. Wir beschreiben Protokoll- und Architekturerweiterungen f{\"u}r die Integration von Kontextinformationen in das XMPP-Protokoll und die Server-Infrastruktur. Der erweiterte Dienst unterst{\"u}tzt insbesondere die Server-seitige Filterung von Nachrichten aufgrund von Kontextinformationen und erm{\"o}glicht dadurch die effiziente Nachrichtenverteilung.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-110&engl=1} } @inproceedings {INPROC-2008-103, author = {Manuel Gonzalo and Klaus Herrmann and Kurt Rothermel}, title = {{Self-Adaptive Load Balancing for Many-To-Many Communication in Wireless Sensor Networks}}, booktitle = {Proceedings of the 7th GI/ITG KuVS Fachgespr{\"a}ch ``Drahtlose Sensornetze''}, address = {Berlin}, publisher = {ACM}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {64--67}, type = {Workshop Paper}, month = {September}, year = {2008}, keywords = {WSN; multisink; routing; many to many; load balancing}, language = {English}, cr-category = {C.2.1 Network Architecture and Design}, contact = {manuel.gonzalo@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {New scenarios in wireless sensor networks, where several independent sinks can ask for different kinds of data, are currently emerging. Former algorithms that route data to a centralized sink, are not appropriate for these scenarios. First solutions for these multi-source to multi-sink scenarios simply create independent trees for each source. As a result, some nodes become hot-spots, since they are included in several trees, whereas nodes around them remain unused. In this paper, we propose a new algorithm that balances the load evenly in the network, extending the network lifetime, while still providing a small delay in packet delivery. Based on the information of one-hop neighbors and the number of hops to the sinks, the algorithm attempts to reduce both the delay and the power consumption. We present the cost function used to select the next hop(s) towards the sinks. The evaluation of the protocol demonstrates its ability to fulfill its target.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-103&engl=1} } @inproceedings {INPROC-2008-102, author = {Klaus Herrmann and Kurt Rothermel}, title = {{Developing user-responsive mobile applications}}, booktitle = {PerAda Magazine}, publisher = {Online}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, type = {Workshop Paper}, month = {October}, year = {2008}, isbn = {http://www.perada-magazine.eu/view.php?article=1270-2008-09-19&category=Mobile+Applications}, keywords = {ALLOW; pervasive adaptation; flow attachment; flow distribution; context-aware flows; horizontal adaptation; vertical adaptation}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-102/INPROC-2008-102.pdf, http://www.perada-magazine.eu/view.php?article=1270-2008-09-19&category=%20Mobile+Applications}, contact = {Klaus.Herrmann@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {A novel workflow-based approach may one day enable adaptive programs to unobtrusively assist people with everyday tasks.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-102&engl=1} } @inproceedings {INPROC-2008-101, author = {Klaus Herrmann and Kurt Rothermel and Gerd Kortuem and Dulay Naranker}, title = {{Adaptable Pervasive Flows - An Emerging Technology for Pervasive Adaptation}}, booktitle = {Proceedings of the Workshop on Pervasive Adaptation at the Second IEEE International Conference on Self-Adaptive and Self-Organizing Systems (SASO 2008)}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, type = {Workshop Paper}, month = {October}, year = {2008}, keywords = {ALLOW; pervasive computing; pervasive adaptation; flow distribution; flow attachment; context-aware flows; horizontal adaptation; vertical adaptation}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-101/INPROC-2008-101.pdf, http://dx.doi.org/10.1109/SASOW.2008.25}, contact = {Klaus.Herrmann@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The era of pervasive computing brings with it a grand challenge: Pervasive applications must adapt to the dynamics entailed in human behavior and constantly changing computing environments. In this paper, we propose Adaptable Pervasive Flows as a novel technology that goes far beyond existing approaches for adapting pervasive computing systems. APFs model applications in a fashion similar to classical workflows while being situated in the real world. The notable advantage of this is that applications as well as their environment can be adapted proactively based on knowledge about future tasks. We introduce the visions, concepts, and challenges of this emerging approach.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-101&engl=1} } @inproceedings {INPROC-2008-10, author = {Stephan Schuhmann and Klaus Herrmann and Kurt Rothermel}, title = {{Direct Backtracking: An Advanced Adaptation Algorithm for Pervasive Applications}}, booktitle = {Proceedings of the 21st International Conference on Architecture of Computing Systems (ARCS 2008); Dresden, Germany, February 25-28, 2008}, editor = {Uwe et al. Brinkschulte}, address = {Berlin Heidelberg}, publisher = {Springer-Verlag}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {Lecture Notes in Computer Science}, volume = {4934}, pages = {53--67}, type = {Conference Paper}, month = {February}, year = {2008}, isbn = {978-3-540-78152-3}, keywords = {Pervasive Computing; Adaptation; Configuration; Backtracking; Pervasive Applications}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-10/INPROC-2008-10.pdf, http://www.springerlink.com/content/167w160l00445832}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The adaptation of pervasive applications is in the focus of many current research projects. While decentralized adaptation is mandatory in infrastructureless ad hoc scenarios, most realistic pervasive application scenarios are situated in heterogeneous environments where additional computation power of resource-rich devices can be exploited. Therefore, we propose a hybrid approach to application configuration that applies centralized as well as decentralized configuration as appropriate in the given environment. In this paper we introduce the Direct Backtracking algorithm that represents an efficient way for centralized configuration and adaptation of pervasive applications in heterogeneous scenarios. In our evaluation, we show that compared with other centralized algorithms, our algorithm significantly reduces adaptation latency as it avoids unnecessary adaptations that arise in many other backtracking algorithms, without significantly increasing memory waste. This is achieved by introducing two mechanisms: 1. proactive backtracking avoidance and 2. intelligent backtracking.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-10&engl=1} } @inproceedings {INPROC-2008-07, author = {Andreas Grau and Steffen Maier and Klaus Herrmann and Kurt Rothermel}, title = {{Time Jails: A Hybrid Approach to Scalable Network Emulation}}, booktitle = {22nd ACM/IEEE/SCS Workshop on Principles of Advanced and Distributed Simulation (PADS 2008)}, publisher = {IEEE Computer Society; ACM}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {7--14}, type = {Workshop Paper}, month = {June}, year = {2008}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-07/INPROC-2008-07.pdf, http://dx.doi.org/10.1109/PADS.2008.19}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {It is essential to evaluate the performance of newly developed distributed software and network protocols. Network emulation enables reproducible evaluation of unmodified real implementations. Software built for distributed systems, such as a large scale peer-to-peer system, requires evaluation scenarios with thousands of communicating nodes. Two approaches for scaling network emulation to such scenario sizes have been proposed in the literature: node virtualization and time virtualization. Node virtualization allows maximizing the utilization of standard hardware used for emulation experiments. Time virtualization enables trading experiment duration for virtually increased resources of the hardware. It stands to reason that a combination of those two approaches may increase scalability even further. However, in existing combinations, either node virtualization implies relatively high overhead or time virtualization requires modifications of the test subject implementation. In this paper, we present a novel hybrid approach called Time Virtualized Emulation Environment (TVEE). It integrates node virtualization with low overhead and time virtualization, which is transparent to the execution of test subjects. We introduce virtual time based on epochs to enable better dynamic hardware utilization during long lasting experiments. Additionally, a mechanism similar to soft timers ensures an accurate reproduction of network properties in the time virtualized emulation. Our evaluations show the accuracy and scalability of time virtualized network emulation. Comparing TCP throughput, TVEE outperforms other approaches using an event based virtual time by an order of magnitude.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-07&engl=1} } @inproceedings {INPROC-2008-06, author = {Gerald G. Koch and Boris Koldehofe and Kurt Rothermel}, title = {{Higher confidence in event correlation using uncertainty restrictions}}, booktitle = {28th IEEE International Conference on Distributed Computing Systems Workshops (ICDCSW'08); 2008}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {417--422}, type = {Workshop Paper}, month = {June}, year = {2008}, issn = {1545-0678}, doi = {http://dx.doi.org/10.1109/ICDCS.Workshops.2008.22}, keywords = {event correlation, uncertainty restriction}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-06/INPROC-2008-06.pdf, http://dx.doi.org/10.1109/ICDCS.Workshops.2008.22}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Distributed cooperative systems that use event notification for communication can benefit from event correlation within the notification network. In the presence of uncertain data, however, correlation results easily become unreliable. The handling of uncertainty is therefore an important challenge for event correlation in distributed event notification systems. In this paper, we present a generic correlation model that is aware of uncertainty. We propose uncertainty constraints that event correlation can take into account and show how they can lead to higher confidence in the correlation result. We demonstrate that the application of this model allows to obtain a qualitative description of event correlation.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-06&engl=1} } @inproceedings {INPROC-2008-03, author = {Frank D{\"u}rr and Kurt Rothermel}, title = {{An Adaptive Overlay Network for World-wide Geographic Messaging}}, booktitle = {Proceedings of the 22nd IEEE International Conference on Advanced Information Networking and Applications (AINA 2008); Gino-wan, Okinawa, Japan, March 25-28, 2008}, publisher = {IEEE}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {875--882}, type = {Conference Paper}, month = {March}, year = {2008}, keywords = {geocast; overlay network; communication; protocol; location-based service; geographic communication; networking; context; context-aware systems}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2008-03/INPROC-2008-03.pdf, http://dx.doi.org/10.1109/AINA.2008.67}, contact = {frank.duerr@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {In this paper, we propose an overlay network supporting world-wide geographic messaging. Our approach is based on hierarchical symbolic coordinates like /usa/fl/miami/. Although hierarchical network topologies lend themselves to the implementation of such overlay networks, they may lead to bottlenecks at the root of the hierarchy, long message paths, and inefficient bandwidth utilization. To avoid these problems, we propose an overlay network that adapts its structure to the users' communication patterns by dynamically adding shortcut`` links to the hierarchy leading to a routing mesh. We present an algorithm that carefully selects shortcuts based on their utility to assure short message paths on the one hand and to reduce the induced overhead on the other hand. Through simulations we show that this approach decreases the average path length significantly and reduces network load to about 50\% compared to hierarchical routing.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2008-03&engl=1} } @article {ART-2008-23, author = {Oliver P. Waldhorst and Christian Blankenhorn and Dirk Haage and Ralph Holz and Gerald G. Koch and Boris Koldehofe and Fleming Lampi and Christoph P. Mayer and Sebastian Mies}, title = {{Spontaneous Virtual Networks: On the Road Towards the Internet's Next Generation}}, journal = {it --- Information Technology -- Methods and Applications of Informatis and Information Technology}, address = {M{\"u}nchen}, publisher = {Oldenbourg Wissenschaftsverlag GmbH}, volume = {50}, number = {6}, pages = {367--375}, type = {Article in Journal}, month = {December}, year = {2008}, issn = {1611-2776}, doi = {10.1524/itit.2008.0508}, keywords = {SpoVNet; Spontane Virtuelle Netze; Next Generation Internet}, language = {English}, cr-category = {C.2.1 Network Architecture and Design, C.2.4 Distributed Systems, C.2.2 Network Protocols, C.2.6 Internetworking}, contact = {Correspondence address: University of Karlsruhe, Institute of Telematics, Zirkel 2, 76131 Karlsruhe, Deutschland, waldhorst@tm.uka.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Novel Internet applications demand global availability of complex services that can adapt dynamically to application requirements. At the same time, pervasive Internet usage and heterogeneous access technologies impose new challenges for service deployment. We present Spontaneous Virtual Networks (SpoVNet), a methodology that enables easy development of new services with transparent support for mobility, multi-homing, and heterogeneous environments. This article presents the overlay-based architecture of SpoVNet that supports the spontaneous deployment of new services as well as a seamless transition towards future networks. SpoVNet´s architecture offers support for the underlay aware adaptation of overlays by the use of cross-layer information. In the context of two exemplary services like a group communication service and an event service as well as two demanding applications – a realtime online game and a video streaming application – we illustrate how SpoVNet is of value in establishing services and applications for the Next Generation Internet.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2008-23&engl=1} } @article {ART-2008-22, author = {Klaus Herrmann}, title = {{Self-Organized Service Placement in Ambient Intelligence Environments}}, journal = {ACM Transactions on Autonomous and Adaptive Systems - Special Issue on Ambient Intelligence}, publisher = {ACM}, type = {Article in Journal}, month = {March}, year = {2008}, language = {English}, cr-category = {C.2.4 Distributed Systems}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Ambient Intelligence (AmI) is an IT concept by which mobile users shall be seamlessly supported in their every-day activities. This includes interactions with remote resources as well as with their current physical environment. We have developed the so-called Ad hoc Service Grid (ASG) infrastructure that supports the latter form of interactions. It allows operators to cover arbitrary locations with Ambient Services in a Drop-and-Deploy fashion. An Ambient Service may autonomously distribute (replicate and migrate) within an ASG network to optimize its availability, response times, and network usage. In this paper, we propose a fully decentralized, dynamic, and adaptive service placement algorithm for AmI environments like the ASG. This algorithm achieves a coordinated global placement pattern that minimizes the communication costs without any central controller. It does not even require additional communication among the replicas. Moreover, placement patterns stabilize if no changes occur in the environment while replicas still retain their ability to adapt. Mechanisms for self-organized placement of services are very important for AmI environments in general since they allow for autonomous adaptations to dynamic changes and, thus, remove the need for manual (re)configuration of a running system. We present a detailed evaluation of the algorithm's performance and compare it with three other algorithms to show its competitiveness. Furthermore, we discuss how the desired self-organizing behavior emerges from the interactions of a few simple, local rules that govern the individual placement decisions. In order to do so, we give an in-depth analysis of a series of hidden effects that are not directly encoded into the placement algorithm but stem from its collective dynamics.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2008-22&engl=1} } @inbook {INBOOK-2008-11, author = {Kurt Rothermel}, title = {{Kontextbezogene Systeme – die Welt im Computer modelliert}}, series = {Digitale Visionen}, publisher = {Springer Berlin Heidelberg}, pages = {31--42}, type = {Article in Book}, month = {April}, year = {2008}, isbn = {978-3-540-77021-3}, language = {German}, cr-category = {H.4 Information Systems Applications}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Ziel des Sonderforschungsbereichs 627 ``Nexus - Umgebungsmodelle f{\"u}r mobile kontextbezogene Systeme'' ist die Erforschung von Methoden und Verfahren f{\"u}r die Definition, die Verwaltung und die Nutzung von digitalen Umgebungsmodellen. Existierende Informationsr{\"a}ume werden mit komplexen Modellen der realen Welt verschr{\"a}nkt und erlauben so neuartige Anwendungen. Insbesondere die Klasse der ortsbezogenen Anwendungen und aktuelle Forschungsgebiete wie das Ubiquitous Computing k{\"o}nnen von solchen Umgebungsmodellen profitieren oder werden sogar durch sie erst erm{\"o}glicht.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INBOOK-2008-11&engl=1} } @book {BOOK-2008-03, author = {Klaus Herrmann}, title = {{Self-Organizing Ambient Intelligence - Principles, Algorithms, and Protocols}}, publisher = {VDM Verlag Dr. M{\"u}ller}, pages = {276}, type = {Book}, month = {April}, year = {2008}, isbn = {978-3-8364-9896-8}, language = {English}, cr-category = {C.2.4 Distributed Systems}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {In the last two decades, the advent of wireless networking technology and the achievements in the miniaturization of electronic devices have set new trends in distributed computing. This ultimately enables a new paradigm for embedding mobile users in intelligent environments that support them in their interactions with their local physical surrounding. This vision is called Ambient Intelligence (AmI). There are still many challenges ahead on the way towards the realization of AmI. One question that is central to the entire concept is: How can we render AmI systems self-organizing such that they can indeed disappear in our environment without creating a massive administrative problem? In this book, we propose a model for a dedicated AmI infrastructure that supports the user in his interaction with his physical environment and with external entities. This infrastructure is called Ad hoc Service Grid (ASG) and provides wireless services in a decentralized and self-organizing fashion. We identify three distinct problems associated with self-organized service provisioning in the ASG model and propose algorithms and protocols that solve them. The problem that is at the center of our work is the self-organized replication and distribution of arbitrary services in an ASG. A set of algorithms is presented that solves this problem in a completely distributed way. The two other problems we tackle are the discovery and lookup of dynamically distributed service replicas and the reconciliation among a dynamic group of replicas. Together, the mechanisms we propose lay the foundation for a general AmI software platform. We will derive the architecture of such a Serviceware from these mechanisms. Detailed experimental results are presented that show the validity of our concepts and identify ways for tailoring our algorithms and protocols to the requirements of specific applications. Furthermore, we propose a new general model and a classification methodology for self-organizing software systems. We employ this model to evaluate our own solutions. The focus of the research work presented in this book is on the global-scale interactions in an AmI system. We call this the macro-level of interactions to separate it from the focus of most current research projects. These projects concentrate more on adaptations at the micro-level, pertaining to the internal structures of specific applications and services. Our work complements these efforts by providing solutions for structuring AmI systems externally, for example by distributing a group of service replicas within an ASG network.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=BOOK-2008-03&engl=1} }