@inproceedings {INPROC-2014-26,
   author = {Andreas Benzing and Boris Koldehofe and Kurt Rothermel},
   title = {{Bandwidth-Minimized Distribution of Measurements in Global Sensor Networks}},
   booktitle = {In Proceedings of the 14th IFIP International Conference on Distributed Applications and Interoperable Systems (DAIS 2014)},
   publisher = {Springer-Verlag},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   series = {Lecture Notes in Computer Science},
   volume = {8460},
   pages = {156--170},
   type = {Conference Paper},
   month = {June},
   year = {2014},
   doi = {10.1007/978-3-662-43352-2_13},
   keywords = {Data Streams; Global Sensor Networks; Optimization},
   language = {English},
   cr-category = {C.2.4 Distributed Systems},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2014-26/INPROC-2014-26.pdf,     http://link.springer.com/chapter/10.1007/978-3-662-43352-2_13},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {Global sensor networks (GSN) allow applications to integrate huge amounts of data using real-time streams from virtually anywhere. Queries to a GSN offer many degrees of freedom, e.g. the resolution and the geographic origin of data, and scaling optimization of data streams to many applications is highly challenging. Existing solutions hence either limit the flexibility with additional constraints or ignore the characteristics of sensor streams where data points are produced synchronously. In this paper, we present a new approach to bandwidth-minimized distribution of real-time sensor streams in a GSN. Using a distributed index structure, we partition queries for bandwidth management and quickly identify overlapping queries. Based on this information, our relay strategy determines an optimized distribution structure which minimizes traffic while being adaptive to changing conditions. Simulations show that total traffic and user perceived delay can be reduced by more than 50\%.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2014-26&engl=1}
}
@inproceedings {INPROC-2012-30,
   author = {Ben W. Carabelli and Andreas Benzing and Georg Seyboth and Rainer Blind and Mathias B{\"u}rger and Frank D{\"u}rr and Boris Koldehofe and Kurt Rothermel and Frank Allg{\"o}wer},
   title = {{Exact Convex Formulations of Network-Oriented Optimal Operator Placement}},
   booktitle = {Proceedings of the 51st IEEE Conference on Decision and Control (CDC2012)},
   publisher = {IEEE},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {3777--3782},
   type = {Conference Paper},
   month = {December},
   year = {2012},
   doi = {10.1109/CDC.2012.6426790},
   keywords = {Optimization; Computer networks; Sensor networks},
   language = {English},
   cr-category = {G.1.6 Numerical Analysis Optimization},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2012-30/INPROC-2012-30.pdf,     http://dx.doi.org/10.1109/CDC.2012.6426790},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {Data processing tasks are increasingly spread across the internet to account for the spatially distributed nature of many data sources. In order to use network resources efficiently, subtasks need to be distributed in the network so data can be filtered close to the data sources. Previous approaches to this operator placement problem relied on various heuristics to constrain the complexity of the problem. In this paper, we propose two generic integer constrained problem formulations: a topology aware version which provides a placement including the specific network links as well as an end-to-end delay aware version which relies on the routing capabilities of the network. A linear programming relaxation for both versions is provided which allows exact and efficient solution using common solvers.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2012-30&engl=1}
}
@inproceedings {INPROC-2011-30,
   author = {Andreas Benzing and Boris Koldehofe and Kurt Rothermel},
   title = {{Efficient Support for Multi-Resolution Queries in Global Sensor Networks}},
   booktitle = {Proceedings of the Fifth International Conference on COMmunication System softWAre and middlewaRE: COMSWARE 2011},
   publisher = {ACM},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {1--12},
   type = {Conference Paper},
   month = {July},
   year = {2011},
   doi = {10.1145/2016551.2016562},
   keywords = {DSPS, global sensor network, indexing, query processing},
   language = {English},
   cr-category = {C.2.4 Distributed Systems},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-30/INPROC-2011-30.pdf,     http://dl.acm.org/authorize?6553117},
   contact = {andreas.benzing@ipvs.uni-stuttgart.de},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {Stream processing has evolved as a paradigm for efficiently sharing and integrating a massive amount of data into applications. However, the integration of globally dispersed sensor data imposes challenges in the effective utilization of the IT infrastructure that forms the global sensor network. Especially, simulations require the integration of sensor streams at widely differing spatial and temporal resolutions. For current stream processing solutions it is necessary to generate a separate data stream for each requested resolution. Therefore, these systems will suffer from high redundancy in data streams, wasting a significant amount of bandwidth and limiting their scalability. This paper presents a new approach to scalable distributed stream processing of data which stems from globally dispersed sensor networks. The approach supports applications in establishing continuous queries for sensor data at different resolutions and ensures efficient bandwidth usage of the data distribution network. Unlike existing work in the context of video stream processing which provides multiple resolutions by establishing separate channels for each resolution, this paper presents a stream processing system that can efficiently split/combine data streams in order to decrease/increase their resolution without loss in data precision. In addition the system provides mechanisms for load balancing of sensor data streams that allow efficient utilization of the bandwidth of the global sensor network.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-30&engl=1}
}
@inproceedings {INPROC-2011-08,
   author = {Gerald G. Koch and Andreas Benzing and Christoph P. Mayer},
   title = {{An Approach for Urban Sensing with Quality-Aware Situation Detection and Efficient Communication}},
   booktitle = {Proceedings of the Workshops der wissenschaftlichen Konferenz Kommunikation in verteilten Systemen 2011 (WowKiVS 2011); Kiel, Germany, March 11th, 2011},
   editor = {Horst Hellbr{\"u}ck and Norbert Luttenberger and Volker Turau},
   publisher = {EASST},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   series = {Electronic Communications of the EASST},
   pages = {1--10},
   type = {Workshop Paper},
   month = {March},
   year = {2011},
   issn = {1863-2122},
   keywords = {Urban sensing; Internet of Things; Complex Event Processing; CEP; Delay Tolerant Network; DTN; Distributed Diagnostic Simulation},
   language = {English},
   cr-category = {C.2.2 Network Protocols,     C.2.4 Distributed Systems,     I.6.3 Simulation and Modeling Applications},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-08/INPROC-2011-08.pdf},
   contact = {gerald.koch@ipvs.uni-stuttgart.de andreas.benzing@ipvs.uni-stuttgart.de mayer@kit.edu},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {Urban Sensing employs physical-world mining to create a digital model of the physical world using a large number of sensors. Handling the large amount of data generated by sensors is costly and requires energy-saving measures for sensing and sensor data transmission. Such schemes often affect data quality and message delay. However, the detection of real-world situations using Complex Event Processing on sensor data has to be dependable and timely and requires precise data. In this position paper, we propose an approach to integrate the contradicting optimization goals of energy-efficient wireless sensor networks and dependable situation detection. It separates the system into the following tiers: First, to support energy-efficiency and allow sparse, unconnected sensor networks, we exploit the mobility of people through Delay Tolerant Networking for collecting sensor data. This frees sensor nodes from energy-expensive routing. Second, we employ Diagnostic Simulation which provides data that is complete, precise and in time and therefore supports quality-aware situation detection.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-08&engl=1}
}
@inproceedings {INPROC-2010-69,
   author = {Andreas Benzing and Boris Koldehofe and Marco V{\"o}lz and Kurt Rothermel},
   title = {{Multilevel Predictions for the Aggregation of Data in Global Sensor Networks}},
   booktitle = {Proceedings of the 14th IEEE/ACM International Symposium on Distributed Simulation and Real Time Applications},
   publisher = {IEEE},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {169--178},
   type = {Conference Paper},
   month = {October},
   year = {2010},
   keywords = {Global Sensor Networks; Distributed Stream Processing; Predictors},
   language = {English},
   cr-category = {C.2.4 Distributed Systems},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2010-69/INPROC-2010-69.pdf,     http://ieeexplore.ieee.org/search/srchabstract.jsp?tp=&arnumber=5636734},
   contact = {andreas.benzing@ipvs.uni-stuttgart.de},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {Real-time simulations are one challenging application domain that is expected to introduce high requirements to global sensor applications. Besides having hard constraints on latency bounds at which data needs to be processed, simulation applications will impose high requirements with respect to available bandwidth. Predictors, originally introduced in the domain of wireless sensor networks for energy saving, are one appealing solution to provide real-time estimates and at the same time significantly reduce the data rates. While in the setting of wireless sensor networks many prediction models have been analyzed, their behavior and use is unclear when applied to distributed data streams where aggregation results are typically processed over multilevel hierarchies. In the context of weather simulations, we propose a distributed R-Tree-based aggregation algorithm that allows for efficient reuse of aggregate queries. In the setting of real temperature readings taken from weather stations during one month, we study the trade-off between updates of the prediction model and the precision of the predicted values. Our evaluations indicate that even in situations where complex prediction models are expected to perform best, simple prediction models give higher benefits with respect to saving bandwidth while providing similar data accuracy.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2010-69&engl=1}
}
@inproceedings {INPROC-2010-18,
   author = {Andreas Benzing and Boris Koldehofe and Kurt Rothermel},
   title = {{Distributed Diagnostic Simulations for the Smart Grid}},
   booktitle = {Accepted Poster at the 1st International Conference on Energy-Efficient Computing and Networking: E-Energy 2010},
   publisher = {Online},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {1--3},
   type = {Conference Paper},
   month = {April},
   year = {2010},
   keywords = {Diagnostic Simulation; Global Sensor Grid},
   language = {German},
   cr-category = {C.2.4 Distributed Systems},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2010-18/INPROC-2010-18.pdf},
   contact = {andreas.benzing@ipvs.uni-stuttgart.de},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {Energy efficiency is usually achieved by reducing the energy consumption as far as possible. With the growing amount of renewable energy sources, energy efficient usage also has to consider what kind of and when power is consumed. By matching the availability of electrical power with the current demands, the amount of unused energy and therefore overall energy production can be reduced. The so called smart grid aims to provide this matching with a broad deployment of smart meters to acquire the current demand. However, current approaches to the smart grid cannot handle the huge amount of sensors and energy sources involved in a scalable way. Most data acquisition systems focus on the lookup and reading of single sensors and therefore do not fit the requirements of a large scale power grid simulation. We propose a Global Sensor Grid (GSG) which provides consumers with data preprocessed to their needs instead of delivering raw sensor data. With this decoupling from the actual sensors, multiple consumers can benefit from improvements in data acquisition and avoidance of the redundant processing of data by each consumer. By integrating so-called diagnostic simulations into the GSG, gaps in sensor coverage can be filled with higher precision than normal interpolation.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2010-18&engl=1}
}
@inproceedings {INPROC-2009-04,
   author = {Andreas Benzing and Klaus Herrmann and Boris Koldehofe and Kurt Rothermel},
   title = {{Identifying the Challenges in Reducing Latency in GSN using Predictors}},
   booktitle = {Workshops der Wissenschaftlichen Konferenz Kommunikation in Verteilten Systemen 2009 (WowKiVS 2009)},
   editor = {Tiziana Margaria and Julia Padberg and Gabriele Taentzer},
   address = {Kassel},
   publisher = {EASST},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   series = {Electronic Communications of the EASST},
   volume = {17},
   pages = {1--6},
   type = {Workshop Paper},
   month = {March},
   year = {2009},
   issn = {1863-2122},
   keywords = {Global Sensor Networks, Wireless Sensor Networks, Predictors},
   language = {English},
   cr-category = {C.2.4 Distributed Systems},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2009-04/INPROC-2009-04.pdf},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {Simulations based on real-time data continuously gathered from sensor networks all over the world have received growing attention due to the increasing availability of measured data. Furthermore, predictive techniques have been employed in the realm of such networks to reduce communication for energy-efficiency. However, research has focused on the high amounts of data transferred rather than latency requirements posed by the applications. We propose using predictors to supply data with low latency as required for accurate simulations. This paper investigates requirements for a successful combination of these concepts and discusses challenges that arise.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2009-04&engl=1}
}