Seite drucken

Publikationen

Bücher | Zeitschriftenartikel | Konferenzbeiträge | Dissertationen | Technische Berichte

Bücher

Volker Turau und Christoph Weyer. Algorithmische Graphentheorie. De Gruyter, Berlin, Germany, 4th edition, Oktober 2015.
@Book{Telematik_Turau_2015_AGT, author = {Volker Turau and Christoph Weyer}, title = {Algorithmische Graphentheorie}, publisher = {De Gruyter}, address = {Berlin, Germany}, edition = {4th}, month = oct, year = 2015, isbn = {978-3-11-041727-2}, }
Bernd-Christian Renner. Steffen Hölldobler et al. (Hrsg.), Editor. GI-Edition Ausgezeichnete Informatikdissertationen 2013. Gesellschaft für Informatik (GI), 2014.
@Book{Telematik_Renner_GI_2013, author = {Bernd-Christian Renner}, editor = {Steffen Hölldobler et al. (Hrsg.)}, title = {GI-Edition Ausgezeichnete Informatikdissertationen 2013}, pages = {191-200}, series = {Gesellschaft für Informatik (GI)}, volume = {D-14}, publisher = {Gesellschaft für Informatik (GI)}, year = 2014, isbn = {978-3-88579-418-9}, }
Marta Z. Kwiatkowska, Rahul Mangharam, Volker Turau und Christoph Weyer, Editoren. 5th Workshop on Medical Cyber-Physical Systems. Schloss Dagstuhl - Leibniz-Zentrum fuer Informatik, 2014.
@Book{Telematik_Turau_MCPS_2014, editor = {Marta Z. Kwiatkowska and Rahul Mangharam and Volker Turau and Christoph Weyer}, title = {5th Workshop on Medical Cyber-Physical Systems}, series = {OASICS}, volume = {36}, publisher = {Schloss Dagstuhl - Leibniz-Zentrum fuer Informatik}, year = 2014, isbn = {978-3-939897-66-8}, }
Volker Turau. Algorithmische Graphentheorie. Oldenbourg, München, Germany, 3rd edition, Oktober 2009.
@Book{Telematik_Turau_2009_AGT, author = {Volker Turau}, title = {Algorithmische Graphentheorie}, publisher = {Oldenbourg}, address = {München, Germany}, edition = {3rd}, month = oct, year = 2009, isbn = {978-3-486-59057-9}, }
Wilfried Elmenreich, Markus Kucera, Bernhard Rinner, Ralf Seepold und Volker Turau, Editoren. Challenges on Complexity and Connectivity in Embedded Systems. Hindawi, 2009.
@Book{Telematik_Turau_2009_EURASIP, editor = {Wilfried Elmenreich and Markus Kucera and Bernhard Rinner and Ralf Seepold and Volker Turau}, title = {Challenges on Complexity and Connectivity in Embedded Systems}, series = {EURASIP Journal of Embedded Systems}, volume = {2009}, publisher = {Hindawi}, year = 2009, issn = {1687-3955}, }
Volker Turau und Christoph Weyer, Editoren. Proceedings of the Third International Workshop on Intelligent Solutions in Embedded Systems (WISES'05). Hamburg University of Technology, Hamburg, Germany, Mai 2005.
@Book{Telematik_Turau_2005_WISES, editor = {Volker Turau and Christoph Weyer}, title = {Proceedings of the Third International Workshop on Intelligent Solutions in Embedded Systems (WISES'05)}, publisher = {Hamburg University of Technology}, address = {Hamburg, Germany}, month = may, year = 2005, isbn = {3-902463-03-1}, }
Volker Turau. Web-basierte Anwendungen entwickeln in JSP 2. dpunkt.verlag, Heidelberg, Germany, November 2003.
@Book{Telematik_Turau_2003_JSP2, author = {Volker Turau}, title = {Web-basierte Anwendungen entwickeln in JSP 2}, publisher = {dpunkt.verlag}, address = {Heidelberg, Germany}, month = nov, year = 2003, isbn = {3-89864-235-6}, }
Volker Turau, Krister Saleck und Marc Schmidt. Java Server Pages und J2EE (Unternehmensweite web-basierte Anwendungen). dpunkt.verlag, Heidelberg, Germany, Juni 2001.
@Book{Telematik_Turau_2001_J2EE, author = {Volker Turau and Krister Saleck and Marc Schmidt}, title = {Java Server Pages und J2EE (Unternehmensweite web-basierte Anwendungen)}, publisher = {dpunkt.verlag}, address = {Heidelberg, Germany}, month = jun, year = 2001, isbn = {3-898-64112-0}, }

Zeitschriftenartikel

Tobias Lübkert, Marcus Venzke, Nhat-Vinh Vo und Volker Turau. Understanding Price Functions to Control Domestic Electric Water Heaters for Demand Response. Computer Science - Research and Development, September 2017.
@Article{Telematik_Demand_Response_DEWH_2017, author = {Tobias Lübkert and Marcus Venzke and Nhat-Vinh Vo and Volker Turau}, title = {Understanding Price Functions to Control Domestic Electric Water Heaters for Demand Response}, pages = , journal = {Computer Science - Research and Development}, volume = {}, month = sep, year = 2017, }
Abstract: A well-known mechanism for demand response is sending price signals to customers a day ahead. Customers then postpone or advance their usage of electricity to minimize cost. Setting up price functions that adapt the customers' load to availability is a big challenge. This paper investigates the feasibility of finding day-ahead price functions to induce a desired load profile of Domestic Electric Water Heaters (DEWHs) minimizing their electricity cost for demand response. Bilevel optimization is applied for a single DEWH using a simplified linear model and full knowledge. This leads to a solvable bilevel problem and allows understanding optimality of price functions and resulting heating profiles. It is shown that with the resulting price functions the DEWH may select many significantly different heating profiles leading to the same cost. Thus the price does not uniquely induce the desired heating profile. The acquired knowledge forms the basis for a procedure to create price functions for controlling the load profile of many DEWHs.
Brahim Neggazi, Volker Turau, Mohammed Haddad und Hamamache Kheddouci. A O(m) Self-Stabilizing Algorithm for Maximal Triangle Partition of General Graphs. Parallel Processing Letters, 27, issue No 2:1–17, Juni 2017.
@Article{Telematik_Tolerance Zone_PPL_2017, author = {Brahim Neggazi and Volker Turau and Mohammed Haddad and Hamamache Kheddouci}, title = {A O(m) Self-Stabilizing Algorithm for Maximal Triangle Partition of General Graphs}, pages = {1-17}, journal = {Parallel Processing Letters}, volume = {27, issue No 2}, month = jun, year = 2017, }
Abstract: The triangle partition problem is a generalization of the well-known graph matching problem consisting of finding the maximum number of independent edges in a given graph, i.e., edges with no common node. Triangle partition instead aims to find the maximum number of disjoint triangles. The triangle partition problem is known to be NP-complete. Thus, in this paper, the focus is on the local maximization variant, called maximal triangle partition (MTP). This paper presents a new self-stabilizing algorithm for MTP that converges in O(m) moves under the unfair distributed daemon.
Brahim Negazzi, Mohammed Haddad, Volker Turau und Hamamache Kheddouci. A Self-Stabilizing Algorithm for Edge Monitoring in Wireless Sensor Networks. Information and Computation, 254, Part 3:367–376, Juni 2017.
@Article{Telematik_T_2017, author = {Brahim Negazzi and Mohammed Haddad and Volker Turau and Hamamache Kheddouci}, title = {A Self-Stabilizing Algorithm for Edge Monitoring in Wireless Sensor Networks}, pages = {367-376}, journal = {Information and Computation}, volume = {254, Part 3}, month = jun, year = 2017, }
Abstract: Self-monitoring is a simple and effective mechanism for surveilling wireless sensor networks, especially to cope against faulty or compromised nodes. A node v can monitor the communication over a link e if both end-nodes of e are neighbors of v. Finding a set of monitoring nodes satisfying all monitoring constraints is called the edge-monitoring problem. The minimum edge-monitoring problem is known to be NP-complete. In this paper, we present a novel self-stabilizing algorithm for computing a minimal edge-monitoring set under the unfair distributed scheduler. For sparse networks the time complexity of this new algorithm is much lower than the currently best known algorithm.
Tobias Lübkert, Marcus Venzke und Volker Turau. Impacts of Domestic Electric Water Heater Parameters on Demand Response. Computer Science - Research and Development, 32:49–64, 2017.
@Article{Telematik_Demand_Response_DEWH_2016, author = {Tobias Lübkert and Marcus Venzke and Volker Turau}, title = {Impacts of Domestic Electric Water Heater Parameters on Demand Response}, pages = {49-64}, journal = {Computer Science - Research and Development}, volume = {32}, year = 2017, }
Abstract: This paper analyzes the impact of the high dimen- sional parameter space of domestic electric water heaters (DEWH) for demand response (DR). To quantify the con- sumer comfort a novel metric is introduced considering a stochastic distribution of different water draw events. Incor- porating three control algorithms from literature, it is shown that all considered parameters of a DEWH except the heat conductivity have a significant impact on consumer satisfac- tion. The effect on DR is mainly influenced by the temper- ature range and the planning horizon, but also by the heat conductivity and the volume. In contrast, the rated power of the heating element and the nominal temperature have no significant impact on the effect on DR. The impacts are an- alyzed by varying these parameters in a simulation of 1000 DEWHs considering three different controllers: a common thermostat, an exchange price dependent nominal temper- ature changing mechanism and an energy scheduling algo- rithm proposed by Du and Lu.
Li-Hsing Yen, Jean-Yao Huang und Volker Turau. Designing Self-Stabilizing Systems Using Game Theory. ACM Transactions on Autonomous and Adaptive Systems, Volume 11, Issue 3, Article 18:1–27, 2016.
@Article{Telematik_Transactions_on_Autonomous_and_Adaptive_Systems_2017, author = {Li-Hsing Yen and Jean-Yao Huang and Volker Turau}, title = {Designing Self-Stabilizing Systems Using Game Theory}, pages = {1-27}, journal = {ACM Transactions on Autonomous and Adaptive Systems}, volume = {Volume 11, Issue 3, Article 18}, year = 2016, }
Abstract: Self-stabilizing systems tolerate transient faults by always returning to a legitimate system state within a finite time. This goal is challenged by several system features such as arbitrary system states after faults, various process execution models, and constrained process communication means. This work designs self-stabilizing distributed algorithms from the perspective of game theory, achieving an intended system goal through private goals of processes. We propose a generic game design for identifying a maximal independent set (MIS) or a maximal weighted independent set (MWIS) among all processes in a distributed system. From the generic game several specific games can be defined which differ in whether and how neighboring players influence each other. Turning the game designs into self-stabilizing algorithms, we obtain the first algorithms for the MWIS problem and also the first self-stabilizing MIS algorithm that considers node degree (including an analysis of its performance ratio). We also show how to handle simultaneous moves of processes in some process execution models. Simulation results indicate that, for various representative network topologies, the new algorithm outperforms existing methods in terms of MIS size and convergence rate. For the MWIS problem, the new algorithms performed only slightly worse than centralized greedy counterparts.
Sven Köhler und Volker Turau. A Distributed Algorithm for Minimum Distance-k Domination in Trees. Journal of Graph Algorithms and Applications, 19(1):223–242, März 2015.
@Article{Telematik_jgaa_2015, author = {Sven Köhler and Volker Turau}, title = {A Distributed Algorithm for Minimum Distance-k Domination in Trees}, pages = {223-242}, journal = {Journal of Graph Algorithms and Applications}, volume = {19}, number = {1}, month = mar, year = 2015, }
Abstract: While efficient algorithms for finding minimal distance-k dominating sets exist, finding minimum such sets is NP-hard even for bipartite graphs. This paper presents a distributed algorithm to determine a minimum (connected) distance-k dominating set and a maximum distance-2k independent set of a tree T. It terminates in O(height(T)) rounds and uses O(logk) space. To the best of our knowledge this is the first distributed algorithm that computes a minimum (as opposed to a minimal) distance-k dominating set for trees. The algorithm can also be applied to general graphs, albeit the distance-k dominating sets are not necessarily minimal.
Sven Köhler und Volker Turau. Self-stabilizing local k-placement of replicas with local minimum variance. Theoretical Computer Science, 591:15–27, 2015.
@Article{Telematik_theoretical_computer_science_2015, author = {Sven Köhler and Volker Turau}, title = {Self-stabilizing local k-placement of replicas with local minimum variance}, pages = {15-27}, journal = {Theoretical Computer Science}, volume = {591}, year = 2015, }
Abstract: Large scale distributed systems require replication of resources to amplify availability and to provide fault tolerance. The placement of replicated resources significantly impacts performance. This paper considers local k-placements: Each node of a network has to place k replicas of a resource among its direct neighbours. The load of a node in a given local k-placement is the number of replicas it stores. The local k-placement problem is to achieve a preferably homogeneous distribution of the loads. We present a novel self-stabilizing, distributed, asynchronous, scalable algorithm for the k-placement problem such that the standard deviation of the distribution of the loads assumes a local minimum.
Andreas Weigel, Martin Ringwelski, Volker Turau und Andreas Timm-Giel. Route-over forwarding techniques in a 6LoWPAN. EAI Endorsed Transactions on Mobile Communications and Applications, 14(5), Dezember 2014.
@Article{Telematik_EAI_6LowPAN_2014, author = {Andreas Weigel and Martin Ringwelski and Volker Turau and Andreas Timm-Giel}, title = {Route-over forwarding techniques in a 6LoWPAN}, journal = {EAI Endorsed Transactions on Mobile Communications and Applications}, volume = {14}, number = {5}, month = dec, year = 2014, }
Abstract: 6LoWPAN plays a major role within the protocol stack for the future Internet of Things. Its fragmentation mechanism enables transport of IPv6 datagrams with the required minimum MTU of 1280 bytes over 802.15.4-based networks. With the goal of a fully standardized WSN protocol stack currently necessitating a route-over approach, i.e., routing at the IP-layer, there are two main choices for any 6LoWPAN implementation with regard to datagram fragmentation: Hop-by-hop assembly or a cross-layered direct mode, which forwards individual 6LoWPAN fragments before the whole datagram has arrived. In addition to these two straightforward approaches, we propose enhancements based on adaptive rate-restriction for the direct forwarding and a retry control for both modes to reduce the number of losses of larger datagrams. An evaluation of these modes in a simulation environment and a hardware testbed indicate that the proposed enhancements can considerably improve PRR and latency within 6LoWPAN networks.
Christian Renner, Stefan Unterschütz, Volker Turau und Kay Römer. Perpetual Data Collection with Energy-Harvesting Sensor Networks. ACM Transactions on Sensor Networks, 11(12):1–12, November 2014.
@Article{Telematik_RUTR_2013_SCIS, author = {Christian Renner and Stefan Unterschütz and Volker Turau and Kay Römer}, title = {Perpetual Data Collection with Energy-Harvesting Sensor Networks}, pages = {1-12}, journal = {ACM Transactions on Sensor Networks}, volume = {11}, number = {12}, month = nov, year = 2014, }
Abstract: A sustainable, uniform, and utility-maximizing operation of energy-harvesting sensor networks requires methods for aligning consumption with harvest. This article presents a lightweight algorithm for online load adaptation of energy-harvesting sensor nodes using supercapacitors as energy buffers. The algorithm capitalizes on the elementary relationship between state of charge and voltage that is characteristic for supercapacitors. It is particularly designed to handle the nonlinear system model, and it is lightweight enough to run on low-power sensor node hardware. We define two energy policies, evaluate their performance using real-world solar-harvesting traces, and analyze the influence of the supercapacitor’s capacity and imprecisions in harvest forecasts. To show the practical merit of our algorithm, we devise a load adaptation scheme for multihop data collection sensor networks and run a 4-week field test. The results show that (i) choosing a duty cycle a priori is infeasible, (ii) our algorithm increases the achievable work load of a node when using forecasts, (iii) uniform and steady operation is achieved, and (iv) depletion can be prevented in most cases.
Christian Renner, Volker Turau und Kay Römer. Online Energy Assessment with Supercapacitors and Energy Harvesters. Sustainable Computing, Informatics and Systems, 4(1):10–23, März 2014.
@Article{Telematik_RTR_2013_SCIS, author = {Christian Renner and Volker Turau and Kay Römer}, title = {Online Energy Assessment with Supercapacitors and Energy Harvesters}, pages = {10-23}, journal = {Sustainable Computing, Informatics and Systems}, volume = {4}, number = {1}, month = mar, year = 2014, issn = {2210-5379}, }
Abstract: Combining energy harvesting with energy-aware load adaptation and scheduling enables perpetually operating sensor networks. The practical realization of this goal yet requires methods for reliable and precise holistic online energy assessment. While the building blocks - assessing residual energy, predicting energy intake, and tracing energy consumption - have been studied in detail, the analysis of their interaction on a real platform has been neglected. This paper answers the question, whether these techniques can be easily joined to give a precise and correct picture of a sensor node's energetic state and behavior. For this purpose, we model the energy flow of a prototype energy-harvesting and supercapacitor-powered sensor node. We show that in a real deployment simple supercapacitor models suffice for energy assessment, while capacity calibration is mandatory yet practicable. We evaluate the joint performance of state-of-the-art energy assessment based on an outdoor field test. We verify the system model and show the feasibility of holistic online energy assessment, which tolerates small configuration errors, achievable with a combination of generic configuration and online calibration. We analyze the feasibility of forecasting a node's future energy reserve and find that the presented method produces accurate results for uniformly distributed consumption profiles.
Volker Turau. Self-stabilizing Algorithms for Efficient Sets of Graphs and Trees. Information Processing Letters, 113(19-21):771–776, September 2013.
@Article{Telematik_T_2013_IPL, author = {Volker Turau}, title = {Self-stabilizing Algorithms for Efficient Sets of Graphs and Trees}, pages = {771-776}, journal = {Information Processing Letters}, volume = {113}, number = {19-21}, month = sep, year = 2013, issn = {0020-0190}, }
Abstract: This paper presents distributed self-stabilizing algorithms to compute the efficiency of trees and optimally efficient sets of general graphs.
Andreas Pfahl, Michael Randt, Carsten Holze und Stefan Unterschütz. Autonomous Light-Weight Heliostat with Rim Drives. Solar Energy, 92:230–240, Juni 2013.
@Article{Telematik_U_2013_HELIOMESH, author = {Andreas Pfahl and Michael Randt and Carsten Holze and Stefan Unterschütz}, title = {Autonomous Light-Weight Heliostat with Rim Drives}, pages = {230-240}, journal = {Solar Energy}, volume = {92}, month = jun, year = 2013, }
Julian Ohrt und Volker Turau. Cross-Platform Development Tools for Smartphone Applications. IEEE Computer, 45(9):72–79, September 2012.
@Article{Telematik_C-M_2012_SurveyOnXMTs, author = {Julian Ohrt and Volker Turau}, title = {Cross-Platform Development Tools for Smartphone Applications}, pages = {72-79}, journal = {IEEE Computer}, volume = {45}, number = {9}, month = sep, year = 2012, }
Abstract: Developers can use cross-platform mobile development tools to create smartphone apps that meet user expectations, but existing XMTs need improvement.
Christian Renner und Volker Turau. Adaptive Energy-Harvest Profiling to Enhance Depletion-Safe Operation and Efficient Task Scheduling. Sustainable Computing: Informatics and Systems, 2(1):43–56, März 2012.
@Article{Telematik_RT_2012_AdaptiveSlotting, author = {Christian Renner and Volker Turau}, title = {Adaptive Energy-Harvest Profiling to Enhance Depletion-Safe Operation and Efficient Task Scheduling}, pages = {43-56}, journal = {Sustainable Computing: Informatics and Systems}, volume = {2}, number = {1}, month = mar, year = 2012, issn = {2210-5379}, }
Abstract: Forecasting the expected energy harvest enables small-sized energy-harvesting sensor nodes to schedule tasks or adapt the radio duty cycle. This ability ensures depletion-safe and efficient operation. Most energy sources exhibit cyclic patterns of intensity, e.g., the sun. These patterns show periods with unequal--low versus high and stable versus varying--energy production and heavily depend on a node's location as well as seasonal and environmental changes. Existing forecast algorithms do not exploit these patterns, but create and update forecasts at static and arbitrary points in time, the main knob being the number of updates per cycle. We present a method enabling sensor nodes to adapt to harvesting patterns at runtime. It is designed for seamlessly replacing the static scheme to improve the accuracy of a wide range of existing forecast algorithms. In our evaluation, we show that (i) the adaptive method traces the energy pattern in real-world deployments accurately, (ii) reacts to seasonal and environmental changes, (iii) increases forecast accuracy, and (iv) reduces the number of prediction updates. These achievements enhance depletion-safe operation and efficient task scheduling with fewer recalculations and adjustments of the duty cycle. They also facilitate the exchange of harvesting forecasts for collaborative node tasks, since less information has to be shared.
Arne Bosien, Volker Turau und Franco Zambonelli. Approaches to Fast Sequential Inventory and Path Following in RFID-enriched environments. International Journal of Radio Frequency Identification Technology and Applications, 4(1):28–48, 2012.
@Article{Telematik_BTZ_2012_RFID, author = {Arne Bosien and Volker Turau and Franco Zambonelli}, title = {Approaches to Fast Sequential Inventory and Path Following in RFID-enriched environments}, pages = {28-48}, journal = {International Journal of Radio Frequency Identification Technology and Applications}, volume = {4}, number = {1}, year = 2012, }
Abstract: Although RFID is mostly used for ticketing, e-passports and supply chain management applications, the technology is also suitable for transponder based navigation systems. There it can be applied to leave a virtual trace on writeable RFID tags. These applications use RFID in a different way, because the tags are stationary and related to each other, since each tag of the path points to the following one. This offers the possibility to develop more efficient algorithms for their detection. In this paper, we suggest to store the identifying masks of subsequent tag IDs on the tags. The approach can easily be used with query-tree anti-collision methods. We examine the requirements for such an approach and describe a concrete algorithm, which is simulated and compared with different anti-collision algorithms.
Volker Turau. Efficient Transformation of Distance-2 Self-Stabilizing Algorithms. Journal of Parallel and Distributed Computing, 72(4):603–612, 2012.
@Article{Telematik_T_2012_JPDC, author = {Volker Turau}, title = {Efficient Transformation of Distance-2 Self-Stabilizing Algorithms}, pages = {603-612}, journal = {Journal of Parallel and Distributed Computing}, volume = {72}, number = {4}, year = 2012, issn = {0743-7315}, }
Abstract: Self-stabilizing algorithms for optimization problems can often be solved more easily using the distance-two model in which each vertex can instantly see the state information of all vertices up to distance two. This paper presents a new technique to emulate algorithms for the distance-two model on the distance-one model using the distributed scheduler with a slowdown factor of O(m) moves. Up until now the best transformer had a slowdown factor of O(n²m) moves. The technique is used to derive improved self-stabilizing algorithms for several graph domination problems. The paper also introduces a generalization of the distance-two model allowing a more space efficient transformer.
Sven Köhler und Volker Turau. Fault-containing self-stabilization in asynchronous systems with constant fault-gap. Distributed Computing, 25(3):207–224, 2012.
@Article{Telematik_KT_2011_DC, author = {Sven Köhler and Volker Turau}, title = {Fault-containing self-stabilization in asynchronous systems with constant fault-gap}, pages = {207-224}, journal = {Distributed Computing}, volume = {25}, number = {3}, year = 2012, issn = {0178-2770}, }
Abstract: This paper presents a new transformation which adds fault-containment properties to silent self-stabilizing algorithms. The transformation features a constant slow-down factor and the fault-gap—that is the minimal time between two containable faults—is also constant. The transformation scales well to arbitrarily large systems and avoids global synchronization. The presented transformation is the first with a constant fault-gap and requires no knowledge of the system size.
Volker Turau und Bernd Hauck. A new Analysis of a Self-Stabilizing Maximum Weight Matching Algorithm with Approximation Ratio 2. Theoretical Computer Science, 412(40):5527–5540, September 2011. Stabilization, Safety and Security.
@Article{Telematik_HT_2010_TCS_Matching, author = {Volker Turau and Bernd Hauck}, title = {A new Analysis of a Self-Stabilizing Maximum Weight Matching Algorithm with Approximation Ratio 2}, pages = {5527-5540}, journal = {Theoretical Computer Science}, volume = {412}, number = {40}, month = sep, year = 2011, keywords = {Self-stabilizing algorithms, approximation algorithm, weighted matching, distributed algorithms}, issn = {0304-3975}, note = {Stabilization, Safety and Security}, }
Abstract: The maximum weight matching problem is a fundamental problem in graph theory with a variety of important applications. Recently Manne and Mjelde presented the first self-stabilizing algorithm computing a 2-approximation of the optimal solution. They established that their algorithm stabilizes after O(2^n) (resp. O(3^n)) moves under a central (resp. distributed) scheduler. This paper contributes a new analysis improving these bounds considerably. In particular it is shown that the algorithm stabilizes after O(nm) moves under the central scheduler and that a modified version of the algorithm also stabilizes after O(nm) moves under the distributed scheduler. The paper presents a new proof technique based on graph reduction to analyze the complexity of self-stabilizing algorithms.
Volker Turau und Bernd Hauck. A fault-containing self-stabilizing (3 - 2/(Delta+1))-approximation algorithm for vertex cover in anonymous networks. Theoretical Computer Science, 412(33):4361–4371, 2011.
@Article{Telematik_HT_2011_TCSVC, author = {Volker Turau and Bernd Hauck}, title = {A fault-containing self-stabilizing (3 - 2/(Delta+1))-approximation algorithm for vertex cover in anonymous networks}, pages = {4361-4371}, journal = {Theoretical Computer Science}, volume = {412}, number = {33}, year = 2011, keywords = {Self-stabilizing algorithms, Fault tolerance, Distributed algorithms, Graph algorithms}, }
Abstract: The non-computability of many distributed tasks in anonymous networks is well known. This paper presents a deterministic self-stabilizing algorithm to compute a 3 - (2 / (Delta+1))-approximation of a minimum vertex cover in anonymous networks. The algorithm operates under the distributed unfair scheduler, stabilizes after O(n+m) moves respectively O(Delta) rounds, and requires O(log n) storage per node. Recovery from a single fault is reached within a constant time and the contamination number is O(Delta). For trees the algorithm computes a 2-approximation of a minimum vertex cover.
Volker Turau. Self-Stabilizing Vertex Cover in Anonymous Networks with Optimal Approximation Ratio. Parallel Processing Letters, 20(2):173–186, 2010.
@Article{Telematik_T_2010_PPL, author = {Volker Turau}, title = {Self-Stabilizing Vertex Cover in Anonymous Networks with Optimal Approximation Ratio}, pages = {173-186}, journal = {Parallel Processing Letters}, volume = {20}, number = {2}, year = 2010, }
Abstract: This paper presents a deterministic self-stabilizing algorithm that approximates a minimum vertex cover in anonymous networks with ratio 2 using the distributed scheduler and the link-register model with composite atomicity. No algorithm with a better approximation ratio can exist. The algorithm stabilizes in O(min{n, Δ², Δ log3 n}) rounds and requires O(Δ) memory per node.
Matthias Witt und Volker Turau. Robust and Low-Communication Geographic Routing for Wireless Ad Hoc Networks. Wireless Communications and Mobile Computing, 10(4):486–510, 2010.
@Article{Telematik_TW_2009_GeographicRouting, author = {Matthias Witt and Volker Turau}, title = {Robust and Low-Communication Geographic Routing for Wireless Ad Hoc Networks}, pages = {486-510}, journal = {Wireless Communications and Mobile Computing}, volume = {10}, number = {4}, year = 2010, }
Abstract: A novel beacon-less algorithm called Blind Geographic Routing (BGR) is presented, which comes with an effective and robust recovery strategy to circumvent voids, and a new technique to avoid simultaneous forwarding by more than one node, features not included in other beacon-less algorithms. BGR is the first beacon-less algorithm that also works in 3D topologies. Additionally, BGR supports different delivery semantics, which specify how close a node must be to the destination location in order to receive the message, and how many nodes shall receive it. These semantics allow for routing not only to designated nodes with network-wide known locations such as sinks, but to arbitrary destinations within the network area. It is shown through extensive simulation that BGR performs well even in the case of mobility, radio irregularity, and location errors, while GPSR as a beacon-based algorithm suffers from severe problems in realistic scenarios that do not follow the unit disk graph model, even with recent enhancements of the original GPSR algorithm.
Volker Turau und Bernd Hauck. A Self-Stabilizing Algorithm for Constructing Weakly Connected Minimal Dominating Sets. Information Processing Letters, 109(14):763–767, 2009.
@Article{Telematik_HT_2009_WCMDS, author = {Volker Turau and Bernd Hauck}, title = {A Self-Stabilizing Algorithm for Constructing Weakly Connected Minimal Dominating Sets}, pages = {763-767}, journal = {Information Processing Letters}, volume = {109}, number = {14}, year = 2009, keywords = {Self-stabilizing algorithms, Fault tolerance, Distributed algorithms, Graph algorithms}, issn = {0020-0190}, }
Abstract: This paper presents a new distributed self-stabilizing algorithm for the weakly connected minimal dominating set problem. It assumes a self-stabilizing algorithm to compute a breadth-first tree. Using an unfair distributed scheduler the algorithm stabilizes in at most O(nmA) moves, where A is the number of moves to construct a breadth-first tree. All previously known algorithms required an exponential number of moves.
Volker Turau und Christoph Weyer. Fault Tolerance in Wireless Sensor Networks through Self-Stabilization. International Journal of Communication Networks and Distributed Systems, 2(1):78–98, 2009.
@Article{Telematik_TW_2009_SelfStabilization, author = {Volker Turau and Christoph Weyer}, title = {Fault Tolerance in Wireless Sensor Networks through Self-Stabilization}, pages = {78-98}, journal = {International Journal of Communication Networks and Distributed Systems}, volume = {2}, number = {1}, year = 2009, }
Abstract: Wireless sensor networks (WSNs) suffer from resource limitations, high failure rates and faults caused by the lossy nature of wireless communication. This can lead to situations, where nodes lose synchrony and programs reach arbitrary states. Traditional approaches to fault tolerance like fault masking or global resets are not feasible for WSNs. Applying the concepts of self-stabilisation to achieve fault tolerance is a promising concept. However, the majority of self-stabilising algorithms found in the literature is based on models not suitable for WSNs. This paper proposes a problem-independent transformation for algorithms that stabilise under the central daemon scheduler such that they meet the demands of a WSN. Furthermore, a comparison with transformers from the literature is made through a series of simulations. Finally, the proposed transformer is evaluated with a real sensor network in a field test.
Norbert Luttenberger, Stefan Fischer, Erik Mähle, Dirk Timmermann und Volker Turau. Multi-hybride Sensornetze. PIK - Praxis der Informationsverarbeitung und Kommunikation, 31(3):141–145, 2008.
@Article{Telematik_LFMTT_2008_MultiHybrideSensornetze, author = {Norbert Luttenberger and Stefan Fischer and Erik Mähle and Dirk Timmermann and Volker Turau}, title = {Multi-hybride Sensornetze}, pages = {141-145}, journal = {PIK - Praxis der Informationsverarbeitung und Kommunikation}, volume = {31}, number = {3}, year = 2008, }
Volker Turau. Linear Self-Stabilizing Algorithms for the Independent and Dominating Set Problems using an Unfair Distributed Scheduler. Information Processing Letters., 103(3):88–93, Juli 2007.
@Article{Telematik_TT_2007_Selfstabilizing, author = {Volker Turau}, editor = {A. Tarlecki}, title = {Linear Self-Stabilizing Algorithms for the Independent and Dominating Set Problems using an Unfair Distributed Scheduler}, pages = {88-93}, journal = {Information Processing Letters.}, volume = {103}, number = {3}, month = jul, year = 2007, }
Abstract: This paper presents distributed self-stabilizing algorithms for the maximal independent and the minimal dominating set problems. Using an unfair distributed scheduler the algorithms stabilizes in at most max{3n-5,2n} resp. 9n moves. All previously known algorithms required O(n2) moves.
James E. Johnson, David E. Langworthy, Leslie Lamport und Friedrich H. Vogt. Formal Specification of a Web Services Protocol. Journal of Logic and Algebraic Programming, 70(1):34–52, 2007.
@Article{Telematik_JLLV_2007_Formal, author = {James E. Johnson and David E. Langworthy and Leslie Lamport and Friedrich H. Vogt}, title = {Formal Specification of a Web Services Protocol}, pages = {34-52}, journal = {Journal of Logic and Algebraic Programming}, volume = {70}, number = {1}, year = 2007, }
Abstract: We describe a use of formal methods to specify and check a Web Services protocol. The Web Services Atomic Transaction protocol was specified in TLA+ and checked with the TLC model checker. A modest effort revealed oversights that caused unanticipated behaviors of the protocol; these were corrected by clarifications and changes to the protocol.
Volker Turau, Christoph Weyer und Matthias Witt. Ein robustes Datenmonitoring-Verfahren für Sensornetzwerke. it - Information Technology, 47(2):63–69, April 2005.
@Article{Telematik_TWW_2005_Datenmonitoring, author = {Volker Turau and Christoph Weyer and Matthias Witt}, editor = {Christian Becker and Pedro José Marrón}, title = {Ein robustes Datenmonitoring-Verfahren für Sensornetzwerke}, pages = {63-69}, journal = {it - Information Technology}, volume = {47}, number = {2}, month = apr, year = 2005, }
Abstract: A new data monitoring method for wireless sensor networks is introduced. The method combines geographic hash tables with in-network aggregation. Queries are processed in regions, whose sensor nodes collect their values in nodes close to a determinated location within the region, where they can easily be requested from outside. The method is robust against node failures and movements and generates very little network traffic. This is confirmed by various simulations.

Konferenzbeiträge

Volker Turau. Computing the Fault-Containment-Time of Self-Stabilizing Algorithms using Markov Chains and Lumping. In Stabilization, Safety, and Security of Distributed Systems - 19th International Symposium(SSS 2017), November 2017, pp. 62–77. Boston, USA.
@InProceedings{Telematik_SSS_2017, author = {Volker Turau}, title = {Computing the Fault-Containment-Time of Self-Stabilizing Algorithms using Markov Chains and Lumping}, booktitle = {Stabilization, Safety, and Security of Distributed Systems - 19th International Symposium(SSS 2017)}, pages = {62-77}, day = {5-8}, month = nov, year = 2017, location = {Boston, USA}, }
Abstract: The analysis of self-stabilizing algorithms is in the vast majority of all cases limited to the worst case stabilization time starting from an arbitrary configuration. Considering the fact that these algorithms are intended to provide fault tolerance in the long run this is not the most relevant metric. From a practical point of view the worst case time to recover in case of a single fault is much more crucial. This paper presents techniques to derive upper bounds for the mean time to recover from a single fault for self-stabilizing algorithms Markov chains in combination with lumping. To illustrate the applicability of the techniques they are applied to a self-stabilizing coloring algorithm.
Tobias Lübkert, Marcus Venzke und Volker Turau. Appliance Commitment for Household Load Scheduling Algorithm: A Critical Review. In 2017 IEEE International Conference on Smart Grid Communications (SmartGridComm), accepted for publication, Oktober 2017. Dresden, Germany.
@InProceedings{Telematik_SGC_2017, author = {Tobias Lübkert and Marcus Venzke and Volker Turau}, title = {Appliance Commitment for Household Load Scheduling Algorithm: A Critical Review}, booktitle = {2017 IEEE International Conference on Smart Grid Communications (SmartGridComm), accepted for publication}, pages = , day = {23-26}, month = oct, year = 2017, location = {Dresden, Germany}, }
Maximilian Köstler und Florian Kauer. A Remote Interface for Live Interaction with OMNeT++ Simulations. In Proceedings of the 4th OMNeT++ Community Summit 2017, September 2017. Bremen, Germany.
@InProceedings{Telematik_OMNETPP_2017, author = {Maximilian Köstler and Florian Kauer}, title = {A Remote Interface for Live Interaction with OMNeT++ Simulations}, booktitle = {Proceedings of the 4th OMNeT++ Community Summit 2017}, number = {arXiv:1709.02822}, day = {07-08}, month = sep, year = 2017, location = {Bremen, Germany}, }
Abstract: Discrete event simulators, such as OMNeT++, provide fast and convenient methods for the assessment of algorithms and protocols, especially in the context of wired and wireless networks. Usually, simulation parameters such as topology and traffic patterns are predefined to observe the behaviour reproducibly. However, for learning about the dynamic behaviour of a system, a live interaction that allows changing parameters on the fly is very helpful. This is especially interesting for providing interactive demonstrations at conferences and fairs. In this paper, we present a remote interface to OMNeT++ simulations that can be used to control the simulations while visualising real-time data merged from multiple OMNeT++ instances. We explain the software architecture behind our framework and how it can be used to build demonstrations on the foundation of OMNeT++.
Florian Kauer, Florian Meyer und Volker Turau. A Holistic Solution for Reliable Over-the-Air Software Updates in Large Industrial Plants. In Proceedings of the 13th Workshop on Intelligent Solutions in Embedded Systems (WISES 2017), Juni 2017. Hamburg, Germany.
@InProceedings{Telematik_WISES_2017, author = {Florian Kauer and Florian Meyer and Volker Turau}, title = {A Holistic Solution for Reliable Over-the-Air Software Updates in Large Industrial Plants}, booktitle = {Proceedings of the 13th Workshop on Intelligent Solutions in Embedded Systems (WISES 2017)}, pages = , day = {12-13}, month = jun, year = 2017, location = {Hamburg, Germany}, }
Abstract: In cyber-physical systems, such as modern industrial plants, complex software is an essential part that enables cost-effective and flexible operation. However, this complexity increases the probability of problems that only reveal themselves after the deployment. This is even more important if security aspects are involved. Therefore, providing the possibility for software updates is an important building block in the design of industrial plants. This paper presents a holistic concept for software updates in an industrial plant with thousands of wirelessly connected embedded devices. Using wireless technology imposes additional difficulties in terms of data rate, packet size and reliability that have to be addressed in particular. The contribution also includes an analytical model to estimate the time until a new firmware is distributed. Evaluations carried out on hardware as well as in the OMNeT++ simulator demonstrate the applicability and scalability of the proposed approach.
Volker Turau und Gerry Siegemund. Scalable Routing for Topic-based Publish/Subscribe Systems under Fluctuations. In Proceedings of International Conference on Distributed Computing Systems - ICDCS 2017, Juni 2017, pp. 1608–1617. Atlanta, USA.
@InProceedings{Telematik_ICDS_2017, author = {Volker Turau and Gerry Siegemund}, title = {Scalable Routing for Topic-based Publish/Subscribe Systems under Fluctuations}, booktitle = {Proceedings of International Conference on Distributed Computing Systems - ICDCS 2017}, pages = {1608-1617}, day = {5-8}, month = jun, year = 2017, location = {Atlanta, USA}, }
Abstract: The loose coupling and the inherent scalability make publish/subscribe systems an ideal candidate for event-driven services for wireless networks using low power protocols such as IEEE 802.15.4. This work introduces a distributed algorithm to build and maintain a routing structure for such networks.The algorithm dynamically maintains a multicast tree for each node. While previous work focused on minimizing these trees we aim to keep the effort to maintain them in case of fluctuations of subscribers low. The multicast trees are implicitly defined by a novel structure called augmented virtual ring. The main contribution is a distributed algorithm to build and maintain this augmented virtual ring. Maintenance operations after sub-and unsubscriptions require message exchange in a limited region only. We compare the average lengths of the constructed forwarding paths with an almost ideal approach. As a result of independent interest we present a distributed algorithm using messages of size O(logn) for constructing virtual rings of graphs that are on average shorter than rings based on depth first search.
Florian Kauer, Maximilian Köstler, Tobias Lübkert und Volker Turau. OpenDSME - A Portable Framework for Reliable Wireless Sensor and Actuator Networks (Demonstration). In Proceedings of the 3rd International Conference on Networked Systems (NetSys 2017), März 2017. Göttingen, Germany.
@InProceedings{Telematik_Netsys_2017, author = {Florian Kauer and Maximilian Köstler and Tobias Lübkert and Volker Turau}, title = {OpenDSME - A Portable Framework for Reliable Wireless Sensor and Actuator Networks (Demonstration)}, booktitle = {Proceedings of the 3rd International Conference on Networked Systems (NetSys 2017)}, day = {13-16}, month = mar, year = 2017, location = {Göttingen, Germany}, }
Abstract: The Deterministic and Synchronous Multi-Channel Extension (DSME) of the IEEE 802.15.4 standard provides a data link layer for time division multiple access in wireless mesh networks. The authors present openDSME, a portable implementation for hardware and simulators which promises reliable message transfer suitable for applications in demanding industrial environments. A demonstration has been developed to illustrate the performance of openDSME in a simulated network and to show its benefits over CSMA/CA.
Gerry Siegemund und Volker Turau. PSVR - Self-Stabilizing Publish/Subscribe Communication for Ad-Hoc Networks (Short Paper). In Proceedings of Stabilization, Safety, and Security of Distributed Systems - 18th International Symposium, November 2016, pp. 346–351. Lyon, France.
@InProceedings{Telematik_SSS_2016, author = {Gerry Siegemund and Volker Turau}, title = {PSVR - Self-Stabilizing Publish/Subscribe Communication for Ad-Hoc Networks (Short Paper)}, booktitle = {Proceedings of Stabilization, Safety, and Security of Distributed Systems - 18th International Symposium}, pages = {346-351}, day = {7-10}, month = nov, year = 2016, location = {Lyon, France}, }
Abstract: PSVR is a novel routing algorithm for pub/sub systems in ad-hoc networks focusing on scenarios where communications links are unstable and nodes frequently change subscriptions. It is a compromise of size and maintenance effort for routing tables due to sub- and unsubscriptions and the length of routing paths. Designed in a self-stabilizing manner it scales well with network size. The evaluation with real world deployment reveals that PSVR only needs slightly more messages than a close to optimal routing structure for publication delivery, and creates shorter routing paths than an existing self-stabilizing algorithm.
Florian Kauer, Maximilian Köstler, Tobias Lübkert und Volker Turau. Formal Analysis and Verification of the IEEE 802.15.4 DSME Slot Allocation. In Proceedings of the 19th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems, November 2016, pp. 140–147. Malta.
@InProceedings{Telematik_MSWIM_Formal_DSME, author = {Florian Kauer and Maximilian Köstler and Tobias Lübkert and Volker Turau}, title = {Formal Analysis and Verification of the IEEE 802.15.4 DSME Slot Allocation}, booktitle = {Proceedings of the 19th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems}, pages = {140-147}, month = nov, year = 2016, location = {Malta}, }
Abstract: Providing dependability is still a major issue for wireless mesh networks, which restrains their application in industrial contexts. The widespread CSMA/CA medium access can provide high throughput and low latency, but can not prevent packet loss due to collisions, especially in very large and dense networks. Time slotted medium access techniques together with a distributed slot management, as proposed by the Distributed Synchronous Multi-channel Extension (DSME) of the IEEE 802.15.4 standard, are promising to provide low packet loss, high scalability and bounded end-to-end delays. However, our implementation, openDSME, exposed some weaknesses. While the allocated slots allow for reliable data transmission, the slot management itself is conducted via CSMA/CA and is thus vulnerable to packet loss, eventually leading to an inconsistent slot allocation. This paper uses the UPPAAL framework for formal analysis and verification of the slot management process. The analysis identifies weaknesses of the slot allocation process under communication and node failures. However, it is shown that inconsistencies are eventually resolved and improvements to the procedure are proposed that reduce the negative impact of failed slot allocation procedures significantly.
Stefan Lohs, Gerry Siegemund, Jörg Nolte und Volker Turau. Self-Stabilization - A Mechanism to Make Networked Embedded Systems More Reliable?. In Proceedings of 35th Symposium on Reliable Distributed Systems (SRDS), September 2016, pp. 317–326. Budapest, Hungary.
@InProceedings{Telematik_SRDS_2016, author = {Stefan Lohs and Gerry Siegemund and Jörg Nolte and Volker Turau}, title = {Self-Stabilization - A Mechanism to Make Networked Embedded Systems More Reliable?}, booktitle = {Proceedings of 35th Symposium on Reliable Distributed Systems (SRDS)}, pages = {317-326}, day = {26-29}, month = sep, year = 2016, location = {Budapest, Hungary}, }
Abstract: The erratic behavior of wireless channels is still a major hurdle in the implementation of robust applications in wireless networks. In the past it has been argued that self-stabilization is a remedy to provide the needed robustness. This assumption has not been verified to the extent necessary to convince engineers implementing such applications. A major reason is that the time in which a self-stabilizing system returns to a valid state is unpredictable and potentially unbound. Failure rates typically depend on physical phenomena and in self-stabilizing systems each node tries to react to failures in an inherently adaptive fashion by the cyclic observation of its neighbors' states. When the frequency of state changes is too high, the system may never reach a state sufficiently stable for a specific task. In this paper we substantiate the conditions under which self-stabilization leads to fault tolerance in wireless networks and look at the myths about the power of self-stabilization as a particular instance of self-organization. We investigate the influences of the error rate and the neighbor state exchange rate on the stability and the convergence time on topology information acquired in real network experiments.
Maximilian Köstler, Florian Kauer, Tobias Lübkert und Volker Turau. Towards an Open Source Implementation of the IEEE 802.15.4 DSME Link Layer. In Proceedings of the 15. GI/ITG KuVS Fachgespräch Sensornetze, University of Applied Sciences Augsburg, Dept. of Computer Science, September 2016. Augsburg, Germany.
@InProceedings{Telematik_FGSN_openDSME, author = {Maximilian Köstler and Florian Kauer and Tobias Lübkert and Volker Turau}, editor = {Juergen Scholz and Alexander von Bodisco}, title = {Towards an Open Source Implementation of the IEEE 802.15.4 DSME Link Layer}, booktitle = {Proceedings of the 15. GI/ITG KuVS Fachgespräch Sensornetze}, pages = , publisher = {University of Applied Sciences Augsburg, Dept. of Computer Science}, day = {22-23}, month = sep, year = 2016, location = {Augsburg, Germany}, }
Abstract: Reliable wireless solutions for large-scale automation are a major challenge today. The IEEE 802.15.4 standard forms the basis for many open and proprietary implementations. To reflect current state-of-the-art techniques, the IEEE has amended standard 802.15.4 with new MAC-layers such as TSCH, which resembles WirelessHART, and the Deterministic and Synchronous Multi-Channel Extension (DSME). This paper introduces openDSME, our implementation of IEEE 802.15.4 DSME. DSME aims at preventing packet collisions through slot reservation in networks where conventional CSMA/CA is not reliable enough. In this document, we will outline core features of DSME and openDSME, and present details of our implementation. Additionally, current research efforts on connected topics will be highlighted.
Stefan Lohs, Jörg Nolte, Gerry Siegemund und Volker Turau. Influence of Topology-Fluctuations on Self-Stabilizing Algorithms. In 2016 International Conference on Distributed Computing in Sensor Systems DCOSS 2016 Poster Abstract, Mai 2016, pp. 122–124. Washington, DC, USA.
@InProceedings{DCOSS_POSTER_2016, author = {Stefan Lohs and Jörg Nolte and Gerry Siegemund and Volker Turau}, title = {Influence of Topology-Fluctuations on Self-Stabilizing Algorithms}, booktitle = {2016 International Conference on Distributed Computing in Sensor Systems DCOSS 2016 Poster Abstract}, pages = {122-124}, day = {26-28}, month = may, year = 2016, location = {Washington, DC, USA}, }
Abstract: Self-stabilizing systems have in theory the unique and provable ability, to always return to a valid system state even in the face of failures. These properties are certainly desirable for domains like wireless ad-hoc networks with numerous unpredictable faults. Unfortunately, the time in which the system returns to a valid state is not predictable and potentially unbound. The failure rate typically depends on physical phenomena and in self-stabilizing systems each node tries to react to failures in an inherently adaptive fashion by the cyclic observation of the states of its neighbors. When state changes are either too quick or too slow the system might never reach a state that is sufficiently stable for a specific task. In this paper, we investigate the influences of the error rate on the (stability) convergence time on the basis of topology information acquired in real network experiments. This allows us to asses the asymptotic behavior of relevant self-stabilizing algorithms in typical wireless networks.
Volker Turau und Christoph Weyer. Cascading Failures Caused by Node Overloading in Complex Networks. In Proceedings of the Joint Workshop on Cyber-Physical Security and Resilience in Smart Grids, April 2016, pp. 1–6. Vienna, Austria.
@InProceedings{Telematik_CPSR-SG2016_SmartGrid, author = {Volker Turau and Christoph Weyer}, title = {Cascading Failures Caused by Node Overloading in Complex Networks}, booktitle = {Proceedings of the Joint Workshop on Cyber-Physical Security and Resilience in Smart Grids}, pages = {1-6}, day = {12}, month = apr, year = 2016, location = {Vienna, Austria}, }
Abstract: It is well known that complex networks are vulnerable to the failure of hubs in terms of structural robustness. An as yet less researched topic is dynamical robustness, which refers to the ability of a network to maintain its dynamical activity against local disturbances. This paper analyzes the impact of overload attacks in complex networks and gives a precise definition of this type of attack using the load redistribution model. The main contribution is a greedy algorithm to select a small number of candidates for an overload attack maximizing the impact with respect to the number of failed nodes and load increase. The quality of the algorithm is analyzed for a real power grid network.
Florian Meier. Ph.D. Forum Abstract: Scalable Wireless Networks for Industrial Control Systems with Time and Reliability Constraints. In Proceedings of the 15th ACM/IEEE Conference on Information Processing in Sensor Networks, April 2016. Vienna, Austria.
@InProceedings{Telematik_IPSN_Meier_PhD_Forum, author = {Florian Meier}, title = {Ph.D. Forum Abstract: Scalable Wireless Networks for Industrial Control Systems with Time and Reliability Constraints}, booktitle = {Proceedings of the 15th ACM/IEEE Conference on Information Processing in Sensor Networks}, pages = , day = {11}, month = apr, year = 2016, location = {Vienna, Austria}, }
Abstract: Using wireless communication instead of laying cables promises high cost savings in many applications. Motivated by the intended deployment of wireless networks in solar tower power plants with up to hundreds of thousands of possible clients, this research shall explore the limits of large-scale wireless networks. Apart from the pure number of supported clients, maintaining reliability and time-bounded communication is a key requirement for such industrial control systems.
Marcus Venzke und Volker Turau. Simulative Evaluation of Demand Response Approaches for Waterbeds. In Proceedings of the 2016 IEEE International Energy Conference (ENERGYCON), April 2016. Leuven, Belgium.
@InProceedings{Telematik_EnergyCon_2016_SimulationDemandResponseWaterbed, author = {Marcus Venzke and Volker Turau}, title = {Simulative Evaluation of Demand Response Approaches for Waterbeds}, booktitle = {Proceedings of the 2016 IEEE International Energy Conference (ENERGYCON)}, pages = , day = {4-8}, month = apr, year = 2016, location = {Leuven, Belgium}, }
Abstract: This paper quantitatively compares five demand response (DR) approaches for waterbeds using simulation. The approaches enable privacy by design with a local control and contribute to the planning phase of the electricity network’s balancing process. Approaches are assessed by their energy consumption, their ability to shift power consumption to times of high availability, and the effort of realization and configuration. Load steps were identified as a risk for power network stability. A classification of DR methods, based on the position of their contribution within the electricity network’s balancing process, is used to distinguish our approach from the DR approaches found in the literature.
Andreas Weigel und Volker Turau. Hardware-Assisted IEEE 802.15.4 Transmissions and Why to Avoid Them. In Conference proceedings of the 8th International Conference on Internet and Distributed Computer Systems, IDCS 2015, September 2015, pp. 223–234. Windsor, UK.
@InProceedings{Telematik_IDCS_2015_6LoWPAN, author = {Andreas Weigel and Volker Turau}, title = {Hardware-Assisted IEEE 802.15.4 Transmissions and Why to Avoid Them}, booktitle = {Conference proceedings of the 8th International Conference on Internet and Distributed Computer Systems, IDCS 2015}, pages = {223-234}, day = {2-4}, month = sep, year = 2015, location = {Windsor, UK}, }
Abstract: 6LoWPAN’s fragmentation mechanism enables transport of IPv6 datagrams with the required minimum MTU of 1280 bytes over IEEE 802.15.4-based networks. Testbed experiments showed disastrously bad datagram success rates for a collection traffic scenario with large, 6LoWPAN-fragmented datagrams, which significantly differed from the simulation results for a comparable scenario. In this paper we present an experimental setup that enables capturing the MAC and transceiver states of participating nodes in realtime. The results of our experiments show, that for the given fragmentation/collection scenario, the usage of the extended operating mode of the transceiver hardware, which provides CSMA/CA, ACKs and retransmissions in hardware, is responsible for nearly all datagram losses. Therefore, we strongly advise against using such hardware-assisted modes of operation in similar traffic scenarios.
Sandra Beyer, Stefan Lohs, Jörg Nolte, Reinhardt Karnapke und Gerry Siegemund. Self-Stabilizing Structures for Data Gathering in Wireless Sensor Networks. In Proceedings of the International Conference on Sensor Technologies and Applications (Sensorcomm), August 2015, pp. 1–8. Venice, Italy.
@InProceedings{Cottbus_Sensorcomm_2015, author = {Sandra Beyer and Stefan Lohs and Jörg Nolte and Reinhardt Karnapke and Gerry Siegemund}, title = {Self-Stabilizing Structures for Data Gathering in Wireless Sensor Networks}, booktitle = {Proceedings of the International Conference on Sensor Technologies and Applications (Sensorcomm)}, pages = {1-8}, month = aug, year = 2015, location = {Venice, Italy}, }
Abstract: Wireless Sensor Networks (WSN) enable a number of applications, with monitoring of habitats, office buildings, or restricted areas most prominent among them. All of these applications have one thing in common: the need to commu- nicate. However, the nature of the wireless medium results in quite a few problems. Lossy communication links with transient faults require acknowledgments, retransmissions, and route re- pair mechanisms. Tree- or similar structures for data gathering scenarios lead to increased load closer to the sink, with congestion, higher buffer space requirements, and energy drain as results. The second problem is often addressed by aggregation and reduction schemes. These schemes are bound to fail, however, when the underlying structure is compromised due to changes in the connectivity between nodes. Therefore, it is necessary to focus on the structures first of all. We address the problem of transient faults by using the inherent fault tolerance of self- stabilizing algorithms when building and using tree- or tiers (communication-) structures. In this paper we show that self- stabilizing structures are suitable for data gathering scenarios in WSN by comparison of the connectivity achieved by our self- stabilizing tiers algorithm and the tree algorithm from Dolev with that of Collection Tree Protocol (CTP), the standard data- gathering protocol for TinyOS.
Gerry Siegemund, Volker Turau und Christoph Weyer. A Dynamic Topology Control Algorithm for Wireless Sensor Networks. In Proceedings of the International Conference on Ad-hoc, Mobile and Wireless Networks, ADHOC-NOW 2015, Juni 2015, pp. 3–18. Athens, Greece.
@InProceedings{Telematik_Adhoc-Now_2015, author = {Gerry Siegemund and Volker Turau and Christoph Weyer}, title = {A Dynamic Topology Control Algorithm for Wireless Sensor Networks}, booktitle = {Proceedings of the International Conference on Ad-hoc, Mobile and Wireless Networks, ADHOC-NOW 2015}, pages = {3-18}, month = jun, year = 2015, location = {Athens, Greece}, }
Abstract: Topology control algorithms (TCAs) are used in wireless sensor networks to reduce interference by carefully choosing communication links. Since the quality of the wireless channel is subject to fluctuations over time TCAs must repeatedly recompute the topology. TCAs ensure quick adjustment to new or deteriorating links while preventing precipitant changes due to transient faults. This paper contributes a novel dynamic TCA that provides a compromise between agility and stability, and constructs connected topologies for low latency routing. Furthermore, it enforces memory restrictions and is of high practical relevance for real sensor network hardware.
Marcus Venzke und Volker Turau. A demand response approach locally implementable for waterbeds. In Proceedings of 1st Workshop on Middleware for a Smarter Use of Electric Energy (MidSEE’15), März 2015, pp. 1–6. Cottbus, Germany.
@InProceedings{Telematik_VT_2015_DemandResponseWaterbed, author = {Marcus Venzke and Volker Turau}, title = {A demand response approach locally implementable for waterbeds}, booktitle = {Proceedings of 1st Workshop on Middleware for a Smarter Use of Electric Energy (MidSEE’15)}, pages = {1-6}, day = {12}, month = mar, year = 2015, location = {Cottbus, Germany}, }
Abstract: The paper presents a demand response scheme for waterbeds that can be implemented in practice today. It balances the requirements of saving energy and shifting power to times with higher power availability by planning heating phases to minimize costs according to a virtual electricity tariff derived from trading prices of an electricity exchange. The approach was successfully validated with a real waterbed under real conditions.
Florian Meier und Volker Turau. An Analytical Model for Fast and Verifiable Assessment of Large Scale Wireless Mesh Networks. In Proceedings of the Design of Reliable Communication Networks (DRCN), März 2015, pp. 185–190. Kansas City, MO, USA.
@InProceedings{Telematik_DRCN_Model, author = {Florian Meier and Volker Turau}, title = {An Analytical Model for Fast and Verifiable Assessment of Large Scale Wireless Mesh Networks}, booktitle = {Proceedings of the Design of Reliable Communication Networks (DRCN)}, pages = {185-190}, month = mar, year = 2015, location = {Kansas City, MO, USA}, }
Abstract: Ensuring reliability is a key requirement for using wireless mesh networks in industrial applications. Analytical models provide a valuable support in the design of reliable networks, especially for large scale applications, where simulations do not provide the required scalability. This paper proposes an analytical model for multi-hop IEEE 802.15.4 networks that incorporates significant improvements compared to previous models. Comparisons of the model with simulations using the MiXiM framework for OMNeT++ exhibit a very good compliance. The analytical model is therefore adequate for assessment of very large wireless mesh networks. Additionally, the model yields new insights into the characteristics of IEEE 802.15.4 networks, regarding the impact of acknowledgment collisions and the influence of hidden nodes on retransmissions.
Gerry Siegemund, Volker Turau und Khaled Maâmra. A Self-stabilizing Publish/Subscribe Middleware for Wireless Sensor Networks. In Proceedings of the International Conference on Networked Systems (NetSys), März 2015, pp. 1–8. Cottbus, Germany.
@InProceedings{Telematik_NetSys_2015, author = {Gerry Siegemund and Volker Turau and Khaled Maâmra}, title = {A Self-stabilizing Publish/Subscribe Middleware for Wireless Sensor Networks}, booktitle = {Proceedings of the International Conference on Networked Systems (NetSys)}, pages = {1-8}, month = mar, year = 2015, location = {Cottbus, Germany}, }
Abstract: This paper presents a scalable, self-stabilizing middleware for channel-based publish/subscribe systems for wireless sensor networks. The middleware eventually provides safety and liveness properties such as the guaranteed delivery of all published messages to all subscribers of the corresponding channel and the correct handling of subscriptions and unsubscriptions, while no error occurs. We consider transient message and memory corruptions and also respect dynamic network changes such as node and link removals and additions. We assume the message passing model and guarantee delivery of publications to new subscribers after O(n) steps.
Maciej Muehleisen, Marcus Venzke, Christoph Petersen, Andreas Timm-Giel und Volker Turau. Reliable Transmission of Aircraft Data over Satellite. In Proceedings of the 5th International Workshop on Aircraft System Technologies (AST 2015), Februar 2015. Hamburg, Germany.
@InProceedings{Telematik_Ast_Workshop_2015, author = {Maciej Muehleisen and Marcus Venzke and Christoph Petersen and Andreas Timm-Giel and Volker Turau}, title = {Reliable Transmission of Aircraft Data over Satellite}, booktitle = {Proceedings of the 5th International Workshop on Aircraft System Technologies (AST 2015)}, month = feb, year = 2015, location = {Hamburg, Germany}, }
Abstract: After almost two years to recover the flight data recorder of Air France Flight 447 and, by January 2015, still no sign of Malaysian Airlines Flight 370, the public and media ask the question: "How is it possible to have almost worldwide Internet access in the cabin but not being able to track the position of an aircraft?" One answer to the question is that the passenger pays for Internet access in the cabin while the airline would have to pay for transmission of sensor data, such as the aircraft position. Furthermore Internet access in the cabin is offered on a best effort basis without any guarantees with regard to delay, throughput and loss rate. In this paper we present a simple system capable of transmitting critical data to the ground and evaluate the statistical distribution of the end-to-end delay a transmitted data packet encounters. Signal Flow Graphs are used to systematically model the transmission system with regard to delays encountered by a packet, including those caused by retransmissions of lost data. Results for the Inmarsat-4 Broadband Global Area Network (BGAN) service are derived, but the method is applicable to many other transmission systems.
Brahim Negazzi, Volker Turau, Mohammed Haddad und Hamamache Kheddouci. A Self-Stabilizing Algorithm for Edge Monitoring Problem. In Proceedings of the 16th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'14), September 2014, pp. 93–105. Paderborn, Germany.
@InProceedings{Telematik_SSS_2014_Edge_Monitoring_Problem, author = {Brahim Negazzi and Volker Turau and Mohammed Haddad and Hamamache Kheddouci}, title = {A Self-Stabilizing Algorithm for Edge Monitoring Problem}, booktitle = {Proceedings of the 16th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'14)}, pages = {93-105}, day = {28-30}, month = sep, year = 2014, location = {Paderborn, Germany}, }
Abstract: Self-monitoring is a simple and effective mechanism for the security of wireless sensor networks(WSNs), especially to cope against compromised nodes. A node v can monitor an edge e if both end-nodes of e are neighbors of v: i.e., e together with v forms a triangle in the graph. Moreover, some edges need more than one monitor. Finding a set of monitoring nodes satisfying all monitoring constraints is called the edge-monitoring problem. The minimum edge-monitoring problem is long known to be NP-complete. In this paper, we present a novel silent self-stabilizing algorithm for computing a minimal edge-monitoring set. Correctness and termination are proven for the unfair distributed daemon.
Gerry Siegemund, Volker Turau und Khaled Maâmra. Brief Announcement: Publish/Subscribe on Virtual Rings. In Proceedings of the 16th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'14), September 2014, pp. 343–345. Paderborn, Germany.
@InProceedings{Telematik_SSS_2014_Virtual_Ring, author = {Gerry Siegemund and Volker Turau and Khaled Maâmra}, title = {Brief Announcement: Publish/Subscribe on Virtual Rings}, booktitle = {Proceedings of the 16th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'14)}, pages = {343-345}, day = {28-30}, month = sep, year = 2014, location = {Paderborn, Germany}, }
Abstract: This paper introduces a scalable, self-stabilizing, channel-based publish/subscribe system for wireless sensor networks. As base structure a virtual ring is maintained. We consider message and memory corruptions and also respect dynamic network changes, such as, node and link removals and additions.
Andreas Pfahl, Michael Randt, Florian Meier, Martin Zaschke, C.P.W. Geurts und Michael Buselmeier. A Holistic Approach for Low Cost Heliostat Fields. In Proceedings of the SolarPACES 2014, September 2014. Beijing, China.
@InProceedings{Telematik_SolarPACES_HolisticHeliostatFields, author = {Andreas Pfahl and Michael Randt and Florian Meier and Martin Zaschke and C.P.W. Geurts and Michael Buselmeier}, title = {A Holistic Approach for Low Cost Heliostat Fields}, booktitle = {Proceedings of the SolarPACES 2014}, month = sep, year = 2014, location = {Beijing, China}, }
Abstract: The AutoR-project takes a holistic approach to reduce the cost of heliostat fields: Wireless control and energy supply enables to use smaller heliostats which need less steel per mirror area (but usually have high wiring cost). A low cost but high efficient drive system is chosen which reduces energy consumption to a minimum amount and leads to low cost for PV cell and energy storage. The usual boundary layer wind tunnels tests for heliostats are proven regarding energy spectra to avoid oversizing of steel structure and drives or failures because of underestimations of the loads. The concepts for wireless control and energy supply, the wind tunnel investigations and the first rim drive heliostat prototype are presented.
Shrirang Abhyankar, Jed Brown, Matthew Knepley, Florian Meier und Barry Smith. Poster Abstract: Abstractions for Expressing Network Problems in PETSc. In SIAM Workshop on Network Science, Juli 2014. Chicago, US.
@InProceedings{SIAM_PETSc, author = {Shrirang Abhyankar and Jed Brown and Matthew Knepley and Florian Meier and Barry Smith}, title = {Poster Abstract: Abstractions for Expressing Network Problems in PETSc}, booktitle = {SIAM Workshop on Network Science}, month = jul, year = 2014, location = {Chicago, US}, }
Abstract: Developing scalable software for large-scale applications, particularly for networks and circuits, is challenging due to the underlying unstructured and irregular geometry of the problem. We present a programming framework recently added to the PETSc library to easily express network problems, and thereby reduce the application development time. A brief overview of the framework is presented and two application examples, one from power grid and the other from radio networks, are discussed.
Andreas Weigel und Volker Turau. An Analytical Model of 6LoWPAN Route-Over Forwarding Practices. In Conference proceedings of the International Conference on Ad-hoc, Mobile and Wireless Networks, ADHOC-NOW 2014, Juni 2014, pp. 279–289. Benidorm, Spain.
@InProceedings{Telematik_AdHocNow_2014_6LoWPAN, author = {Andreas Weigel and Volker Turau}, title = {An Analytical Model of 6LoWPAN Route-Over Forwarding Practices}, booktitle = {Conference proceedings of the International Conference on Ad-hoc, Mobile and Wireless Networks, ADHOC-NOW 2014}, pages = {279-289}, day = {22-27}, month = jun, year = 2014, location = {Benidorm, Spain}, }
Abstract: 6LoWPAN has been developed to bring IPv6 to even the smallest resource-constrained devices, enabling the vision of an Internet of Things. To be compliant to IPv6’s minimum MTU of 1280 Bytes, its fragmentation mechanism allows transmission of datagrams the size of up to 2048 Bytes. Within low power and lossy environments, fragmen- tation of datagrams can lead to an increase in end-to-end loss rates and to a waste of bandwidth by propagation of fragments of an already lost datagram. We present an extension to an existing analytical, bit-error- based model, which takes into account different route-over forwarding practices in the presence of fragmentation and use it to assess their in- fluence on the end-to-end success rate and the expected number of bits sent. While being not precisely accurate due to the neglect of effects like (self-induced) collisions, the model provides insight into the effects to be expected when using 6LoWPAN’s fragmentation mechanism.
Julian Ohrt und Volker Turau. Building-Linked Location-Based Instantaneous Services System. In Proceedings of the 5th International Conference on Ambient Systems, Networks and Technologies (ANT2014), Juni 2014, pp. 445–452. Hasselt, Belgium. Acceptance rate 36%.
@InProceedings{Telematik_Ohrt_2014_BLISS, author = {Julian Ohrt and Volker Turau}, title = {Building-Linked Location-Based Instantaneous Services System}, booktitle = {Proceedings of the 5th International Conference on Ambient Systems, Networks and Technologies (ANT2014)}, pages = {445-452}, day = {4}, month = jun, year = 2014, location = {Hasselt, Belgium}, note = {Acceptance rate 36%}, }
Abstract: For services which are meant to be used mainly inside buildings, a distribution using global app stores is inappropriate. Instead this work presents a provisioning system (BLISS) for building-linked location-based services. The multi-purpose application MultiApp implements the client-side of the BLISS specification. When a user enters a building, MultiApp instantaneously detects available services and allows to install and execute them. The client part of services is executed within the MultiApp environment and can provide functionalities similar to those offered by native applications. BLISS facilitates developing indoor location-based services by providing bi-directional communication between service providers and clients.
Andreas Weigel, Christian Renner, Volker Turau und Holger Ernst. Wireless Sensor Networks for Smart Metering. In Energy Conference and Exhibition (ENERGYCON), 2014 IEEE International, Mai 2014, pp. 722–729. Dubrovnik, Croatia.
@InProceedings{Telematik_EnergyCon_2014_SmartMetering, author = {Andreas Weigel and Christian Renner and Volker Turau and Holger Ernst}, title = {Wireless Sensor Networks for Smart Metering}, booktitle = {Energy Conference and Exhibition (ENERGYCON), 2014 IEEE International}, pages = {722-729}, day = {13-16}, month = may, year = 2014, location = {Dubrovnik, Croatia}, }
Abstract: Smart metering will change the way we assess and control energy consumption. The necessary two-way communication between energy utilities and smart meters yet requires further research. In par- ticular, cheap, low-maintenance, and reliable alterna- tives to existing approaches must be analyzed. We believe that self-organizing wireless sensor networks are a promising candidate. In this paper, we perform a requirement analysis for smart metering using wireless sensor network technology; we propose an architecture including a set of protocols; and we conduct a real-world evaluation with a testbed of 64 smart meters. With regard to latency and network formation time, the sys- tem was able to fulfill the identified requirements. The results show that the attained reliability for some traffic patterns is low. Further analysis revealed the use of link-layer broadcasts for one-to-many communication as a cause
Florian Meier, Marco Fink und Udo Zölzer. The JamBerry - A Stand-Alone Device for Networked Music Performance Based on the Raspberry Pi. In Proceedings of the Linux Audio Conference (LAC'14), Mai 2014. Karlsruhe, Germany.
@InProceedings{LAC_JamBerry, author = {Florian Meier and Marco Fink and Udo Zölzer}, title = {The JamBerry - A Stand-Alone Device for Networked Music Performance Based on the Raspberry Pi}, booktitle = {Proceedings of the Linux Audio Conference (LAC'14)}, month = may, year = 2014, location = {Karlsruhe, Germany}, }
Abstract: Today's public Internet availability and capabilities allow manifold applications in the field of multimedia that were not possible a few years ago. One emerging application is the so-called Networked Music Performance, standing for the online, low-latency interaction of musicians. This work proposes a stand-alone device for that specific purpose and is based on a Raspberry Pi running a Linux-based operating system.
Andreas Timm-Giel, Volker Turau und Martin Ringwelski. Adaptive Failure Detection and Correction in Dynamic Patient-Networks. In 5th Workshop on Medical Cyber-Physical Systems, April 2014, pp. 38–48. Berlin, Germany.
@InProceedings{Telematik_mcps_2014, author = {Andreas Timm-Giel and Volker Turau and Martin Ringwelski}, title = {Adaptive Failure Detection and Correction in Dynamic Patient-Networks}, booktitle = {5th Workshop on Medical Cyber-Physical Systems}, pages = {38-48}, day = {14}, month = apr, year = 2014, location = {Berlin, Germany}, }
Abstract: Wireless sensors have been studied over recent years for different promising applications with high value for individuals and society. A good example are wireless sensor networks for patients allowing for better and more efficient monitoring of patients in hospitals or even early discharge form hospital and monitoring at home. These visions have hardly led research as reliability is and issue with wireless networks to be known error-prone. In life critical applications like health care this is not an aspect to be handled carelessly. Fail-safety is an important property for patient monitoring systems. The AA4R project of the Hamburg University of Technology researches on a fail-safe patient monitoring system. Our vision is a dynamically distributed system using suitable devices in the area of a patient. The data in the network is stored with redundancy on several nodes. Patient data is analyzed in the network and uploaded to a medical server. As devices appear, disappear and fail, so do the services being executed on those devices. This article focuses on a Reincarnation Service (RS) to track the functionality of the processes. The RS takes suitable actions when a failure is detected to correct or isolate the failure. Checking of the nodes is done adaptively to achieve a good response time to failures and reduce the power consumption.
Gerry Siegemund, Volker Turau, Christoph Weyer, Stefan Lobs und Jörg Nolte. Brief Announcement: Agile and Stable Neighborhood Protocol for WSNs. In Proceedings of the 15th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'13), November 2013, pp. 376–378. Osaka, Japan.
@InProceedings{Telematik_SSS_2013_Neighborhood, author = {Gerry Siegemund and Volker Turau and Christoph Weyer and Stefan Lobs and Jörg Nolte}, title = {Brief Announcement: Agile and Stable Neighborhood Protocol for WSNs}, booktitle = {Proceedings of the 15th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'13)}, pages = {376-378}, day = {13-16}, month = nov, year = 2013, location = {Osaka, Japan}, }
Abstract: Self-stabilizing algorithms (SSA) are defined on the assumption that either the system's topology is fixed over time or topology changes are isolated events occurring at a very low rate. These assumptions are not valid in wireless sensor networks (WSNs) where link qualities change rapidly. The contribution of this paper is a neighbourhood management protocol (NMP) providing a neighbourhood relation sufficiently stable to apply existing SSAs in WSNs.
Brahim Negazzi, Volker Turau, Mohammed Haddad und Hamamache Kheddouci. A Self-Stabilizing Algorithm for Maximal p-Star Decomposition of General Graphs. In Proceedings of the 15th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'13), November 2013, pp. 74–85. Osaka, Japan.
@InProceedings{Telematik_SSS_2013_MaxPStar, author = {Brahim Negazzi and Volker Turau and Mohammed Haddad and Hamamache Kheddouci}, title = {A Self-Stabilizing Algorithm for Maximal p-Star Decomposition of General Graphs}, booktitle = {Proceedings of the 15th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'13)}, pages = {74-85}, day = {13-16}, month = nov, year = 2013, location = {Osaka, Japan}, }
Abstract: A p-star is a complete bipartite graph K{1,p} with one center node and p leaf nodes. In this paper we propose the first distributed self-stabilizing algorithm for graph decomposition into p-stars. For a graph G and an integer p>=1, this decomposition provides disjoint components of G where each component forms a p-star. We prove convergence and correctness of the algorithm under an unfair distributed daemon. The stabilization time is 2*floor(n/p+1)+2 rounds.
Julian Ohrt und Volker Turau. Simple Indoor Routing on SVG Maps. In Proceedings of the workshop Location-based services for Indoor Smart Environments (LISE'13) hosted at the 4th International Conference on Indoor Positioning and Indoor Navigation (IPIN'13), Oktober 2013. Montbéliard, France.
@InProceedings{Telematik_Ohrt_2013_SvgMaps, author = {Julian Ohrt and Volker Turau}, title = {Simple Indoor Routing on SVG Maps}, booktitle = {Proceedings of the workshop Location-based services for Indoor Smart Environments (LISE'13) hosted at the 4th International Conference on Indoor Positioning and Indoor Navigation (IPIN'13)}, day = {28}, month = oct, year = 2013, location = {Montbéliard, France}, }
Abstract: Until now no general applicable technology for indoor localization has prevailed. As a result, there are many approaches to model buildings for indoor navigation being developed. Most of them are very expensive to apply. This work presents a tool for graphically adding navigational data to existing maps. It further demonstrates how to use the created map for routing as pure web application which can be combined with any positioning technology. As SVG is used as format for the map, it analyses performance of rendering and manipulating SVGs on different devices. We show that even large maps can be displayed on current mobile Android devices sufficiently fast for usage as indoor navigation application.
Andreas Weigel, Martin Ringwelski, Volker Turau und Andreas Timm-Giel. Route-Over Forwarding Techniques in a 6LoWPAN. In Proceedings of the 5th International Conference on Mobile Networks and Management (monami'13), September 2013, pp. 122–135. Cork, Irland.
@InProceedings{Telematik_ICMNM_2013_6LoWPAN, author = {Andreas Weigel and Martin Ringwelski and Volker Turau and Andreas Timm-Giel}, title = {Route-Over Forwarding Techniques in a 6LoWPAN}, booktitle = {Proceedings of the 5th International Conference on Mobile Networks and Management (monami'13)}, pages = {122-135}, day = {23-25}, month = sep, year = 2013, location = {Cork, Irland}, }
Abstract: 6LoWPAN plays a major role within the protocol stack for the future Internet of Things. Its fragmentation mechanism enables transport of IPv6 datagrams with the required minimum MTU of 1280 bytes over 802.15.4-based wireless sensor networks. With the envisioned goal of a fully standardized WSN protocol stack currently necessitating a route-over approach, i.e. routing at the IP-layer, there are two main choices for any 6LoWPAN implementation with regard to datagram fragmentation: Hop-by-hop assembly or a cross-layered direct mode, which forwards individual 6LoWPAN fragments before the whole datagram has arrived. In addition to these two straightforward approaches, we propose enhancements based on adaptive rate-restriction for the direct forwarding and a retry control for both modes to reduce the number of losses of larger datagrams. Our evaluation of the basic and enhanced forwarding modes within simulations and a hardware testbed indicate that the proposed enhancements can considerably improve packet reception rate and latency within 6LoWPAN networks.
Stefan Unterschütz und Volker Turau. Reliable Signaling an Emergency Shutdown in Large-Scale, Wireless Controlled Industrial Plants. In Proceedings of the 10th ACM International Symposium on Mobility Management and Wireless Access (MOBIWAC '12), November 2012, pp. 53–62. Paphos, Cyprus Island.
@InProceedings{Telematik_UT_2012_Shutdown, author = {Stefan Unterschütz and Volker Turau}, title = {Reliable Signaling an Emergency Shutdown in Large-Scale, Wireless Controlled Industrial Plants}, booktitle = {Proceedings of the 10th ACM International Symposium on Mobility Management and Wireless Access (MOBIWAC '12)}, pages = {53-62}, day = {21-22}, month = nov, year = 2012, location = {Paphos, Cyprus Island}, }
Abstract: This paper considers the use of wireless mesh networks as a communication infrastructure for monitoring and controlling industrial plants and processes such as solar power plants. In the latter, several thousands, tiltable and rotatable flat mirrors (heliostats) focus sunlight on a receiver tower. Solar power plants require a reliable and highly scalable communication infrastructure. Especially in case of a hazardous situation, the safety system must rapidly alert all heliostats, so that they drive into a stow position. The paper picks up this topic and presents a concept for a reliable wirelessly controlled emergency shutdown, even in cases when the connectivity of the network no longer holds. At this juncture, we face the challenge of communication in large-scale and extremely dense wireless networks. To this end, we introduce a robust broadcasting algorithm based on connected dominating sets. Analytical results of this paper are substantiated by simulations. Finally, prospects of wireless controlled safety systems are discussed.
Helge Klimek, Björn Greßmann und Volker Turau. Protocols for Resource Constrained Infrastructure Networks. In Proceedings of the 10th ACM International Symposium on Mobility Management and Wireless Access (MobiWac '12), Oktober 2012. Paphos, Cyprus.
@InProceedings{Telematik_MOBIWAC_2012_ProtocolsInfrastructureNetwork, author = {Helge Klimek and Björn Greßmann and Volker Turau}, title = {Protocols for Resource Constrained Infrastructure Networks}, booktitle = {Proceedings of the 10th ACM International Symposium on Mobility Management and Wireless Access (MobiWac '12)}, day = {20-25}, month = oct, year = 2012, location = {Paphos, Cyprus}, }
Abstract: This paper introduces two protocols for communication in infrastructure networks consisting of a central server, stationary basestations and mobile devices. Mobile devices use IEEE 802.15.4 to communicate with the basestations. Among other things, the proposed protocols differ in their location management and in the routing of downlink and uplink packets. Through extensive simulations the protocols are compared with the focus on latency and packet loss metrics. The strength of each protocol depends on the traffic pattern caused by an application. This paper concludes with a recommendation for the usage of each protocol.
Sven Köhler, Volker Turau und Gerhard Mentges. Self-stabilizing local k-placement of replicas with minimal variance. In Proceedings of the 14th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'12), Springer, Oktober 2012, pp. 16–30. Toronto, Canada.
@InProceedings{Telematik_KT_SSS12, author = {Sven Köhler and Volker Turau and Gerhard Mentges}, title = {Self-stabilizing local k-placement of replicas with minimal variance}, booktitle = {Proceedings of the 14th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'12)}, pages = {16-30}, series = {Lecture Notes in Computer Science}, volume = {7596}, publisher = {Springer}, day = {1-4}, month = oct, year = 2012, location = {Toronto, Canada}, }
Abstract: Large scale distributed systems require replication of resources to amplify availability and to provide fault tolerance. The placement of replicated resources significantly impacts performance. This paper considers local k-placements: Each node of a network has to place k replicas of a resource among its direct neighbors. The load of a node in a given local k-placement is the number of replicas it stores. The local k-placement problem is to achieve a preferably homogeneous distribution of the loads. We present a novel self-stabilizing, distributed, asynchronous, scalable algorithm for the k-placement problem such that the standard deviation of the distribution of the loads assumes a local minimum.
Martin Ringwelski, Christian Renner, Andreas Reinhardt, Andreas Weigel und Volker Turau. The Hitchhiker's Guide to Choosing the Compression Algorithm for Your Smart Meter Data. In Proceedings of the IEEE International Energy Conference and Exhibition (EnergyCon'12), September 2012. Florence, Italy.
@InProceedings{Telematik_RRWRT_2012_CompressionGuide, author = {Martin Ringwelski and Christian Renner and Andreas Reinhardt and Andreas Weigel and Volker Turau}, title = {The Hitchhiker's Guide to Choosing the Compression Algorithm for Your Smart Meter Data}, booktitle = {Proceedings of the IEEE International Energy Conference and Exhibition (EnergyCon'12)}, day = {9-12}, month = sep, year = 2012, location = {Florence, Italy}, }
Abstract: Smart meters are increasingly penetrating the market, resulting in enormous data volumes to be communicated. In many cases, embedded devices collect the metering data and transmit them wirelessly to achieve cheap and facile deployment. Bandwidth is yet scarce and transmission occupies the spectrum. Smart meter data should hence be compressed prior to transmission. Here, solutions for personal computers are not applicable, as they are too resource-demanding. In this paper, we propose four lossless compression algorithms for smart meters. We analyze processing time and compression gains and compare the results with five off-the-shelf compression algorithms. We show that excellent compression gains can be achieved when investing a moderate amount of memory. A discussion of the suitability of the algorithms for different kinds of metering data is presented.
K. H. Lütjens, A. Lau, T. Pfeiffer, S. Loth, V. Gollnick, H. Klimek, B. Greßmann, S. Löwa, C. Blank und J. Binnebesel. Airport2030 – Lösungen für den effizienten Lufttransport der Zukunft. In Deutscher Luft- und Raumfahrtkongress, September 2012. Berlin, Germany.
@InProceedings{EffizienterLufttransportDerZukunft2012, author = {K. H. Lütjens and A. Lau and T. Pfeiffer and S. Loth and V. Gollnick and H. Klimek and B. Greßmann and S. Löwa and C. Blank and J. Binnebesel}, title = {Airport2030 – Lösungen für den effizienten Lufttransport der Zukunft}, booktitle = {Deutscher Luft- und Raumfahrtkongress}, month = sep, year = 2012, location = {Berlin, Germany}, }
Christian Renner und Volker Turau. State-of-Charge Assessment for Supercap-Powered Sensor Nodes: Keep it Simple Stupid!. In Proceedings of the International Workshop on Algorithms and Concepts for Networked Sensing Systems Powered by Energy Harvesters (EnHaNSS'12), Juni 2012. Antwerp, Belgium.
@InProceedings{Telematik_RT_2012_CapModels, author = {Christian Renner and Volker Turau}, title = {State-of-Charge Assessment for Supercap-Powered Sensor Nodes: Keep it Simple Stupid!}, booktitle = {Proceedings of the International Workshop on Algorithms and Concepts for Networked Sensing Systems Powered by Energy Harvesters (EnHaNSS'12)}, day = {11}, month = jun, year = 2012, location = {Antwerp, Belgium}, }
Abstract: Electric double-layer capacitors, also known as supercaps, have several advantages over traditional energy buffers: They do not require complex charging circuits, offer virtually unlimited charge-discharge cycles, and generally enable easy state-of-charge assessment. A closer look yet reveals that leakage and internal reorganization effects hamper state-of-charge assessment by means of terminal voltage, particularly after a charging cycle. Sophisticated models capture this effect at the cost of an increased calculation and parameter-estimation complexity. As this is hardly feasible on low-power, low-resource sensor nodes, we evaluate the performance of simple models on a real energy-harvesting sensor node platform. We show that model errors are as low as 1-2% on average and never exceed 5% in our experiments, supporting that there is no need to employ more complex models on common sensor node platforms, equipped with unreliable ADC readings and uncertain consumption due to hardware variation in the same order of magnitude.
Christian Renner, Florian Meier und Volker Turau. Holistic Online Energy Assessment: Feasibility and Practical Application. In Proceedings of the 9th IEEE International Conference on Networked Sensing Systems (INSS'12), Juni 2012. Antwerp, Belgium. Best Student Paper Award.
@InProceedings{Telematik_RT_2012_HolisticEnergyAssessment, author = {Christian Renner and Florian Meier and Volker Turau}, title = {Holistic Online Energy Assessment: Feasibility and Practical Application}, booktitle = {Proceedings of the 9th IEEE International Conference on Networked Sensing Systems (INSS'12)}, day = {11-14}, month = jun, year = 2012, location = {Antwerp, Belgium}, note = {Best Student Paper Award}, }
Abstract: Combining energy harvesting with energy-aware scheduling enables perpetually operating sensor networks. The practical realization of this goal yet requires reliable and precise holistic online energy assessment. While the building blocks--assessing residual energy, predicting energy intake, and tracing energy consumption--have been studied in detail, the analysis of their interaction on a real platform has been neglected. This paper answers the question, whether these techniques can be easily joined to give a precise and correct picture of a sensor node's energetic state and behavior. For this purpose, we model the energy flow of a prototype energy-harvesting sensor node and evaluate the joint performance of state-of-the-art energy assessment based on a field test. We verify the system model and show the feasibility of holistic energy assessment, which tolerates small configuration errors, achievable with a combination of generic configuration and online calibration. We also analyze the feasibility of forecasting a node's future energetic state, and find that the presented method gives sufficient results for uniformly distributed consumption profiles.
Stefan Unterschütz und Volker Turau. Fail-Safe Over-The-Air Programming and Error Recovery in Wireless Networks. In Proceedings of the 10th Workshop on Intelligent Solutions in Embedded Systems (WISES'12), Juni 2012. Klagenfurt, Austria.
@InProceedings{Telematik_UT_2012_OTAP, author = {Stefan Unterschütz and Volker Turau}, title = {Fail-Safe Over-The-Air Programming and Error Recovery in Wireless Networks}, booktitle = {Proceedings of the 10th Workshop on Intelligent Solutions in Embedded Systems (WISES'12)}, day = {5-6}, month = jun, year = 2012, location = {Klagenfurt, Austria}, }
Stefan Unterschütz, Andreas Weigel und Volker Turau. Cross-Platform Protocol Development Based on OMNeT++. In Proceedings of the 5th International Workshop on OMNeT++ (OMNeT++'12), März 2012. Desenzano, Italy.
@InProceedings{Telematik_UWT_2012_CometOS, author = {Stefan Unterschütz and Andreas Weigel and Volker Turau}, title = {Cross-Platform Protocol Development Based on OMNeT++}, booktitle = {Proceedings of the 5th International Workshop on OMNeT++ (OMNeT++'12)}, day = {23}, month = mar, year = 2012, location = {Desenzano, Italy}, }
Christian Renner, Florian Meier und Volker Turau. Policies for Predictive Energy Management with Supercapacitors. In Proceedings of the 8th IEEE International Workshop on Sensor Networks and Systems for Pervasive Computing (PerSeNS'12), März 2012. Lugano, Switzerland.
@InProceedings{Telematik_RT_2012_Epol, author = {Christian Renner and Florian Meier and Volker Turau}, title = {Policies for Predictive Energy Management with Supercapacitors}, booktitle = {Proceedings of the 8th IEEE International Workshop on Sensor Networks and Systems for Pervasive Computing (PerSeNS'12)}, day = {19-23}, month = mar, year = 2012, location = {Lugano, Switzerland}, }
Abstract: This paper presents an algorithm to dynamically determine the maximum supported uniform demand for energy of sensor nodes powered by energy harvesters using supercapacitors as energy buffers. Knowledge about the maximum uniform consumption is required to adapt the sensor node's duty cycle or task schedule to achieve uniform, utility-maximizing, and depletion-safe operation. Our algorithm makes use of a supercapacitors' relationship between state-of-charge and voltage, is particularly designed to handle the non-linear system model, and is lightweight enough to run on low-power sensor node hardware. We define three energy policies, evaluate their performance using a real-world solar-harvesting trace, and analyze the influence of the supercapacitor's capacity and errors of the energy forecast.
Christian Renner, Florian Meier und Volker Turau. Poster Abstract: Energy Assessment in Praxis. In Adjunct Proceedings of the 9th European Conference on Wireless Sensor Networks (EWSN'12), Februar 2012. Trento, Italy.
@InProceedings{Telematik_RT_2012_EnergyAssessment, author = {Christian Renner and Florian Meier and Volker Turau}, title = {Poster Abstract: Energy Assessment in Praxis}, booktitle = {Adjunct Proceedings of the 9th European Conference on Wireless Sensor Networks (EWSN'12)}, day = {15-17}, month = feb, year = 2012, location = {Trento, Italy}, }
Abstract: Combining energy harvesting with energy-aware scheduling enables perpetually operating sensor networks. Practical realization yet requires precise holistic online energy assessment. The building blocks are available, but the analysis of their interaction has been neglected. To close the gap, we evaluate the joint performance of energy assessment components. Our experiments substantiate that holistic energy assessment is feasible and that small configuration errors are tolerable.
Stefan Unterschütz, Christian Renner und Volker Turau. Opportunistic, Receiver-Initiated Data-Collection Protocol. In Proceedings of the 9th European Conference on Wireless Sensor Networks (EWSN'12), Februar 2012. Trento, Italy.
@InProceedings{Telematik_URT_2012_Orinoco, author = {Stefan Unterschütz and Christian Renner and Volker Turau}, title = {Opportunistic, Receiver-Initiated Data-Collection Protocol}, booktitle = {Proceedings of the 9th European Conference on Wireless Sensor Networks (EWSN'12)}, day = {15-17}, month = feb, year = 2012, location = {Trento, Italy}, }
Abstract: This paper presents and evaluates ORiNoCo, a novel data-collection and event-reporting protocol for sensor networks. ORiNoCo is built upon the asynchronous duty-cycle protocol RI-MAC and breaks with the tradition of exchanging extensive neighborhood information, a cornerstone of many competing collection protocols and one of their major source of communication overhead and energy expenditure. The merit of this venture is an opportunistic, energy-efficient, latency-reducing, and self-stabilizing protocol. ORiNoCo comes at virtually no extra costs in terms of memory demand and communication overhead compared to RI-MAC. We derive theoretical boundaries for the improvements in radio efficiency, latency, and energy-consumption. ORiNoCo is verified with these findings via simulation and compared with CTP. ORiNoCo achieves lower energy-consumption while reducing end-to-end delays.
Sven Köhler und Volker Turau. Space-efficient fault-containment in dynamic networks. In Proceedings of the 13th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'11), Springer, Oktober 2011, pp. 311–325. Grenoble, France.
@InProceedings{Telematik_KT_SSS11, author = {Sven Köhler and Volker Turau}, title = {Space-efficient fault-containment in dynamic networks}, booktitle = {Proceedings of the 13th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'11)}, pages = {311-325}, series = {Lecture Notes in Computer Science}, volume = {6976}, publisher = {Springer}, day = {10-12}, month = oct, year = 2011, location = {Grenoble, France}, }
Abstract: Bounding the impact of transient small-scale faults by self-stabilizing protocols has been pursued with independent objectives: Optimizing the system's reaction upon topological changes (e.g. super-stabilization), and reducing system recovery time from memory corruptions (e.g. fault-containment). Even though transformations adding either super-stabilization or fault-containment to existing protocols exists, none of them preserves the other. This paper makes a first attempt to combine both objectives. We provide a transformation adding fault-containment to silent self-stabilizing protocols while simultaneously preserving the property of self-stabilization and the protocol's behavior in face of topological changes. In particular, the protocol's response to a topology change remains unchanged even if a memory corruption occurs in parallel to the topology change. The presented transformation increases the memory footprint only by a factor of 4 and adds O(1) bits per edge. All previously known transformations for fault-containing self-stabilization increase the memory footprint by a factor of 2m/n.
Stephan Kubisch, Michael Randt, Reiner Buck, Andreas Pfahl und Stefan Unterschütz. Wireless Heliostat and Control System for Large Self-Powered Heliostat Fields. In Proceedings of the 17th International Symposium on Concentrated Solar Power and Chemical Energy Technologies (SolarPACES'11), September 2011. ,Granada Spain.
@InProceedings{Telematik_U_2011_HELIOMESH, author = {Stephan Kubisch and Michael Randt and Reiner Buck and Andreas Pfahl and Stefan Unterschütz}, title = {Wireless Heliostat and Control System for Large Self-Powered Heliostat Fields}, booktitle = {Proceedings of the 17th International Symposium on Concentrated Solar Power and Chemical Energy Technologies (SolarPACES'11)}, day = {20-23}, month = sep, year = 2011, location = {,Granada Spain}, }
Abstract: The HELIOMESH project pursues the goal to evaluate and validate the feasibility of a wireless mesh network as control technology in a field of self-powered heliostats, thus eliminating the need for cabling. To enhance precision of control, an auto-calibration method was implemented. The team chose a combination of a practical approach combined with simulations to ensure scalability for large heliostats field to be build in the future: About 100 small communication devices, so called HelioNodes, are deployed in the DLR Solar Tower Demonstration Plant heliostat field, controlled by a base station located in the tower. The deployment validates the feasibility and the industrial capability of the wireless mesh control system. In simulations, the good performance of the wireless communication is shown for huge fields. Additionally, the auto-calibration technology was optimized and successfully tested using self-developed, self-powered 8m² heliostats. These heliostats were tested and optimized, with a focus on power management and drive efficiency. Results prove that stepper motors are a good choice in case state of the art electronics are used for control.
Jürgen Jessen, Marcus Venzke und Volker Turau. Design Considerations for a Universal Smart Energy Module for Energy Harvesting in Wireless Sensor Networks. In Proceedings of the Ninth Workshop on Intelligent Solutions in Embedded Systems (WISES 2011), Juli 2011, pp. 35–40. Regensburg, Germany.
@InProceedings{Telematik_JVT_SmartSupply, author = {Jürgen Jessen and Marcus Venzke and Volker Turau}, title = {Design Considerations for a Universal Smart Energy Module for Energy Harvesting in Wireless Sensor Networks}, booktitle = {Proceedings of the Ninth Workshop on Intelligent Solutions in Embedded Systems (WISES 2011)}, pages = {35-40}, day = {07-08}, month = jul, year = 2011, location = {Regensburg, Germany}, }
Abstract: This paper presents the design of a universal energy module for nodes in wireless sensor networks. It supports a wide range of energy harvesters and energy storage systems. The focus is on the efficient conversion and storage of energy and to provide a smart platform for higher level energy management functions. The module provides maximum power point tracking and supports hybrid harvesters.
Stefan Unterschütz und Volker Turau. Construction of Connected Dominating Sets in Large-Scale MANETs Exploiting Self-Stabilization. In Proceedings of the 5th International Workshop on Localized Algorithms and Protocols for Wireless Sensor Networks (LOCALGOS'11), Juni 2011. Barcelona, Spain.
@InProceedings{Telematik_UT_2011_CDS, author = {Stefan Unterschütz and Volker Turau}, title = {Construction of Connected Dominating Sets in Large-Scale MANETs Exploiting Self-Stabilization}, booktitle = {Proceedings of the 5th International Workshop on Localized Algorithms and Protocols for Wireless Sensor Networks (LOCALGOS'11)}, day = {29}, month = jun, year = 2011, location = {Barcelona, Spain}, }
Björn Greßmann, Helge Klimek und Volker Turau. Intelligent Passenger Flows in Airport Terminals Using a Digital Boarding Assistance. In Proceedings of the 8th International Workshop on Intelligent Transportation (WIT'11), März 2011. Hamburg, Germany.
@InProceedings{WIT2011C10, author = {Björn Greßmann and Helge Klimek and Volker Turau}, title = {Intelligent Passenger Flows in Airport Terminals Using a Digital Boarding Assistance}, booktitle = {Proceedings of the 8th International Workshop on Intelligent Transportation (WIT'11)}, day = {22-23}, month = mar, year = 2011, location = {Hamburg, Germany}, }
Abstract: In this paper we present a Digital Boarding Assistance (DigiBa) system for passengers in airport terminals. By providing navigation, notification and information services, passengers are enabled to move efficiently through the terminal. Based on functional requirements of such a system, the paper presents a prototype implementation on an embedded mobile device with restricted resources. Challenges concerning channel access in dense networks and indoor navigation on a device with limited hardware capabilities are outlined.
Holger Machens und Volker Turau. Avoiding Publication and Privatization Problems on Software Transactional Memory. In 17th GI/ITG Conference on Communication in Distributed Systems (KiVS 2011), Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik, Februar 2011, pp. 97–108. Kiel, Germany.
@InProceedings{Telematik_MT_2011_KIVS, author = {Holger Machens and Volker Turau}, title = {Avoiding Publication and Privatization Problems on Software Transactional Memory}, booktitle = {17th GI/ITG Conference on Communication in Distributed Systems (KiVS 2011)}, pages = {97-108}, series = {OpenAccess Series in Informatics (OASIcs)}, volume = {17}, publisher = {Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik}, day = {25}, month = feb, year = 2011, location = {Kiel, Germany}, }
Abstract: This paper presents a new approach to exclude problems arising from dynamically switching between protected concurrent and unprotected single-threaded use of shared data when using software transactional memory in OO languages such as Java. The approach is based on a simple but effective programming model separating transactions from non-transactional operation. It prevents the application programmer from errors but does not force the software transactional memory library to observe non-transactional access and thereby preserves modularity of the software. A prototypical toolchain for validation and source code instrumentation was implemented as a proof of concept.
Christian Renner, Sebastian Ernst, Christoph Weyer und Volker Turau. Prediction Accuracy of Link-Quality Estimators. In Proceedings of the 8th European Conference on Wireless Sensor Networks (EWSN'11), Februar 2011. Bonn, Germany. Acceptance rate 20%.
@InProceedings{Telematik_REWT_HoPS, author = {Christian Renner and Sebastian Ernst and Christoph Weyer and Volker Turau}, title = {Prediction Accuracy of Link-Quality Estimators}, booktitle = {Proceedings of the 8th European Conference on Wireless Sensor Networks (EWSN'11)}, day = {23-25}, month = feb, year = 2011, location = {Bonn, Germany}, note = {Acceptance rate 20%}, }
Abstract: The accuracy of link-quality estimators (LQE) is mission-critical in many application scenarios in wireless sensor networks (WSN), since the link-quality metric is used for routing decisions or neighborhood formation. Link-quality estimation must offer validity for different timescales. Existing LQEs describe and approximate the current quality in a single value only. This method leads to a limited accuracy and expressiveness about the presumed future behavior of a link. The LQE developed in this paper incorporates four quality metrics that give a holistic assessment of the link and its dynamic behavior; therefore, this research is an important step to achieving a higher prediction accuracy including knowledge about the short- and long-term behavior.
Sven Köhler und Volker Turau. A new Technique for proving Self-Stabilization under the Distributed Scheduler. In Proceedings of the 12th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'10), Springer, September 2010, pp. 65–79. New York, NY, USA.
@InProceedings{Telematik_KT_ProofTechnique, author = {Sven Köhler and Volker Turau}, title = {A new Technique for proving Self-Stabilization under the Distributed Scheduler}, booktitle = {Proceedings of the 12th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'10)}, pages = {65-79}, series = {Lecture Notes in Computer Science}, volume = {6366}, publisher = {Springer}, day = {20-22}, month = sep, year = 2010, location = {New York, NY, USA}, }
Abstract: Proving stabilization of a complex algorithm under the distributed scheduler is a non-trivial task. This paper introduces a new method which allows to extend proofs for the central scheduler to the distributed scheduler. The practicability of the method is shown by applying it to two existing algorithms, for which stabilization under the distributed scheduler was an open problem.
Sven Köhler und Volker Turau. Fault-containing self-stabilization in asynchronous systems with constant fault-gap. In Proceedings of the 30th IEEE International Conference on Distributed Computing Systems (ICDCS'10), IEEE Computer Society, Juni 2010, pp. 418–427. Genoa, Italy.
@InProceedings{Telematik_KT_FaultContain, author = {Sven Köhler and Volker Turau}, title = {Fault-containing self-stabilization in asynchronous systems with constant fault-gap}, booktitle = {Proceedings of the 30th IEEE International Conference on Distributed Computing Systems (ICDCS'10)}, pages = {418-427}, publisher = {IEEE Computer Society}, day = {21-25}, month = jun, year = 2010, location = {Genoa, Italy}, }
Abstract: This paper presents a new transformation which adds fault-containment properties to any silent self-stabilizing protocol. The transformation features a constant slow-down factor and the fault-gap – that is the minimal time between two containable faults – is constant. The transformation scales well to arbitrarily large systems and avoids global synchronization.
Christian Renner, Volker Turau und Christoph Weyer. Performance of Energy-Efficient TDMA Schemes in Data-Gathering Scenarios with Periodic Sources. In Proceedings of the 7th IEEE International Conference on Networked Sensing Systems (INSS'10), Juni 2010. Kassel, Germany. Acceptance rate 22%.
@InProceedings{Telematik_RTW_EnergyEfficientTDMA, author = {Christian Renner and Volker Turau and Christoph Weyer}, title = {Performance of Energy-Efficient TDMA Schemes in Data-Gathering Scenarios with Periodic Sources}, booktitle = {Proceedings of the 7th IEEE International Conference on Networked Sensing Systems (INSS'10)}, day = {15-18}, month = jun, year = 2010, location = {Kassel, Germany}, note = {Acceptance rate 22%}, }
Abstract: Energy-efficient transportation of periodical sensor readings towards a single sink in wireless sensor networks is a challenging task. In general, two data-gathering strategies exist: on-demand and bulk data forwarding. For both strategies, cross-layer techniques are a promising approach, where TDMA is tailored to the underlying routing tree. Therefore, different TDMA schemes are compared regarding achievable throughput, packet delay, and energy-efficiency for various sampling rates and scenarios. Existing schemes perform well in dedicated topologies only. The new and simple TDMA scheme presented in this paper outperforms its predecessors in all scenarios under consideration. These findings are substantiated by both theoretical analysis and extensive simulation.
Björn Greßmann, Helge Klimek und Volker Turau. Towards Ubiquitous Indoor Location Based Services and Indoor Navigation. In Proceedings of the 7th IEEE Workshop on Positioning Navigation and Communication (WPNC2010), März 2010. Dresden, Germany.
@InProceedings{WPNC10, author = {Björn Greßmann and Helge Klimek and Volker Turau}, title = {Towards Ubiquitous Indoor Location Based Services and Indoor Navigation}, booktitle = {Proceedings of the 7th IEEE Workshop on Positioning Navigation and Communication (WPNC2010)}, day = {11-12}, month = mar, year = 2010, location = {Dresden, Germany}, }
Abstract: Outdoor navigation services have become ubiquitously available due to small handheld devices such as GPS enabled mobile phones or dedicated mobile navigation systems. Two main drivers were necessary in order to provide widespread location based services: Acquiring positioning information with a certain degree of precision and widespread (mobile) access to computer networks to use the position information with a large information basis such as the Internet. Envisioned is a future, where indoor navigation and location based services are used as naturally as outdoor location based services are now. To achieve this long term vision where users seamlessly navigate for example from work desk to departure gate at the airport and use location based services on the way, various challenges have to be solved. In this paper, these challenges and open issues are discussed. The paper proposes an architecture which abstracts from different mobile devices and localization technologies. Additionally, it sketches the use of indoor topology information to increase the accuracy of indoor localization. These two presented concepts form a basis for a transition period until standards for ubiquitous indoor location based services have emerged.
Christian Renner und Volker Turau. CapLibrate: Self-Calibration of an Energy Harvesting Power Supply with Supercapacitors. In Proceedings of the GI/ITG Workshop on Energy-aware Systems and Methods, Februar 2010. Hannover, Germany.
@InProceedings{Telematik_RT_2010_CapLibrate, author = {Christian Renner and Volker Turau}, title = {CapLibrate: Self-Calibration of an Energy Harvesting Power Supply with Supercapacitors}, booktitle = {Proceedings of the GI/ITG Workshop on Energy-aware Systems and Methods}, day = {22-23}, month = feb, year = 2010, location = {Hannover, Germany}, }
Abstract: Achieving perpetual and self-sustaining operation of wireless sensor nodes is an important topic of current research in the field of energy harvesting. Closely related to this is the employment of energy budgeting, i.e., effective utilization of available and future energy resources without pushing a node towards the hazard of energy depletion. Therefore, reliable prediction of node lifetime in context of the available energy within a given time is required. This in turn requires self-calibration of the sensor nodes and their energy harvesting supply. In this paper, we explore and assess models for a supercapacitor-based harvesting supply. The parameters of the models are discussed and determined, so that fast, reliable, and energy-efficient calibration becomes possible. Moreover, measurement results for a specific hardware platform are discussed and a roadmap for a self-calibration algorithm is presented.
Volker Turau und Bernd Hauck. A Self-Stabilizing Approximation Algorithm for Vertex Cover in Anonymous Networks. In Proceedings of the 11th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'09), Springer, November 2009, pp. 341–353. Lyon, France.
@InProceedings{Telematik_HT_2009_VC, author = {Volker Turau and Bernd Hauck}, title = {A Self-Stabilizing Approximation Algorithm for Vertex Cover in Anonymous Networks}, booktitle = {Proceedings of the 11th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS'09)}, pages = {341-353}, series = {Lecture Notes in Computer Science}, volume = {5873}, publisher = {Springer}, day = {3-6}, month = nov, year = 2009, location = {Lyon, France}, }
Abstract: This paper presents a deterministic self-stabilizing algorithm that computes a 3-approximation vertex cover in anonymous networks. It reaches a legal state after O(n+m) moves or 2n + 1 rounds respectively and recovers from a single fault within a constant containment time. The contamination number is 2 Delta + 1. An enhanced version of this algorithm achieves a 2-approximation on trees.
Christian Renner, Jürgen Jessen und Volker Turau. Poster: Energy Estimation for Harvesting Supplies with Supercaps. In Proceedings of the Workshop on Self-Organizing Wireless Sensor and Communication Networks, Oktober 2009. Hamburg, Germany.
@InProceedings{Telematik_RJT_2009_EnergyEstimation, author = {Christian Renner and Jürgen Jessen and Volker Turau}, title = {Poster: Energy Estimation for Harvesting Supplies with Supercaps}, booktitle = {Proceedings of the Workshop on Self-Organizing Wireless Sensor and Communication Networks}, day = {8-9}, month = oct, year = 2009, location = {Hamburg, Germany}, }
Arne Bosien und Volker Turau. RFID for Mobile Applications. In Proceedings of the Workshop on Self-Organizing Wireless Sensor and Communication Networks, Oktober 2009, pp. 27–33. Hamburg, Germany.
@InProceedings{Telematik_SOMSED_2009_MOBILE_RFID, author = {Arne Bosien and Volker Turau}, title = {RFID for Mobile Applications}, booktitle = {Proceedings of the Workshop on Self-Organizing Wireless Sensor and Communication Networks}, pages = {27-33}, day = {8-9}, month = oct, year = 2009, location = {Hamburg, Germany}, }
Abstract: The availability of fast anti-collision algorithms is crucial for most RFID applications. This paper aims to evaluate these algorithms for applications in which it is not intended to identify the entirety of moving objects but to detect as much tags as needed to allow orientation. The navigation of Automated Guided Vehicles (AGV) by distributed landmarks is an example which clarifies the discriminative requirements compared to supply chain tasks. For the former purpose redundant information can be gained from different tags. This requires the detection of an application dependent percentage of all tags. Because AGVs are moving, the detection and read and write operations have to be close together and very fast, since repetitive communication is not always possible.
Christoph Weyer, Volker Turau, Andreas Lagemann und Jörg Nolte. Programming Wireless Sensor Networks in a Self-Stabilizing Style. In Proceedings of the Third International Conference on Sensor Technologies and Applications (SENSORCOMM'09), Juni 2009. Athens, Greece.
@InProceedings{Telematik_WLT_2009_SelfWISE, author = {Christoph Weyer and Volker Turau and Andreas Lagemann and Jörg Nolte}, title = {Programming Wireless Sensor Networks in a Self-Stabilizing Style}, booktitle = {Proceedings of the Third International Conference on Sensor Technologies and Applications (SENSORCOMM'09)}, day = {18-23}, month = jun, year = 2009, location = {Athens, Greece}, }
Abstract: Wireless Sensor Networks (WSNs) operate in an unstable environment and thus are subject to arbitrary transient faults. Self-stabilization is a promising technique to add tolerance against transient faults in a self-contained non-masking way. A core factor for the applicability of a given self-stabilizing algorithm is its convergence time. This paper analyses the average stabilization time of three algorithms commonly regarded as central building blocks for WSNs. The analysis is accomplished with SelfWISE, a framework providing programming abstractions for selfstabilizing algorithms. The performed analysis considers the target models as well as network size and density. This demonstrates the usability of SelfWISE for evaluating selfstabilizing algorithms under a wide range of models.
Christoph Weyer, Christian Renner, Volker Turau und Hannes Frey. TinyAID: Automated Instrumentation and Evaluation Support for TinyOS. In Proceedings of the Second International Workshop on Sensor Network Engineering (IWSNE'09), Juni 2009. Marina del Rey, CA, USA.
@InProceedings{Telematik_WRTF_2009_TinyAID, author = {Christoph Weyer and Christian Renner and Volker Turau and Hannes Frey}, title = {TinyAID: Automated Instrumentation and Evaluation Support for TinyOS}, booktitle = {Proceedings of the Second International Workshop on Sensor Network Engineering (IWSNE'09)}, day = {10}, month = jun, year = 2009, location = {Marina del Rey, CA, USA}, }
Abstract: TinyAID is a tool that supports automated instrumentation and evaluation of TinyOS-based distributed applications. Two types of instrumentations are provided: logging of call chains and message flows within the network. TinyAID assists the debugging process by post evaluation of the logged data. A main benefit is the visualization component for representing traces in their spatial and temporal order. The instrumentation and evaluation concepts are evaluated in two case studies: the SelfWISE framework and a selection of routing algorithms. Due to the automated process of TinyAID the evaluation could be performed without a deeper knowledge of the implementations under test. In the first case TinyAID revealed a weakness in the TOSSIM random number generator. The second case demonstrates the power of TinyAID to visualize the quality of protocols in a unified manner, without any manual changes to the specific source code.
Stefan Unterschütz. Methodologies for Comparing Clustering Algorithms in Wireless Sensor Networks. In First IEEE Germany Student Conference in Electrical and Computer Engineering (ISC'09), Mai 2009. Hamburg, Germany.
@InProceedings{Telematik_UT_2009_CLustering, author = {Stefan Unterschütz}, title = {Methodologies for Comparing Clustering Algorithms in Wireless Sensor Networks}, booktitle = {First IEEE Germany Student Conference in Electrical and Computer Engineering (ISC'09)}, day = {15}, month = may, year = 2009, location = {Hamburg, Germany}, }
Marcus Venzke, Mikko Jania und Volker Turau. VoIP over WLAN: Replacing Professional Mobile Radio on Airports. In Proceedings of the Second International Workshop on Aircraft System Technologies (AST'09), März 2009. Hamburg, Germany.
@InProceedings{Telematik_VJT_2009_VoIP, author = {Marcus Venzke and Mikko Jania and Volker Turau}, title = {VoIP over WLAN: Replacing Professional Mobile Radio on Airports}, booktitle = {Proceedings of the Second International Workshop on Aircraft System Technologies (AST'09)}, day = {26-27}, month = mar, year = 2009, location = {Hamburg, Germany}, }
Abstract: This paper proposes and analyses the idea of replacing professional mobile radio for airport ground handlers by VoIP systems based on WLAN. The proposed communication scheme is adjusted to business processes at airports. It provides push-to-talk unicast and group messages (determined by business tasks or location) with priorities, encrypted transmission, and mailboxes. The resulting architecture and proof-of-concept prototype consists of a server and software clients reusing already installed hardware and WLAN infrastructure, and uses peer-to-peer RDP voice streams. Bandwidth considerations estimate a maximum of 72 concurrent streams per access point on WLAN for IEEE 802.11g (54 Mbit/s) and 13 streams for IEEE 802.11b (11 Mbit/s), enhanced with a factor 3 to 5 if IEEE 802.11e is used as quality of service support.
Christoph Weyer und Volker Turau. SelfWISE: A Framework for Developing Self-Stabilizing Algorithms. In Proceedings of the 16th ITG/GI - Fachtagung Kommunikation in Verteilten Systemen (KiVS'09), März 2009, pp. 67–78. Kassel, Germany.
@InProceedings{Telematik_TW_2009_SelfWISE, author = {Christoph Weyer and Volker Turau}, title = {SelfWISE: A Framework for Developing Self-Stabilizing Algorithms}, booktitle = {Proceedings of the 16th ITG/GI - Fachtagung Kommunikation in Verteilten Systemen (KiVS'09)}, pages = {67-78}, day = {2-6}, month = mar, year = 2009, location = {Kassel, Germany}, }
Abstract: This paper introduces SelfWISE, a framework for enabling wireless sensor networks to be programmed in a self-stabilizing manner. The framework eases the formal specification of algorithms by abstracting from low-level details such as wireless channel and hardwarespecific characteristics. SelfWISE consists of a language for expressing self-stabilizing algorithms, a runtime environment for simulating algorithms in wireless sensor networks, and supporting tools. The hereby applied transformation of formally described algorithms into the simulation environment preserves the self-stabilizing properties. Development, evaluation, and debugging of self-stabilizing algorithms is considerably facilitated by utilizing SelfWISE.
Kay Römer und Christian Renner. Aggregating Sensor Data from Overlapping Multi-Hop Network Neighborhoods: Push or Pull?. In Proceedings of the International Conference on Networked Sensing Systems (INSS'08), Juni 2008, pp. 107–110. Kanazawa, Japan.
@InProceedings{Telematik_RR_2008_PushOrPull, author = {Kay Römer and Christian Renner}, title = {Aggregating Sensor Data from Overlapping Multi-Hop Network Neighborhoods: Push or Pull?}, booktitle = {Proceedings of the International Conference on Networked Sensing Systems (INSS'08)}, pages = {107-110}, day = {17-19}, month = jun, year = 2008, location = {Kanazawa, Japan}, }
Abstract: Network neighborhoods are a key communication abstraction in sensor networks, allowing sensor nodes to collect and aggregate sensor data from nearby other nodes. In many applications, multi-hop neighborhoods of several nodes overlap, such that nodes participate in many neighborhoods, having to contribute their data items to all containing neighborhoods. We consider two orthogonal approaches to efficiently support this data aggregation problem. A push-based approach, where each node floods its data item in a multi-hop neighborhood, and a pull-based approach, where each node collects data from nodes in a multi-hop network neighborhood using a spanning tree. Our goal is to identify situations where one approach outperforms the other. For this, we implement these protocols in TOSSIM, study overhead and yield as a function of the fraction of nodes in the network that perform data aggregation over a multi-hop neighborhood, and report our findings.
Volker Turau, Christoph Weyer und Christian Renner. Efficient Slot Assignment for the Many-to-One Routing Pattern in Sensor Networks. In Proceedings of the First International Workshop on Sensor Network Engineering (IWSNE'08), Juni 2008. Santorini Island, Greece.
@InProceedings{Telematik_TWR_2008_SlotAssignmentManyOne, author = {Volker Turau and Christoph Weyer and Christian Renner}, title = {Efficient Slot Assignment for the Many-to-One Routing Pattern in Sensor Networks}, booktitle = {Proceedings of the First International Workshop on Sensor Network Engineering (IWSNE'08)}, day = {11}, month = jun, year = 2008, location = {Santorini Island, Greece}, }
Abstract: In this paper an efficient TDMA slot assignment for the many-to-one routing pattern in wireless sensor networks is presented and analyzed. This assignment scheme is based on a simple to implement heuristic, named spatial path-based reuse (SPR). By considering several metrics, the superiority of this heuristic with respect to energy consumption and runtime compared to proposals found in the literature is demonstrated.
Arne Bosien, Marcus Venzke und Volker Turau. A rewritable RFID environment for AGV navigation. In Proceedings of the 5th International Workshop on Intelligent Transportation (WIT'08), März 2008, pp. 87–92. Hamburg, Germany.
@InProceedings{Telematik_BVT_2008_AVG_RFID_Environment, author = {Arne Bosien and Marcus Venzke and Volker Turau}, title = {A rewritable RFID environment for AGV navigation}, booktitle = {Proceedings of the 5th International Workshop on Intelligent Transportation (WIT'08)}, pages = {87-92}, day = {18-19}, month = mar, year = 2008, location = {Hamburg, Germany}, }
Abstract: The paper analyses potentials, challenges, and applications of using rewritable, stationary RFID tags for marking routes for autonomous vehicles in manufacturing environments. This approach promises to be flexible, robust, and inexpensive. Two algorithms are proposed also considering additional sensors.
Volker Turau und Christoph Weyer. TDMA-Schemes for Tree-Routing in Data Intensive Wireless Sensor Networks. In Proceedings of the First International Workshop on Protocols and Algorithms for Reliable and Data Intensive Sensor Networks (PARIS'07), Oktober 2007. Pisa, Italy.
@InProceedings{Telematik_TW_2007_TDMASchemesTreeRouting, author = {Volker Turau and Christoph Weyer}, title = {TDMA-Schemes for Tree-Routing in Data Intensive Wireless Sensor Networks}, booktitle = {Proceedings of the First International Workshop on Protocols and Algorithms for Reliable and Data Intensive Sensor Networks (PARIS'07)}, day = {8}, month = oct, year = 2007, location = {Pisa, Italy}, }
Abstract: A particular class of data intensive wireless sensor networks are those networks where sensors periodically measure data with high rates. The focus of this work is on the efficient transport of high volumes of sampled data through a multi-hop network with limited resources using a routing tree. This paper analyzes TDMA schemes for this purpose with respect to buffer usage and energy consumption. In particular, it is shown, that classical TDMA schemes are not optimal for tree-routing in data-intensive sensor networks.
Volker Turau und Christoph Weyer. Long-term Reliable Data Gathering Using Wireless Sensor Networks. In Proceedings of the Fourth International Conference on Networked Sensing Systems (INSS'07), Juni 2007, pp. 252–259. Braunschweig, Germany.
@InProceedings{Telematik_LVMHTM_2007_Long-termReliableDataGathering, author = {Volker Turau and Christoph Weyer}, title = {Long-term Reliable Data Gathering Using Wireless Sensor Networks}, booktitle = {Proceedings of the Fourth International Conference on Networked Sensing Systems (INSS'07)}, pages = {252-259}, day = {6-8}, month = jun, year = 2007, location = {Braunschweig, Germany}, }
Abstract: This paper presents the design of a long-term reliable data gathering service for many-to-one communication in wireless sensor networks: all nodes send periodically delaytolerant data to a single node. The service operates reliably despite strict resource constraints, poor link qualities, and frequent disconnects. This paper presents a novel protocol for gathering periodically measured data including a solution for the wearleveling problem of the EEPROM. Furthermore, theoretical limits of this approach based on available bandwidth and local memory are provided. Finally, preliminary results of an implementation of the service are presented. In particular a detailed analysis of the energy consumption during the different phases of this experiment is provided.
Volker Turau und Christoph Weyer. Scheduling Transmission of Bulk Data in Sensor Networks using a Dynamic TDMA Protocol. In Proceedings of the International Workshop on Data Intensive Sensor Networks (DISN'07), Mai 2007, pp. 321–325. Mannheim, Germany.
@InProceedings{Telematik_TW_2007_SchedulingBulkData, author = {Volker Turau and Christoph Weyer}, title = {Scheduling Transmission of Bulk Data in Sensor Networks using a Dynamic TDMA Protocol}, booktitle = {Proceedings of the International Workshop on Data Intensive Sensor Networks (DISN'07)}, pages = {321-325}, day = {1}, month = may, year = 2007, location = {Mannheim, Germany}, }
Abstract: Sensor networks are increasingly used for applications in which sensors periodically measure data with high sampling rates. The reliable transport of high volumes of sampled data through a multi-hop network with limited resources requires sophisticated algorithms. This paper presents a novel protocol for this task that uses minimal energy, provides high throughput, and requires only small amounts of additional buffer. The protocol is based on a dynamic TDMA scheme and is robust against omission failures.
Steffen Loth, Marcus Venzke, Dietmar Möller, Axel Husfeldt, Volker Turau und Christoph Meier. Car Management on Aprons (CARMA) - Developing Integrated Solutions for Vehicle Management at Mid-Size Airports. In Proceedings of the First International Workshop on Aircraft System Technologies (AST'07), März 2007, pp. 257–266. Hamburg, Germany.
@InProceedings{Telematik_LVMHTM_2007_CARMA, author = {Steffen Loth and Marcus Venzke and Dietmar Möller and Axel Husfeldt and Volker Turau and Christoph Meier}, title = {Car Management on Aprons (CARMA) - Developing Integrated Solutions for Vehicle Management at Mid-Size Airports}, booktitle = {Proceedings of the First International Workshop on Aircraft System Technologies (AST'07)}, pages = {257-266}, day = {29-30}, month = mar, year = 2007, location = {Hamburg, Germany}, }
Abstract: The paper investigates the development of systems for vehicle management on airport aprons, using current A-SMGCS experiences, with a focus on fleet management and turn around processes of mid-size airports. An architecture is proposed that is derived from A-SMGCS, reducing cost by only supporting cooperative targets and off-the-shelf hardware. Available candidate technologies for implementing the architecture_s components are discussed, pointing out criteria for selection. Systems for vehicle management on aprons are important, because the continuous reductions of aircraft turn-around times increase the pressure on airports and ground handling companies to optimize infrastructure and resources.
Peter Golibrzuch, Alexander Holbreich und Simon Zambrovski. Enterprise Application Deployment: A model driven approach. In Software Engineering 2007 - Beiträge zu den Workshops, März 2007. Hamburg, Germany.
@InProceedings{Telematik_GHZ_2007_EnterpriseAppDeplyment, author = {Peter Golibrzuch and Alexander Holbreich and Simon Zambrovski}, title = {Enterprise Application Deployment: A model driven approach}, booktitle = {Software Engineering 2007 - Beiträge zu den Workshops}, day = {29}, month = mar, year = 2007, location = {Hamburg, Germany}, }
Helge Klimek. PDD Applied: A Model Driven Approach. In Software Engineering 2007 - Beiträge zu den Workshops, März 2007. Hamburg, Germany.
@InProceedings{Telematik_K_2007_PDDApplield, author = {Helge Klimek}, title = {PDD Applied: A Model Driven Approach}, booktitle = {Software Engineering 2007 - Beiträge zu den Workshops}, day = {29}, month = mar, year = 2007, location = {Hamburg, Germany}, }
N. I. Damm, Dietrich Fahrenholtz und Volker Turau. On Fluctuation Resilience of Second Generation Distributed Hash Tables. In Proceedings of the 15th ITG/GI - Fachtagung Kommunikation in verteilten Systemen (KiVS'07), Februar 2007, pp. 105–110. Bern, Switzerland.
@InProceedings{Telematik_DFT_2007_FluctuationResilience, author = {N. I. Damm and Dietrich Fahrenholtz and Volker Turau}, title = {On Fluctuation Resilience of Second Generation Distributed Hash Tables}, booktitle = {Proceedings of the 15th ITG/GI - Fachtagung Kommunikation in verteilten Systemen (KiVS'07)}, pages = {105-110}, month = feb, year = 2007, location = {Bern, Switzerland}, }
Abstract: Every Peer-to-Peer system destined for wide-spread use has to face the challenges imposed by peer population dynamics, which result from peers joining and leaving the system at their own discretion. So any Distributed Hash Table (DHT) design must take precautions against this peer population fluctuation (aka. churn) to sustain efficient lookup performance. Although important, an analysis of the influence of fluctuation on the performance of second generation DHTs in a unified attempt has not been done yet. An existing performance versus cost analysis by Li et al. aims at finding optimal parameters for DHTs being evaluated. However, their analysis focuses on one fluctuation scenario only. In this paper, we analyse second generation DHTs covering a wide range of topologies in a simulation framework under different fluctuation rates and evaluate their performance. Overall Kademlia attains the best lookup performance but its bandwidth consumption goes up significantly when increasing fluctuation rate. With a limited bandwidth budget and high fluctuation rate, Kelips lookup performance is the best among all examined DHTs.
Dietrich Fahrenholtz, Volker Turau und Andreas Wombacher. On Optimal Replication Group Splits in P2P Data Stores Based on the Hypercube. In Proceedings of the 15th ITG/GI - Fachtagung Kommunikation in Verteilten Systemen (KiVS'07), Februar 2007, pp. 155–162. Bern, Switzerland.
@InProceedings{Telematik_FTW_2007_ReplicationGroupHypercube, author = {Dietrich Fahrenholtz and Volker Turau and Andreas Wombacher}, title = {On Optimal Replication Group Splits in P2P Data Stores Based on the Hypercube}, booktitle = {Proceedings of the 15th ITG/GI - Fachtagung Kommunikation in Verteilten Systemen (KiVS'07)}, pages = {155-162}, month = feb, year = 2007, location = {Bern, Switzerland}, }
Abstract: P2P data stores excel if availability of inserted data items must be guaranteed. Their inherent mechanisms to counter peer population dynamics make them suitable for a wide range of application domains. This paper presents and analyzes the split maintenance operation of our P2P data store. The operation aims at reorganizing replication groups in case operation of them becomes suboptimal. To this end, we present a formal cost model that peers use to compute optimal points when to run performance optimizing maintenance. Finally, we present experimental results that validate our cost model by simulating various network conditions.
Volker Turau und Christoph Weyer. Randomized Self-stabilizing Algorithms for Wireless Sensor Networks. In Proceedings of the First International Workshop on Self-Organizing Systems (IWSOS'06), September 2006, pp. 74–89. Passau, Germany.
@InProceedings{Telematik_TW_2006_RandomizedSelfStabilizing, author = {Volker Turau and Christoph Weyer}, title = {Randomized Self-stabilizing Algorithms for Wireless Sensor Networks}, booktitle = {Proceedings of the First International Workshop on Self-Organizing Systems (IWSOS'06)}, pages = {74-89}, day = {18-20}, month = sep, year = 2006, location = {Passau, Germany}, }
Abstract: Wireless sensor networks (WSNs) pose challenges not present in classical distributed systems: resource limitations, high failure rates, and ad hoc deployment. The lossy nature of wireless communication can lead to situations, where nodes lose synchrony and programs reach arbitrary states. Traditional approaches to fault tolerance like replication or global resets are not feasible. In this work, the concept of self-stabilization is applied to WSNs. The majority of self-stabilizing algorithms found in the literature is based on models not suitable for WSNs: shared memory model, central daemon scheduler, unique processor identifiers, and atomicity. This paper proposes problem-independent transformations for algorithms that stabilize under the central daemon scheduler such that they meet the demands of a WSN. The transformed algorithms use randomization and are probabilistically self-stabilizing. This work allows to utilize many known self-stabilizing algorithms in WSNs. The proposed transformations are evaluated using simulations and a real WSN.
Matthias Witt und Volker Turau. The Impact of Location Errors on Geographic Routing in Sensor Networks. In Proceedings of the Second International Conference on Wireless and Mobile Communications (ICWMC'06), Juli 2006, pp. 76. Bucharest, Romania.
@InProceedings{Telematik_WT_2006_LocationErrorRouting, author = {Matthias Witt and Volker Turau}, title = {The Impact of Location Errors on Geographic Routing in Sensor Networks}, booktitle = {Proceedings of the Second International Conference on Wireless and Mobile Communications (ICWMC'06)}, pages = 76, day = {29-31}, month = jul, year = 2006, location = {Bucharest, Romania}, }
Abstract: Geographic routing in wireless sensor networks is based on the prerequisite that every node has information about its current position, for instance via GPS or some localization algorithm. This location information has a certain degree of inaccuracy in real deployments. The majority of geographic routing algorithms, however, has been designed for nodes with exact position information. We show that location errors yield bad performance or even complete failures. Two elaborated geographic routing algorithms for sensor networks, GPSR and BGR, are evaluated with the nodes having inaccurate location information, varying the standard deviation of the position error between zero and the transmission range. Simulation studies show a vast decrease of the packet delivery ratio. To enhance both algorithms, fixes for them are presented to improve the delivery ratio and to save energy in case of location errors.
Volker Turau, Matthias Witt und Marcus Venzke. Field Trials with Wireless Sensor Networks: Issues and Remedies. In Proceedings of the Second International Conference on Wireless and Mobile Communications (ICWMC'06), Juli 2006, pp. 86. Bucharest, Romania.
@InProceedings{Telematik_TWV_2006_FieldTrialsWSN, author = {Volker Turau and Matthias Witt and Marcus Venzke}, title = {Field Trials with Wireless Sensor Networks: Issues and Remedies}, booktitle = {Proceedings of the Second International Conference on Wireless and Mobile Communications (ICWMC'06)}, pages = 86, day = {29-31}, month = jul, year = 2006, location = {Bucharest, Romania}, }
Abstract: Extensive field trials are essential to evaluate protocols and algorithms for wireless sensor networks. The high costs of such trials demand for a systematic approach. This paper discusses the issues of setting up a field trial such as packaging, logging, and deployment. Details about a concrete field trial to evaluate a topology discovery algorithm are presented.
Volker Turau. Computing Bridges, Articulations, and 2-Connected Components in Wireless Sensor Networks. In Proceedings of the Second International Workshop on Algorithmic Aspects of Wireless Sensor Networks (ALGOSENSORS'06), Juli 2006, pp. 164–175. Venice, Italy.
@InProceedings{Telematik_TURAU_2006_ComputingBridgesUA, author = {Volker Turau}, title = {Computing Bridges, Articulations, and 2-Connected Components in Wireless Sensor Networks}, booktitle = {Proceedings of the Second International Workshop on Algorithmic Aspects of Wireless Sensor Networks (ALGOSENSORS'06)}, pages = {164-175}, day = {15}, month = jul, year = 2006, location = {Venice, Italy}, }
Abstract: This paper presents a simple distributed algorithm to determine the bridges, articulation points, and 2-connected components in asynchronous networks with an at least once message delivery semantics in time O(n) using O(lg n)-length messages. The algorithm does not assume a FIFO rule for message delivery. Previously known algorithms either use longer messages or need more time. The algorithm meets the requirements of wireless senor networks and can be applied in several areas relevant to this field such as topology control, clustering, localization and virtual backbone calculations.
Dietrich Fahrenholtz und Volker Turau. Improving Churn Resistance of P2P Data Stores Based on the Hypercube. In Proceedings of the the 5th International Symposium on Parallel and Distributed Computing (ISPDC'06), Juli 2006, pp. 263–270. Timisoara, Romania.
@InProceedings{Telematik_FT_2006_ImprovingChurnResistance, author = {Dietrich Fahrenholtz and Volker Turau}, title = {Improving Churn Resistance of P2P Data Stores Based on the Hypercube}, booktitle = {Proceedings of the the 5th International Symposium on Parallel and Distributed Computing (ISPDC'06)}, pages = {263-270}, day = {6-9}, month = jul, year = 2006, location = {Timisoara, Romania}, }
Abstract: P2P data stores as opposed to pure P2P networks display their special strength if availability of inserted data items must be guaranteed. Their inherent mech- anisms to counter peer population fluctuation, where peers continuously join or leave the network, make P2P data stores suitable for a wide range of application do- mains. This paper examines one of their maintenance operations called fusion. It reorganizes parts of our P2P data store in case the peer population shrinks so much that data availability is threatened. We present a formal cost model that is used to estimate the optimal point when a fusion is to be invoked. Finally, the paper presents experimental results showing our cost model is valid by simulating various network conditions.
Marcus Venzke, Peng Kong und Volker Turau. A Generic Java Interface for Vertical Integration of Wireless Sensor Networks. In Proceedings of the Fourth Workshop on Intelligent Solutions in Embedded Systems (WISES'06), Juni 2006. Vienna, Austria.
@InProceedings{Telematik_VKT_2006_VerticalIntegrationSensorNet, author = {Marcus Venzke and Peng Kong and Volker Turau}, title = {A Generic Java Interface for Vertical Integration of Wireless Sensor Networks}, booktitle = {Proceedings of the Fourth Workshop on Intelligent Solutions in Embedded Systems (WISES'06)}, day = {30}, month = jun, year = 2006, location = {Vienna, Austria}, }
Abstract: The paper presents a generic, high-level Java interface for the vertical integration of wireless sensor networks. The intuitive interfaces are implemented in a framework that is easy to use. The classes of the framework can be extended to meet the requirements of a wide range of applications. In particular, the framework supports sending packets to and receiving packets from nodes of the sensor network. Packet types are represented as Java classes generated from meta-data based on XML Schema. This approach fosters short development cycles and provides the productivity needed in vertical integration applications. The ScatterWeb platform is used as a sample platform for sensor networks.
Volker Turau, Matthias Witt und Christoph Weyer. Analysis of a Real Multi-hop Sensor Network Deployment: The Heathland Experiment. In Proceedings of the Third International Conference on Networked Sensing Systems (INSS'06), Juni 2006, pp. 6–13. Chicago, Illinois, USA.
@InProceedings{Telematik_TWW_2006_HeathlandDeployment, author = {Volker Turau and Matthias Witt and Christoph Weyer}, title = {Analysis of a Real Multi-hop Sensor Network Deployment: The Heathland Experiment}, booktitle = {Proceedings of the Third International Conference on Networked Sensing Systems (INSS'06)}, pages = {6-13}, month = jun, year = 2006, location = {Chicago, Illinois, USA}, }
Abstract: This paper reports on the results and experience gained during a real-world deployment of a sensor network based on the ESB platform in the heathlands of Northern Germany. The goal of the experiment was to gain a deeper insight into the problems of real deployments as opposed to simulated networks. The focus of the experiment was on the long- and short-term reliability of radio links, estimation of link qualities, the influence of the link quality on multi-hop routing, and on neighborhood exploration.
Arsalan Minhas und Friedrich H. Vogt. Service Orientation for Dynamic Enterprises. In Proceedings of the International Conference on Logistics and Supply Chain Management (LSCM'06), Januar 2006. Hong Kong.
@InProceedings{Telematik_AV_2006_ServiceOrientationDynamicEnterprises, author = {Arsalan Minhas and Friedrich H. Vogt}, title = {Service Orientation for Dynamic Enterprises}, booktitle = {Proceedings of the International Conference on Logistics and Supply Chain Management (LSCM'06)}, day = {5-7}, month = jan, year = 2006, location = {Hong Kong}, }
Abstract: Business data is one of the most critical components of the IT portfolio of any enterprise. However enterprises are facing a major challenge of providing a holistic view of it when the data spans across multiple heterogeneous systems with different data models embedded in them. To achieve maximum benefits from the SOA, it is crucial to create a common data management approach that handles all aspects of integrating information exposed through different autonomous services in an enterprise. We present an approach by which it becomes possible to provide the holistic view of business data by actively driving simplicity and SOA project acceleration. It allows us to integrate the supply chain applications of an enterprise and hence building a competitively differentiated supply chain for the future.
Boris Gruschko, Friedrich H. Vogt und Simon Zambrovski. Business Activities in an Industrial Context. In Proceedings of the International Conference on Logistics and Supply Chain Management (LSCM'06), Januar 2006. Hong Kong.
@InProceedings{Telematik_GVZ_2006_BusinessActivity, author = {Boris Gruschko and Friedrich H. Vogt and Simon Zambrovski}, title = {Business Activities in an Industrial Context}, booktitle = {Proceedings of the International Conference on Logistics and Supply Chain Management (LSCM'06)}, day = {5-7}, month = jan, year = 2006, location = {Hong Kong}, }
Abstract: In this paper we show an approach to business activity modelling, with emphasis on identification of Services, messages being exchanged between them, collaboration scenarios and coordination protocols to be considered for the fulfilment of those scenarios. The modelling technique has been developed during business process analysis at Lufthansa Technik AG. An airframe related components overhaul process has been researched, in order to advise the concerned department, on application of loosely coupled systems. The analysis provides a basis for the inception of a SOA-based system, for the handling of airframe related components. The presented technique is not limited to the aerospace industry, but constitutes a generic approach to Service-Oriented Modelling. The main focus of this technique is the transformation from traditional, activity-based model, towards a model based upon message exchange between the participating Services. Further transition leads to the identification of collaboration patterns involved in the business activity. Given those patterns it is possible, to prove the applicability of standardized coordination protocols to the particular collaboration. We derive a methodology for structural approach to the management of business activities in SOA context, based on our experience gathered during the described analysis.
Dietrich Fahrenholtz und Andreas Wombacher. A Formal Communication Model for Lookup Operations in a Hypercube-based P2P Data Store. In Proceedings of the 1st International Conference on n Collaborative Computing: Networking, Applications and Worksharing, Dezember 2005. San Jose, USA.
@InProceedings{Telematik_FaWom_2005_LookUpHypercube, author = {Dietrich Fahrenholtz and Andreas Wombacher}, title = {A Formal Communication Model for Lookup Operations in a Hypercube-based P2P Data Store}, booktitle = {Proceedings of the 1st International Conference on n Collaborative Computing: Networking, Applications and Worksharing}, day = {19-21}, month = dec, year = 2005, location = {San Jose, USA}, }
Abstract: P2P data stores achieve high data availability by introducing replication of data. As a consequence, searching data may require to follow several routing paths introducing additional communication. A formal model of this additional communication is introduced and evaluated based on a hypercube based P2P data store.
Friedrich H. Vogt und Arsalan Minhas. Using Service Orientation to Drive Business Processes. In Proceedings of the 9th IEEE International Multi Topic Conference (MTC'05), Dezember 2005. Karachi, Pakistan.
@InProceedings{Telematik_VOGTM_2005_SOABP, author = {Friedrich H. Vogt and Arsalan Minhas}, title = {Using Service Orientation to Drive Business Processes}, booktitle = {Proceedings of the 9th IEEE International Multi Topic Conference (MTC'05)}, day = {13-25}, month = dec, year = 2005, location = {Karachi, Pakistan}, }
Abstract: This contribution proposes an approach that is necessary to model cross enterprise business processes using Service Oriented Modeling and its realization by leveraging standard Web Services protocols. It stresses the need for validation of produced models at every step of development which is essential to reduce the mistakes at early stages and raise the level of confidence. It also assures that all important aspects are considered at the right level of abstraction whereas programmatic support allows reducing project completion time.
Boris Gruschko, Friedrich H. Vogt und Simon Zambrovski. Enabling the usage of formal methods by creation of convenient tools. In Proceedings of the 2nd International Workshop on Web Services and Formal Methods (WSFM'05), September 2005. Versailles, France.
@InProceedings{Telematik_GVZ_2005_TLAEclipse, author = {Boris Gruschko and Friedrich H. Vogt and Simon Zambrovski}, title = {Enabling the usage of formal methods by creation of convenient tools}, booktitle = {Proceedings of the 2nd International Workshop on Web Services and Formal Methods (WSFM'05)}, day = {1-3}, month = sep, year = 2005, location = {Versailles, France}, }
Abstract: Creation of formal specifications is being considered a relief for the difficulties of inception and construction of distributed systems. Numerous formal methods exist for the purpose of description of distributed systems and protocols. The creation of formal specifications for these systems lacks the extensive support by tools vendors. This results in lack of sophisticated tools, which help the developer to overcome the initial training investment, shallowing the learning curve. Thus, the development of formal specification for the systems under construction stays an expensive undertaking, which lacks the immediate results, important for the overall acceptance of formal methods by the industry. In this paper we describe a plugin for the Eclipse IDE, developed to simplify the task of authoring formal specifications in the TLA+ environment. This plugin provides features, expected from an IDE for a common programming language, such as syntax highlighting, autocompletion and execution assistance.
Friedrich H. Vogt, Simon Zambrovski, Boris Gruschko, Peter Furness und Alastair Green. Implementing Web Service Protocols in SOA: WS-Coordination and WS-Business Activity. In Proceedings of the 7th IEEE International Conference on E-Commerce Technology Workshops (CEC'05), Juli 2005. München.
@InProceedings{Telematik_VZGFG_2005_WSCWSA, author = {Friedrich H. Vogt and Simon Zambrovski and Boris Gruschko and Peter Furness and Alastair Green}, title = {Implementing Web Service Protocols in SOA: WS-Coordination and WS-Business Activity}, booktitle = {Proceedings of the 7th IEEE International Conference on E-Commerce Technology Workshops (CEC'05)}, day = {19-22}, month = jul, year = 2005, location = {München}, }
Abstract: Web Service protocol standards should be unambiguous and provide a complete description of the allowed behavior of the protocols_ participants. Implementation of such protocols is an error-prone process, firstly because of the lack of precision and completeness of the standards, and secondly because of erroneous transformation of semantics from the specification to the final implementation. Applying the TLA+ paradigm we first consider the protocol on an abstract level. Safety properties taken from real world scenarios are compared to the facilities of the protocol. As result, we identified some limitation of applicability of the WS-BA protocol to abstract application use cases, modelled from the real world scenarios. These limitations are an omission of possible activities seen in the real world. Further, WS-C and WS-BA make assumptions about the internal structures of the participants, violating SOA paradigm. The former error could be detected by the use of formal methods. The latter can be circumvented by a sophisticated implementation strategy. The proposed strategy of implementing WS-Coordination and WS-BusinessActivity allows non-intrusive integration of the transactional framework, considering SOA requirements. This paper describes the results of analysis and some design decisions taken during the proof-of-concept implementation of WS-C and WS-BA frameworks.
Volker Turau, Christian Renner, Marcus Venzke, Sebastian Waschik, Christoph Weyer und Matthias Witt. The Heathland Experiment: Results And Experiences. In Proceedings of the Workshop on Real-World Wireless Sensor Networks (REALWSN'05), Juni 2005. Stockholm, Sweden.
@InProceedings{Telematik_TRVWWW_2005_Heathland, author = {Volker Turau and Christian Renner and Marcus Venzke and Sebastian Waschik and Christoph Weyer and Matthias Witt}, title = {The Heathland Experiment: Results And Experiences}, booktitle = {Proceedings of the Workshop on Real-World Wireless Sensor Networks (REALWSN'05)}, day = {20-21}, month = jun, year = 2005, location = {Stockholm, Sweden}, }
Abstract: This paper reports on the experience gained during a real-world deployment of a sensor network based on the ESB platform in the heathlands of Northern Germany. The goal of the experiment was to gain a deeper insight into the problems of real deployments as opposed to simulated networks. The focus of this report is on the quality of radio links and the influence of the link quality on multi-hop routing.
Volker Turau, Dietrich Fahrenholtz und Marcus Venzke. Online Assessment for University Admission: Goals, Problems, and Experience. In Proceedings of the 9th International Computer Assisted Assessment Conference (CAA'05), Juni 2005, pp. 457–467. Loughborough, UK.
@InProceedings{Telematik_TFV_2005_OnlineAssessment, author = {Volker Turau and Dietrich Fahrenholtz and Marcus Venzke}, title = {Online Assessment for University Admission: Goals, Problems, and Experience}, booktitle = {Proceedings of the 9th International Computer Assisted Assessment Conference (CAA'05)}, pages = {457-467}, day = {5-6}, month = jun, year = 2005, location = {Loughborough, UK}, }
Abstract: This paper reports on the experience gained during the implementation and operation of an online assessment system for recruitment of engineering and computer science students. We identified problems that have to be solved to make online assessment a worthwhile building block of university admission. The presented work includes techniques for evaluating and monitoring online assessment processes.
Jurga Kazlauskaite, Arsalan Minhas und Friedrich H. Vogt. Applying Service Oriented Architecture in the Aerospace Industry. In Proceedings of the International Mass Customization Meeting (IMCM'05), GITO-Verlag, Berlin, Juni 2005. Klagenfurt, Austria.
@InProceedings{Telematik_KMV_2005_SOA, author = {Jurga Kazlauskaite and Arsalan Minhas and Friedrich H. Vogt}, title = {Applying Service Oriented Architecture in the Aerospace Industry}, booktitle = {Proceedings of the International Mass Customization Meeting (IMCM'05)}, publisher = {GITO-Verlag, Berlin}, day = {2-3}, month = jun, year = 2005, location = {Klagenfurt, Austria}, }
Abstract: This paper proposes the sequence of steps that are necessary to produce efficiently working Service Oriented Architecture for cross enterprise business processes and stresses the need for verification and programmatic support at every step of development. Verification of produced models at early stages allows the reduction of mistakes and assures that all important aspects have been included whereas programmatic support reduces the 'double' work and allows reducing project completion time.
Matthias Witt und Volker Turau. BGR: Blind Geographic Routing for Sensor Networks. In Proceedings of the Third Workshop on Intelligent Solutions in Embedded Systems (WISES'05), Mai 2005, pp. 51–61. Hamburg, Germany.
@InProceedings{Telematik_WT_2005_BGR, author = {Matthias Witt and Volker Turau}, title = {BGR: Blind Geographic Routing for Sensor Networks}, booktitle = {Proceedings of the Third Workshop on Intelligent Solutions in Embedded Systems (WISES'05)}, pages = {51-61}, day = {20}, month = may, year = 2005, location = {Hamburg, Germany}, }
Abstract: This paper introduces BGR, a new beacon-less geographic routing algorithm for wireless sensor networks. Data packets are forwarded toward the destination, and nodes which hear the packet compete for becoming the next hop. A recovery strategy is provided for the case of empty forwarding areas. The main innovation is a strategy to avoid simultaneous forwarding situations, which would otherwise cause packet failures. It is confirmed by simulation that BGR sends very few packets and is reliable in fields with sufficiently high node density. Furthermore, BGR is compared with similar algorithms after developing a general framework for beacon-less algorithms with an integrative terminology. Different kinds of forwarding areas are compared.
Marcus Venzke, Christoph Weyer und Volker Turau. Application Specific vs. Standard Web Service Interfaces for the Vertical Integration of Fieldbus Systems. In Proceedings of the Third Workshop on Intelligent Solutions in Embedded Systems (WISES'05), Mai 2005, pp. 153–162. Hamburg, Germany.
@InProceedings{Telematik_VWT_2005_WebService, author = {Marcus Venzke and Christoph Weyer and Volker Turau}, title = {Application Specific vs. Standard Web Service Interfaces for the Vertical Integration of Fieldbus Systems}, booktitle = {Proceedings of the Third Workshop on Intelligent Solutions in Embedded Systems (WISES'05)}, pages = {153-162}, day = {20}, month = may, year = 2005, location = {Hamburg, Germany}, }
Abstract: The paper compares two approaches for developing Web service interfaces for the vertical integration of TTP/A fieldbus systems. High-level abstractions are provided by application specific interfaces, generated from metadata describing fieldbus systems. In contrast standardised interfaces such as OPC XML DA only allow lower levels of abstractions. But these enable accessing the fieldbus system from a broad range of standard clients, while high-level abstractions reflecting the application programmer's view on the system facilitate the development of more specific clients and workflows.
Marcus Venzke. Specifications using XQuery Expressions on Traces. In Proceedings of the First International Workshop on Web Services and Formal Methods (WS-FM'04), Dezember 2004. Pisa, Italy. Published in: Electronic Notes in Theoretical Computer Science, Volume 105, p. 109-118, 10 December 2004.
@InProceedings{Telematik_Venzke_2004_Specifications, author = {Marcus Venzke}, editor = {Mario Bravetti and Gianluigi Zavattaro}, title = {Specifications using XQuery Expressions on Traces}, booktitle = {Proceedings of the First International Workshop on Web Services and Formal Methods (WS-FM'04)}, month = dec, year = 2004, location = {Pisa, Italy}, note = {Published in: Electronic Notes in Theoretical Computer Science, Volume 105, p. 109-118, 10 December 2004}, }
Abstract: This paper contributes to the interoperability of web services by proposing the flexible specification technique SXQT in conjunction with the automatic validation, a straightforward approach for detecting non-conformance. SXQT allows different levels of abstraction by specifying individual requirements on a web service's protocol, i.e. its SOAP messages and behaviour including SOAP modules. The automatic validation detects non-conformance by comparing occurring message sequences with the protocol's specification.
James E. Johnson, David E. Langworthy, Leslie Lamport und Friedrich H. Vogt. Formal Specification of a Web Services Protocol. In Proceedings of the First International Workshop on Web Services and Formal Methods (WS-FM'04), Dezember 2004. Pisa, Italy. Published in: Electronic Notes in Theoretical Computer Science, Volume 105, p. 147-158, 10 December 2004.
@InProceedings{Telematik_JLLV_2004_TLA, author = {James E. Johnson and David E. Langworthy and Leslie Lamport and Friedrich H. Vogt}, editor = {Mario Bravetti and Gianluigi Zavattaro}, title = {Formal Specification of a Web Services Protocol}, booktitle = {Proceedings of the First International Workshop on Web Services and Formal Methods (WS-FM'04)}, month = dec, year = 2004, location = {Pisa, Italy}, note = {Published in: Electronic Notes in Theoretical Computer Science, Volume 105, p. 147-158, 10 December 2004}, }
Abstract: We describe a use of formal methods to specify and check a Web Services protocol. The Web Services Atomic Transaction protocol was specified in TLA+ and checked with the TLC model checker. A modest effort revealed oversights that caused unanticipated behaviors of the protocol; these were corrected by clarifications and changes to the protocol.
Volker Turau und Christoph Weyer. Location-aware In-Network Monitoring in Wireless Sensor Networks. In Proceedings of the 34th Jahrestagung der Gesellschaft für Informatik e.V. (INFORMATIK'04), Volume 2, Workshop Sensor Networks, September 2004, pp. 355–359. Ulm, Germany.
@InProceedings{Telematik_TW_2004_InNetworkMonitoring, author = {Volker Turau and Christoph Weyer}, title = {Location-aware In-Network Monitoring in Wireless Sensor Networks}, booktitle = {Proceedings of the 34th Jahrestagung der Gesellschaft für Informatik e.V. (INFORMATIK'04), Volume 2, Workshop Sensor Networks}, pages = {355-359}, day = {20-24}, month = sep, year = 2004, location = {Ulm, Germany}, }
Abstract: This paper presents a data-centric and location-aware procedure to perform in-network evaluation of queries in sensor networks. The algorithm is a hybrid of geographic hash tables and in-network aggregation. It increases data availability and accounts for topology changes and generates mostly local network traffic.
Dietrich Fahrenholtz und Volker Turau. A Tree-based DHT Approach to Scalable Weakly Consistent Data Management. In Proceedings of the First International Workshop on P2P Data Management, Security and Trust (PDMST'04), IEEE Computer Society Press, August 2004, pp. 991–998. Zaragoza, Spain.
@InProceedings{Telematik_FT_2004_TreebasedDHT, author = {Dietrich Fahrenholtz and Volker Turau}, title = {A Tree-based DHT Approach to Scalable Weakly Consistent Data Management}, booktitle = {Proceedings of the First International Workshop on P2P Data Management, Security and Trust (PDMST'04)}, pages = {991-998}, publisher = {IEEE Computer Society Press}, month = aug, year = 2004, location = {Zaragoza, Spain}, }
Volker Turau, Marcus Venzke, Christoph Weyer und Yesenia Vigil. Vertical Integration of TTP/A Fielbus Systems Using Web Services. In Proceedings of the First International Conference on Informatics in Control, Automation and Robotics (ICINCO'04), August 2004, pp. 390–393. Setubal, Portugal.
@InProceedings{Telematik_TVW_2004_VerticalIntegration, author = {Volker Turau and Marcus Venzke and Christoph Weyer and Yesenia Vigil}, title = {Vertical Integration of TTP/A Fielbus Systems Using Web Services}, booktitle = {Proceedings of the First International Conference on Informatics in Control, Automation and Robotics (ICINCO'04)}, pages = {390-393}, month = aug, year = 2004, location = {Setubal, Portugal}, }
Abstract: This paper presents a generic technique to expose data and control of fieldbus systems to applications located at the level of operational management. To provide a high degree of interoperability between the operational level and different fieldbus systems we utilize standardized techniques such as XML, HTTP, and Web services which can be deployed independently of the platform. The proposed service is based on the interface file system for TTP/A smart transducers. The defined interface provides high level abstractions appropriate for the integration into business applications and considers the latency introduced by the internet protocols.
Volker Turau, Marcus Venzke und Christoph Weyer. A Web Service for TTP/A Fieldbus Systems based on Meta-Data. In Proceedings of the Second Workshop on Intelligent Solutions in Embedded Systems (WISES'04), Juni 2004, pp. 159–168. Graz, Austria.
@InProceedings{Telematik_TVW_2004_MetaData, author = {Volker Turau and Marcus Venzke and Christoph Weyer}, title = {A Web Service for TTP/A Fieldbus Systems based on Meta-Data}, booktitle = {Proceedings of the Second Workshop on Intelligent Solutions in Embedded Systems (WISES'04)}, pages = {159-168}, month = jun, year = 2004, location = {Graz, Austria}, }
Abstract: This paper is concerned with the vertical integration of fieldbus systems. It presents a generic technique to expose data and control of fieldbus systems in a semantically rich way to applications located at the level of operational management. To provide a high degree of interoperability between the operational level and different fieldbus systems we utilize standardized techniques such as XML, HTTP, and Web services which can be deployed independently of the platform. The proposed service is based on the interface file system for TTP/A smart transducers. The defined interface provides high level abstractions appropriate for the integration into business applications and considers the latency introduced by the internet protocols. The operations of the service are automatically generated from meta-data descriptions of the smart transducers and their combination into larger clusters.
Muhammad F. Kaleem. Towards Identifying Representative Characteristics of Web Services Compositions. In Proceedings of the 7th International Conference on Business Information Systems, April 2004. Poznan, Poland.
@InProceedings{Telematik_Kaleem_2004_WSCompositions, author = {Muhammad F. Kaleem}, editor = {Witold Abramowicz}, title = {Towards Identifying Representative Characteristics of Web Services Compositions}, booktitle = {Proceedings of the 7th International Conference on Business Information Systems}, month = apr, year = 2004, location = {Poznan, Poland}, }
Muhammad F. Kaleem. Focusing on Interactions for Composition for Robust Composite Services. In Proceedings of the 1st Australian Workshop on Engineering Service-Oriented Systems (AWESOS 2004), April 2004. Melbourne, Australia.
@InProceedings{Telematik_Kaleem_2004_RobustCompositeServices, author = {Muhammad F. Kaleem}, title = {Focusing on Interactions for Composition for Robust Composite Services}, booktitle = {Proceedings of the 1st Australian Workshop on Engineering Service-Oriented Systems (AWESOS 2004)}, month = apr, year = 2004, location = {Melbourne, Australia}, }
Marcus Venzke. Automatic Validation of Web Services. In Proceedings of the 8th CaberNet Radicals Workshop, Oktober 2003. Ajaccio, Corsica.
@InProceedings{Telematik_Venzke_2003_Validation, author = {Marcus Venzke}, editor = {Witold Abramowicz}, title = {Automatic Validation of Web Services}, booktitle = {Proceedings of the 8th CaberNet Radicals Workshop}, day = {5-8}, month = oct, year = 2003, location = {Ajaccio, Corsica}, }
Volker Turau. Die Rolle von Web-Services im Middleware Spektrum. In Proceedings of the 26th European Congress Fair of Technical Communications (ONLINE'03), September 2003. Düsseldorf, Germany.
@InProceedings{Telematik_Turau_2003_WebServices, author = {Volker Turau}, title = {Die Rolle von Web-Services im Middleware Spektrum}, booktitle = {Proceedings of the 26th European Congress Fair of Technical Communications (ONLINE'03)}, month = sep, year = 2003, location = {Düsseldorf, Germany}, }
Muhammad F. Kaleem. A Classification Framework for Approaches and Methodologies to make Web Services Compositions Reliable. In Proceedings of the First European Workshop on Object Orientation and Web Service (EOOWS'03), Juli 2003. Darmstadt, Germany.
@InProceedings{Telematik_Kaleem_2003_ReliableWSCompositions, author = {Muhammad F. Kaleem}, title = {A Classification Framework for Approaches and Methodologies to make Web Services Compositions Reliable}, booktitle = {Proceedings of the First European Workshop on Object Orientation and Web Service (EOOWS'03)}, month = jul, year = 2003, location = {Darmstadt, Germany}, }
Volker Turau. HTTPExplorer: Exploring the Hypertext Transfer Protocol. In Proceedings of the 8th Annual Conference Innovation and Technology in Computer Science Education (ITiCSE'03), Juli 2003. Thessaloniki, Greece.
@InProceedings{Telematik_Turau_2003_HTTPExplorer, author = {Volker Turau}, title = {HTTPExplorer: Exploring the Hypertext Transfer Protocol}, booktitle = {Proceedings of the 8th Annual Conference Innovation and Technology in Computer Science Education (ITiCSE'03)}, month = jul, year = 2003, location = {Thessaloniki, Greece}, }
Marcus Venzke und Stefan Pitzek. Accessing Fieldbus Systems via Web Services. In Proceedings of the First Workshop on Intelligent Solutions in Embedded Systems (WISES'03), Juni 2003. Vienna, Austria.
@InProceedings{Telematik_VP_2003_WebServices, author = {Marcus Venzke and Stefan Pitzek}, title = {Accessing Fieldbus Systems via Web Services}, booktitle = {Proceedings of the First Workshop on Intelligent Solutions in Embedded Systems (WISES'03)}, day = {27}, month = jun, year = 2003, location = {Vienna, Austria}, }
U. Gröning und Friedrich H. Vogt. ZULIS - Zulieferlogistik-Informationssystem für KMU im Flugzeugbau. In Proceedings of the 12th Hamburger Logistik-Kolloquium, März 2003. Hamburg, Germany.
@InProceedings{Telematik_GV_2003_ZULIS, author = {U. Gröning and Friedrich H. Vogt}, title = {ZULIS - Zulieferlogistik-Informationssystem für KMU im Flugzeugbau}, booktitle = {Proceedings of the 12th Hamburger Logistik-Kolloquium}, month = mar, year = 2003, location = {Hamburg, Germany}, }
Volker Turau. A Caching System for Web Content Generated from XML Sources Using XSLT. In Proceedings of the OOIS 2002 Workshops on Advances in Object-Oriented Information Systems, Springer, September 2002, pp. 197–206. Montpellier, France.
@InProceedings{Telematik_Turau_2002_XSLTCache, author = {Volker Turau}, title = {A Caching System for Web Content Generated from XML Sources Using XSLT}, booktitle = {Proceedings of the OOIS 2002 Workshops on Advances in Object-Oriented Information Systems}, pages = {197-206}, series = {Lecture Notes in Computer Science}, volume = {2426}, publisher = {Springer}, month = sep, year = 2002, location = {Montpellier, France}, }
Volker Turau. A framework for automatic generation of web-based data entry applications based on XML. In Proceedings of the 2002 ACM Symposium on Applied Computing, ACM, März 2002, pp. 1121–1126. Madrid, Spain.
@InProceedings{Telematik_Turau_2002_framework, author = {Volker Turau}, title = {A framework for automatic generation of web-based data entry applications based on XML}, booktitle = {Proceedings of the 2002 ACM Symposium on Applied Computing}, pages = {1121-1126}, publisher = {ACM}, month = mar, year = 2002, location = {Madrid, Spain}, }

Dissertationen

Holger Machens. Cloned Transactions: A New Execution Concept for Transactional Memory. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2015.
@PhdThesis{Telematik_Machens_2015_Diss, author = {Holger Machens}, title = {Cloned Transactions: A New Execution Concept for Transactional Memory}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, year = 2015, }
Abstract: Transactional memory aims to replace mutual exclusion in critical sections with transactions on shared data to improve the scalability of concurrent applications and eliminate traditional issues of parallel programming such as deadlocks/livelocks. One key aspect of transaction processing is the concurrency control, which is responsible to find an interleaving or overlapping schedule for running transactions accessing the same shared data and provide a result equal to some serial execution of the same transactions. In this regard, former research focused on single-threaded concurrency control schemes using trial and error approach: The transaction repeats executing the critical section until no conflict with other transactions was detected. This thesis proposes the application of helper threads in transactional memory to achieve a parallelised transaction processing, which is able to compute the same critical section in respect to different serialisation orders with other transactions. While traditional concurrency control has to rollback and start another attempt in the same thread, this approach aims to compute the next attempt in a helper thread in a parallel to current attempt computed by a leading thread. Due to the nature of transactions and concurrent shared memory applications in general, the introduction of helper threads comes with several new aspects to be considered on the conceptional and the implementation level. The work presents concepts for helper thread aided concurrency controls independently executing the same transaction in parallel instead of sharing information of the leader thread, to lower the contention. For example, the detection of conflicts is delegated to a helper thread which executes the same transaction on the same state of shared data in parallel instead of validating the data read by the leader. In this manner parallelised transaction processing has been proposed which executes a transaction in parallel with different validation schemes: lazy and eager validation. Because the reaction time on conflicts and execution time differ, they drift apart and compute results for different serialisation orders. The work also presents several requirements and sub-systems needed to run parallelised transactions: The use of so-called transactional wrappers or pure functions to speedup access to thread private data in transactional sections cannot be granted, because the provate data of the application thread is now concurrently accessed by the helper thread. Also, a concept has been developed to clone the state of the transaction start and transfer the state of the helper committed transaction back to the leader. The existing sandboxing approach of Dalessandro and Scott to suppress and prevent errors in transactions resulting from lazy validation has been improved and memory management inside transactions was adapted. While the development approaches can compete in some cases and show good scalability especially in higher concurrency, the evaluation shows an unexpected large loss of performance, too. An investigation of hardware characteristics in respect to memory and cache read/write latency revealed several scalability issues with concurrent access to the same address.These issues have significant impact on highly concurrent applications, which seriously affects the use of transaction in general and parallelised transactions in particular.
Helge Klimek. Überlast-Behandlung für ortsbezogene Dienste in drahtlosen Infrastruktur-Netzen in Gebäuden. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2014.
@PhdThesis{Telematik_Klimek_2014_Diss, author = {Helge Klimek}, title = {Überlast-Behandlung für ortsbezogene Dienste in drahtlosen Infrastruktur-Netzen in Gebäuden}, publisher = {Cuvillier Verlag, Göttingen, Germany}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, edition = {1st}, year = 2014, isbn = {978-3-95404-835-9}, }
Abstract: Drahtlose Infrastruktur-Netze bestehen aus mobilen Geräten, welche drahtlos mit einem Backend aus fest installierten Basisstationen und Server kommunizieren. Die Basisstationen und der Server sind über eine kabelgebundene Schnittstelle, zum Beispiel Ethernet, miteinander verbunden. Die mobilen Geräte empfangen und senden Daten immer direkt zu Basisstationen, eine direkte Kommunikation zwischen den mobilen Geräten ist nicht vorgesehen. Infrastruktur-Netze in Gebäuden können genutzt werden um ortsbezogene Dienste anzubieten. In dieser Arbeit wird als Fallbeispiel der Gebäudekomplex eines Flughafens mit den für einen Flughafen spezifischen Diensten Indoor-Navigation, Benachrichtigung von Passagieren, Informationsabfragen durch Passagiere sowie Werbebotschaften betrachtet. Führen Benutzer diese Dienste aus und betreten oder verlassen eine Zelle, ändert sich die Last auf diese Zelle. Die Mobilität kann dazu führen, dass sehr viele Benutzer in eine Funkzelle eintreten und so deren Leistungsfähigkeit überschritten wird. In einem solchen Fall sind alle Geräte in der Zelle von der Überlastung betroffen. Es werden Verfahren vorgestellt, um Überlast zu erkennen, zu reduzieren, sowie zu vermeiden. Bei der Vermeidung geht es darum, unter Ausnutzung von anwendungsbezogenem Wissen Überlastungs-Situationen von vornherein zu umgehen. Die Überlast-Erkennung dient zur Ermittlung des Netz-Zustands und bildet mit ihrer Bewertung die Grundlage zur Überlast-Reduktion. Sie kann zentral oder verteilt auf die Netzknoten erfolgen. Eine wichtige Nebenbedingung dabei ist, dass die Netz-Ressourcen nicht durch weitere Kommunikation zur Behandlung von Überlast zusätzlich belastet werden. Erkennungs-Verfahren, die Informationen an den Kommunikations-Endpunkten ermitteln und auf Verlustraten oder Latenzen aufbauen, liefern in Infrastruktur-Netzen mit mobilen Benutzern keine zuverlässigen Ergebnisse: Verluste und Verzögerungen resultieren nicht ausschließlich aus der Überlastung einer Zelle, sondern auch aus falschen Ortsinformationen in den Übergangsprotokollen. Mit den Basisstationen als zentraler Kommunikationspunkt für alle Geräte in ihrer Zelle bietet sich jedoch ein guter Ansatzpunkt, mit netzunterstützten Verfahren Überlast-Informationen aus dem Netz zu extrahieren. Die vorgestellten Verfahren zielen auf die zelluläre Struktur des Netzes und werden in Simulationen für zwei unterschiedliche Kommunikations-Protokolle untersucht. Nachrichten können zur Behandlung über einen größeren Zeitraum und so über eine größere Fläche verteilt werden, zum Beispiel indem bei elastischen Anwendungen die Zeitschranken für Neu-Übertragungen vergrößert werden. Reicht dies allein nicht aus, besteht die Möglichkeit die Kommunikation einzuschränken, beispielsweise indem festgelegt wird, welche Anwendungen von mobilen Geräten ausgeführt werden dürfen. In Simulationen kann gezeigt werden, dass die Überlast-Vermeidung für das beschriebene Fallbeispiel wirkungsvoll das Eintreten von Überlastungssituationen in einer Zelle verhindern kann. Insbesondere die netzunterstützten Verfahren, die das Paketaufkommen und den Funkkanal betrachten, zeigen eine gute Erkennungsleistung. Die Kombination aus Überlast-Erkennung und –Reduktion kann, je nach Szenario, Überlast deutlich abfedern. Es gibt jedoch Szenarien, in denen die physikalischen Grenzen des Systems überschritten werden. Hier helfen die eingesetzten Verfahren dabei, das System schnell wieder in einen nutzbaren Zustand zurückzubringen.
Sven Köhler. Scalable Fault-Containing Self-Stabilization in Dynamic Networks. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2014.
@PhdThesis{Telematik_Köhler_2013_Diss, author = {Sven Köhler}, title = {Scalable Fault-Containing Self-Stabilization in Dynamic Networks}, publisher = {Cuvillier Verlag, Göttingen, Germany}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, edition = {1st}, year = 2014, isbn = {978-3-95404-782-6}, }
Abstract: Self-stabilizing distributed systems provide a high degree of non-marking fault-tolerance. They recover from transient faults of any scale or nature without human intervention. In general, however, the time needed to recover from small-scale transient faults may not differ significantly from the time needed to recover from large-scale transient faults. Bounding the impact of small-scale faults has been pursued with two independent objectives: reducing the time needed to recover from state corruptions, e.g., fault-containment, and optimizing the system’s reaction upon topological changes, e.g., super-stabilization. The objective of fault-containing self-stabilization is to limit the effects of the corruption of a single node’s state to a local area, i.e., to contain the fault, and to ensure that correctness of the output is regained within constant time. Transformations that add the property of fault-containment to any silent self-stabilizing algorithm exist. However, their fault-gap, i.e., the time needed to prepare for the containment of another fault, is linear in the number of nodes. Hence, these transformations do not perform well in large networks. The root cause of this is the use of global synchronization and reset. This thesis presents a novel scheme for local synchronization. Based on it, a new transformation for adding fault-containment to silent self-stabilizing algorithms is developed. Its fault-gap and slowdown are constant. These are major improvements over previous solutions. The effects of a state corruption are strictly limited to the 2-hop neighborhood of the fault. Similar to previous work, the transformation creates backups of a node’s local state to detect and revert state corruptions. However, the number of backups per node is reduced from O(∆) to 2 backups per node. In order to balance the number of backups stored by each node, this thesis presents a self-stabilizing algorithm for computing a placement of backups such that the standard deviation of the number of backups stored per node assumes a local minimum. Super-stabilizing algorithms are not only self-stabilizing, but also guarantee that a safety property is satisfied while the system recovers from a topology change. This thesis introduces the notion of fault-containing super-stabilization and presents a transformation that can be used to add fault-containment to any silent super-stabilizing algorithm. Fault-containing super-stabilizing distributed algorithms are fault-containing, super-stabilizing, and guarantee that the safety property is satisfied within constant time even if a corruption of a single node’s state and a topology change occur at the same time. The transformations and algorithms presented in this thesis all work under the most general model used in self-stabilization research: the unfair distributed scheduler. Their correctness is proven using a new technique called serialization introduced in this thesis. It is based on the observation that it is possible to replace the parallel execution of a distributed algorithm with a sequential execution, provided the algorithm satisfies a particular condition.
Stefan Unterschütz. Methodologies and Protocols for Wireless Communication in Large-Scale, Dense Mesh Networks. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2014.
@PhdThesis{Telematik_Unterschuetz_2014_Diss, author = {Stefan Unterschütz}, title = {Methodologies and Protocols for Wireless Communication in Large-Scale, Dense Mesh Networks}, publisher = {Cuvillier Verlag, Göttingen, Germany}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, edition = {1st}, year = 2014, isbn = {978-3-95404-707-9}, }
Abstract: This dissertation examines concepts for wireless communication in large-scale, dense mesh networks, which can be used in future for plant control or building automation. It is shown that recent communication approaches for resource-constrained, IEEE 802.15.4 hardware do not scale well. This motivates the development of methodologies and protocols for reliable wireless communication in large-scale networks. This work covers the following topics: a "toolbox" for the development, programming, testing, and simulation of communication protocols for embedded systems; the decomposition of large networks into smaller subnets; concepts for scalable broadcasting and routing; the realization of selected network services such as emergency shutdowns and software updates.
Bernd-Christian Renner. Sustained Operation of Sensor Nodes with Energy Harvesters and Supercapacitors. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2013.
@PhdThesis{Telematik_Renner_2013_Diss, author = {Bernd-Christian Renner}, title = {Sustained Operation of Sensor Nodes with Energy Harvesters and Supercapacitors}, publisher = {Books on Demand GmbH, Norderstedt, Germany}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, edition = {1st}, year = 2013, isbn = {978-3-7322-3319-9}, }
Abstract: Sensor nodes powered by energy harvesters and supercapacitors open the door to unlimited and uninterrupted operation. This dissertation closes the persistent gap of system integration w.r.t. holistic online energy assessment, develops a new concept for harvest forecasting while assessing the behavior and quality of known approaches, and proposes a novel load adaptation scheme to achieve sustained and uniform sensor node operation with low complexity and computational overhead. For this purpose, a prototype of an energy harvester with a supercapacitor for off-the-shelf sensor nodes is developed and used for practical evaluation.
Arne Bosien. RFID-basierte Navigation für autonome Fahrzeuge. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2012.
@PhdThesis{Telematik_Bosien_2012_Diss, author = {Arne Bosien}, title = {RFID-basierte Navigation für autonome Fahrzeuge}, publisher = {Books on Demand GmbH, Norderstedt, Germany}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, edition = {1st}, year = 2012, isbn = {978-3-8448-0979-4}, }
Abstract: In dieser Arbeit wurden die Möglichkeiten eines pheromonbasierten Navigationsverfahrens mittels wiederbeschreibbarer RFID-Tags untersucht. Im Gegensatz zu anderen Ansätzen wird hier auf eine eindeutige Fahrzeuglokalisierung verzichtet. Es wurden Algorithmen für die Navigation entwickelt und in einem Test-System evaluiert. Um eine höhere Fahrgeschwindigkeit zu erreichen, wurden Antikollisionsalgorithmen für das Inventory optimiert. Des Weiteren wurde ein neuer Inventory-Ansatz ausgearbeitet, der insbesondere für die untersuchten Navigationssysteme geeignet ist.
Bernd Hauck. Time- and Space-Efficient Self-Stabilizing Algorithms. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2012.
@PhdThesis{Telematik_Hauck_2012_Diss, author = {Bernd Hauck}, title = {Time- and Space-Efficient Self-Stabilizing Algorithms}, publisher = {Cuvillier Verlag, Göttingen, Germany}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, edition = {1st}, year = 2012, isbn = {978-3-95404-324-8}, }
Abstract: Self-stabilization is a general approach to design a system to tolerate arbitrary transient faults. This thesis presents new time- and space-efficient self-stabilizing algorithms for well-known problems in graph theory and provides new complexity analyzes for existing algorithms. The main focus of this thesis is on the proof techniques used in the complexity analyzes and the design of the algorithms.
Dietrich Fahrenholtz. A Hypercube-based Peer-to-Peer Data Store Resilient against Peer Population Fluctuation. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2008.
@PhdThesis{Telematik_Fahrenholtz_2008_Diss, author = {Dietrich Fahrenholtz}, title = {A Hypercube-based Peer-to-Peer Data Store Resilient against Peer Population Fluctuation}, publisher = {Cuvillier Verlag, Göttingen, Germany}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, edition = {1st}, year = 2008, isbn = {978-3-86727-498-2}, }
Matthias Witt. Robust and Low-Communication Geographic Routing for Wireless Ad Hoc Networks. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2008.
@PhdThesis{Telematik_Witt_2008_Diss, author = {Matthias Witt}, title = {Robust and Low-Communication Geographic Routing for Wireless Ad Hoc Networks}, publisher = {Cuvillier Verlag, Göttingen, Germany}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, edition = {1st}, year = 2008, isbn = {978-3-86727-733-4}, }
Marcus Venzke. Spezifikation von interoperablen Webservices mit XQuery. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, Dezember 2003.
@PhdThesis{Telematik_Venzke_2003_Spezifikation, author = {Marcus Venzke}, title = {Spezifikation von interoperablen Webservices mit XQuery}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, month = dec, year = 2003, }
Abstract: The thesis solves interoperability issues regarding Web Services. The W3C standard for the specification of their interfaces (WSDL) is made more precise. This is done by developing a specification technique (SXQT), that allows specifying interfaces using expressions of first order logic (in XQuery). Compliance with such specifications is checked with the automatic validation.

Technische Berichte

Gerry Siegemund und Volker Turau. PSVR - Self-stabilizing Publish/Subscribe Communication for Ad-hoc Networks. Technical Report arXiv:1609.06841, arXiv.org e-Print archive, Cornell University, September 2016.
@TechReport{Telematik_2016_PSVR, author = {Gerry Siegemund and Volker Turau}, title = {PSVR - Self-stabilizing Publish/Subscribe Communication for Ad-hoc Networks}, number = {arXiv:1609.06841}, institution = {arXiv.org e-Print archive}, address = {Cornell University}, month = sep, year = 2016, }
Abstract: This paper presents the novel routing algorithm PSVR for pub/sub systems in ad-hoc networks. Its focus is on scenarios where communications links are unstable and nodes frequently change subscriptions. PSVR presents a compromise of size and maintenance effort for routing tables due to sub- and unsubscriptions and the length of routing paths. Designed in a self-stabilizing manner it scales well with network size. The evaluation reveals that PSVR only needs slightly more messages than a close to optimal routing structure for publication delivery, and creates shorter routing paths than an existing self-stabilizing algorithm. A real world deployment shows the usability of the approach.
Florian Meier und Volker Turau. Analytical Model for IEEE 802.15.4 Multi-Hop Networks with Improved Handling of Acknowledgements and Retransmissions. Technical Report arXiv:1501.07594, arXiv.org e-prints, Januar 2015.
@TechReport{Telematik_ARXIV_Multihop_Networks, author = {Florian Meier and Volker Turau}, title = {Analytical Model for IEEE 802.15.4 Multi-Hop Networks with Improved Handling of Acknowledgements and Retransmissions}, number = {arXiv:1501.07594}, institution = {arXiv.org e-prints}, month = jan, year = 2015, }
Abstract: The IEEE 802.15.4 standard allows for the deployment of cost-effective and energy-efficient multi-hop networks. This document features an in-depth presentation of an analytical model for assessing the performance of such networks. It considers a generic, static topology with Poisson distributed data-collection as well as data-dissemination traffic. The unslotted CSMA/CA MAC layer of IEEE 802.15.4 is closely modeled as well as an enhanced model of the neighborhood allows for consideration of collisions of packets including interferences with acknowledgements. The hidden node problem is taken into account as well as a formerly disregarded effect of repeated collisions of retransmissions. The model has been shown to be suitable to estimate the capacity of large-scale multi-hop networks.
Volker Turau. Analyzing the Fault-Containment Time of Self-Stabilizing Algorithms - Case Study for Graph Coloring. Technical Report, November 2014.
@TechReport{Telematik_2014_CORR, author = {Volker Turau}, title = {Analyzing the Fault-Containment Time of Self-Stabilizing Algorithms - Case Study for Graph Coloring}, journal = {CoRR}, volume = {abs/1410.6669}, month = nov, year = 2014, }
Abstract: The paper presents techniques to derive upper bounds for the mean time to recover from a single fault for self-stabilizing algorithms in the message passing model. For a new ∆ + 1-coloring algorithm we analytically derive a bound for the mean time to recover and show that the variance is bounded by a small constant independent of the network’s size. For the class of bounded-independence graphs (e.g. unit disc graphs) all containment metrics are in O(1).
Gerry Siegemund, Volker Turau, Stefan Lohs und Jörg Nolte. Directed Link Utilization with Mahalle+. In Proceedings of the 12th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'13), September 2013. Cottbus, Germany.
@InProceedings{Telematik_STLN_2013_DirectedLinkUtil, author = {Gerry Siegemund and Volker Turau and Stefan Lohs and Jörg Nolte}, title = {Directed Link Utilization with Mahalle+}, booktitle = {Proceedings of the 12th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'13)}, day = {12-13}, month = sep, year = 2013, location = {Cottbus, Germany}, }
Abstract: Self-stabilization provides non-masking fault toler- ance in distributed systems. Self-stabilizing algorithms (SSA) are defined on the assumption that either the system’s topology is fixed over time or topology changes are isolated events occurring at a very low rate. These assumptions are not valid in wireless sensor networks (WSNs) where link qualities change rapidly. Therefore, neighborhood management protocols (NMP) are used to ensure the stability of the network topology for a longer time period. Furthermore, symmetrical links between nodes are more desirable than unsymmetrical ones, therefore, unidirectional links are often omitted. This paper presents an augmentation of the NMP Mahalle+to transparently utilize certain unidirectional links to increase the performance of SSAs running on top of Mahalle+.
Holger Machens und Volker Turau. Opacity of Memory Management in Software Transactional Memory. Technical Report Report arXiv:1308.2881, arXiv.org e-Print archive, Cornell University, August 2013.
@TechReport{Telematik_MT_2013_OPACITY_of_MM_in_TM, author = {Holger Machens and Volker Turau}, title = {Opacity of Memory Management in Software Transactional Memory}, number = {Report arXiv:1308.2881}, institution = {arXiv.org e-Print archive}, address = {Cornell University}, month = aug, year = 2013, }
Abstract: Opacity of Transactional Memory is proposed to be established by incremental validation. Quiescence in terms of epoch-based memory reclamation is applied to deal with doomed transactions causing memory access violations. This method unfortunately involves increased memory consumption and does not cover reclamations outside of transactions. This paper introduces a different method which combines incremental validation with elements of sandboxing to solve these issues.
Gerry Siegemund und Stefan Lohs. GlueAPI - Joining REFLEX and CometOS. Technical Report urn:nbn:de:gbv:830-tubdok-12285, Hamburg University of Technology, Hamburg, Germany, 2013.
@TechReport{Telematik_Siegemund_2013_GlueAPI, author = {Gerry Siegemund and Stefan Lohs}, title = {GlueAPI - Joining REFLEX and CometOS}, number = {urn:nbn:de:gbv:830-tubdok-12285}, institution = {Hamburg University of Technology}, address = {Hamburg, Germany}, year = 2013, }
Abstract: Wireless sensor networks (WSN) are build for various tasks in arbitrary environments. Operating systems for sensor nodes, the components of WSNs, appear in multiple forms, from a variety of vendors, universities, or private persons. The GlueAPI is a merge layer to combine the usability of two such operating systems: REFLEX of the Brandenburg University of Technology and CometOS of the Hamburg University of Technology. Both operating systems are suitable for simulations using the OMNeT++ framework and several hardware platforms.
Stefan Lohs, Gerry Siegemund, Jörg Nolte und Volker Turau. Mission Statement: ToleranceZone A Self-Stabilizing Middleware for Wireless Sensor Netzworks. In Proceedings of the 11th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'12), September 2012. Darmstadt, Germany.
@InProceedings{Telematik_LSNT_2012_TZone_Mission, author = {Stefan Lohs and Gerry Siegemund and Jörg Nolte and Volker Turau}, title = {Mission Statement: ToleranceZone A Self-Stabilizing Middleware for Wireless Sensor Netzworks}, booktitle = {Proceedings of the 11th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'12)}, day = {13-14}, month = sep, year = 2012, location = {Darmstadt, Germany}, }
Abstract: Wireless sensor networks (WSN) can be used in a wide range of monitoring and controlling applications. These networks consist of nodes with sparse resources, which makes application implementation challenging. Therefore, many mid- dleware systems were developed in the last decade. Furthermore, unattended and long-living deployments of WSNs need fault-tolerant software architectures. The goal of the TOLERANCEZONE project is to design a self-stabilizing middleware, which supports the development of autonomously recovering and highly fault-tolerant WSN applications.
Stefan Unterschütz und Volker Turau. A Hybrid Testbed for a Seamless Combination of Wireless Sensor Networks and OMNeT++ Simulations. In Proceedings of the 11th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'12), September 2012. Darmstadt, Germany.
@InProceedings{Telematik_UT_2012_Testbed, author = {Stefan Unterschütz and Volker Turau}, title = {A Hybrid Testbed for a Seamless Combination of Wireless Sensor Networks and OMNeT++ Simulations}, booktitle = {Proceedings of the 11th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'12)}, day = {13-14}, month = sep, year = 2012, location = {Darmstadt, Germany}, }
Helge Klimek, Björn Greßmann und Volker Turau. Report on Protocols for Resource Constrained Infrastructure Networks. Technical Report urn:nbn:de:gbv:830-tubdok-11642, Hamburg University of Technology, Hamburg, Germany, Juli 2012.
@TechReport{Klimek_Gressmann_Protocols-TechReport, author = {Helge Klimek and Björn Greßmann and Volker Turau}, title = {Report on Protocols for Resource Constrained Infrastructure Networks}, number = {urn:nbn:de:gbv:830-tubdok-11642}, institution = {Hamburg University of Technology}, address = {Hamburg, Germany}, month = jul, year = 2012, }
Abstract: This report introduces three protocols for communication in infrastructure networks consisting of a central server, stationary basestations and mobile devices. Mobile devices use IEEE 802.15.4 to communicate with the basestations. Among other things, the proposed protocols differ in their location management and in the routing of downlink and uplink packets. Through extensive simulations the protocols are compared with the focus on latency and packet loss metrics. The strength of each protocol depends on the traffic pattern caused by an application. The report concludes with a recommendation for the usage of each protocol.
Stefan Unterschütz und Volker Turau. Self-Stabilizing MAC Protocols for Large-Scale, Heavy Loaded Sensor Networks under Consideration of Hidden Nodes. Technical Report urn:nbn:de:gbv:830-tubdok-11639, Hamburg University of Technology, Hamburg, Germany, Juli 2012.
@TechReport{Unterschuetz_MAC-TechReport, author = {Stefan Unterschütz and Volker Turau}, title = {Self-Stabilizing MAC Protocols for Large-Scale, Heavy Loaded Sensor Networks under Consideration of Hidden Nodes}, number = {urn:nbn:de:gbv:830-tubdok-11639}, institution = {Hamburg University of Technology}, address = {Hamburg, Germany}, month = jul, year = 2012, }
Abstract: In large-scale, heavy loaded sensor networks the hidden node problem significantly restricts the attainable throughput. This paper examines this issue and depicts why most TDMA as well as dedicated hy- brid MAC protocols are still negatively affected by this phenomenon. The concept of probabilistic self-stabilization is adopted to provide a framework for implementable reservation MAC protocols that avoid packet loss caused by signal interferences even under high load. These protocols base upon two main primitives: continuity in channel access, allowing predictability, and acknowledgments, permitting to discover packet loss. The designed TDMA and CSMA protocols are able to cope with the hidden node problem and with topology changes and achieve a high throughput in a steady state. The protocols are simulated and compared with IEEE’s 802.15.4 unslotted CSMA/CA protocol.
Christian Renner, Stefan Unterschütz und Volker Turau. Power Management for Wireless Sensor Networks Based on Energy Budgets. Technical Report urn:nbn:de:gbv:830-tubdok-11065, Hamburg University of Technology, Hamburg, Germany, Juli 2011.
@TechReport{Renner_Unterschuetz_PowerManagement-TechReport, author = {Christian Renner and Stefan Unterschütz and Volker Turau}, title = {Power Management for Wireless Sensor Networks Based on Energy Budgets}, number = {urn:nbn:de:gbv:830-tubdok-11065}, institution = {Hamburg University of Technology}, address = {Hamburg, Germany}, month = jul, year = 2011, }
Abstract: This paper proposes and assesses analytical tools for large-scale monitoring applications with wireless sensor networks powered by energy-harvesting supplies. We introduce the concept of an energy budget, the amount of energy available to a sensor node for a given period of time. The presented tools can be utilized to realize distributed algorithms that determine a schedule to perform the monitoring task and the inherent communication. Scheduling is based on the energy budgets of the nodes or on latency requirements. In this context, we derive theoretical results for the energy consumption of the individual nodes plus the latency of event-reporting. These results are verified by simulations and a real testbed implementation.
Helge Klimek, Björn Greßmann und Volker Turau. Indoor Navigation and Location Based Services Scenario for Airports. Technical Report urn:nbn:de:gbv:830-tubdok-10856, Hamburg University of Technology, Hamburg, Germany, Februar 2011.
@TechReport{Telematik-Klick_Gressmann_Turau-INLBS-TechReport, author = {Helge Klimek and Björn Greßmann and Volker Turau}, title = {Indoor Navigation and Location Based Services Scenario for Airports}, number = {urn:nbn:de:gbv:830-tubdok-10856}, institution = {Hamburg University of Technology}, address = {Hamburg, Germany}, month = feb, year = 2011, }
Abstract: This report describes usage scenarios of the architecture for indoor navigation and location based services (INLBS) developed in the Airport2030 project. The expandable architecture offers a framework and predefined services with a runtime environment and aims at enabling ubiquitous INLBS in any building with the users’ mobile device. The architecture consists of a mobile user platform (MUP) installed on mobile devices and a stationary facility platform (SFP) which is running on backend servers. For communication between MUP and SFP a communication and positioning infrastructure (CPI) is used. The SFP abstracts from different mobile hardware and communication and ranging technologies for ease of development. A runtime environment contains the service container which invokes life cycle functionality of the different services. Applications which are accessed from the MUP are developed using the services in the service container.
Jürgen Jessen, Marcus Venzke und Volker Turau. Smart Energy Module for Wireless Sensor Nodes. In Proceedings of the 9th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'10), September 2010, pp. 9–12. Würzburg, Germany.
@InProceedings{Telematik_JVT_SmartEnergyModule, author = {Jürgen Jessen and Marcus Venzke and Volker Turau}, title = {Smart Energy Module for Wireless Sensor Nodes}, booktitle = {Proceedings of the 9th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'10)}, pages = {9-12}, day = {16-17}, month = sep, year = 2010, location = {Würzburg, Germany}, }
Abstract: This paper presents the design of a universal energy module for wireless sensor nodes, which supports a wide range of energy harvesters and energy storages. The focus is on the efficient conversion and storage of energy and to provide hardware support for higher level management functions. The module facilitates maximum power point tracking to improve the harvester efficiency. By supporting hybrid harvesters, the module can make better use of the time-dependent availability of environmental energy sources.
Sebastian Ernst, Christian Renner, Christoph Weyer und Volker Turau. Holistic Packet Statistics for Neighborhood Management in Sensor Networks. In Proceedings of the 9th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'10), September 2010, pp. 17–20. Würzburg, Germany.
@InProceedings{Telematik_ERWT_HoPS, author = {Sebastian Ernst and Christian Renner and Christoph Weyer and Volker Turau}, title = {Holistic Packet Statistics for Neighborhood Management in Sensor Networks}, booktitle = {Proceedings of the 9th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'10)}, pages = {17-20}, day = {16-17}, month = sep, year = 2010, location = {Würzburg, Germany}, }
Abstract: Knowledge of neighboring nodes is a fundamental requirement of many algorithms in the field of wireless sensor networks. The neighborhood relation of nodes is defined by their ability to communicate directly and not by their proximity. Due to the temporal changes of the wireless channel, link qualities must be continuously estimated. In this paper a new approach based on holistic packet statistics is presented. Unlike existing estimation techniques it forswears from squeezing a link's characteristics into a single value. The benefit of this approach is substantiated by an evaluation utilizing real-world and synthetic data.
Andreas Lagemann, Jörg Nolte, Christoph Weyer und Volker Turau. Mission Statement: Applying Self-Stabilization to Wireless Sensor Networks. In Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09), August 2009, pp. 47–49. Hamburg, Germany.
@InProceedings{Telematik_LNWT_2009_SelfWISE, author = {Andreas Lagemann and Jörg Nolte and Christoph Weyer and Volker Turau}, title = {Mission Statement: Applying Self-Stabilization to Wireless Sensor Networks}, booktitle = {Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09)}, pages = {47-49}, day = {13-14}, month = aug, year = 2009, location = {Hamburg, Germany}, }
Abstract: Long living and unattended deployments of wireless sensor networks requires fault-tolerant solutions. Self-stabilizing algorithms are providing these properties in an elegant and verifiable way. Recently, a lot of research has been performed to determine appropriate means to apply these promising technique to wireless sensor networks. In this paper the current state of the art in this field is given. Additionally, three major challenges are presented for achieving self-stabilizing sensor networks.
Christoph Weyer, Christian Renner, Volker Turau und Hannes Frey. A Roadmap for Hardware and Software Support for Developing Energy-Efficient Sensor Networks. In Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09), August 2009, pp. 67–70. Hamburg, Germany.
@InProceedings{Telematik_WRTF_2009_Roadmap, author = {Christoph Weyer and Christian Renner and Volker Turau and Hannes Frey}, title = {A Roadmap for Hardware and Software Support for Developing Energy-Efficient Sensor Networks}, booktitle = {Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09)}, pages = {67-70}, day = {13-14}, month = aug, year = 2009, location = {Hamburg, Germany}, }
Abstract: Support for developing energy-efficient applications for wireless sensor networks is still scarce. In this paper a roadmap of a combined hardware and software approach is presented. The main idea is to collect state information and trace energy consumption of an application running in a testbed of real sensor nodes.
Felix Hackbarth, Thomas Meyerhoff, Harald Sauff, Bryce T. Bradford, Luis Torres, Helge Klimek, Björn Gressmann, Christian Renner, Martin Stemick, Christoph Weyer und Sebastian Georgi. SomSed - The Evolution of an Experimental Wireless Sensor Network Towards a Research Platform. In Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09), August 2009, pp. 27–30. Hamburg, Germany.
@InProceedings{Telematik_HMSB_2009_SomSeD, author = {Felix Hackbarth and Thomas Meyerhoff and Harald Sauff and Bryce T. Bradford and Luis Torres and Helge Klimek and Björn Gressmann and Christian Renner and Martin Stemick and Christoph Weyer and Sebastian Georgi}, title = {SomSed - The Evolution of an Experimental Wireless Sensor Network Towards a Research Platform}, booktitle = {Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09)}, pages = {27-30}, day = {13-14}, month = aug, year = 2009, location = {Hamburg, Germany}, }
Abstract: The exploratory focus of the SomSed research field is the interdisciplinary research on self organizing mobile sensor and data networks. Since the founding of SomSed in 2007, great progress in scientific research has been achieved and much practical knowledge has been gathered using a prototype network permanently installed. This prototype network, from hereon referred to as CampusNet, is the basis for further investigations and offers the possibility to perform long term measurements in a large scale and real environment. The scope of this paper is to outline the current status of the SomSed research field and to briefly discuss future developments.
Torsten Stremlau, Christoph Weyer und Volker Turau. tinyMoBot: A Platform for Mobile Sensor Networks. In Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09), August 2009, pp. 43–44. Hamburg, Germany.
@InProceedings{Telematik_SW_2009_LEGO, author = {Torsten Stremlau and Christoph Weyer and Volker Turau}, title = {tinyMoBot: A Platform for Mobile Sensor Networks}, booktitle = {Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09)}, pages = {43-44}, day = {13-14}, month = aug, year = 2009, location = {Hamburg, Germany}, }
Abstract: In many application scenarios of wireless sensor networks parts or the whole network consist of mobile sensor nodes. Currently, no common platform is available. This paper describes a project that has developed a mobile sensor node, based on standard components: a Crossbow IRIS mote and LEGO MINDSTORMS NXT components, i.e., motors and sensors.
Lars Niemann, Marcus Venzke, Christian Renner und Volker Turau. Clock Synchronization of TinyOS-based Sensor Networks with DCF77. In Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09), August 2009, pp. 45–46. Hamburg, Germany.
@InProceedings{Telematik_NVRT_2009_DCF77, author = {Lars Niemann and Marcus Venzke and Christian Renner and Volker Turau}, title = {Clock Synchronization of TinyOS-based Sensor Networks with DCF77}, booktitle = {Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09)}, pages = {45-46}, day = {13-14}, month = aug, year = 2009, location = {Hamburg, Germany}, }
Abstract: The paper presents an approach of applying DCF77 time radio signals to provide a clock with global time in sensor networks based on TinyOS. Some nodes containing DCF77 receiver hardware reliably decode time signals even if these are distorted to some extent. The clock with global time is provided by compensating clock drift. Time is distributed in the network with a protocol generating timestamps on the MAC layer.
Christian Renner, Jürgen Jessen und Volker Turau. Lifetime Prediction for Supercapacitor-powered Wireless Sensor Nodes. In Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09), August 2009, pp. 55–58. Hamburg, Germany.
@InProceedings{Telematik_RJT_2009_Supercap, author = {Christian Renner and Jürgen Jessen and Volker Turau}, title = {Lifetime Prediction for Supercapacitor-powered Wireless Sensor Nodes}, booktitle = {Proceedings of the 8th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'09)}, pages = {55-58}, day = {13-14}, month = aug, year = 2009, location = {Hamburg, Germany}, }
Abstract: Energy-aware task scheduling is a novel research direction for wireless sensor networks. It depends on accurate models for lifetime prediction. In other terms, nodes must be aware of present and future energy resources. This paper addresses the first step towards reaching this goal: It explores discharging-characteristics of supercapacitors, discusses analytical discharging-models for lifetime prediction, and evaluates these models by comparing them with real discharging curves.
Bernd Hauck. Worst-Case Analysis of a Self-Stabilizing Algorithm Computing a Weakly Connected Minimal Dominating Set. Technical Report urn:nbn:de:gbv:830-tubdok-5126, Hamburg University of Technology, Hamburg, Germany, Oktober 2008.
@TechReport{Telematik_Hauck_2008_WorstCaseSelfStabilizingWeaklyConnectedMDSet, author = {Bernd Hauck}, title = {Worst-Case Analysis of a Self-Stabilizing Algorithm Computing a Weakly Connected Minimal Dominating Set}, number = {urn:nbn:de:gbv:830-tubdok-5126}, institution = {Hamburg University of Technology}, address = {Hamburg, Germany}, month = oct, year = 2008, }
Abstract: Recently, Srimani and Xu presented a self-stabilizing algorithm that computes a weakly connected minimal dominating set. They prove an upper bound of O(2^n) until stabilization but they do not provide a lower bound. This paper verifies by giving an example that their algorithm indeed requires O(2^n) moves on a certain graph.
Sebastian Georgi, Christoph Weyer, Martin Stemik, Christian Renner, Felix Hackbarth, Ulf Pilz, Jens Eichmann, Tobias Pilsak, Harald Sauff, Luis Torres, Klaus Dembowski und Fabian Wagner. SomSeD: An Interdisciplinary Approach for Developing Wireless Sensor Networks. In Proceedings of the 7th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'08), September 2008. Berlin, Germany.
@InProceedings{Telematik_GWSR_2008_SOMSeD, author = {Sebastian Georgi and Christoph Weyer and Martin Stemik and Christian Renner and Felix Hackbarth and Ulf Pilz and Jens Eichmann and Tobias Pilsak and Harald Sauff and Luis Torres and Klaus Dembowski and Fabian Wagner}, title = {SomSeD: An Interdisciplinary Approach for Developing Wireless Sensor Networks}, booktitle = {Proceedings of the 7th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'08)}, day = {25-26}, month = sep, year = 2008, location = {Berlin, Germany}, }
Abstract: The research field "Self organized mobile Sensor and Data-networks" (SomSeD) is introduced. Its purpose is the in- vestigation of Wireless Sensor Networks (WSN). It benefits from interdisciplinary exchange between various institutes of the Hamburg University of Technology (TUHH). Due to different design constraints (such as energy-efficiency and package size) compared to well known classical computer networks, all aspects of the development of WSNs must be reconsidered. This paper describes the advantage of having experts of various faculties both in computer science and electrical engineering in a single research field. In addition to the introduction of the participating institutes, the de- ployment of a WSN on the TUHH campus will be outlined.
Christoph Weyer, Stefan Unterschütz und Volker Turau. Connectivity-aware Neighborhood Management Protocol in Wireless Sensor Networks. In Proceedings of the 7th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'08), September 2008. Berlin, Germany.
@InProceedings{Telematik_WUT_2008_Mahalle, author = {Christoph Weyer and Stefan Unterschütz and Volker Turau}, title = {Connectivity-aware Neighborhood Management Protocol in Wireless Sensor Networks}, booktitle = {Proceedings of the 7th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'08)}, day = {25-26}, month = sep, year = 2008, location = {Berlin, Germany}, }
Abstract: Neighborhood relations are changing over time in wireless sensor networks due to different hardware or environmental effects. These effects and memory limitations require a balanced neighborhood management to ensure agility, stability, symmetry, and connectivity. The proposed neighborhood management protocol Mahalle is optimized with regard to these four criteria. Agility and stability are achieved by ALE, a new adaptive link estimator.
Matthias Witt und Volker Turau. Geographic Routing in 3D. In Proceedings of the 6th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'07), Juli 2007, pp. 75–78. Aachen, Germany.
@InProceedings{Telematik_WT_2007_3DRouting, author = {Matthias Witt and Volker Turau}, title = {Geographic Routing in 3D}, booktitle = {Proceedings of the 6th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'07)}, pages = {75-78}, day = {16-17}, month = jul, year = 2007, location = {Aachen, Germany}, }
Abstract: Existing geographic routing algorithms assume a two-dimensional topology. Dedicated wireless sensor network scenarios demand for algorithms that operate in three-dimensional environments. This paper discusses issues which arise when making the step from 2D to 3D. Simulation studies show that 3D routing is less efficient than its 2D counterpart when comparing topologies with the same average node degree.
Matthias Witt und Volker Turau. Delivery Semantics for Geographic Routing. In Proceedings of the 5th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'06), Juli 2006. Stuttgart, Germany.
@InProceedings{Telematik_WT_2006_DeliverySemantics, author = {Matthias Witt and Volker Turau}, title = {Delivery Semantics for Geographic Routing}, booktitle = {Proceedings of the 5th GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'06)}, day = {17-18}, month = jul, year = 2006, location = {Stuttgart, Germany}, }
Abstract: Geographic routing algorithms use locations rather than node addresses as destinations. But since it is not always guaranteed that there is indeed a node exactly at the destination location, there must exist a description which nodes shall be allowed to consume a message. In some cases, the message must not be consumed by a node at another location (e. g., if the sink is the destination), whereas in other cases, nodes in the vicinity may also consume it. This has to be chosen by the application, so the routing protocol should support different delivery semantics. Another question is if only one node may consume the message, or if multiple destination nodes are allowed. This paper proposes three orthogonal delivery parameters: closeness, multiplicity, and accept-outside.
Dietrich Fahrenholtz. Addendum to 'Performance of Lookup Operations in a Hypercube-based P2P Data Store: Theoretical Model and Performance Evaluation'. Technical Report Report No. TR-2006-07-01, URN: urn:nbn:de:gbv:830-opus-3116, Hamburg University of Technology, Hamburg, Germany, Juli 2006.
@TechReport{Telematik_FWT_2006_AddendumLookupHypercube, author = {Dietrich Fahrenholtz}, title = {Addendum to 'Performance of Lookup Operations in a Hypercube-based P2P Data Store: Theoretical Model and Performance Evaluation'}, number = {Report No. TR-2006-07-01, URN: urn:nbn:de:gbv:830-opus-3116}, institution = {Hamburg University of Technology}, address = {Hamburg, Germany}, month = jul, year = 2006, }
Abstract: This is an addendum to our report "Performance of Lookup Operations in a Hypercube-based P2P Data Store: Theoretical Model and Performance Evaluation". Here we explore two questions: First, what is the probability of a lookup to get lost and, second, what is the probability that it will be duplicated at least once. To this end, we approach the questions on a probability theoretical basis and derive equations for both probabilities, means and variances. Graphs elucidate the behavior of the model.
Dietrich Fahrenholtz, Andreas Wombacher und Volker Turau. Performance of Lookup Operations in a Hypercube-based P2P Data Store : Theoretical Model and Performance Evaluation. Technical Report Report No. TR-2005-12-01, URN: urn:nbn:de:gbv:830-opus-1057, Hamburg University of Technology, Hamburg, Germany, Dezember 2005.
@TechReport{Telematik_FWT_2005_LookupHypercube, author = {Dietrich Fahrenholtz and Andreas Wombacher and Volker Turau}, title = {Performance of Lookup Operations in a Hypercube-based P2P Data Store : Theoretical Model and Performance Evaluation}, number = {Report No. TR-2005-12-01, URN: urn:nbn:de:gbv:830-opus-1057}, institution = {Hamburg University of Technology}, address = {Hamburg, Germany}, month = dec, year = 2005, }
Abstract: One way for Peer-to-Peer data stores to achieve high data availability is to replicate their data. This is necessary to counter the effects of peer population dynamics also known as churn. A consequence of churn is that locating a data item may require a peer to resend search messages thus introducing additional communication. A formal model of this communication pertaining to data item lookups is introduced and evaluated using simulation in this paper. Results hold true for hypercube-based P2P data stores.
Matthias Witt, Christoph Weyer und Volker Turau. Monitoring Energy Consumption In Wireless Sensor Networks. In Proceedings oth the Fourth GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'05), März 2005. Zürich, Switzerland.
@InProceedings{Telematik_WWT_2005_Monitoring, author = {Matthias Witt and Christoph Weyer and Volker Turau}, title = {Monitoring Energy Consumption In Wireless Sensor Networks}, booktitle = {Proceedings oth the Fourth GI/ITG KuVS Fachgespräch "Drahtlose Sensornetze" (FGSN'05)}, month = mar, year = 2005, location = {Zürich, Switzerland}, }
Abstract: This note introduces an approach to monitor the consumption of energy in wireless sensor networks based on video streams composed from sequences of temperature maps. It is used to compare and evaluate beacon-less geographic routing algorithms.
Dietrich Fahrenholtz und Volker Turau. Fluctuation in Peer-to-Peer Networks: Mitigating Its Effect on DHT Performance. Technical Report Report arXiv:cs.NI/0406027 v1, arXiv.org e-Print archive, Cornell University, Juni 2004.
@TechReport{Telematik_FT_2004_P2PFluctuation, author = {Dietrich Fahrenholtz and Volker Turau}, title = {Fluctuation in Peer-to-Peer Networks: Mitigating Its Effect on DHT Performance}, number = {Report arXiv:cs.NI/0406027 v1}, institution = {arXiv.org e-Print archive}, address = {Cornell University}, month = jun, year = 2004, }
Abstract: Due to the transient nature of peers, any Peer-to-Peer network is in peril to falling apart if peers do not receive routing table updates periodically. To this end, maintenance, which affects every peer, ensures connectedness and sustained data operation performance. However, a high rate of change in peer population usually incurs lots of network maintenance messages and can severely degrade overall performance. We discuss three methods how to tackle and mitigate the effect of peer fluctuation on a tree-based distributed hash table.