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Publications

Journal Articles | Conference Contributions | PhD Theses | Technical Reports

Journal Articles

Gerry Siegemund and Volker Turau. A Self-stabilizing Publish/Subscribe Middleware for IoT Applications. ACM Transactions on Cyber-Physical Systems (TCPS), 2, Issue 2, Article 12:1–12, June 2018.
@Article{Telematik_Siegemund_2018, author = {Gerry Siegemund and Volker Turau}, title = {A Self-stabilizing Publish/Subscribe Middleware for IoT Applications}, pages = {1-12}, journal = {ACM Transactions on Cyber-Physical Systems (TCPS)}, volume = {2, Issue 2, Article 12}, month = jun, year = 2018, }
Abstract: This article presents a middleware that provides a communication and data dissemination infrastructure suitable for the operation environment of the Internet of Things (IoT). The middleware realizes the channel-based publish/subscribe paradigm that has been identified as a valid means to asynchronously disseminate data in IoT applications. The novelty lies in the routing algorithm PSVR that greatly reduces the path lengths to deliver publications and its suitability for scenarios with a high subfluctuation rate. The middleware is self-stabilizing and eventually provides safety and liveness properties such as the guaranteed delivery of all published messages to all subscribers and the correct handling of subscriptions and unsubscriptions, while no error occurs. The evaluation of the middleware, based on simulations and a real deployment, shows that it has a low memory footprint and scales well with the number of nodes.

Conference Contributions

Volker Turau and Gerry Siegemund. Scalable Routing for Topic-based Publish/Subscribe Systems under Fluctuations. In Proceedings of International Conference on Distributed Computing Systems - ICDCS 2017, June 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.
Gerry Siegemund and 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.
Stefan Lohs, Gerry Siegemund, Jörg Nolte and 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 J{\"o}rg 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.
Stefan Lohs, Jörg Nolte, Gerry Siegemund and Volker Turau. Influence of Topology-Fluctuations on Self-Stabilizing Algorithms. In 2016 International Conference on Distributed Computing in Sensor Systems DCOSS 2016 Poster Abstract, May 2016, pp. 122–124. Washington, DC, USA.
@InProceedings{DCOSS_POSTER_2016, author = {Stefan Lohs and J{\"o}rg 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.
Sandra Beyer, Stefan Lohs, Jörg Nolte, Reinhardt Karnapke and 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 J{\"o}rg 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 and 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, June 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.
Gerry Siegemund, Volker Turau and Khaled Maâmra. A Self-stabilizing Publish/Subscribe Middleware for Wireless Sensor Networks. In Proceedings of the International Conference on Networked Systems (NetSys), March 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.
Gerry Siegemund, Volker Turau and 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.
Gerry Siegemund, Volker Turau, Christoph Weyer, Stefan Lobs and 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 J{\"o}rg 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.

PhD Theses

Gerry Siegemund. Self-stabilizing Algorithms in Wireless Sensor Networks. PhD Thesis, Hamburg University of Technology, Hamburg, Germany, 2017.
@PhdThesis{Telematik_Siegemund_2017_Diss, author = {Gerry Siegemund}, title = {Self-stabilizing Algorithms in Wireless Sensor Networks}, school = {Hamburg University of Technology}, address = {Hamburg, Germany}, year = 2017, }
Abstract: The presented dissertation focuses on the applicability of self-stabilizing algorithms in systems using wireless communication. Especially wireless sensor networks (WSN) which use low power radios that are prone to message loss and corruption. Furthermore, temporary node failures (e.g., due to exhausted batteries) are common sources of nonconformances. Thus, distributed algorithms, middleware systems, and applications have to respond to these faults. A typical approach is to foresee such error situations and program routines to react to them. Algorithms defined in a self- stabilizing manner (SSA) on the other hand always converge to a defined system state and remain in it while no fault occurs. Hence, the anticipation of error situations is no longer a necessity. Entities in a distributed system (nodes) share certain informations among their neighborhood (adjacent nodes) and react following the distinct routine of the used SSA. To this day self-stabilization is primarily a theoretical approach, well studied concerning, e.g., the bounds of execution steps. Profound practical evaluation, espe- cially in the presents of rapidly changing neighbor states, as common in WSNs, is still an open issue. This work firstly establishes necessities to use SSAs in the wireless domain, con- cluding that a certain degree of forced stability concerning a nodes neighborhood is vital. Nevertheless, such a topology control cannot be rigid, e.g., by using a fixed predefined setup, because node additions or removals cannot be supported. Hence, a topology control algorithm (TCA) is introduced, generating a trade-off between forced stability and agility. Using this TCA as a cornerstone, multiple SSAs are evaluated, and high level al- gorithms are developed, culminating in a publish/subscribe middleware defined in a self-stabilizing fashion. The publish/subscribe system relies on a self-stabilizing spanning tree algorithm and a novel self-stabilizing virtual ring algorithm. Further- more, the publication routing uses shortcuts in the virtual ring, decreasing routing paths in the process. The presented algorithms are evaluated using simulations employing realistic radio models, as well as implementation on sensor node hardware with low power radios, low computation power, and restricted memory. The novel publish/subscribe system is executable on such limited hardware, uses less messages to deliver data to pub- lishers than a comparable tree-based approach, due to the mentioned shortcuts, and scales well with the network size. It achieves a compromise between the size and maintenance effort for routing tables and the length of routing paths. Concluding, the dissertation provides an incentive to use self-stabilization algo- rithms in wireless sensor network applications. As shown, even high level systems like a publish/subscribe middleware can be realized with this inherently fault-tolerant approach.

Technical Reports

Gerry Siegemund and 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.
Gerry Siegemund, Volker Turau, Stefan Lohs and 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 J{\"o}rg Nolte}, title = {Directed Link Utilization with Mahalle+}, booktitle = {Proceedings of the 12th GI/ITG KuVS Fachgespr{\"a}ch "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+.
Gerry Siegemund and 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 and 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 J{\"o}rg Nolte and Volker Turau}, title = {Mission Statement: ToleranceZone A Self-Stabilizing Middleware for Wireless Sensor Netzworks}, booktitle = {Proceedings of the 11th GI/ITG KuVS Fachgespr{\"a}ch "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.