Volker Turau

Volker Turau
Technische Universität Hamburg | TUHH · Institute of Telematics

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171
Publications
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Publications

Publications (171)
Preprint
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Wireless mesh networks are a promising technology for connecting sensors and actuators with high flexibility and low investment costs. In industrial applications, however, reliability is essential. Therefore, two time-slotted medium access methods, DSME and TSCH, were added to the IEEE 802.15.4 standard. They allow collision-free communication in m...
Article
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 nove...
Preprint
Full-text available
Testbeds are a key element in the evaluation of wireless multi-hop networks. In order to relieve researchers from the hassle of deploying their own testbeds, remotely controllable testbeds, such as the FIT/IoT-LAB, are built. However, while the IoT-LAB has a high number of nodes, they are deployed in constraint areas. This, together with the comple...
Preprint
It is known for some time that a random graph $G(n,p)$ contains w.h.p. a Hamiltonian cycle if $p$ is larger than the critical value $p_{crit}= (\log n + \log \log n + \omega_n)/n$. The determination of a concrete Hamiltonian cycle is even for values much larger than $p_{crit}$ a nontrivial task. In this paper we consider random graphs $G(n,p)$ with...
Article
Full-text available
The analysis of self-stabilizing algorithms is often limited to the worst case stabilization time starting from an arbitrary state, i.e., a state resulting from a sequence of faults. Considering the fact that these algorithms are intended to provide fault tolerance in the long run, this is not the most relevant metric. A common situation is that a...
Article
Full-text available
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 in...
Article
Wireless communications techniques are finding their way into industrial applications, but commercial wireless technologies lack the dependability required for critical applications in very large networks. In many wireless-controlled industrial facilities, safety regulations mandate real-time communications for tasks such as emergency shutdowns. Th...
Chapter
It is known for some time that a random graph G(n, p) contains w.h.p. a Hamiltonian cycle if p is larger than the critical value \(p_{crit}= (\log n + \log \log n + \omega _n)/n\). The determination of a concrete Hamiltonian cycle is even for values much larger than \(p_{crit}\) a nontrivial task. In this paper we consider random graphs G(n, p) wit...
Article
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...
Article
Full-text available
This paper analyzes the impact of the high dimensional parameter space of domestic electric water heaters (DEWH) for demand response (DR). To quantify the consumer comfort a novel metric is introduced considering a stochastic distribution of different water draw events. Incorporating three control algorithms from literature, it is shown that all co...
Conference Paper
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 t...
Conference Paper
\(\mathcal {PSVR}\) 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-stab...
Article
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. Design...
Conference Paper
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 tim...
Conference Paper
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 gi...
Conference Paper
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 f...
Article
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 gi...
Conference Paper
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...
Article
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 moni...
Article
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 pro...
Article
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 an...
Conference Paper
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....
Article
Full-text available
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...
Conference Paper
This paper presents a demand response scheme for waterbeds that can be implemented with currently available infrastructure. It balances the requirements of saving energy and shifting power to times with higher power availability by scheduling heating phases such that costs according to an electricity exchange's virtual electricity tariff are minimi...
Article
Full-text available
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, M...
Article
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 relation...
Conference Paper
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 moni...
Conference Paper
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, fragmentation of datagrams...
Conference Paper
Full-text available
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 particular, cheap, low-maintenance, and reliable alternatives to existing approaches must be analyzed. We believe that self-organizing wireless sensor networks a...
Article
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.
Conference Paper
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 cor...
Conference Paper
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 neighborhood management...
Conference Paper
Full-text available
Until now no general applicable technology for indoor localization has prevailed. Similarly, 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...
Article
Full-text available
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 app...
Article
Full-text available
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 pap...
Article
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 consumpt...
Conference Paper
Full-text available
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 p...
Article
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 sc...
Conference Paper
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 gi...
Conference Paper
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...
Article
Developers can use cross-platform mobile development tools to create smartphone apps that meet user expectations, but existing XMTs need improvement.
Conference Paper
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 detai...
Conference Paper
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...
Article
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 sync...
Article
Full-text available
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...
Conference Paper
Full-text available
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 c...
Article
Full-text available
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...
Article
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 sched...
Conference Paper
Full-text available
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...
Conference Paper
Full-text available
Software development for wireless sensor networks can be accomplished with dedicated operating systems such as Contiki or TinyOS. However, protocol design and verification as well as debugging is still challenging. On the other hand, high-level simulation environments, e. g., OMNeT++, allow convenient and rapid development, but the resulting code h...
Article
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...
Conference Paper
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 co...
Conference Paper
Full-text available
Wireless networks are an emerging technology which are employed for a growing number of applications. Maintenance and extensibility necessitate software updates after an initial deployment. Wireless updates are in most cases preferred, e.g. in large-scale networks or inaccessible deployments. Recent research either focused on reliable and fast tran...
Conference Paper
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-stab...
Article
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(2n) (resp. O(3n)) moves under a central (resp. d...
Conference Paper
Full-text available
Available algorithms for the distributed construction of connected dominating sets in mobile ad hoc networks are inapplicable or suffer from a high complexity. This is mainly due to the resource-restricted nature of wireless devices, such as sensor nodes, and the error-prone character of the communication medium. This work introduces and evaluates...
Article
The non-computability of many distributed tasks in anonymous networks is well known. This paper presents a deterministic self-stabilizing algorithm to compute a (3−2Δ+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(Δ) rounds...
Conference Paper
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...
Conference Paper
Full-text available
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-transactio...
Conference Paper
Full-text available
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 po...
Article
Full-text available
This report explains in an in depth example how our architecture for indoor navigation and location based services (INLBS) works. The expandable architecture offers a framework API and predefined services with a runtime environment and aims at enabling ubiquitous INLBS where users can use their mobile devices in any building.
Conference Paper
Full-text available
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 distribute...
Conference Paper
Full-text available
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. There...
Article
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, Δlog3n}) rounds and requir...
Conference Paper
Full-text available
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 syn...
Conference Paper
Full-text available
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) ac...
Conference Paper
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. The...
Conference Paper
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 2D + 12{\it \Delta} + 1. An enhanced version o...
Conference Paper
Full-text available
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. Ava...
Conference Paper
Full-text available
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 rep...
Article
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. A...
Article
Full-text available
Wireless sensor networks operate in an unstable envi-ronment 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 anal...
Article
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...
Article
Full-text available
Technology advances and a growing field of applications have been a constant driving factor for embedded systems over the past years. However, the increasing complexity of embed-ded systems and the emerging trend to interconnections between them lead to new challenges. Intelligent solutions are necessary to solve these challenges and to provide rel...
Conference Paper
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 hardware-specific characteristics, SelfWISE consists of a language for expressing self-stabiliz...
Article
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, discus...
Article
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. Ap...
Article
Full-text available
Neighborhood relations are changing over time in wireless sensor networks due to dierent hardware or environmental eects. These eects and memory limitations require a bal- anced neighborhood management to ensure agility, stability, symmetry, and connectivity. The proposed neighborhood management protocol Mahalle is optimized with regard to these fo...
Article
Full-text available
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 t...