arXiv subjects

Stefan Fischer

Publications and source records attributed to Stefan Fischer.

25 records · Page 2Linked to original sources

arXiv2014

A Security Architecture for Mobile Wireless Sensor Networks

Wireless sensor networks increasingly become viable solutions to many challenging problems and will successively be deployed in many areas in the future. However, deploying new technology without security in mind has often proved to be unreasonably dangerous. We propose a security architecture for self-organizing mobile wireless sensor networks that prevents many attacks these networks are exposed to. Furthermore, it limits the security impact of some attacks that cannot be prevented. We analyse our security architecure and show that it provides the desired security aspects while still being a lightweight solution and thus being applicable for self-organizing mobile wireless sensor networks.

cs.CR↗

arXiv2012

Plasmon enhanced upconversion luminescence near gold nanoparticles - Simulation and analysis of the interactions

We investigate plasmon resonances in gold nanoparticles to enhance the quantum yield of upconverting materials. For this purpose, we use a rate equation model that describes the upconversion of trivalent erbium based upconverters. Changes of the optical field acting on the upconverter and the changes to the transition probabilities of the upconverter in the proximity of a gold nanoparticle are calculated using Mie theory and exact electrodynamic theory respectively. With this data, the influence on the luminescence of the upconverter is determined using the rate equation model. The results show that upconversion luminescence can be increased in the proximity of a spherical gold nanoparticle due to the change in the optical field and the modification of the transition rates.

physics.optics↗

arXiv2010

Empowered by Wireless Communication: Self-Organizing Traffic Collectives

In recent years, tremendous progress has been made in understanding the dynamics of vehicle traffic flow and traffic congestion by interpreting traffic as a multi-particle system. This helps to explain the onset and persistence of many undesired phenomena, e.g., traffic jams. It also reflects the apparent helplessness of drivers in traffic, who feel like passive particles that are pushed around by exterior forces; one of the crucial aspects is the inability to communicate and coordinate with other traffic participants. We present distributed methods for solving these fundamental problems, employing modern wireless, ad-hoc, multi-hop networks. The underlying idea is to use these capabilities as the basis for self-organizing methods for coordinating data collection and processing, recognizing traffic phenomena, and changing their structure by coordinated behavior. The overall objective is a multi-level approach that reaches from protocols for local wireless communication, data dissemination, pattern recognition, over hierarchical structuring and coordinated behavior, all the way to large-scale traffic regulation. In this article we describe three types of results: (i) self-organizing and distributed methods for maintaining and collecting data (using our concept of Hovering Data Clouds); (ii) adaptive data dissemination for traffic information systems; (iii) methods for self-recognition of traffic jams. We conclude by describing higher-level aspects of our work.

cs.NI↗

arXiv2005

Deterministic boundary recognition and topology extraction for large sensor networks

We present a new framework for the crucial challenge of self-organization of a large sensor network. The basic scenario can be described as follows: Given a large swarm of immobile sensor nodes that have been scattered in a polygonal region, such as a street network. Nodes have no knowledge of size or shape of the environment or the position of other nodes. Moreover, they have no way of measuring coordinates, geometric distances to other nodes, or their direction. Their only way of interacting with other nodes is to send or to receive messages from any node that is within communication range. The objective is to develop algorithms and protocols that allow self-organization of the swarm into large-scale structures that reflect the structure of the street network, setting the stage for global routing, tracking and guiding algorithms.

cs.DC↗

arXiv2005

Koordinatenfreies Lokationsbewusstsein (Localization without Coordinates)

Localization is one of the fundamental issues in sensor networks. It is almost always assumed that it must be solved by assigning coordinates to the nodes. This article discusses positioning algorithms from a theoretical, practical and simulative point of view, and identifies difficulties and limitations. Ideas for more abstract means of location awareness are presented and the resulting possible improvements for applications are shown. Nodes with certain topological or environmental properties are clustered, and the neighborhood structure of the clusters is modeled as a graph. Eines der fundamentalen Probleme in Sensornetzwerken besteht darin, ein Bewusstsein fuer die Position eines Knotens im Netz zu entwickeln. Dabei wird fast immer davon ausgegangen, dass dies durch die Zuweisung von Koordinaten zu erfolgen hat. In diesem Artikel wird auf theoretischer, praktischer und simulativer Ebene ein kritischer Blick auf entsprechende Verfahren geworfen, und es werden Grenzen aufgezeigt. Es wird ein Ansatz vorgestellt, mit dem in der Zukunft eine abstrakte Form von Lokationsbewusstsein etabliert werden kann, und es wird gezeigt, wie Anwendungen dadurch verbessert werden koennen. Er basiert auf einer graphenbasierten Modellierung des Netzes: Knoten mit bestimmten topologischen oder Umwelteigenschaften werden zu Clustern zusammengefasst, und Clusternachbarschaften dann als Graphen modelliert.

cs.DC↗

arXiv2005

Shawn: A new approach to simulating wireless sensor networks

We consider the simulation of wireless sensor networks (WSN) using a new approach. We present Shawn, an open-source discrete-event simulator that has considerable differences to all other existing simulators. Shawn is very powerful in simulating large scale networks with an abstract point of view. It is, to the best of our knowledge, the first simulator to support generic high-level algorithms as well as distributed protocols on exactly the same underlying networks.

cs.DC↗

arXiv2004

Neighborhood-Based Topology Recognition in Sensor Networks

We consider a crucial aspect of self-organization of a sensor network consisting of a large set of simple sensor nodes with no location hardware and only very limited communication range. After having been distributed randomly in a given two-dimensional region, the nodes are required to develop a sense for the environment, based on a limited amount of local communication. We describe algorithmic approaches for determining the structure of boundary nodes of the region, and the topology of the region. We also develop methods for determining the outside boundary, the distance to the closest boundary for each point, the Voronoi diagram of the different boundaries, and the geometric thickness of the network. Our methods rely on a number of natural assumptions that are present in densely distributed sets of nodes, and make use of a combination of stochastics, topology, and geometry. Evaluation requires only a limited number of simple local computations.

cs.DS↗