Jochen Koberstein

Minimal transmission power as distance estimation for precise localization in sensor networks

Positioning sensor nodes requires distance information to reference points. Due to resource limitations in sensor networks, distance determination in low-cost sensor nodes without additional hardware is difficult. Known techniques such as distance estimation based on received signal strength (RSSI) are mostly inaccurate or have limitations. We propose a new method to measure the distance between a transmitting node and a receiving node using the minimal transmission power. The determined distance is more precise than RSSI, has a low variance and is therefore particularly suitable for positioning. Finally, we implemented a demonstrator application using weighted centroid localization to show the practical implementation.

Graph-based mobility model for urban areas fueled with real world datasets

Mobile ad-hoc networks (MANETs) and especially mobile Wireless Sensor Networks (mWSNs) are embedded in the environment and therefore stand under strong influence of its specific characteristics. Beside e.g. sensor input, nodes motion patterns are supposed to be a very basic factor regarding performance. Hence simulations may need to account scenario specific mobility patterns while keeping the tradeoff related to simulation complexity in mind. This contribution proposes a graph based mobility model, designed to resemble probabilistic node movements according to real world node paths like they may be induced by road grids. The model is presented along with a real world mWSN sample deployment from which the paths are extracted and against which the simulation fine-tuned.

The XCast Approach for Content-Based Flooding Control in Distributed Virtual Shared Information Spaces—Design and Evaluation

In this paper, we assume that sensor nodes in a wireless sensor network cooperate by posting their information to a distributed virtual shared information space that is built on the basis of advanced XML technology. Using a flooding protocol to maintain the shared information space is an obvious solution, but flooding must be tightly controlled, because sensor nodes suffer from severe resource constraints. For this purpose we propose a content-based flooding control approach (”XCast”) whose performance is analyzed in the paper both analytically and by ns2 simulations. Results show that already a generic XCast instance effectively controls the number of messages generated in a sensor network. It is argued that application-specific XCast instances may expose an even better behavior.

System-Level WSN Application Software Test Using Multi-platform Hardware Abstraction Layers

Software development for Wireless Sensor Networks (WSNs) suffers from the adverse condition that WSN software systems can usually not be tested on a system-level in their final operations environment, as WSN deployment is an expensive and time-consuming process. Several authors therefore propose to interlock application software test tightly with simulation. In this paper, we introduce an XML-based description language that allows the WSN programmer to define a common Hardware Abstraction Layer (HAL) for seamless transfer of WSN application code between WSN node target platforms and simulator-provided platforms. We show how a common network simulator can be enhanced to fully support system-level testing of WSN application code, make some comments on the resulting changes in the software development process, and finally illustrate our approach by an example.

XCast-Kommunikation im Virtual Shared Information Space

ZUSAMMENFASSUNG Der Einsatz eines Client/Server-Kooperationsparadigmas ist für mobile Ad-Hoc Netzwerke problematisch, da nicht von der ständigen Verfügbarkeit und Erreichbarkeit von Servern ausgegangen werden kann. In diesem Artikel wird daher das serverlose Kooperationsparadigma des virtual shared information space vorgestellt, welches durch eine XML-basierte datenzentrierte Kommunikationsform namens XCast realisiert wird. Im zweiten Teil des Artikels wird eine Anwendung vorgestellt, die auf der Basis von XCast einen virtual shared information space für eine endliche Informationsmenge etabliert. Die Leistungsbewertung zeigt, dass die Anzahl der dazu nötigen Pakete von einem sog. Dokumentengrenzwert abhängt. Die in der Literatur etablierte Vorstellung, dass eine datenzentrierte Kommunikation innerhalb von mobilen Ad-Hoc Netzen vorteilhaft ist, konnte mit Hilfe dieses Grenzwertes mathematisch vorhergesagt und simulativ bestätigt werden.