Reinhard Exel

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In the recent years, the term wireless factory automation began raising interest. Its probably most appreciated feature, mobility, is yet acknowledged as the key for new applications. Nevertheless, this apparent freedom comes with a palette of requirements, whereof one is localisation. Although locating systems have been an extensive research topic for(More)
The use of wireless technologies in Factory Automation is attractive due to several advantages (mobility, cost, etc.); however, to satisfy the requirements of industrial applications, they have to be improved in terms of real-time performance. Handover is a particular weakness in cellular wireless systems, e. g., in IEEE 802.11, since it may introduce delay(More)
Clock synchronization protocols for packet-oriented networks, like IEEE 1588, depend on time stamps drawn from a local clock at distinct points in time. Due to the fact that software-generated time stamps suffer from jitter caused by nondeterministic execution times, many implementations for high precision clock synchronization rely on hardware support.(More)
The introduction of wireless networks in the factory floor offers many advantages. Besides a new flexibility for automation, also features like the localisation of wireless devices ease the use of this technology. However, for the application on the factory floor real-time guarantees have to be given, which can be ensured by schemes like TDMA, which is(More)
Time based localisation methods like GPS are widely used for outdoor navigation, whereas indoor navigation is typically performed only on a cell-basis or based on the Received Signal Strength Indicator. Since RSSI is not able to fulfil all current requirements, Time of Arrival and Time Difference of Arrival based approaches have recently gained focus. As(More)
This work deals with the characterization of IEEE 802.15.4 using the Chirp Spread Spectrum (CSS) physical layer. A new test bench, which has full bandwidth capability and extreme flexibility thanks to the FPGA-based probes, is used for managing reproducible measurement results. Several scenarios and algorithms have been considered for the estimation of the(More)
In distributed systems, clock synchronization performance is hampered by delays and jitter accumulated not only in the network, but also in the timestamping procedures of the devices being synchronized. This is particularly critical in software timestamp-based synchronization where both software- and hardware-related sources contribute to this behavior.(More)