Dr.-Ing.

Kuhn, Thomas

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  • Publication
    Mode-based scheduling with fast mode-signaling - a method for efficient usage of network time slots
    ( 2014)
    Braun, Tobias
    ;
    Gotzhein, Reinhard
    ;
    Kuhn, Thomas
    Today, communication in real-time systems is based on time-triggered or event-triggered protocols, or combinations thereof. Each of these solutions has its benefits and tradeoffs regarding timeliness and bandwidth usage. In this work, we present a new method called mode-based slot scheduling with fast mode-signaling, which can substantially improve bandwidth usage in many scenarios of industrial relevance, while preserving timeliness. With mode-based slot scheduling, a well-controlled amount of dynamic contention for network time slots is possible. Fast mode-signaling is used to reach consensus on the current transmission mode with the highest preference extremely fast and reliably among all network nodes. We present the implementation of our method with TTCAN - a time-triggered protocol in the automotive domain -, and evaluation results.
  • Publication
    Virtual prototyping of distributed embedded systems with FERAL
    ( 2014)
    Braun, Tobias
    ;
    Christmann, Dennis
    ;
    Gotzhein, Reinhard
    ;
    Igel, Anuschka
    ;
    Kuhn, Thomas
    Distributed embedded systems are found in time- and safety-critical domains, such as avionics and automotive. Virtual prototyping is a suitable approach for the development of such systems, since it enables early testing and early evaluation of design decisions in realistic simulated environments. Existing simulators only focus on specific aspects and application domains. However, an accurate prediction of the overall system behaviour of complex distributed embedded systems requires the consideration of multiple aspects together, e.g., communication and functional behaviour. Therefore, a mechanism for the rapid coupling of simulators is required to create holistic simulation environments. In this paper, we survey our modular simulator framework FERAL, which provides a generic solution to virtual prototyping by enabling the rapid coupling and exchange of diverse simulators, even with heterogeneous simulation models. Thus, simulators operating on different abstraction levels can be applied together. We demonstrate the adaptation of FERAL by incorporating several simulators, in particular, existing simulators (Simulink, ns-3), and our newly developed simulators for the automotive communication technologies CAN and FlexRay. We then demonstrate FERAL's capabilities by evaluating different design alternatives for an adaptive cruise control system in a real world scenario.
  • Publication
    Black Burst Synchronization (BBS) - A protocol for deterministic tick and time synchronization in wireless networks
    ( 2011)
    Gotzhein, Reinhard
    ;
    Kuhn, Thomas
    In this paper, we present Black Burst Synchronization (BBS), a modular protocol for multi-hop tick and time synchronization in wireless ad hoc networks, located at MAC level. For the successful operation of BBS, it is crucial that collisions of synchronization messages that are sent (almost) simultaneously by two or more nodes are non-destructive. This is achieved by collision-protected bit encodings with black bursts, periods of transmission energy of defined length on the medium, starting at determined points in time. Under reasonable assumptions, BBS provides low and bounded tick and clock offsets, guarantees a very small and constant convergence delay, has low and bounded complexity regarding computation, storage, time, and structure, and is robust against topology changes at runtime. This makes it a candidate for user level applications such as data fusion and networked control systems, and especially for system level tasks such as duty cycling and multi-hop medium slotting. To validate its predicted behavior, we have implemented and deployed BBS on MICAz motes.