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2007 : Establishing Wireless Time-Triggered Communication using a Firefly Clock Synchronization Approach

Author(s)
R. Leidenfrost, Wilfried Elmenreich
Abstract
The application area of wireless sensor networks often include the deployment in harsh environments. Therefore, the devices are mainly battery-powered but nevertheless must provide a lifetime in the order of months to years. This requires the use of energy efficient protocols. Such protocols need to support duty-cycling, where a node only enables the transceiver module for a short time if it expects a message or wants to transmit to other nodes. However, whereas most protocols are aimed at reducing the duty-cycle, our approach also establishes a time-triggered approach, which takes advantage of the a priori known transmission events. Such a technique requires a global notion of time and therefore is based on algorithms for maintaining synchronization. This ensures that every node has the same local view of the global time. The controllers running this algorithm often have to be very inexpensive and make use of the cheap on-chip oscillators which generally entail big clock drifts and thus requires a frequently resynchronization and/or a precise clock drift calibration. Additionally, the network topology and unidirectional communication connections also have a deep impact on the precision of the synchronization algorithm. For this reason we introduce an alternative biologically-inspired synchronization algorithm together with a clock rate calibration scheme to build up synchronicity. Synchronicity is the ability to organize simultaneous collective actions across a sensor network. Hence our approach is based on distributed synchronous clocking and is a type of internal synchronization. In contrast to centralized clock synchronization schemes, the distributed synchronization approach has the inherent advantage for complete scalability and graceful degradation. This thereby achieved common notion of time is also used to establish a time-triggered protocol. In order to perform a rapid development, this approach was first simulated with a modified probabilistic wireless sensor network simulator for different network topologies and parameter choices. The results are then compared with the outcomes of several testbed experiments based on ZigBee nodes from Atmel.
Bibtex
@bachelorsthesis{ leidenfrost:2007,
  author =      "R. Leidenfrost and W. Elmenreich",
  title =       "Establishing Wireless Time-Triggered Communication using a Firefly Clock Synchronization Approach",
  address =     "Treitlstr. 3/3/182-1, 1040 Vienna, Austria",
  school =      "Technische Universit{\"a}t Wien, Institut f{\"u}r Technische Informatik",
  year =        "2007"
}
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