Real-time communications over wired/wireless PROFIBUS networks supporting inter-cell mobility

摘要

PROFIBUS is an international standard (IEC 61158, EN 50170) for factory-floor communications, with several thousandsof installations worldwide. Taking into account the increasing need for mobile devices in industrial environments,one obvious solution is to extend traditional wired PROFIBUS networks with wireless capabilities. In this paper, we outlinethe major aspects of a hybrid wired/wireless PROFIBUS-based architecture, where most of the design options weremade in order to guarantee the real-time behaviour of the overall network. We also introduce the timing unpredictabilityproblems resulting from the co-existence of heterogeneous physical media in the same network. However, the major focusof this paper is on how to guarantee real-time communications in such a hybrid network, where nodes (and whole segments)can move between different radio cells (inter-cell mobility). Assuming a simple mobility management mechanismbased on mobile nodes performing periodic radio channel assessment and switching, we propose a methodology to computevalues for specific parameters that enable an optimal (minimum) and bounded duration of the handoff procedure.