wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

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Preambles
Thilo Sauter
Institute for Integrated Sensor Systems
Austrian Academy of Sciences
Wiener Neustadt, Austria
Communication is a prerequisite for distributed systems. Such systems can be loosely defined as a group
of individual computer systems that appear to the user as a single coherent system. The spatially dispersed
nature of industrial processes, on the scale of a factory floor or electric power grid, is actually
often used as a guide for the design and layout of automation systems. This can be observed, for example,
in network-based control, where the control loop can actually be distributed over different processors
in a network. In this environment, the basic principles of distributed systems apply. However, while the
classic theory of distributed systems has been developed keeping mainly general-purpose computer
systems in mind, industrial automation focuses on dedicated systems with highly specialized hardware
and software.
Therefore, in what follows, the relevant aspects of distributed systems are revisited from the
viewpoint of industrial communication systems. It begins with a discussion of the classic ISO/
OSI model. Although the basic principle of communication layering is very significant for communication
in automation processes, not all layers defined in the reference model are of equal
importance.
Furthermore, special attention is given to three different aspects: wireless, integration, and quality of
service. Wireless communication today has a fixed place in many of the application areas of automation.
Wireless-related topics such as wireless sensor networks, low-power wireless communication nodes,
and RFID are discussed in detail. The integration of heterogeneous systems into a coherent application
environment is another crucial issue that is addressed. Finally, quality of service is revisited for
industrial communication systems, ranging from real-time communication for safety and security to
network-based control.
Group 1.1: Layers
Thilo Sauter
Institute for Integrated Sensor Systems
Austrian Academy of Sciences
Wiener Neustadt, Austria
The design of complex communication systems is not possible without a structured approach. Therefore,
a layered structure is commonly adopted. A landmark for communication system development was the
definition of the open system interconnection (OSI) model, a generic framework that is presented in
the first chapter of this group (Chapters 1 through 3). Within this model, it is primarily the lower layers
that are important for industrial communications in order to guarantee the performance needed
for a given application domain. Special attention will therefore be given to the large variety of wired
electrical, optical, and wireless communication media, as well as the many methods devised for access
control. For larger networks that are gaining importance in distributed systems, flat network structures
are not adequate for electrical and logical reasons. Therefore, the information flow through the network
has to be controlled by appropriate routing strategies, which has been a topic of interest for researchers
and developers for a long time. Experience with the first industrial communication systems, however,
showed that the OSI model was insufficient to ensure the interoperability that was a major requirement
of industry. A substantial amount of work has been, and still is, devoted to the definition of high-level
profiles that, depending on device type or application domain, further constrain the degrees of freedom
for system developers and implementers.
© 2011 by Taylor and Francis Group, LLC