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

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WirelessHART, ISA100.11a, and OCARI 53-13<br />

End device<br />

(RFD)<br />

Industrial facility backbone<br />

Time<br />

server<br />

Workshop<br />

coordinator<br />

Cell coordinator<br />

Sink node<br />

Cell coordinator<br />

Sink node<br />

Workshop<br />

Sink path<br />

Sink node<br />

Cell coordinator<br />

FIGURE 53.12<br />

OCARI network topology.<br />

53.4.4 application Layer<br />

OCARI APL is based on the specification released by the ZigBee Alliance. It defines some additional<br />

profiles such as<br />

• “Sensor 4-20” that deals with the well-known 4–20.mA<br />

• “Sensor binary” for binary sensor including electronic PNP commutation transistor<br />

• “Accelerometer” for vibration analysis (up to 5.kHz) used in condition-based maintenance<br />

application<br />

It also supports the well-known <strong>communication</strong> models:<br />

• Request/reply<br />

• Publish/subscribe (event-based notification)<br />

• Periodic notification<br />

53.5 Coexistence of the Three Protocols<br />

From the users’ point of view, a single wireless standard for the <strong>industrial</strong> automation world would be<br />

the most appealing solution. Even if protocols discussed here are quite similar, e.g., all of them are based<br />

on the same PHY, they are not identical. In particular, protocols used for the upper <strong>communication</strong>s<br />

© <strong>2011</strong> by Taylor and Francis Group, LLC

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