Wireless Technologies in Process Automation - Herkules.oulu.fi - Oulu

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Figure 2. An example about industrial sensor/actuator network combining several
network technologies (Low et al., 2005).
Next, the wireless technologies applied in process industry are shortly introduced.
Proprietary technologies are excluded, and therefore, Z-Wave and Wavenis mentioned in
Figure 2 are not discussed (it should be noted, however, that proprietary technologies
may have applications in some cases (Sallinen et al., 2007). After introduction, some of
the related standards in industry are presented and finally, a technology roadmap is
discussed.
2.2 Wireless Local Area Networks (WLAN, 802.11)
Wireless local area networks (WLAN), or commercially Wireless Fidelity (Wi-Fi),
operate at 2.4 GHz or 5 GHz ISM bands and offer speeds up to 54 Mbps. They support
two modes: ad-hoc and infrastructure. The ad-hoc mode allows stations to spontaneously
form a wireless LAN, in which all stations communicate with each other in peer-to-peer
manner. The infrastructure mode, the network has an access point (AP), through which
each client station communicates. A typical Wi-Fi AP may have range of 45 m indoors
and 90 m outdoors. The properties of the most important 802.11 standards (802.11a,
802.11b, and 802.11g) can be found for example from (Cisco).
In process automation, Wi-Fi Networks can serve as the backbone for data concentration
and networking. For example, it can used in conjunction with short-range, low-power
devices in a wireless field network to collect data from the gateway further sending it to
the control room or other data collection point (Emerson, 2006b).
The advantages of WLAN in process automation include high range, open standards,
robustness, cost-effectiveness, easy accessibility to process control by mobile workers
and high data transmit rate (Emerson, 2006b). Recently, also the security has increased
with two important security enhancements, Wi-Fi Protected Access (WPA) and WPA2,
which replace older and less secure technology, Wireless Equivalent Policy (WEP).