At the most recent ODVA conference, where industrial
network topics are the order of the day (ODVA is the organization that supports network technologies built on the Common
Industrial Protocol, such as DeviceNet, EtherNet/IP, CompoNet and
ControlNet), one of the hot topics being discussed was wireless. One session in
particular, presented by Paul Brooks of Rockwell Automation and Paul Didier of
Cisco, focused on the current real world utility of wireless and the benefits
of moving to 802.11n in an industrial environment.
Though wireless network use is still very much in its
infancy for industrial use, Brooks and Didier are confident that WiFi will
follow Ethernet into greater use in automation and control systems. However, they
expect that wide use of WiFi in the industrial arena is still several years off
largely due to the level of existing investments in wired networks coupled with
the fact that wireless technology capabilities tend to lag a bit behind wired.
In addition, Brooks noted that, from performance, energy and
flexibility aspects, WiFi is not as capable as specific industrial wireless
protocols such as WirelessHART or ISA 100. To illustrate his point, Brooks pointed out that, in control and safety applications, latency and
fidelity remain the biggest challenge for wireless devices. Therefore,
synchronization and motion applications tend to operate better when connected via wired
But with an array of business drivers pushing greater use of
wireless into the industrial area, such as the elimination of wires,
portability/mobility of devices, asset tracking, remote monitoring and video
surveillance, large market opportunities exist in industry for wireless devices.
Therefore, device designers should concentrate on applications involving moving
operators, moving machinery and applications where running wires is difficult
and costly, suggested Didier.
"The key for wireless device designers is to ensure that the
user experience is the same with a wireless device as it is with wired device,"
A large portion of their presentation focused on the
benefits of updating to the 802.11n standard. Advantages for device designers inherent
in the 802.11n include:
MIMO (multiple inputs, multiple outputs), which ensures
signals are received in-phase and increases receiver sensitivity;
Maximum Ratio Combining - multiple signals are
sent and combined at the receiver,†
thereby increasing fidelity;
Packet aggregation - multiple packets are
combined into one data packet, providing a big boost for network data management
in time-critical industrial automation applications;and
Backward compatibility with 2.4 GHz and 5 GHz as
well as the 802.11 a, b and g standards. Didier added that, for optimal
results, time-critical applications should run on 5 GHz with all else on 2.4 GHz
to increase fidelity.
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