The industrial automation industry is ready for broad use of
wireless networks in process control and factory automation
systems. The Wi-Fi technologies are ready for adoption by
industry network consortiums, particularly for use where
Ethernet and the Internet Protocols are currently used. Unfortunately,
standards for the device level wireless (ISA100.11a)
are not yet finally approved.

In most cases, Wi-Fi can be tried where one of the Ethernet-
based networks such as FOUNDATION™ Fieldbus HSE, Ether-
Net/IP, Modbus/TCP, or PROFInet can be used. At this time,
considerable network planning will be necessary to make sure
that all nodes are within the actual radio range of today's wireless
access points. The investment should be made in only
Wireless-N devices, and of the commercial grade, not the less
expensive home grade. Wi-Fi networks have dead spots that
must be recognized during installation so that positions can be
adjusted to receive transmissions. External antennas can usually
be used to move the reception zone without moving the
unit; only devices that have external antenna jacks should be
purchased. Often, the external antennas need to be directional,
which will extend the network to the limits required for the
installation.

The real payoff from wireless for industrial automation will
come when field devices having standardized wireless connections
are available. Supplier proprietary specifications for their
wireless devices should be avoided unless there is a reasonable
migration path to ISA100.11a.

The wireless network technology tradeoffs are being evaluated
in the work to establish ISA100. To some extent, some of these
issues were evaluated to design WirelessHART, but against a
very limited application environment. In the opinion of this
author, unless there are unusual circumstances, the wireless
connection of HART instruments should be made only with
ISA100.11a conforming adapters, rather than using WirelessHART
equivalents. WirelessHART is a single-purpose network
and may cause some problems when installed in the
same area as ISA100.11a networks. Since ISA100.11a has been
designed as a universal network, it has the connectivity, flexibility,
and security for integration of all field devices, including
HART.