Freeland continues, "For example, condition monitoring of balance-of-plant machinery will not be hardwired (although it could be) because of the cost and disruption of installation. It will be done wirelessly because the low cost gives a good payback. There are also many applications for sensing and RTLS on mobile assets where hardwiring is not practical."
So the problem facing wireless field sensor networks is not just the issue of convergence to a common standard, which by all accounts appears unlikely. It is also the unlooked-for competition from traditional wired sensors and multiplexers due to the pricing, at least at present, of wireless sensors. If standards don't converge, and prices do not come down, wireless field sensors may well be relegated to the odd, out-of-the-way sensor application that can't be done any other way.
Ariana Drivdahl, product marketing manager for industrial wireless for Moxa Americas Inc., notes; "Convergence of wireless and remote automation is already happening. There is a growing number of interesting applications that utilize wireless technologies like GPRS, HSDPA and Wi-Fi to enable remote monitoring of industrial processes."
How important are WiFi, VoIP, WiMax and other "backbone" technologies to the industrial wireless space? Honeywell's One Wireless has always emphasized the backbone, as Ray Rogawski pointed out at Honeywell User Group Americas in June. Gareth Johnston, lead wireless engineer for ABB Ltd., responds, "Quite important because there are already mobile workers and site security using these technologies."
David Crump of Opto22, notes that the importance of WiFi, VoIP and other backbone technologies is "huge because Wi-Fi is 'wireless Ethernet,' a well-established, widely deployed and proven networking standard. WiMax is essentially high-powered Wi-Fi, and VoIP is, as the name implies, Internet Protocol (IP)-based. Thus, any industrial application that uses Ethernet, wired or wireless, as the physical medium, and IP to effectively broker all the requests between the application layer and the physical layer has a far greater ability to integrate into existing applications and play nice with all the other industrial technologies and networks that are out there."
According to a report on surveys ("The State of Industrial Wireless—2010" www.controlglobal.com/wirelesscommunication.html) jointly conducted by ControlGlobal.com and Apprion, Inc., "While sensors for condition monitoring continue to garner significant interest and will certainly drive further wireless adoption, the increased interest in wireless appears to be focused on other application areas. Video monitoring, communications and workforce mobility are the three application areas receiving the greatest interest today."
Another ControlGlobal.com/Apprion report ("The State of Industrial Wireless Communications—2010," indicates, "Use of IP-based Wireless Local Area Networks (WLAN) will increase 73% over the next three years, while other network types will decline or remain flat. The need for greater mobility and unified communications are two factors driving IP/WLAN networks. Sixty-one percent of plants are engaged in developing a unified communications strategy or are in the process of implementing a unified communications strategy."
There you have it. The real important issues aren't convergence or which standard to support. The real issues for wireless in the process automation environment are just what they've always been for every technology that comes along: What can I do with it that I can't do without it, and how much is it going to cost before I see payback. The more things change, the more they stay the same.
Walt Boyes is editor in chief of Control.