up data rates. Data encoding and aggregation algorithms help decrease overhead while increasing signal clarity and speeds. Through it all, the standards process has emphasized backward compatibility with earlier 802.11 specifications, though the overall throughput is necessarily reduced when in compatibility modes working with older Wi-Fi devices.

Meanwhile, to step from the future back into the present, any enablement or enhancement to factory life through Wi-Fi, regardless of how cutting-edge or exploratory it might be, depends on standard processes for technology planning and implementation.

“It boils down to the same three things, whether you’re dealing with Wi-Fi, wireless Hart, wired networks or a person with a clipboard,” says Whitehead. “The first is performance, the second is reliability and the third is security. Wireless doesn’t have the same inherent reliability as a bundle of cables in many an application. Plus, if you decide that wireless is the solution, you need to remember that performance and reliability are affected environmental factors. You need to know what other wireless co-exists with your installation, since existing radio traffic has the potential for radio frequency overlap. And you have to remember that if Wi-Fi drops packets, it will cycle through retries. While 30 seconds one way or the other won’t bother you if you’re downloading an MP3 audio file at home, in a control situation with time-outs built into the protocol, you risk nuisance trips or downright outages.”

Standard procedures are emphasized by Peterson as well. “Every solution involves software, hardware, services and customization, and each one has to be scrutinized,” he says. “What do you want to do? What will you want to do in the future? You need to involve the stakeholders first to see what needs to be done. Then you evaluate the site, and for Wi-Fi, you’ll want to do a radio frequency site survey to see what’s in the air, so to speak. Then it’s just a matter of installing the wireless, the applications, and checking it all out. A finished installation will include planning for after-install services—training, maintenance, ongoing evaluation. You can’t just say, ‘Here’s a box, have fun.’ ”

There are a range of questions around architecture, focusing first on the exact location of the radio, then on the transfer of data to whatever end-point is chosen.

“You’re looking at a virtually infinite number of ways to put systems together,” says Whitehead. “As the application space settles down and people share the basic concepts, these will no doubt resolve to a few different primary strategies. Right now, however, I doubt that anyone would feel comfortable starting from scratch, working on their own. Everyone in the space—suppliers, consultants, device makers, end-users, everyone—has the responsibility to make sure they are deploying things they understand. Standards are increasingly fleshed out with reference architectures that provide suggestions for deployment. Plus, as standards proliferate, more and more people will be comfortable with the technologies involved. Once that happens, you’ll find more and more people able to see both the capabilities and the shortfalls of a given approach.”

Wireless Industrial Networking Alliance
www.wina.org

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