Will there be room for industrial wireless?

Dear Control Engineering: After reading the article on Overcoming Barriers to Wireless Adoption, I have to ask, aren’t we running out of wireless space nationally? Is there a possibility that we’ll lose the frequency allocation for industrial devices so more kids can watch videos on their phones? It seems that’s where the money is, and money talks.

You’re observations are at least partially correct in that wireless space, or spectrum is getting tighter, and wireless video is a major element of that. Trying to pack more into the available “air” is part of the motivation for AT&T wanting to buy T-Mobile.

If you’re wondering what spectrum is exactly, here’s a definition from the U.S. FCC Website:

“What is Spectrum? Spectrum is the range of electromagnetic radio frequencies used to transmit sound, data, and video across the country. It is what carries voice between cell phones, television shows from broadcasters to your TV, and online information from one computer to the next, wirelessly. The FCC and the National Telecommunications and Information Administration (NTIA) share responsibility for managing the spectrum. NTIA manages spectrum used by the Federal government (e.g., military, NASA) and the FCC is responsible for spectrum used by others, including individuals (e.g., garage door openers and wireless Internet connections), commercial operators (e.g., radio and television broadcasters, mobile phone providers), and public safety and health officials (e.g., police and emergency medical technicians).

“Frequency bands are reserved for different uses. For example, 88 – 108 MHz is used to broadcast FM radio to your car. Whereas, one of the groups of frequency bands used for cell phones is 824-849 MHz and 869-894 MHz. Because there is a finite amount of spectrum and a growing demand for it, effectively managing the available spectrum is an important priority for the FCC. With the FCC Spectrum Dashboard, the public can now learn more about spectrum licenses across the country and areas where spectrum is currently available.”

The FCC has an interesting place on it’s Website that shows how wireless spectrum is allocated. It’s really amazing how thin the slices are.

All that air space is getting used up, and most of the new use is coming via the cell phone industry. Cisco Systems says that data traffic on mobile networks during 2010 was three times the total amount of data traffic on the Internet in 2000. Moreover, the number of smart phones increased 57% last year, so you can see where the demand is coming from.

When the FCC closed down analog TV broadcasting in 2008, it opened up a big chunk of spectrum that is now coming into use. It also prohibited the use of many devices that used the slivers of space between UHF TV stations. I have some wireless microphones that are now illegal because the FCC has said that the frequencies they use are now reserved for other purposes. They still work, but one of these days I may find that they pick up a different type of transmission. Reallocating those old TV frequencies will help. Don’t be surprised if all over-the-air TV broadcasting goes away completely before too long. That will open up more.

One of the things that will help protect industrial users is that many plants can use the same space. Wireless instruments and Wi-Fi backhaul does not use much bandwidth, nor does it transmit very far. Plants don’t have to be all the far apart to use the same frequencies. But, as the article pointed out, when you are considering wireless deployments, you should do a site survey. You should also choose wireless technologies that are the most immune to the types of interference in your area now, and those that are most likely to crop up in the future.

–Peter Welander, pwelander@cfemedia.com

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