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Q&A: What the FCC's Wi-Fi expansion means for you

And why Aerohive's Matthew Gast has an engineer's crush on the FCC chairman

By , Network World
January 23, 2013 10:04 AM ET

Network World - Mobile devices like the iPhone 5 are embracing the 5GHz band, and that trend will expand as 802.11ac radios become prevalent even on smartphones starting in 2013. 

The FCC announced a New Year's Wi-Fi gift during the International CES show earlier this month: a proposal to dramatically expand the unlicensed spectrum in the 5GHz frequency band for use by Wi-Fi devices. The announcement comes as a growing number of vendors are announcing products that will support the "Gigabit Wi-Fi" 802.11ac standard  in 2013.

Matthew Gast
Matthew Gast

To find out the implications of the FCC's plan, we talked with Matthew Gast, director of product management for Aerohive Networks (responsible for the software powering Aerohive's controllerless access points, and author of "802.11n: A Survival Guide").

Gast blogged, enthusiastically and gratefully, after FCC Chairman Julius Genachowski announced the spectrum move, even admitting he had an "engineer-crush" on the chairman as a result.

[For more information on this band, and 11ac, check these links:

FAQ: iPhone 5 and 5GHz Wi-Fi

Fast 11ac adoption seen for smartphones

Resources for 802.11ac 'Gigabit' Wi-Fi]

So, does Genachowski know you have an engineer crush on him?

I don't think so. What I didn't put in the blog is that I was [once] at the FCC supporting a technical board meeting. The chairman came in and spent two hours with us, an amazing amount of time. I introduced myself to him, and I'm sure he has no idea who I am. When I saw him, I thought "I hope I look that good when I get to his age." [Genachowski is 50.]

In your blogpost, you say the FCC is adding 195MHz of spectrum for Wi-Fi. For us non-spectrum-geeks, is that a lot?

The FCC is saying that it's 35% more spectrum. That sounds like a nice number. What I then did was made some educated guesses about the number of 20MHz channels this would add to the 5GHz band. And if you look at the channels, it's actually 60% more spectrum.

How do you figure?

The "existing" 5GHz channels - before the new FCC announcement -- were these: 22 20MHz-wide channels in three bands.

[Gast's technical breakdown is as follows:

5.17-5.33MHz: 36, 40, 44, 48, 52, 56, 60, 64

5.49-5.725MHz (these are the Dynamic Frequency Selection channels, which Wi-Fi radios must avoid if they're used by weather or other radars): 100, 104, 108, 112, 116, 132, 136, 140, 144

5.735-5.835MHz: 149, 153, 157, 161, 165]

In that second band, FCC removed three channels between 116 and 123 - 120, 124 and 128. This gap was for [protecting] a new wind shear radar [in effect, a special kind of weather radar] being developed by the Federal Aviation Administration for airports. The FCC concluded that outdoor Wi-Fi was interfering with this radar. That decision blew a hole in the middle of the available spectrum in this band.

The newest FCC announcement adds back the 3 channels in the DFS. It also adds new spectrum, so you have two [entirely] new bands. My best guess is that this new spectrum is good for 10 totally new channels. My guess at channel numbering is:

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