New Radio Frequency Uses

December 3, 2010 11:22 AM

Recently the FCC auctioned off parts of the radio frequency spectrum that were freed up with the transition to digital TV. Can someone summarize exactly what happened and what those frequencies are being used for?

I have a suspicion that the emergence of the 3G and 4G networks are a result of this frequency freeing up, but I've also heard about Google wanting frequencies to be free, and there being controversy about that, and I've heard rumors of super-routers and all sorts of other interesting new technology. There is so much information out there that I'm getting confused researching it and I'm hoping someone more familiar with it can sum things up.

posted by brenton to computers & internet (6 answers total)

Start with the Wikipedia page, and then read here about what they're doing with it.

Short version, Verizon is using it to launch their 4G (LTE) network this year, and AT&T, which already had holdings in the 700mhz range, will use it to launch an LTE network at some point next year.
posted by Oktober at 11:35 AM on December 3, 2010

For whatever it's worth, the freeing of spectrum and the transition to digital TV are unrelated. The FCC has been working for decades on freeing up spectrum which had been allocated to TV. (For instance, 800 MHz cellular is using spectrum that originally was UHF channels 70-78 IIRC.)
posted by Chocolate Pickle at 11:45 AM on December 3, 2010

For whatever it's worth, the freeing of spectrum and the transition to digital TV are unrelated.

No, as a matter of fact, they aren't, or at least not entirely. I worked for the FCC during 2008, and let me tell you, freeing up this spectrum for other uses was actually a pretty important rationale for the whole project.

EM in the 700-800MHz range has the desirable property of being able to go a long way and through a lot of stuff. It has the rather undesirable property of requiring a rather significant chunk of spectrum per data channel, but hey, there are trade-offs to everything. So the "carrot," if you will, for forcing TV stations to switch to digital was that they'd wind up getting two, three, or even more channels in exchange for the one they were operating in the 700-800MHz band.

A lot of that space is now actually being used for emergency responder communications devices--or at least that was the idea--and Google did manage to win a concession on the C-block of that spectrum before it bid. It didn't win the bid, but Verizon will be forced to use it as an open network as a condition of the license.

Here's a chart of the current spectrum allocation as of 2003. You can see that there are a lot more things going on at the top of the spectrum than at the bottom.

As a kind of bonus science fact, some of the really low radionavigation spectrum actually overlaps in frequency with the human audible range, i.e. if you were to make that wave a physical vibration instead of EM, you'd be able to hear it.
posted by valkyryn at 12:20 PM on December 3, 2010 [2 favorites]

valkyryn, I've actually been studying that chart that you linked to, and it was partly a motivation for this post. (Actually I was looking at the one included in the Wikipedia page that both Oktober and I linked to, which seems to be identical to the ntia.doc.gov chart.) That chart communicates to me that there's a lot going on, but because I didn't know what it looked like before the changes, it doesn't give me a good perspective of what exactly changed and which parts are new. Where are the white spaces that Google was up in arms about? Where is 3G? Where is 4G?

Also, I'm fascinated with this audible-light concept. Is it possible to create a resonator that would convert the light vibrations into physical (and thus audible) vibrations in a way that is significantly simpler than a radio? Very cool, at any rate.

Would love to hear any more insight from you, valkyryn.
posted by brenton at 1:43 PM on December 3, 2010

The "white spaces," as I understand them, were buffers in the spectrum surrounding each TV channel, not only to prevent local stations adjacent to each other in the spectrum from interfering with each other, but to prevent interference from stations in neighboring broadcast areas. Basically, things weren't allocated all that efficiently the first time around, and the FCC is making a point of doing it better this time.

At this point we're reaching the end of my knowledge. I'm a lawyer, not an engineer, so I'm approaching this more from a regulatory than a technical angle. The FCC spectrum dashboard might be interesting.

The "audible-light" concept probably wouldn't be that difficult if you were a halfway-decent electrical engineer. I'm not, so I got nuthin' for you, but others might.
posted by valkyryn at 2:26 PM on December 3, 2010

Valkyryn, the point I was trying to make is that the FCC started trying to reclaim UHF TV channels long before anyone even was thinking about digital TV.

The "white spaces" to which you refer are known as "guard bands".
posted by Chocolate Pickle at 6:10 PM on December 3, 2010