For those not familiar with this spectrum, today much of it is used by UHF television stations. The upcoming auction is being called an incentive auction because TV stations willing to give up their public spectrum or to be relocated within the spectrum will share in the proceeds of the sale of their spectrum.
But stations aren’t being mandated to leave this spectrum and the recent public notice discusses for the first time what might happen to stations that elect to remain on the public airwaves. The FCC proposes to ‘repack’ a stations frequency and to put it anywhere within the 600 MHz range in such a way as to optimize the 600 MHz frequency in a given market.
The controversial part of the idea is that stations could be placed into spectrum that is used by somebody else. For instance a TV station could be put into spectrum that is reserved today for wireless microphones. Or even more controversial, a station could be placed into what is called the duplex gap, which is a spectrum buffer that sits between major pieces of spectrum and that is used to reduce interference between different technologies. The easiest way to think of the duplex gap is to envision it as a buffer channel that nobody gets to use.
This FCC’s ideas aren’t pleasing anybody. TV stations are now worried that they will end up in parts of the spectrum that will be polluted by other traffic and that will mar transmission quality. And the wireless carriers are unhappy since the TV stations might end up interfering with cellular calls. It’s going to be interesting to read the comments that the FCC gets on this issue and to see how they can resolve it. The auction will quickly fall apart if the stations all decide to not participate.
There are many other interesting parts to this auction. The FCC would like to assign some of the 600 MHz band as unlicensed spectrum for use for WiFi. The 600 MHz band is one of the more useful spectrum bands around in terms of transmission characteristics. It can go long distances and can travel easily through walls and buildings (just think back to the ease of receiving UHF channels on your TV in the basement). The FCC also wants to create more room for ‘white space devices’ that can use the spectrum for high-speed wireless data transmission.
But not everybody is enthusiastic about the ways that the FCC plans to do this. The FCC’s plans are to very aggressively squeeze as much use as possible out of the spectrum and to allow white space devices to operate in the guard bands at power levels that might impair licensed spectrum. AT&T has said that it might not participate in the auction if it believes that the spectrum it buys will be compromised.
The fear expressed by radio engineers is that the current proposal will cause noticeable interference. For example, they say that a device using the white space, say a tablet, and a cellphone using a licensed portion of the 600 MHz might interfere with each other when used together in the same room.
There are already a lot of devices using this frequency today. In addition to the low power TV stations it’s used widely by wireless microphones, medical telemetry and radio astronomy, and there is fear that the repackaging is going to harm all of these uses.
I don’t know if the FCC has anything harder to solve than our shortage of spectrum. The demand for spectrum has grown rapidly and many of the existing bands get easily congested with traffic at peak times. The wireless carriers are clamoring for more spectrum while at the same time there are dozens of other uses of the spectrum including public safety and the military that must be considered in any wireless plan.
I don’t know if it would be possible to develop a good spectrum allocation plan if you started from scratch today, but it seems nearly impossible to satisfy everybody as we try to fit new uses of spectrum over top of a spectrum allocation that was made in a very different time. I don’t envy the FCC the task of figuring this out.