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The 700mhz Spectrum Auction In Perspective
YIAAL writes "Writing in Popular Mechanics, Robert X. Cringely looks at the upcoming auction of the 700mbz spectrum, which is currently used for soon-to-be-defunct analog TV. 'Why are all these companies so excited? Because the 60 MHz of spectrum that's about to be auctioned is the last prime real estate for mobile communications that will be available in the U.S. for decades to come ... Some pundits (that would be me) think Google will bid to win its spectrum block, then will trade that block to Sprint/Nextel for some of that company's 2.5-GHz WiMAX licenses that are far better suited for data.' Plus, the prospect of offering unlicensed data service in the 'white space' between existing broadcast channels."
Based on the auction rules, there is nothing limiting the potential licensees to which technologies they use the licenses for. (Except maybe the blocks designated for public safety.) The cost of each license is probably enough to prevent it. The cost and the geographic limitations that is; most licenses are fairly small (designed for potential Commercial Mobile Radio Services [CMRS]) the exception being Block C in the Upper 700 MHz with is broken into 12 geographic area groupings.
Traditional analog broadcasts had higher power ratings and larger coverage areas than allowed by the new licenses. The reasons being that the broadcasts were all one direction and the broadcasters were attempting to get the signal to as many people as possible. The new licenses are designed with CMRS in mind. CMRS doesn't use the coverage TV broadcast did, the more coverage the more transmitters requiring a piece of the network. Whereas, TV there was just one transmitter. Because CMRS is all about two way communication, it makes more sense to keep the each transmitting network small and have many of them. That way you can let, say, 20 people transmit within a range of frequencies on 10th avenue and one block over allow a different set of 20 people to transmit within the same range (the network serving 40 people across the two city blocks). Increase the power rating, hence the range, now the same geographic area only serves 20 people because there isn't enough spectrum space to serve more within the frequency range. (Okay, very crude example with very little actual engineering. Somebody familiar with current GSM standards could provide a much more accurate example. But, this should convey the concept.)
Because the licenses were designed with CMRS in mind, the power ratings are lower and the size of each "cell" is smaller. In order to have effective TV broadcast you would have to buy many of the license to ensure you didn't cause interference over another licensee's geographic coverage.
Furthermore, it doesn't make sense for a broadcasting company to spend large dollars on new licenses when those broadcasters are all transitioning to digital TV. It makes more sense to just go with the transition and tell consumers that it isn't their fault because the government made them do.
Basically, there is really nothing in the auction rules themselves, but economically speaking it would not be a wise business decision.
The article is just plain wrong when it states that the 2.5GHz band is superior for data, it is not. Throughput is primarily dependent on bandwidth, so 20MHz at in the 700MHz spectrum will effectively carry the same amount of data as 20MHz in the 2500MHz spectrum.
As someone who professionally designs cellular networks I can tell you that for data services 20MHz at 2.5GHz is much better than the same 20MHz at 700MHz. The data rate is determined not only by the channel bandwidth but also by the amount of interference that is generated by neighboring base stations. This interference depends on the RF propagation characteristics. At 2.5GHz the RF signals die off much faster with the distance than at 700MHz. As a result your interference levels will be lower at 2.5GHz. The downside is, of course, that cell coverage area of each individual base station will get smaller and you have to deploy them at substantially higher density. Rule of thumb: for voice you are coverage limited and you want your 700MHz (or 850MHz, ATT, Verizon) and big cells. For data you want small cells and high frequency band (2 or 2.5GHz).
Just my two cents from the tranches.