The FCC has released a nearly 500-page decision that lays out the rules for the broadcast spectrum incentive auction. Broadcasters willing to sell their spectrum back to the government will tell the FCC their selling price, and mobile radio operators that want to use that spectrum for LTE cellular phone service will bid for it. The hope is that they will bid enough money to pay off those broadcasters, pay for a nationwide public safety radio network, and cover the channel relocation costs for other broadcasters that chose not sell their spectrum. If so, the FCC will declare victory.
But if the auction succeeds, not everyone will be happy.
The big losers will be users of wireless microphones (WMs), and folks hoping to use unlicensed white spaces devices (WSDs) for data networks.
There are two classes of WMs, licensed and unlicensed.
Licensed WMs are used primarily by broadcasters, cable operators and program production companies like ESPN. In a companion proceeding, the FCC recently decided to allow additional entities to qualify for WM licenses. They include professional sound companies and larger sports venues, Broadway theaters, and churches that use more than 50 WMs. Licensed WM users are protected against interference from WSDs. Other theaters, churches and venues like hotels that host meetings use unlicensed WMs. Unlicensed WMs are not protected against WSD interference. Most of these WMs, both licensed and unlicensed, operate on UHF broadcast television frequencies.
ESPN is a major user of WMs. It told the FCC that a typical college football game uses 25 UHF WM frequencies, each 100 kHz wide, spread across 9 TV channels. A Monday night NFL game uses 40 UHF WM frequencies spread over 12 TV channels.
In order to avoid interference to TV viewers, there are FCC rules that restrict where WMs can be used when operating on frequencies used by nearby TV stations. And those TV broadcasts could cause interference to WMs as well. So the first choice would be frequencies not used by nearby TV stations, namely, white spaces frequencies.
In the FCC’s White Spaces proceeding, the FCC decided to set aside two TV channels in each market that were both free of TV broadcast stations and free of unlicensed WSDs, in order to assure WMs of interference-free operation. Well, that assurance is now gone. Now the FCC hopes to designate one TV channel in each market that will be free of TV broadcasts and will be shared by WMs and WSDs.
The frequencies to be auctioned to the LTE operators are in the “600 MHz Band.” But the precise number of TV channels will depend on the auction results. In one scenario, for example, if enough broadcasters are willing to sell their spectrum, and bidders will pay enough for it, then 126 MHz can be repurposed covering TV channels 31-51 (572-698 MHz). In another scenario, only 84 MHz will be repurposed, TV channels 38-51 (614-698 MHz). The precise auction procedures that will determine the amount of spectrum to be repurposed are very, very complicated.
The FCC has evaluated 11 scenarios, with the amount of repurposed spectrum varying from 42 MHz to 144 MHz. Each scenario consists of an LTE channel plan, a duplex gap, and guard bands. The LTE channel plan consists of pairs of 5 MHz blocks, one block for base stations paired with one for mobile devices. The duplex gap is 11 MHz and limits interference between base stations and mobile devices. There are two 3 MHz guard bands on either side of TV channel 37 to prevent interference into radio astronomy observatories.
There is another guard band of varying bandwidth at the lower end of the repurposed spectrum. Its purpose is to avoid interference between the upper end of the TV broadcast stations and the lower end of LTE operations.
Under the new rules, the guard bands and the duplex gap can be shared by WMs and unlicensed WSDs.
Originally the UHF TV spectrum went from 470-890 MHz, 70 channels numbered from 14 to 83. In the early 1970s, the FCC reallocated TV channels 70–83 (806–890 MHz) for the first generation of cellular and for public safety mobile communications. Subsequently, the 60 MHz in channels 60–69 (746-806 MHz) and the 48 MHz in channels 52-59 (698-746 MHz) were reallocated.
With each reallocation, there were fewer unoccupied channels for use by WMs. For the last two reallocations, comprising the 700 MHz band, the big winner was the U.S. Treasury….
and public safety agencies, which got free spectrum. And that’s what is happening again this time. Broadcasters should break even—either they get paid for giving up spectrum, or they get reimbursed for the cost of moving to a different frequency. Public safety agencies get money to operate a nationwide mobile network. And the wireless microphone users get squeezed again.