Baby monitors. Bluetooth headsets. Wi-Fi Internet access. E-Z Pass. These are just some of the common technologies used by consumers every day that run on free, public airwaves known as unlicensed spectrum.
Unlicensed spectrum is the interstate highway of the wireless world: Anyone can use it, provided they stay within their lane. Advocates say freeing up more unlicensed spectrum could spawn new technologies, such as super Wi-Fi networks capable of covering entire neighborhoods or even cities. But some lawmakers remain wary of giving away something so valuable for free, and Congress is watching closely as the Federal Communications Commission makes critical decisions about unlicensed spectrum as it prepares to hold a spectrum auction next year.
Any device that sends or receives signals to transmit sound, video or data uses spectrum, and most of the spectrum in the United States is designated for the use of a particular government agency or commercial industry under licenses allocated by the FCC, which aims to prevent the nation’s countless devices from interfering with each other.
Wireless carriers have proven ravenous in their demand for spectrum in recent years, as consumers’ mobile data consumption has skyrocketed, but the amount of spectrum available remains scarce. That has driven the value of the most-technically-useful spectrum into the billions of dollars and prompted wireless carriers to buy up whatever spectrum licenses they can find, subject to the FCC’s approval. The spectrum crunch has also created pressure on the government to free up more airwaves for commercial use.
To initiate next year’s spectrum auction, the FCC will solicit offers from TV broadcasters to either pull their stations off the air or have them repacked into another channel. The agency will then assemble the various chunks of newly released spectrum in the 600 megahertz block and auction them to wireless carriers, in hopes of maximizing revenue.
The high cost of spectrum has shut out all but the largest telecom and technology companies from being able to experiment in the wireless space. Realizing this, the FCC first acted in 1989 to allow for some unlicensed use in high- frequency airwaves known as “junk bands.” Any company is allowed to make new devices that operate wirelessly in this spectrum, so long as they don’t interfere with other devices making use of the band.
Gradually, the availability of unlicensed spectrum for experimentation produced a number of innovations, including baby monitors, garage door openers and wireless microphones. The FCC acted again in the ’90s, freeing up more spectrum for unlicensed use, which ultimately spawned commercial Wi-Fi technology. By 1999, the computing world had adopted standards for Wi-Fi, and the technology took off.
Today Wi-Fi has become a crucial part of most communications networks, including wired broadband and wireless providers, who offload a significant portion of their data traffic to wireless networks. The growth of Wi-Fi has attracted a new level of interest in unlicensed spectrum, starting with the unused spectrum between TV channels known as the “white spaces.”
In 2010, the FCC adopted an order allowing developers to create devices that use the white spaces, after establishing a set of databases meant to prevent interference. A host of companies, including Google and Microsoft, have shown significant interest in the area; the search giant is in the final stages of being approved as a database manager by the FCC.
But the amount of white spaces spectrum available for unlicensed use in the long term depends on the FCC, which is under political pressure from House Republicans to maximize the amount of spectrum for sale to wireless carriers.
Rep. Greg Walden, R-Ore., who chairs the Energy and Commerce Subcommittee on Communications and Technology, prefers licensing 600 MHz spectrum to wireless carriers for two reasons: The airwaves are better suited to covering long distances; and to maximize the revenue raised from the auction, according to a committee aide. The aide noted, though, that Walden has expressed support for licensed and unlicensed spectrum.
“The additional spectrum will help address the spectrum crunch commercial wireless providers face and will increase bandwidths and speeds for Wi-Fi users,” Walden said. “The subcommittee will continue its oversight of both the FCC and the [National Telecommunications and Information Administration] to ensure the benefits of this legislation inure to both licensed and unlicensed users.”
But Rep. Anna G. Eshoo of California, the subcommittee’s senior Democrat, notes that the unlicensed wireless sector is generating $50 billion to $100 billion per year for the U.S. economy.
“This kind of growth cannot be ignored,” Eshoo said. “The FCC should ensure that the 600 MHz band plan is structured so that spectrum for unlicensed innovation is available on a nationwide basis. This will produce great economic benefits and could yield untold technological discovery.”
Interestingly, Senate Commerce, Science and Transportation Chairman Jay Rockefeller, D-W.Va., also backs those wanting to maximize the amount of spectrum sold at auction. “I come down on the auction side,” he said in an interview. “We need the money for D Block,” the national public safety communications network that will be funded by auction proceeds.
The FCC’s band plan will lay out how much spectrum will be up for auction, depending on how much is relinquished by the TV broadcasters, and may include some of the white space spectrum that is currently unlicensed.
“Repacking, or the reassignment of channels to broadcast television stations that remain on air after the incentive auction, is required to free up contiguous blocks of spectrum for mobile broadband use,” an FCC spokesman said. “As directed by Congress, the FCC will ensure this process makes all reasonable efforts to preserve the coverage area and population served of each broadcast television licensee.”
Experts believe that plenty of white spaces and unlicensed spectrum will be available in rural areas where it can be used for broadband. But the large urban markets are another story, with crowded spectrum conditions and few unused channels.
A Democratic aide underscored the necessity of setting aside blocks of spectrum for unlicensed use on a nationwide basis by arguing that manufacturers are unlikely to take much interest in developing new devices that don’t work in New York or Los Angeles.
The pressure for the FCC to auction as much spectrum as possible means device makers and others looking to tap unlicensed spectrum in the 600 MHz band may instead be limited to the use of “guard bands,” as outlined in the 2012 payroll tax cut extension (PL 112-96) that authorized the auction. Guard bands are small chunks of spectrum reserved between larger blocks in order to prevent adjacent networks from interfering with each other.
As Walden noted at a recent hearing, that law authorizes the FCC to create guard bands as technically needed. The commission is authorized by the statute to permit some unlicensed uses in the guard bands, provided they don’t cause interference with the licensed users in adjacent spectrum.
Several industry experts emphasized that an important issue in the debate is which guard bands are ideal for unlicensed use, including what size bands are optimal for wireless equipment manufacturers.
But the FCC is weighing a wide range of band plans and hasn’t tipped its hand on the size or nature of its final proposal. Whether those guard bands would be enough to deliver on the promise of super Wi-Fi remains anyone’s guess.