Free the Radio Spectrum

The Federal Communications Commission (FCC), the government entity that manages the commercial and public radio spectrum in the United States, has proposed making 500 megahertz of spectrum available for broadband within the next 10 years of which 300 MHz between 225 MHz and 3.7 GHz will likely be made available for mobile use within five years. The extra bandwidth, recaptured from broadcasters after the digital television transition, is certainly needed, given that AT&T reports that its mobile broadband traffic has increased 5000 percent over the last three years and that other carriers have also seen significant growth. However, under the current approach to allocating spectrum, this 500 MHz will do little to ease the looming spectrum crunch.

It’s time to rethink the way we allocate spectrum. Under current regulations, spectrum real estate is valuable but exclusive. In the past, that exclusivity was the only way to prevent multiple users from interfering with each other. But advances in radio technology means that today such exclusivity is no longer necessary; instead, it creates false scarcity. So we must change our decades-old approach to managing the public airwaves.

When the FCC began allocating spectrum in the 1930s, radios required wide swaths of spectrum to communicate. Without single players occupying designated bands, a cacophony of interference would have destroyed audio fidelity and later, with television, picture quality.

Today radios that can share spectrum make such protections from interference unnecessary. Just as car drivers can change lanes to avoid congestion, these "smart radios," also called "cognitive radios," are transceivers that listen to available frequencies and communicate over any channels that are currently unused. These radios not only shift frequencies but can also be programmed with the necessary protocols for use in different bands, such as for speaking the "language" of various blocks of spectrum used for Wi-Fi, television, or cellphones. This means that vast swaths of spectrum no longer need be locked into single use, or left unused, as a hedge against interference.

Unfortunately, the FCC’s policies still assume the use of antiquated technology, and therefore that license holders must maintain absolute control of spectrum space at all times. These regulations must be updated to reflect the technological realities of smart radios.

Wi-Fi serves as a striking example of what is possible. A relatively narrow piece of the airwaves that’s open for unlicensed access, Wi-Fi has enabled home networking, roaming connectivity in hotels, cafes, and airplanes, and community broadband networks around the world. The explosion of communications in Wi-Fi’s 2.4 and 5 gigahertz frequencies has led to a host of new services and applications. However, these frequencies have trouble with walls, hills, and long distances. To support next-generation networking, a logical next step would be to allow technology developers access to a bigger and better swath of unlicensed wireless spectrum through the use of smart radios.

Policy allowing these new radios, tagged Opportunistic Spectrum Access (OSA), would give birth to a new generation of connectivity. With smart radios, unlicensed devices could share the same bandwidth as licensed users, finding unused frequencies in real time and filling in during the milliseconds when licensed users are not using their bands. In essence, they would work the same way as today’s iTrip or many home wireless phones, which scan a number of different channels and choose the one with the least interference.

Developers working on smart radio devices are excited about the possibilities of OSA. The technology allows for more affordable broadband for rural populations where low population density has deterred private infrastructure investment. It would mean more affordable and robust networking over longer ranges than today’s Wi-Fi, helping municipalities working to update aging communications systems and public safety officials working in both urban and remote areas. Similarly, OSA could increase opportunities for wireless Internet service providers and networking in businesses, universities, and cities. Successful community wireless networks including Urbana-Champaign, Illinois; Athens, Greece; and Dharamsala, India, could be expanded over greater distances.

The great benefit of OSA is the ability to open more access to spectrum while avoiding the challenges of moving current users to other bands. For example, smart radio device developers could access unused frequencies in the so-called white spaces of broadcast television. These white spaces, created when the FCC allocated spectrum to television broadcasters, are empty channels that were left unoccupied to prevent interference. In many rural areas, as much as 80 percent of this television spectrum is currently unused.

Today companies like Spectrum Bridge and Shared Spectrum Co. are already building next-generation networks using OSA. Spectrum Bridge has built a prototype network using TV frequencies in Claudville, Va. And Shared Spectrum has developed OSA technologies for use in battlefield communications, using these devices’ frequency-hopping capabilities to help avoid jamming efforts by hostile forces.

The FCC recognizes that this spectrum could be made available. In 2008 it issued an order authorizing the use of "White Space Devices (WSDs) that can detect TV signals at levels that are 1/1000th the signal power a television needs to display a picture, scan for interference, and move their bandwidth accordingly, avoiding interference with television broadcasts." To date, however, rollout of such products has stalled because the FCC has not followed through with necessary supplemental rulings, such as creating the required geolocational database of spectrum assignments to help identify which frequencies are in use in each area. Meanwhile, as a part of the national broadband plan, the FCC has committed to repurposing TV bands for exclusive use.

Potential spectrum also exists outside the television bands. Most spectrum allocations, such as the 270 000 held by government agencies alone, are woefully underutilized. Based on the best available data, collected in 2004 as part of a National Science Foundation research project, less than 10 percent of our current spectrum is used at any given point in time (including in major cities).

If the FCC continues the current policies of restricting spectrum use to exclusive entities and the highest bidders, they will continue choking what FCC Chairman Julius Genachowski has called "the oxygen of mobile broadband service." By adopting OSA policies, the FCC will allow expansive access to spectrum without disrupting existing users. Current license holders could preserve priority use in their assigned bands, but secondary users could communally use the 90 percent of spectrum that is typically not in active use.

At this point, implementing OSA is a policy consideration, not a technological challenge. In the National Broadband Plan released by the FCC in March, the commission recommends expeditiously completing the regulations related to TV white spaces. In our view, these rulings must be expanded to include a greater spread of underused spectrum. Spectrum will always be a finite resource, but policy needs to evolve alongside the technology to increase the efficiency and number of devices that can take advantage of this public resource.