Interference Problems Seen as Likely to Grow as Wireless Explodes

At the highest levels, management of the “radio spectrum environment” is one of the FCC’s most important responsibilities, said Hatfield, now a senior fellow at Silicon Flatirons and a former acting administrator of the NTIA. FCC management of the spectrum involves allocating spectrum for various uses, establishing technical and service rules, distributing the right to operate within the allocation and enforcing the technical and service rules, he said.

“Too often in my opinion, the critical importance of the interference resolution and enforcement step in managing the spectrum environment is underappreciated, or worse yet, overlooked,” Hatfield said. “So is the failure to fully appreciate its rapidly changing environment.” Failure of the FCC to protect the spectrum environment endangers public safety, homeland security and national defense, he said.

The U.S. is seeing “explosive growth” in the number of wireless devices that must operate in close proximity, Hatfield said. The number of other electronic devices that emit electromagnetic radiation is also on the rise, he said. The increased densification of “often disparate devices and systems increases the risk of disruptive and harmful interference,” Hatfield said.

Many changes being made to increase spectral efficiency “present challenges to traditional systems and techniques used to detect, identify, locate, mitigate, report and, where necessary, prosecute those responsible for causing harmful interference,” Hatfield said. “These underlying technological developments can enable deliberate, malicious and potentially widely disruptive attacks on the nation’s critical infrastructure.”

Jamming and spoofing of spectrum signals demonstrate the vulnerabilities of the system, Hatfield said. With spoofing, a fake GPS signal could lead a navigation device in a vehicle to think it's in one place when it’s in another “with potentially disastrous results,” he said. “A fake telemetry signal could be used to tell a valve in a flood control system to open when it should really be closed.” Spoofing is “particularly pernicious because unlike jamming the signal looks and acts like a normal signal,” he said. “You can kind of tell if you’re being jammed.”

The agency’s approach on spectrum changed markedly 20 years ago when it approved rules for PCS spectrum used by carriers, said Charla Rath, Verizon vice president-wireless policy development. Before, the FCC took a more regulated approach when it allocated cellular spectrum, the first used for mobile phones, she said. “With PCS, [the FCC] set out some high-level technical rules and then they basically told us ‘if you have problems at the borders, solve them, don’t tell us.”

With PCS a carrier launches in an area knowing “the geographic boundary doesn’t quite suit the way you’re going to serve your community, so you talk to whoever has that adjacent license and you come up with an agreement,” Rath said. Carriers have one coverage map they show the world, versus the real map full of areas with spurious emissions that pose coverage problems, she said. The FCC has no idea what’s in the agreements between carriers, she said.

The commission is modernizing its field enforcement offices and that likely will continue through January, said Charles Cooper, acting field director of the Enforcement Bureau. “We’ve been more focused on RF interference mitigation and resolution.” In the past 12 months, the bureau has done about 1,000 RF interference investigations, with 350 tied to public safety, he said. Other investigations have focused on interference to broadcasters, land mobile radio systems, cellular and amateur radio, he said.

High-powered, continuous transmissions, like those from pirate radio stations, are the easiest to detect, Cooper said. On the low-power end, the “visibility” of interference is much less, he said. “The interference tends to be more from unintentional transmitters” such as from electronic equipment that’s not operating properly, he said. Intermittent interference is the most difficult, he said.

Cooper said that when he ran the FCC field office in Los Angeles, the worst call “was some public safety entity saying I have something happening on my public safety channel, it comes on one or two days a week, yet when it does it’s causing harmful interference.” The FCC has to put a lot of resources into addressing periodic emitters and they’re often difficult to find, he said. Spectrum sharing is causing an increase in problems, starting with the 5 GHz band, where spectrum incumbents are seeing interference from unlicensed devices, Cooper said.