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“Things are evolving” on how the FCC looks at interference risk, said Julius Knapp, chief of the FCC Office of Engineering and Technology, at the conclusion of a Silicon Flatirons conference Friday on Risk Assessment in Spectrum Policy. “I’m heartened that the topic should be explored,” Knapp said. The interference debate can sometimes determine whether a new service is ever launched, he said.
The FCC historically has taken a cautious approach on such issues as out-of-band emissions and aggregation, Knapp said. “As we’re packing more into the spectrum and we’ve got innovations that are looking to try to gain access to the spectrum, more and more of the dialogue has been about interference,” he said. Spectrum incumbents often describe the risk in extreme terms when a new use of the spectrum is being discussed, he said.
The FCC’s analysis of the risk of interference is based on the maximum power level from a device, Knapp said. “We do the analysis at the maximum and the transmitters for the most part aren’t operating at the maximum,” he said. “Why? You don’t want to have a great phone that works for 10 minutes. You’re going to preserve battery life.”
When the FCC analyzes out-of-band emissions, “We assume that there are emissions everywhere,” Knapp said. “But usually they aren’t. They’re usually in a handful of spots.” Devices are designed to minimize out-of-band emissions, Knapp said. “They don’t want to interfere with themselves.” There’s also a lot of debate about aggregate emissions and what happens when a device is used throughout a city, he said. “There’s been a lot of debate lately and it’s a key element for gaining access to spectrum.”
Knapp said, for example, the FCC did a long analysis of ground-penetrating radar. “When you did the analysis [the radars] killed GPS and just about everything else in their area,” he said. The FCC crafted rules for the radars. “They still are being used and, as near as I can tell, they haven’t bothered a soul,” Knapp said.
Knapp said engineers disagree as much as lawyers. “For anybody who thinks that the engineers sit down and all come up with the same answer, you haven’t been in a room full of engineers,” he said. The engineers “in some ways are worse” than lawyers, he said. Lawyers expect gray areas and are used to debate, he said. “Engineers are trained to work the problem and there’s a solution; there’s one solution,” Knapp said. “So there’s a lot of passion” behind the arguments.
Policymakers struggle when engineers disagree, Knapp said. When policymakers are told that a new use of spectrum will mean dropped calls to 911 or be harmful to TV reception in a tornado “it’s really hard thing for them to gauge what to make of all of the information that’s put in front of them,” he said. “Yes, they rely on the staff, but they listen to the participants too.”
Joan Marsh, AT&T vice president-federal regulatory, said she has “battle scars” from spectrum fights, saying AT&T’s fight to deploy in wireless communications service (WCS) spectrum took almost 10 years. AT&T wanted to deploy LTE and Sirius XM’s concern was the deployment would mute its receivers, she said. Finally, in 2012, the two were able to agree on a definition of “harmful interference,” she said (see 1208300052). “That is not trivial.”
The work on an agreement was data driven and required extensive testing, Marsh said. Even after the two companies reached agreement they had to coordinate deployment. “If something happens that is unexpected, there are certain remedies available,” she said. “You need the full package and none of those steps are trivial, they’re all difficult.” Marsh contrasted the experience on WCS with LightSquared’s attempts to deploy a terrestrial network. The fight over LightSquared became political “and as soon as you politicize interference, you’ve lost,” she said. “You’re no longer searching for solutions.”
There’s no “noise-free” RF environment left, Marsh said. “Every time we go out there, we are managing noise,” she said. “The question becomes when does the interference become harmful. … Nobody has the right to expect an interference-free environment; it just doesn’t happen.”
NTIA’s Peter Tenhula, speaking at the conference, disputed the notion that the federal government is the largest spectrum incumbent. Only 17 percent of “beachfront” spectrum is in federal hands and more than half is shared, he said. He cited the 960-1215 MHz band. “That’s a shared band and it’s allocated to aeronautical navigation, aeronautical mobile and radio navigation satellite,” he said. “Who are the beneficiaries of those federal systems, the air-traffic control systems, the GPS?” Tenhula asked. “It’s the general public and to call that a federal band is not accurate.” Tenhula is deputy associate administrator for spectrum management.