Ex-FCC Chief Technologist Urges Harm-Claim Thresholds in Spectrum Decisions

Former FCC chief technologist Jon Peha, now a professor Carnegie Mellon University, suggests that for the next five years any NPRM contemplating a major change in how spectrum will be used in a band “should proactively include a proposal to use a harm claim threshold in that band, and possibly adjacent bands as appropriate.” That approach would “give the spectrum community the experience it needs in trying to apply general principles to specific cases,” he said: “If a harm claim threshold is adopted, this has potential to facilitate major changes in how spectrum is used in the future, by preventing harmful co-channel interference when policies are changed to allow new forms of sharing, and by preventing harmful adjacent channel interference.”

Peha said the FCC should encourage the most cost-effective approach to curbing interference. “We have seen cases where there is little incentive to deploy a system that can withstand interference in the most cost effective way, thereby shifting a disproportionate share of the burden to operators of the transmitters causing the interference,” he said.

Looking at receivers is a “positive step” by the commission, said the National Public Safety Telecommunications Council. “One size does not fit all” and “any potential receiver interference immunity performance characteristics would need to be technically feasible for manufacturers and available at reasonable cost for public safety entities.” NPSTC questioned the use of a harm claim threshold. “It is hard to imagine a public safety radio technician saying to a Chief of Police, Sheriff, or Fire Chief, ‘you should plan on some disruptions to communications’ while your officers, deputies, firefighters or Emergency Medical Service (EMS) personnel are approaching a car/driver with unknown firepower, working a hostage situation, responding to a terrorist attack, trying to quell a riot, fighting a fire, or responding to an urgent need for medical assistance,” the group said.

The Enterprise Wireless Alliance noted that no wireless system operates in a vacuum. “If systems in adjacent bands include receivers that are not designed with adequate interference immunity, EWA members and the FCC become embroiled in avoidable interference complaints -- a waste of valuable resources,” the alliance said. The FCC should regulate receivers “only if less intrusive approaches prove inadequate,” the group said: ‘Voluntary industry action should be pursued with FCC involvement through policy pronouncements or even regulatory requirements as a backstop. Industry-driven work through organizations such as the ITU, the 3GPP [3rd Generation Partnership Project], and others has been a hallmark of international wireless standards collaboration.”

“The FCC cannot fine-tune spectrum management with only half the orchestra,” TechFreedom said. “Without engaging government users, there will be little progress made toward finding broad solutions to increased spectrum congestion,” the group said: “The FCC can work to make commercial spectrum users more efficient, but if the government doesn’t deal with highly inefficient legacy government systems, this proceeding cannot achieve its intended purpose.”

The National Academy of Sciences, through its Committee on Radio Frequencies, asked the FCC to take into account the specific concerns of radio astronomy and earth remote sensing. The high sensitivity of passive users “is driven by the need to observe very weak signals emitted from natural sources and, specifically, to measure very small changes in those signals, either spatially (e.g., subtle features in maps of emission from the sky or Earth) or temporally (e.g., the fractions-of-a-percent change per decade in terrestrial signatures associated with climate change),” the committee said: “The high spectral selectivity is driven by the need for such measurements to be accurate and repeatable, and thus as immune as possible from interference.”