My testimony (pdf; my oral testimony at time code 0:17:23 in the YouTube video on the hearing web page; the members' questions start at 0:27:00; some press here and here) tried to make four points:
- We need to improve the ability of radio systems in one frequency band to tolerate reasonable signals in adjacent bands.
- Receiving system operators must bear some of the responsibility, but need to know what those responsibilities are.
- Regulators can bring receiving systems into the mix by setting harm claim thresholds (aka interference limits or receiver protection limits), i.e. the interference levels that a service needs to tolerate without being able to bring a harmful interference claim.
- Congress can play a role by keeping up the pressure, allowing the FCC to move ahead, and funding FCC technical investigations.
First, while most people talk about “spectrum crunch” in terms of a shortage of spectrum, the crunch that really matters is the need to squeeze ever more services into increasingly crowded frequencies. Solving that problem requires improving the ability of radios in one frequency band to tolerate reasonable signals in adjacent bands.
The FCC and NTIA (and corresponding regulators in other countries) can help by drawing boundary lines more clearly, that is, by clarifying both the rights that radio services have to be protected from harm, and their responsibilities to tolerate interference.
Second, receiver performance is key. Receivers in one band – or more accurately, the receivers and transmitters of a radio system in that band – that cannot tolerate reasonable signal levels in an adjacent band unfairly impose costs on others while reaping the benefits, like cheaper equipment, themselves.
So far, the FCC and other regulators have handled such interference almost entirely by placing the burden on the neighbor, for example by reducing their transmit power – sometimes to zero, precluding the introduction of valuable new services. However, it takes two to tango: the receiving system operator also needs to bear some responsibility – but it needs to know what those responsibilities are.
Third, I proposed that the FCC can bring receiving systems into the mix by setting harm claim thresholds. (The name has evolved as the policy community has developed this idea; it also goes by “interference limits” or “receiver protection limits” see e.g. the PCAST spectrum report and my earlier posts.) Harm claim thresholds state the interference levels (in-band and out-of-band) that a service needs to tolerate without being able to bring a harmful interference claim. No regulator-mandated receiver standards are required. Harm claim thresholds let manufacturers and operators figure out the best way to deal with interference, for example by deploying suitable receivers. Such an approach minimizes government intrusion in the marketplace while maximizing the value of radio operating permissions, a vital national resource.
However, there may be a few cases where harm claim thresholds will not be sufficient. Additional measures, perhaps even mandated receiver standards, may be unavoidable in a few cases, but should be a last resort.
Finally, I argued Congress can play a decisive role in solving this problem (1) by continuing to focus attention on the issue; (2) by making clear that the FCC can use regulatory approaches like this one, i.e. that new legislation isn’t required before moving forward; and (3) by funding the FCC to commission the engineering studies that are needed to inform smart regulatory frameworks.
Postscript: Rep. Walden, who chairs the sub-committee, apparently liked my tent analogy for receiver interference tolerance, so I posted that, too.