FCC’s Technological Advisory Council outlines risk-informed interference assessment

Interference arguments at the FCC would become more objective and less dependent on wordplay under a proposal by the FCC’s Technological Advisory Council (TAC).

Risk-informed interference assessment is a quantitative methodology intended to draw out the trade-offs between risks and benefits of new services. By using it interference assessments would move from, in the words of a TAC report, “What’s the worst that can happen?” to “What can happen, how likely is it, and what are the consequences?”

To apply this model, one inventories all expected harmful interference scenarios and estimates the likelihood and consequence of each one. The report uses as an example the following chart from a report to UK regulator Ofcom on WiMAX/TV interference:

Fig6

This chart depicts the percentage of locations at the the TV coverage edge subject to interference from WiMAX handsets for a particular desired/undesired ratio, C/I. The lower that ratio, the greater the likelihood of interference.

A family of risk curves can be prepared showing the risk sensitivity to different operating parameters and interference types, as the report depicts in the following example:

Fig7

Such a family of curves might guide a regulator in setting the transmit power ceiling and in prioritizing on which interference modes to focus.

The TAC says the FCC can start using this method now. It can be introduced gradually, supplementing current analysis methods such as looking at the worst-case. The FCC could, for example, quantify interference likelihoods and consequences instead of using language such as “reasonably low” to describe probability. The FCC could request analysis and disclosure of the likelihoods and consequences of interference in FCC proceedings, such as in comments to Notices of Proposed Rulemaking. As a pilot, the report suggests applying the approach to site-specific waiver requests, since they come up regularly, and their limited scope reduces the geographic impact of risk-informed decisions.

Risk-informed interference assessment can give the FCC a more nuanced, objective basis on which to decide on new services. Outside the FCC, it can give others a more critical mindset from which to discuss interference issues.