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Blog Editor’s Note: “Silicon Flatirons” is a program of Colorado Law at the University of Colorado that focuses on the digital world.

The publication “Policy Tracker” reported on the most recent Silicon Flatirons event and its recommendations for resolving spectrum conflicts.

Spectrum allocation, and particularly the Lightsquared/Ligado issue, has long been of interested to this group and at their annual events. We participated in a panel discussion at their virtual event in 2020.

This year’s event issued five recommendations to avoid future conflicts like the one over Ligado Networks and GPS:

  • Perform better and more varied measurements of radio propagation, interference scenarios, performance degradations, etc., particularly for non-terrestrial network uses of terrestrial spectrum and vice versa.
  • Develop a framework for harmful interference that includes mission impact and technology impact.
  • Assess, create and characterize interference mitigation technologies for expanding coexistence opportunities, such as MIMO.
  • Embrace risk-informed over worst-case interference analyses, including economic factors such as the cost of remediation.
  • Pursue disruptive technologies and new incentives for spectrum sharing.

When interviewed for the Policy Tracker article, we suggested that, overall, these kinds of things were easier said than done.

Some specific concerns we have are:

  • The recommendation to perform more, better and varied measurements of radio propagation, interference scenarios, etc. is good, but more scenarios take more effort. To date, most folks have done work they think covers the majority of cases and use rules of thumb, logical extensions of the work they did, and/or safety margins for the rest of the cases. They could do more but at what cost and for what benefit?
  • The idea that “harmful interference” should include mission and technical impacts is a good one.  In the navigation world doing so will required real-world testing and recognizing the differences between radio communications and radio navigation,
  • Assessing, creating, and characterizing interference mitigation technologies that would allow for greater coexistence is also a good idea. But they have to be affordable and implemented. For example, It’s possible for GPS receivers to be made to avoid Ligado interference, but they’re pricier and bulkier. How do we get manufacturers to build and market them, and how do we get users to buy them?
  • The risk-informed versus worst-case-scenario approach sounds good initially, but requires a lot of care in implementation. We don’t want to get to a place where we are saying ‘we don’t mind the bridge breaking occasionally’ or ‘it’s OK to lose an airplane every now and again as long as Ligado gets to use adjacent spectrum.’ Risk informed is great, as long as it is done in a safety-of-life context.