In Denmark, they traffic regulating orginization is disussing these issues with the comercial parties. I am still missing the resume of the latest meeting.
Anti-collision is discussed, ADS-B was suggested, but everybody was afraid it would flood the frequency. So maybe something ADS-B like ? And policies about what drone will give way to which. Most ideas hinted, that GPS would be used to determine and broadcast position.
This still needs to be something for which planes can get receivers as well, and possible broadcast a wider ranging signal so clear a path in front of it approaching an airport.