They'd use Ka-band frequencies like those Iridium is using for interlinks (not user connections) with its latest satellites, and Amazon is asking for clearance to use anti-interference technology to avoid headaches. And yes, Amazon is aware of the potential problems with space debris. The satellites would deorbit themselves in less than 10 years whether or not they were still in contact with Earth.

Amazon didn't mention a timeline for putting the satellites into orbit. However, the FCC filing shows that it has been thinking about this plan for a while. Whether or not it's timely is another story. SpaceX is already launching its first broadband satellites, and plans roughly three times as many. Although it will take years for satellite constellations like these to roll out, there's a concern that Amazon might already be at a disadvantage.