The US is looking well beyond traditional cellular frequency bands and backhaul options in its hunt for new mobile broadband spectrum. As it prepares to open up the 3.5 GHz band and, next year, auction the 600 MHz broadcast spectrum, the FCC is also engaged in projects ranging from satellite bands to drones. Google, of course, has been testing drones – as well as tethered balloons and other mechanisms – to support broader wireless broadband delivery. This month, it has supported an FCC proposal to authorize the study of high-altitude platform stations (HAPS) to deliver broadband. These stations are 20-50 kilometers above ground – high enough to cover large areas, but low enough to support dense coverage and low latency.…