28 GHz is the most popular band of millimetre wave high-frequency spectrum. It was generally little used in the U.S. but now Verizon plans to pass 30 million homes in the first phase of the buildout. Europe chose 26 GHz because satellites were using 28 GHz. There is little gear available other than for 26-30 GHz. Verizon controls 800 MHz of the band in the U.S.
39 GHz, some AT&T controlled, requires 50% more antennas than 28 GHz and is not as popular. AT&T cutbacks in mmWave mean 39 GHz mostly will be on the shelf for years.
60 GHz, shared in the U.S., was developed by Intel as WiGig but didn't find a market. CCS, Facebook, Qualcomm, and others are reviving it, especially for backhaul. The FCC has allocated 14 GHz. With enough very small antennas, performance looks good.
Other bands above 15 GHz lack equipment or supporters, so are years away. The U.S. FCC is about to auction 24 GHz.
Low and mid-band
3.3 GHz to 4.2 GHz is the emerging new band, with enough available spectrum for several companies to expect the ideal 100 MHz.