According to reports that surfaced this Friday, Google has obtained permission from the Federal Communications Commission (FCC) to perform airborne and terrestrial millimeter wave testing throughout the United States. The FCC's go-ahead is effective from March 17th, 2016 to April 1st, 2018. It covers frequencies in the 71-76 GHz and 81-86 GHz range, both for terrestrial and airborne transmitters. Given how Google's request for this experimental license was met with quite a bit of informal objections in the States, the grant is only valid as long as Google doesn't cause any kind of harmful interference to the already existing and authorized operations in the country. Naturally, the tech giant will also have to abide by the FCC RF safety standards. Google has also already preemptively commented on the concerns about potential health hazards to humans, animals, and plants in the vicinity of its testing grounds in a January letter sent to the FCC. In the letter, the tech company states that its planned experiments are far less risky in terms of potential RF exposure than many other "transmissions the Commission routinely authorizes."
As for what exactly Google is testing here, the millimeter-wave radio technology pertains to transmissions or waves that are longer than infrared waves or x-rays but shorter than radio waves. Millimeter waves belong to part of the electromagnetic spectrum which corresponds to radio band frequencies between 30 GHz and 300 GHz, which is also known as the Extremely High Frequency (EHF) range. The millimeter-wave technology is also capable of transmitting gigabits of data per second and can produce speeds up to 40 times faster than the ones available over the currently supported 4G LTE networks. To put it simply, millimeter waves could easily be the basis for the fifth generation mobile networks (5G) of the future.
Google has actually already started testing millimeter-wave technology as a part of the so-called Project Skybender several months ago in Spaceport America, New Mexico. That experiment is officially running until July and was also sanctioned by the FCC, but the difference between that grant and the one that's now being reported about is that the latter applies to the entire US. Apart from Project Skybender, these latest tests are also likely connected to Project Loon which is focused on developing huge air balloons which act as cell towers and are capable of bringing Internet access to remote locations. This possibility is further reinforced by the fact that the original application for the grant mentions Astro Teller, Google's scientist who has been overseeing Loon and related projects in the past.