You can credit Moore’s Law for our ability to use millimeter wave spectrum commercially for access functions, not just point-to-point backhaul (including terrestrial microwave and satellite bent pipe operations).
Basically, cheap computation means we can process the signals cheaply enough to use them to support retail consumer access services, as well as backhaul on a point-to-point basis.
The U.S. Federal Communications Commission now is launching a Spectrum Horizons effort to support commercial use of spectrum above 95 GHz, something that would have been commercially impossible in the past, using analog radio.
As there are low-attenuation windows (free space) around 30 GHz, so there are lower-attenuation regions between 60 GHz and 100 GHz, so the FCC sees additional opportunities around 105 GHz, 115 GHz and then from about 200 GHz to 275 GHz as well.
Many of the potential applications could focus on local area communications, but some backhaul apps are being discussed.
At the moment, spectrum above 95 GHz is not permitted, except on an experimental basis.
Spectrum Horizons will allow entrepreneurs to develop ways of commercially using such spectrum, using licensed and unlicensed approaches.
On a near-term basis, the FCC is asking for input on new rules allowing fixed point-to-point use of up to 102.2 Gigahertz of spectrum in various bands. The FCC says those rules will be based on current rules for use of 70 GHz, 80 GHz and 90 GHz assets.
Those rules create national, but non-exclusive licenses using a database manager to manage interference.
But both point-to-multipoint systems and mobile services will be allowed.
As has been the case in recent rulemakings, the FCC also will seek to make significant chunks of spectrum--as much as 15.2 gigahertz in this case--available for unlicensed use. Such unlicensed access would be based on existing rules for unlicensed use of the 57 GHz to 71 GHz band.
Experimental licenses would be entertained for spectrum in the 95 GHz to 3 THz range.
Signals in millimeter wave bands are significantly affected by the presence of oxygen and water vapor within the atmosphere, although the amount of signal attenuation due to oxygen and water vapor varies with frequency and other factors.
Attenuation caused by oxygen is significant throughout the millimeter wave spectrum, but increases dramatically around 60 GHz, 120 GHz, and 183 GHz.
it should be possible to deploy communication services throughout much of the spectrum between 95 GHz and 275 GHz. From 80 GHz to 115 GHz, the atmospheric loss increases by only 0.5 decibel (dB) per km.
Even up to 145 GHz, the loss is less than 1 dB/km and less than 2 dB/km below 170 GHz. Above the sharp peak at 183 GHz, the propagation loss falls to below 4 dB/km until above 250 GHz.
Because fixed point-to-point links have been successfully deployed in the 70/80/90 GHz band, it is realistic to presume that similar services might be deployed up to 115 GHz.
Mobile services may also be possible in some bands above 95 GHz. From 39 GHz to 105 GHz, the atmospheric loss increases by only 0.15-0.5 dB/km.
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