The U.S. Federal Communications Commission is hoping to release about 500 MHz of mid-band 12-GHz spectrum for shared use by mobile operators, with satellite operators having exclusive use of that spectrum now. The FCC expects shared access will enable such new uses, with adequate safeguards preventing interference with existing users.
As always, that is a contentious matter, as we have seen with aeronautical frequencies in the C-band that also are shared between different industries.
One irony of the proposed spectrum sharing is that two direct-to-home satellite video providers--DirecTV and Dish Network--are key 12-GHz licensed users, as is SpaceX. But Dish Network itself wants to use its spectrum to support its own 5G operations.
Dish touts several studies suggesting sharing is technically possible. SpaceX is more worried about potential interference.
The FCC obviously believes coexistence is possible, though the protection mechanisms will likely be different from shared use of the Citizens Broadband Radio Service spectrum. Though satellite signals are much weaker in comparison to mobile network signals, 12-GHz radio signals are highly directional, which suggests one way interference protection should be possible.
Much as terrestrial microwave signal paths avoid interference by path diversity, sharing supporters will argue that the different paths (satellite to ground station and cell tower to terrestrial user) will work by path diversity. Think of the satellite signals as happening in the vertical plane, while mobile signals happen in the horizontal plane.
Issues to be resolved include the effectiveness of beam steering radios that would allow 5G networks to better target their signals. Regulating power levels, limiting mobile use in some areas, dynamic spectrum sharing and reliance on 12-GHz assets now in present use are some of the ways interference can be avoided, proponents say.
Lower power levels for small cells will help.
SpaceX obviously worries more than a geostationary satellite operator would, as SpaceX satellites are in low-earth orbit, hence arguably less protected by path diversity. Perhaps the bigger issue is how to deal with exceptions to the non-interfering mobile operations.
As a long term matter, satellite and mobile entities have clashed over spectrum issues for many decades. Also, over the longer term, mobile interests have generally gotten additional spectrum when satellite interests have opposed it.
A betting person would tend to lean to approval of mobile shared use of 12 GHz spectrum, with some safeguard mechanisms in specific instances.
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