Carriers complain that the parts of the spectrum reserved for smartphone use are increasingly crowded, at least in urban areas.
Education groups and the wireless industry have been asking the FCC to license the rest for years.
Tribal Nations will get a chance to apply for the unassigned licenses; the remaining licenses will be auctioned off.
"Too much of this spectrum, which is prime spectrum for next generation mobile operations, including 5G, has lain fallow for more than 20 years," the FCC proposal says.
"We are replacing an outdated regulatory regime, developed in the days when educational TV was the only use envisioned for this spectrum."
Critics of the new proposal say the FCC's plan will hand more control over public airwaves to commercial interests at the expense of communities and educational organizations.