The Federal Communications Commission is drawing up rules for extremely high frequency spectrums that could be used in "5G" mobile broadband.

4G (fourth generation cellular technology) LTE in the US relies on frequencies from 700MHz to 2.5GHz, with the lower frequencies being best suited for covering long distances and penetrating building walls. The FCC's vote today proposes new "flexible use service rules in the 28GHz, 37GHz, 39GHz, and 64-71GHz bands," and seeks public comment on other bands above 24GHz that could also be used.

The FCC has said these frequencies could enable speeds between 1Gbps and 10Gbps. But it will take a lot of work to overcome distance limitations and physical obstacles that can block the signals.

"It was once thought that frequencies above 28GHz could not support mobile services because their wavelengths were too short and the signal propagation losses were too high," FCC Commissioner Mignon Clyburn said at today's meetings. "But industry engineers have now turned these weaknesses into strengths by finding ways to use short wavelengths to build dynamic beam-forming antennas to support high-capacity networks that are small enough to fit into handsets. Many expect that these engineering advances will lead to 5G networks that will offer much higher data speeds and substantially lower latency than what commercial mobile services offer today."

There is "little doubt" that future 5G devices will also use spectrum below 1GHz, Clyburn said. Using both low- and high-frequency spectrum would help carriers achieve broad coverage and faster speeds.

While today's vote isn't a final one, the FCC said it intends to authorize a mix of licensed, unlicensed, and shared spectrums. Cellular transmissions may coexist with satellite ones under the proposed rule-making.

Verizon and CTIA-The Wireless Association both praised the FCC's vote today and said they look forward to working with the commission to hammer out the details.

Although Verizon has said it wants to begin 5G commercial deployment by 2017, 4G will likely remain the norm for a few years. An industry group named Next Generation Mobile Networks predicts that 5G won't take off until 2020.

At the other end of the spectrum, the FCC is planning an auction for next year that will free up 600MHz airwaves for LTE coverage. This will help carriers like T-Mobile expand 4G coverage, especially in rural areas.