Hungry for more Wi-Fi capacity, the telecom industry is looking to snatch control of underutilized airwaves reserved for the auto industry. But this is coming just as carmakers begin to make progress on developing and adopting technologies for connected and autonomous cars that currently rely on that spectrum.

The big picture: Tech and telecom companies have been fighting for years over spectrum to support exploding demand for mobile services and smartphones. Automakers have had exclusive access to a band of spectrum for almost 20 years but haven't done much with it, prompting telecom providers to argue, "Use it or lose it."

The FCC is looking at a third possibility — share it.

The dilemma: Some safety advocates and automakers worry that commercial Wi-Fi will interfere with vehicle-to-vehicle communications in an emergency.

"The last thing you want is to be approaching an intersection and your kids are streaming a video in the back seat and a car is about to run a red light but you don’t get the safety message."

— James Barbaresso, SVP of intelligent transportation systems, at infrastructure advisory firm HNTB

What's happening: The Federal Communications Commission is assessing whether cars and Wi-Fi services can safely share the same frequency.

The agency just completed the first phase of a study that found Wi-Fi can operate in the 5.9 GHz band set aside for vehicle communication without interference.

"Not so fast," says the U.S. Department of Transportation, which insists that all 3 test phases be completed before making any decisions.

Meanwhile, the advent of new cellular vehicle-to-everything (C-V2X) technology — based on improved cellular networks — is muddying the debate over spectrum-sharing.

The background: In 1999, the FCC set aside part of the communications spectrum in the 5.9 GHz band for the development of dedicated short-range communication (DSRC) that would allow vehicles to communicate with each other and with devices planted alongside roads.

But DSRC technology has been slow to develop, and only now is beginning to be deployed.

Toyota, Lexus and Cadillac models will be equipped with DSRC by 2021 and dozens of states are installing the roadside units.

"OEMs have been sinking tons of money into DSRC applications to demonstrate this would work. They want to see a return on their investment."

— James Barbaresso

Meanwhile, a coalition of other automakers and telecom operators are pushing instead for the fast rollout of C-V2X technology.

Because C-V2X leverages cellular networks, it won’t require a massive deployment of roadside units.

Supporters say consumers are familiar with cellular service from their mobile phone service and C-V2X will one day migrate to even faster 5G technology.

What to watch: The FCC has already signaled the debate may have shifted away from spectrum-sharing and that further tests might be unnecessary, suggesting a cellular approach will be the winner. Europe is leaning toward DSRCbut the progress of C-V2X in China may prove decisive, per the World Economic Forum's Eric Jillard.

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