Federal regulators moved toward letting television broadcasters use channels more efficiently to free airwaves for high-speed Internet use. The Federal Communications Commission voted 5-0 at a meeting in Washington Tuesday to begin writing rules that are part of the Obama administration’s commitment to devote more airwaves for smartphones and mobile Web use.

“The explosive growth in mobile communications threatens to outpace the infrastructure,” said FCC Chairman Julius Genachowski. “If we don’t act to update our spectrum policies for the 21st century we’re going to run into a wall — a spectrum crunch.”