The nation's wireless networks currently use 547 MHz of spectrum for mobile data, but the Federal Communications Commission is trying to clear up another 500 MHz for their use.
As spectrum gets freed up, wireless companies are actively buying unused spectrum from TV and radio stations and from defunct wireless ventures. But it doesn't come cheap.
For instance, AT&T last week bought between six and 12 MHz of spectrum for its 4G network from Qualcomm. The chip company had been using it for the now defunct FLO TV, and sold it for about $2 billion.