AT&T took "real risks to develop this under-utilized band," she added.

In August, to acquire NextWave Wireless, a holder of WCS and other spectrum, for about US$600 million.

The FCC also heard a staff report saying that U.S. mobile carriers had met a Tuesday deadline to provide alerts to customers nearing their monthly limits on voice, data or texts and customers using their mobile phones in places where they would be hit with international data roaming fees.

The -- unexpectedly high mobile bills -- in 2010, and the agency worked out an agreement with CTIA a year ago.

All of the members of CTIA, a mobile carrier trade group, have in two of four categories: voice, data, texting and international roaming. In an agreement with the FCC, CTIA members committed to provide alerts for all four categories by April 17.