On the day when the carrier is starting to take pre-orders for the new generation of Apple's iPhone, AT&T CEO Randall Stephenson says that mobile voice quality on his company's network is almost where it should be. Heavy use of the iPhone for browsing has had a negative effect on how the network has been operating in major cities like New York and San Francisco. The CEO said, "We've been going hard at the voice quality issue," and the game plan has been to end problems with the network by the end of this summer. Stephenson was interviewed this morning on CNBC and stated that data volume over mobile networks has risen 5000% in the last 3 years alone-a time period that coincides with the launch of the first iPhone in 2007. the carrier will throw more money at its network this year-$19 billion-than any other company in the industry. By 2015, the executive said that AT&T will be the number one firm in the mobile broadband business in the U.S. and possibly throughout the world. "We made a huge bet on mobile broadband, to create what we think is the best," Stephenson said.