The volume of mobile data traffic grew from just over 1 billion megabytes in the third quarter of 2007 to about 30.3 billion megabytes in the third quarter of this year, CTO John Donovan told an audience of developers at the Sencha Conference in San Francisco. That growth rate of about 30 times is down from three-year growth of about 50 times earlier this year, he said. However, expansion is hardly screeching to a halt.

"If you look in absolute numbers, it's still a tremendous growth rate," Donovan said. He attributed the change to the difficulty of an already very large number to keep increasing rapidly.

AT&T has come under much criticism over the past few years for not keeping up with the demand for data capacity from the popular iPhone and other mobile devices. The carrier continues to upgrade its network to meet that demand, deploying HSPA+ this year and planning a LTE (Long-Term Evolution) rollout next year.

Eighty percent of AT&T's mobile network has been upgraded to HSPA+, which will offer two or two-and-a-half times the performance of HSPA 7.2, AT&T's current top-end cellular technology, Donovan said Tuesday. The carrier recently introduced USB modems that can use HSPA+ as well as LTE. It is also upgrading the backhaul from its cell sites to Ethernet on fiber links.