AT&T has created different mobile calling models for every major city in America as it tries to improve a network that has come under fire for poor performance as the data-friendly iPhone has proliferated, an executive said Thursday.

Other carriers just use one nationwide calling model to plan for all cities, claimed Chief Technology Officer John Donovan, speaking at the Open Mobile Summit conference in San Francisco.

The nation's second-largest mobile operator has a hard time planning for bandwidth needs in the rapidly changing mobile world, Donovan said. AT&T has seen rapidly growing mobile data usage -- and much criticism over its 3G coverage -- as the exclusive iPhone carrier in the U.S.

"If a network is not fully loaded, it's hard to know exactly how much demand is out there," Donovan said. "You put all you can in the ground, and they eat it all up, and then you put more in there, and they eat it all up."

The explosive growth in use of mobile data, which Donovan said has risen 4,932 percent at AT&T over the past 12 quarters, or in other words three years, has forced the carrier to throw out its traditional planning models, he said.

Wall Street Journal columnist Walt Mossberg pressed Donovan to talk about coverage in San Francisco, saying he regularly hears from readers about poor AT&T coverage in the city.

AT&T is in the midst of leveraging its prime 850MHz radio spectrum for 3G in San Francisco, a step that is 90 percent complete, Donovan said.

"We've seen a significant improvement here in San Francisco, and we expect by year end we'll have a great experience here," Donovan said. Securing sites and zoning approvals for infrastructure is one of the issues that can hold up network improvements, he said. "It's not a question of commitment, will, understanding or power. It's how fast you can get the assets on the ground," Donovan said.

Also at the conference, Donovan said AT&T is pushing toward IPv6 (Internet Protocol, Version 6), the major new step in the Internet's underlying software that will exponentially expand the number of available IP addresses. Based on the current rate of depletion, analysts have forecast that addresses under the current protocol, IPv4, will run out some time in 2011. The additional addresses in IPv6 may be especially vital in the wireless world, where not only handheld devices but embedded sensors and other machines may need addresses.

"We have a major program under way to transform ourselves to IPv6," Donovan said. He receives monthly forecasts of the date when IPv4 addresses will run out, to make sure the carrier is on track.

Donovan also said AT&T ultimately would like to make applications for any of its phones run across all of them, plus PCs and TVs. He envisions subscribers looking at a summary at the end of the day, possibly over IPTV, of all the applications and content they've downloaded and what other platforms they can add them to.

"As a customer, I've already made a choice somewhere about what I like, so I just want to port that over," Donovan said.

Asked whether this cross-platform strategy might erode all the efforts of Apple, Microsoft, Google and others to distinguish their mobile platforms through application lineups, Donovan said the most important thing is what experience the customer wants, and whoever delivers that will win. "The business models will naturally contend," he said.