AT&T is doubling the capacity of its high-speed mobile broadband network in order to accommodate a slate of new data-heavy devices that may include a new iPhone from Apple.

The company uses a high-speed packet access network to provide 3G services, and it currently tops out at 3.6 Mbps downlink speed. The second-largest U.S. carrier is in the process of using software upgrades to boost that to 7.2 Mbps download speed.

AT&T already has beefed up its 3G network in two test networks and plans to extend those capabilities to its nationwide network. The HSPA technology theoretically has a capability of 14.4 Mbps, but the carrier likely won't max out this network because competitors like Sprint Nextel and Verizon Wireless are already rolling out the next generation of mobile broadband. AT&T will use Long Term Evolution technology for its 4G network, and it will have a few test markets live in 2010.

The move to bolster its data network comes as the carrier is seeing an uptick in mobile data usage primarily from devices like Apple's iPhone 3G. The mobile operator has faced criticism from iPhone users regarding 3G connectivity, and AT&T has not been able to keep up with network demands at events like South by Southwest. The carrier could see even more demand for mobile data this summer if Apple comes out with a new iPhone model, which is widely expected by industry watchers.

As AT&T sees fewer landline customers, the carrier views mobile data as a strong growth sector, and it's not just for smartphones and cell phones. The mobile operator is extending the subsidy model to the red-hot netbook category by discounting an Aspire One laptop for customers who sign up for two years of mobile broadband. This model could become more attractive as netbooks gain popularity, and rivals like Verizon are reportedly eyeing a similar program.

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