As was broadly expected ahead of a new, more video-centric iPhone launch, AT&T this morning announced their plans to upgrade the carrier's wireless broadband network. According to AT&T, the latest HSPA 7.2 upgrade will begin later this year, and bumps the network's currently maximum theoretical downstream speed from 3.6Mbps to 7.2Mbps. Employees have told us the upgrades are already live in at least two test markets.

In addition to the speed bump, AT&T says they're doubling the wireless spectrum dedicated to 3G in most of the company's metropolitan markets, while adding thousands of new cell site backhaul connections. AT&T technicians are also busy deploying about 2,100 new cell sites across the country during 2009.

The company's 3G mobile broadband network is now available in nearly 350 U.S. major metropolitan areas, though as their sometimes-accurate coverage map attests, there's plenty of work left to be done. AT&T says they plan about twenty additional metro deployments this year. As for HSPA 7.2 on your laptop or netbook, AT&T says they'll introduce multiple HSPA 7.2-compatible laptop cards "later this year."

AT&T has previously stated they plan to begin testing faster LTE technology beginning in 2010, HSPA has a lot of life left., and the company intends to milk the standard for some time. After the HSPA 7.2 upgrade, AT&T can move on to the evolved-HSPA (HSPA+) upgrade, which should approach 20Mbps. Ericsson says they'll be supporting commercial deployment of HSPA gear capable of 42Mbps by the end of this year.

But of course this is all downstream bandwidth. On the upstream side of the fence, AT&T in 2008 finished their HSUPA upgrades, which boosted the upstream capability of their 3G wireless network to between 500kbps and 800kbps. It also goes without saying that the speeds AT&T trots out in their press releases quite often aren't anything like the speeds seen by real users in the wild.

So, can we use our Slingbox app over 3G yet?