AT&T Inc. (NYSE: T) has confirmed that it is moving to 21Mbit/s HSPA+ as it upgrades its 3G network rather than the 14.4 Mbit/s variant it previously favored.

"Theoretical maximum downlink speeds are 21 Mbps, though real-world performance will be less and vary due to a number of factors," an AT&T spokeswoman confirmed to LR Mobile Wednesday evening in an email. AT&T says that it has now implemented the upgrade across 80 percent of its 3G network and intends to cover 250 million people in the US by the end of the year.

Why this matters
By the end of 2010, AT&T will, on paper, have the largest fast 3G footprint to pit against Verizon Wireless 's LTE launch. HSPA+ offers average download speeds of around 4 to 10 Mbit/s, compared to a megabit or less for most earlier 3G offerings.

There could be a gating factor on HSPA and HSPA+, however, as the AT&T spokeswoman points out. The carrier will get better performance out of the network as it adds higher-performance "Ethernet, fiber-optic backhaul" to its cell sites. "We're in the midst of this process now, and will continue through 2011," the spokeswoman notes.

For more
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— Dan Jones, Site Editor, Light Reading Mobile