Fourth generation networks can be implemented using a couple of different approaches, notably Worldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution (LTE). AT&T has decided on LTE, which Bloom says could deliver speeds that are 10 to 20 times faster than its existing 3G network. AT&T plans to test the networks this year and deploy them in 2011. Bloom says this coincides with the availability of a "wide variety" of LTE-compatible devices.

Verizon will beat that timeline, however, with plans to launch its 4G LTE wireless network in 25 to 30 markets this year. By 2013, Verizon says, its 4G network should reach all 285 million people currently in reach of its 3G network. Verizon has no plans to implement HSPA 7.2 in the interim, however.

Sprint, in contrast, has opted for WiMax, which can provide speeds of up to 10 Mb/s. By leveraging its partnership with Clearwire, Sprint already provides a 4G service in 27 markets in the U.S., with service for five more--including New York and San Francisco--expected later this year.

T Mobile is currently focused on 3G, with plans to upgrade the software on its existing network to HSPA+ and speeds between 10.8 Mb/s and 18 Mb/s broadly available by the middle of this year. The company says that ultimately, it plans to go with LTE for 4G.

Chua says it's difficult to say whether WiMAX or LTE is superior, because a lot depends on the way the network is set up. "Generally, the peak data rates that are technically specified for LTE are a little bit higher than WiMax, but you and I are never going to see those peak rates, because no network will ever be architected that way."

"Consumers don't care about technological underpinnings," says Kelly Schlageter, a communications manager at Sprint Nextel. "They just want quality, affordable 4G services that work where and when they want. Today, our 4G network delivers unmatched performance, and people can experience 4G mobile broadband right now--without having to wait for the development of alternative technologies."

Regardless of the wireless protocol implemented, 4G networks should improve network performance for everyone. Initially, Chua says, most 4G users will be accessing the network on laptops, because high-definition video won't be much of a draw for folks using a small cell phone screen. "It's the laptop users who are often clogging up the networks," he says. "If you can move the laptops to 4G, then you can get more capability on the 3G network, and better serve the iPhones."