What's the deal with 4G?

Reader kitty87 writes: You've been writing a lot about "4G" tech like WiMax, but some of us are still getting our heads around plain-old 3G. Can you give us a quick primer on what 4G means and why it's important? You bet—but first, a little background.

When we talk about 2G, 3G, and so on, we're referring to generations of cellular wireless networks. You could call the old, voice-only analog AMPS network (remember those vintage car phones from the 80s with the distinctive winged antennas near the trunk?) 1G, while digital GSM (think AT&T and T-Mobile) and CDMA (Sprint, Verizon Wireless) networks—which handle both voice and data—count as 2G. On their own, 2G networks can send data such as SMS messages and caller ID info, but otherwise, they're pretty poky.

Moving further up the ladder, you get 2.5G add-on technologies like EDGE (for GSM networks) and 1XRTT (for CDMA), which deliver data speeds that are just a bit faster than dial-up, followed by 3G networks such as EV-DO (CDMA) and UMTS/HSDPA (GSM), which give you data speeds somewhere between DSL and cable modems. (Check out my earlier post for help with this alphabet soup of wireless terms.)

Now that most of the major U.S. carriers have 3G under their belts (save T-Mobile, which is still looking to launch its own 3G network), everyone's looking to the next big thing: 4G.

In general, 4G networks promise even faster data speeds than 3G—speeds that will rival, if not surpass, the throughput you'd get over the speediest cable modems. And indeed, once 4G networks go mainstream, you're not really going to need a wired DSL or cable modem anymore.

Here in the U.S., wireless operators are looking at two main 4G technologies: WiMax, which is essentially a turbo-charged version of Wi-Fi, and LTE (Long Term Evolution), which is the next step in existing GSM/UMTS cellular networks. (A third 4G technology—UMB, or Ultra Mobile Broadband—has yet to gain traction Stateside.)

So far, WiMax has a bit of a head start here in the States. Wireless carrier Sprint already has three WiMax test markets (Chicago, Baltimore, and Washington, D.C.) up and running, and it's promised to officially launch its WiMax network—dubbed Xohm, and pronounced "Zoom" [update: oops, it's actually pronounced "zome," as in "home"; sorry, folks]—later this year (in just a handful of areas, mind you).

Here's the problem, though: Sprint's been going through some tough times lately, and it's not clear how the carrier is going to cover the cost of a national WiMax rollout (estimated at a cool $5 billion). There have been rumors that cable operators like Comcast and Time Warner (neither of which want to be left out of the 4G party) are interested in partnering with Sprint on Xohm, but there's been no official word so far. Meanwhile, this month's planned launch of the first few Xohm markets has been delayed until later this year.

Meanwhile, AT&T and Verizon Wireless are banking their 4G fortunes on LTE. Both carriers have just paid billions to the FCC for rights to the 700MHz swath of wireless spectrum, and both look financially poised to crank out nationwide LTE networks with all due speed. That said, it'll take the FCC some time to clear the 700MHz spectrum (which will be occupied by analog TV broadcasts until next year's digital TV changeover), so we're looking a couple of years or so until AT&T and Verizon are ready to launch their respective LTE networks.

Either way you slice it, we'll be getting blazing-fast wireless data for our cell phones and at home—it's simply a matter of when (and how), not if. In the short term, it looks like Sprint might cross the 4G tape first with its WiMax network, but it could be years before Sprint's Xohm is available nationwide—and by that time, AT&T and Verizon's LTE networks stand a good chance of closing the gap. In any case, most of us will probably have to settle for 3G until about 2010 (unless Sprint, with the help of some big-name partners, manages to put the pedal to the metal).

Want the technical nitty-gritty? Then check out the Wikipedia entries for WiMax, LTE, and UMB, for all the detail you can stand.

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