There's a lot of talk about 4G wireless right now. Sprint has 4G. Verizon's getting 4G. And T-Mobile may or may not be running 4G. In this week's Ask an Analyst, I try to untangle the 4G mystery.

Greg asks, "I'm leaning towards the Motorola Droid 2 for Verizon Wireless, but I couldn't help but notice the absence of any mention of 4G. Will it be 4G compatible, or should we wait?"

The short answer is: You'll need new phones to access Verizon's upcoming 4G network, and no, don't wait. If you're on Verizon Wireless, there won't be 4G phones until the middle of next year. Even then, Verizon will be building out 4G for years to come. 3G will be just fine for most people through 2011, unless they absolutely demand ultimate speed. (Check out the slideshow below for some devices which claim to be 4G.)

The Long Answer: What is 4G?

Here's the long answer.

For consumers, 4G is mostly about Internet speeds. If you don't care about the Web speeds on your phone or modem, then you probably don't care about 4G.

There's actually no widely accepted definition of "4G." The ITU, a global standards body, recently formally defined 4G to exclude every existing technology that anyone is claiming to be 4G, so the official definition is now useless in practical terms. I'll give you my own definition.

A "G" is a generation of wireless technology. Each generation offers significantly faster Internet access than the previous generation, but it's incompatible with the previous generation—you have to upgrade your phone to use it, and carriers usually have to install new hardware.

The first G was the old analog cellular systems. 2G systems are digital, but slow. Many phones still use 2G. Internet speeds on 2G phones range from 9.6 Kbits/s to about 200 Kbps. 3G systems run from about 384 Kbps to—well, we'll get to that.

4G systems such as LTE and WiMAX claim to have real-life speeds of 5 Mbits/s or greater, much like a home cable connection. The most recent versions of these technologies promise speeds in the hundreds of Mbits/s, faster than any home Internet connection available right now. 4G systems are also "all-IP." Down the road, they'll be able to replace the old circuit-switched voice phone calling with voice-over-IP systems.

Various aspects of 4G may also make it easier to install the Internet in a wider range of gadgets, such as digital cameras, gaming systems, and picture frames.

Complicating things, AT&T and T-Mobile are currently installing new 3G technologies which are faster than some of the initial 4G technologies. HSPA+ is thoroughly 3G—it's just a software upgrade to existing networks—but it's screamingly fast. T-Mobile's version can run at 7 Mbps in real life, and they have a pathway to quadruple that within the next few years. Just so they don't get left out of all the 4G chatter, T-Mobile has unilaterally decided to declare their HSPA+ to be "4G."

4G isn't just faster than 3G. Since 4G systems have more capacity than typical 3G systems, they usually don't have the bandwidth caps that 3G networks have (at least for now.) That makes 4G (for now) viable as a replacement for home wired broadband. Clearwire and some cable companies are selling 4G WiMAX as a home Internet solution.

For now, here's what you ask: Is my wireless Internet access too slow? If the answer is yes, then look at 4G.

Who Has 4G?
Right now, Sprint has 4G in two phones (the HTC EVO 4G and the Samsung Epic 4G) and a bunch of modems. Sprint's 4G WiMAX network covers many but not all major cities of the U.S.

T-Mobile's HSPA+, a 3G technology with 4G speeds, is available in most major U.S. cities. It works with the T-Mobile Rocket 2 modem and the G2 and myTouch 4G phones.

Verizon will introduce 4G LTE later this year, starting with modems; phones will come next year. AT&T will introduce HSPA+ later this year, to be followed by 4G LTE in 2011.

Finally, MetroPCS has 4G LTE in three cities: Dallas, Detroit and Las Vegas. The company sells one 4G phone, the Samsung Craft. But MetroPCS's version of 4G (for now) has 3G speeds, because MetroPCS never had 3G and is just now catching up.