3G phones have the capability of doing great things at data speeds approaching those of home Internet connections. At least, that's how cell-phone companies want you to think.

Using that same thought process though, any and every child born in this country has a chance of someday becoming president.

In both cases, these goals are possible, but not necessarily probable.

Now that all four of the major U.S. cell-phone companies have, or are in the process of rolling out high-speed cellular data networks (EV-DO in the case of

Verizon

(VZ) - Get Verizon Communications Inc. Report

and

Sprint

(S) - Get SENTINELONE, INC. Report

or UMTS/HSDPA from

AT&T

(T) - Get AT&T Inc. Report

and

T-Mobile

), it's time to take a look at just how fast these networks allow data to flow.

EV-DO (Evolution-Data Optimized) works on CDMA and TDMA networks. In its latest form, called Rev. A, it is capable of data speeds approaching 3.1 Mbit/s.

UMTS (Universal Mobile Telecommunication System) and HSDPA (High Speed Download Packet Access) are the preferred high-speed systems for GSM-based networks. On paper, UMTS/HSDPA systems can support down-link speeds up to 14.4 Mbit/s. In the future, HSPA+ systems might provide as much as 42 Mbit/s downlinks.

All of these numbers from each of these systems are the extreme upper limits. What that really translates to is if you're outdoors, in a very secluded area, with no one around for miles -- and your phone has perfect "line-of-sight" connectivity to the transmit/receive cell and you a fully charged battery -- then, maybe (if the weather is just right and the wind is blowing in a favorable direction) you could, possibly, begin to approach these upper speed limits.

But this is the real world. We usually don't use our cell phones under perfect conditions. Instead, we use them in urban canyons, crowded highways, restaurants, subways and worst of all: indoors. Forget 3G, we're lucky if we can usually find or sustain a 1G or 2G connection.

That's why

Research In Motion

TheStreet Recommends

(RIMM)

stuck with 2G radios in its Blackberry devices for so long. Same for

Apple's

(AAPL) - Get Apple Inc. (AAPL) Report

original iPhone. They work and, as a bonus, they use less of your handset's battery power than any of these new 3G devices.

But consumers always want the newest and latest. And right now that means the promise of much-higher speeds with 3G phones.

Verizon and Sprint's EV-DO systems were deployed a lot earlier than the GSM systems and therefore have an edge when it comes to signal coverage. AT&T has been touting its new high-speed network -- especially as it relates to the Apple 3G phone. But a detailed look at their its coverage map shows a spattering of blue 3G areas. When you zoom in, you find those blue areas are not as plentiful as you might be led to think.

Now assuming that you have a 3G phone and are in the 3G "zone," that still doesn't assure you of a super-fast high-speed connection. Sometimes it's the phone itself (Apple is tweaking the iPhone 3G's software to lock-in on 3G signals) and sometimes it's where you're using the phone (are there enough 3G antennas where you're standing). This is not an exact science.

T-Mobile is just in the process of rolling out its 3G network. Because it's using different 3G frequencies from anyone else on the planet (new ones they won in recent government auctions) its brand new New York City 3G network affords a unique chance to test a fast cellular connection with few distractions.

I've been playing with a

Nokia

(NOK) - Get Nokia Oyj Sponsored ADR Report

(6263) and a

SonyEricsson

(TM506) handset and can honestly say that right now text/data download speeds are very fast.

That might be a big plus for early adopters of the first

Google

(GOOG) - Get Alphabet Inc. Class C Report

/Android-based smartphone -- rumored to be manufactured by HTC for sale by T-Mobile and available at retail stores this fall.

Remember, while we're busy worrying about 3G, the rest of the world is looking forward to the next big thing: 4G. You'll be reading a lot about the burgeoning methods called LTE (Long Term Evolution) and WiMAX, which promise even faster data speeds.

Those faster speeds will mean better audio and video communications, faster downloads and more. That could help cell phones become the premier electronic device of future generations.

Gary Krakow is TheStreet.com's senior technology correspondent.