The biggest surprise at this year’s Consumer Electronics Show was how AT&T and T-Mobile showed off their 4G networks. If that sounds confusing to you because you didn’t know that either them were in the 4G game, then you had the same reaction I did. Unlike Sprint/Clearwire (with WiMAX) and Verizon (with LTE), neither AT&T nor T-Mobile has been building out 4G networks in the US. So how did they make 4G networks appear out of thin air? Well, the short answer is that they didn’t.

What AT&T and T-Mobile did was to re-brand their enhanced 3G networks (sometimes called 3.5G) by simply renaming them “4G” networks. Voila! In other words, this is mostly a marketing ploy.

However, to be fair, both T-Mobile and AT&T have been making legitimate upgrades to their 3G networks that actually approach 4G speeds — at least the same kinds of 4G speeds that Sprint/Clearwire sees on its WiMAX network. Verizon’s LTE has even higher speeds.

The problem is that the enhanced 3G networks of both T-Mobile and AT&T are based on GSM technology, so they are still voice networks that are essentially retrofitted to handle data. On the other hand, WiMAX and LTE are both IP-based networks that use OFDM technology and are designed to natively handle data traffic. That’s what makes them “4G” or next generation networks, even more than the raw bandwidth numbers. This shows up when you look at the latency of these networks, which is typically 50-100ms (milliseconds) vs. 200-500ms for the enhanced 3G networks.

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Nevertheless, International Telecommunications Union (ITU) recently relaxed its standards to allow for LTE, WiMAX, and HSPA+ to all fall under the label of 4G. For the reasons mentioned above, I agree with LTE and WiMAX getting the 4G label, but not HSPA+.

Based on what we learned at CES, here are the plans that T-Mobile and AT&T outlined for their next generation networks.

T-Mobile’s 4G approach
T-Mobile talked a really big game at CES, saying it “delivered the fastest wireless data performance in the top 100 U.S. markets during the second half of 2010″ based on a Nielsen study (done before Verizon rolled out its LTE network). However, PC Magazine’s 2010 report on the fastest mobile networks showed T-Mobile consistently trailing AT&T and Sprint’s WiMAX network in average speeds (and that study was done before Verizon zoomed ahead of them all with LTE in December 2010). In other words, T-Mobile is actually fourth among the big four in the US when it comes to maximum network speeds.

T-Mobile’s “4G” is based on a 3G standard called HSPA+ that T-Mobile has been deploying in roughly the 100 largest metro areas in the US. At CES, the company said it plans to double its network speeds in 25 US metro areas covering 140 million Americans by mid-2011. T-Mobile claims that its peak downloads speeds in those areas will be 42 Mbps, but those are theoretical speeds. Verizon’s LTE is capable of theoretical peak speeds of up to 100 Mbps, but in the real world the upper limits are 10-20 Mbps. I’ll be impressed if T-Mobile’s HSPA+ can get up to 5-8 Mbps in the real world.

To make matters worse, T-Mobile is about to start running an ad campaign saying that it has “America’s Largest 4G Network.” That is a misleading claim that I hope won’t fool too many people.

AT&T’s 4G approach
While T-Mobile had actually been fudging its 4G story for a several months leading up to CES (and before the ITU’s 4G standards change), AT&T unveiled its re-branded “4G” network at the show. And, honestly, AT&T actually had a better story to tell than T-Mobile. The company has already rolled out HSPA+ to nearly 100% of its US network and it has some real speed numbers to show for it. The AT&T 3G network is capable of 4-5 Mbps downloads and 1.5 Mbps uploads, which rival WiMAX speeds, although it still has much higher latency than both WiMAX and LTE.

So, like T-Mobile, AT&T is now labeling its 3G HSPA+ network as “4G,” but its network does actually have more 4G-like qualities to brag about. On the other hand, unlike T-Mobile, AT&T has plans to upgrade its network to LTE. At CES, AT&T said it plans to begin its LTE rollout in mid-2011 and have nearly its entire network upgraded to LTE by the end of 2013 (the same time period Verizon plans to have its LTE rollout finished). But, it’s important to remember that Verizon owns more 700MHz spectrum than AT&T for LTE, which will allow it to build a more widespread and more robust network. AT&T could catch up by buying additional spectrum, as it did last year when it bought Qualcomm’s chunk of 700Mhz.

AT&T looks more likely than T-Mobile to challenge Verizon’s 4G dominance, but it still has to prove that it can effectively build wireless networks to handle modern data loads. Its reputation has been severely tarnished by its perpetual inability to deal with the load put on its network by millions of iPhone users. Despite its HSPA+ upgrade in 2010, all of the iPhones at CES last week brought the Las Vegas AT&T network to its knees once again. That doesn’t inspire much confidence that AT&T is ready to become a 4G powerhouse.