AT&T is trouncing Verizon in LTE performance tests. Here’s AT&T’s explanation why

Sometimes getting beat to market isn’t a bad thing. Though AT&T(s t) was a full year behind Verizon Wireless(s vz)(s vod) in deploying its LTE systems, it’s now routinely outscoring Verizon on multiple network speed and performance tests.

Last spring, RootMetrics clocked AT&T’s average LTE network speeds a full 4.3 Mbps faster than Verizon’s. PCMag’s recent extensive nationwide tests crowned AT&T speed king in every region of the U.S., though it found Verizon’s 4G network more reliable and more ubiquitous. PCWorld’s own 13-city test reached similar conclusions on 4G download speeds, though it found Verizon’s network was superior on the upload.

RootMetrics iPhone App.Screen Shot.Nov 2010

Part of the explanation lies in congestion. Verizon’s network is hardly brimming over – it’s maintaining average speeds in excess of 10 Mbps – but it has more LTE devices on its network by virtue of having sold them for far longer. Cellular capacity is ultimately shared capacity so the more devices you have competing for airtime the slower everyone’s speeds will be. But this is quickly becoming less of a point of difference on their networks, considering smartphone replacement cycles are so short. Samsung and Apple just flooded both networks with millions of new Galaxy S 4s and iPhone 5s.

AT&T Senior EVP of technology and network operations John Donovan has an alternate explanation: AT&T took its time to build a better network.

We’ve been hearing this from a lot of operators. Both Sprint(s s) and T-Mobile(s tmus) claim that by being late to LTE they’ve been able to take advantage of the latest gear, giving them superior networks. There’s some truth to that, especially when it comes to future network upgrades. But in a call with a group of reporters and bloggers Wednesday, Donovan laid out specifics on why AT&T’s rollout improved on Verizon’s.

Why LTE  is better eaten as soup than as broth

It was a “gut-wrenching decision” to let its prime competitor take the early lead on LTE, Donovan said, but it allowed AT&T to plan its network in a different way and use new technologies more effectively.

Crowd density dense network featureFirst off, AT&T was able to build a denser network. Verizon was so quick to LTE because its 3G networks were still poking along at sub-megabit EV-DO speeds. That led Verizon to focus on coverage – delivering mobile broadband to as many places as possible to overcome its 3G limitations.

Meanwhile, AT&T was less concerned about coverage since most people could decent speeds on its HSPA+ networks, and more focused on building more powerful networks where capacity was most needed, Donovan said. The more cells there are any given area, the more customers the network can support and the faster speeds it can deliver to each customer.

Of course, this sounds a bit like a rationalization for why Verizon’s coverage is far superior to AT&T (Verizon’s LTE reaches 500 markets compared to AT&T’s 326, and Verizon stretches further into the suburbs of most of cities). But Donovan does raise a good point. If AT&T’s average speeds are significantly faster, it means its networks are much further away from reaching capacity. At the current rates, Verizon will start experiencing congestion sooner than AT&T.

Either carrier will likely head off that congestion before it becomes an issue simply by adding more capacity. Verizon is already building LTE network No. 2. AT&T’s second LTE network is probably still several years away, but AT&T is keeping with its densification theme by aggressively pursuing small cells. It plans to deploy 40,000 of the little buggers in the next few years.

My radio has seemed awfully remote lately

One of the emerging technologies AT&T was able to take advantage was the remote radio head, Donovan said. Remote in this instance doesn’t mean emotional distance. Rather it refers to the radio’s location at the cell site.

base-station-images-e12916713808271Traditional cellular architectures tend to cram all of the active electronics into a base station cabinet at the bottom of the tower. The wireless signal then crawls up the tower through coaxial cable before it’s beamed out through the antenna. The problem with this setup is the signal loses a lot of power during the journey.

By putting the radio at the top of the tower next to the antenna, AT&T was able to mitigate much of that power loss, giving it much more powerful signal the moment it leaves the antenna, Donovan said. More power means greater range and a more resilient signal, which translates into faster speeds and higher capacity, especially at the cell edge where things tend to get wonky.

Basically AT&T’s radio architecture gives it a power boost over Verizon, which is relying on the traditional radio base station scheme, Donovan said. There are a few other network tweaks Donovan pointed out that give AT&T an edge. He said AT&T has more fiber running to its cell sites. It also managed to add more spectrum in cities like Chicago and Miami where its networks were undersized. He added that AT&T has a much more distributed mobile core, meaning data traffic is getting onto the internet faster producing a lower latency network. (Clarification: Though AT&T’s LTE has some of the lowest measured latency among U.S. networks, it’s not beating out Verizon. PCMag recored lower latency on Verizon’s network in all but one U.S. region.)

That last point is telling because it shows mobile networks are improving in other ways than speed. We’re reaching the point where discussions of speed are becoming academic. Ten Mbps to a smartphone is plenty. As I’ve written before, what now matters most is the overall mobile experience and the prices we actually pay for mobile internet access.

Still, AT&T’s faster network nothing to scoff at. In this case, speed means more than just speed. It means AT&T still has more capacity, and capacity is every carrier’s and every customer’s best friend.

Density image courtesy of Shutterstock user higyou