Stay on Top of Emerging Technology Trends Get updates impacting your industry from our GigaOm Research Community

T-Mobile(s tmus) customers in the country’s biggest cities may have recently noticed their 4G speeds boosted considerably. On T-Mobile’s Q3 earnings call, CEO John Legere revealed that it has doubled the amount of spectrum used by its LTE networks in 40 of the top 50 U.S. metro markets, effectively doubling the theoretical speeds of its 4G service and dramatically increasing the overall capacity available to its customers.

T-Mobile is now using 20 MHz of Advanced Wireless Service (AWS) spectrum for LTE in these upgraded cities, which puts its networks on par with the systems launched by Verizon Wireless(s vz)(s vod) and AT&T(s t). Those carriers are adding capacity and boosting speeds on their networks as well, but T-Mobile has another surprise in store. Legere said the carrier in 2014 will double its LTE bandwidth again in the biggest cities, launching 40 MHz networks in at least 22 of the top 25 markets.

That’s an impressive feat considering that less than two years ago T-Mobile didn’t have the spectrum to deploy any LTE at all, much less a 40 MHz network. But it’s failed acquisition by AT&T landed it a big consolation of prize of 4G airwaves, and its merger with MetroPCS gave it key spectrum in some of the country’s biggest urban markets. Still a lot of credit is due T-Mobile CTO Neville Ray, who moved extremely quickly to put that new spectrum to use. T-Mobile’s LTE footprint now covers 203 million people in 254 markets, only eight months after its rollout began.

The U.S. mobile industry is no longer in a race to see who can bring their first LTE networks online. Instead, carriers are now competing to see who can upgrade their current 4G services and add more capacity the fastest. While T-Mobile is running at good pace, it looks like Verizon will beat it to 40 MHz, which can support theoretical speeds of 150 Mbps. Verizon is also using the AWS airwaves for its next LTE network, and there have already been sighting of its live signals in New York and other big cities.

Sprint(s s) has also launched a service called Spark, which aggregates the capacity of its multiple LTE networks across several spectrum bands. It’s promising average speeds of 50 Mbps to 60 Mbps over Spark, which are indeed impressive. The problem is Spark is only available in five cities today and its looks as if new cities will come online relatively slowly.

AT&T currently holds the speed crown, as attested to by multiple nationwide speed tests. But with T-Mobile’s upgraded network, it will definitely challenge Ma Bell for that title. T-Mo’s old 10 MHz networks were averaging about 12 Mbps, according to PCMag’s comprehensive June report, so a doubling of speeds would put it clearly in the lead. Though T-Mo’s upgraded networks are technically the same size as AT&T and Verizon’s, those carriers have a lot more customers with LTE devices. That means T-Mobile has a lot more free capacity available to support faster links to more people.