Having a broad range of frequencies across low, middle and high bands will be a critical differentiator for T-Mobile US as it rolls out 5G.

Ulf Ewaldsson, T-Mobile's senior vice president of technology transformation, made spectrum the focus of a talk on Tuesday at the Big 5G Event in Denver. The combination of low-band and mid-band spectrum for coverage, with millimeter-wave frequencies for additional capacity in densely populated areas, is key to delivering a good customer experience, he said.

Summarizing T-Mobile's position in an interview following the session, Ewaldsson said the carrier is well positioned in each area of spectrum to deliver a full-service 5G network.

T-Mobile has yet to name a launch date for commercial 5G, and Ewaldsson declined to break that news. The company is waiting for two things before a rollout is possible: Device availability and stable millimeter-wave networks, he said. He cited true mobility, rather than signals in a limited number of spots, as is an important part of 5G service.

Ewaldsson said he was surprised to see other operators introduce services in millimeter-wave bands. AT&T launched 5G late last year for businesses in parts of 12 cities, and Verizon has introduced mobile 5G in parts of Chicago and Minneapolis. Verizon is on track to expand that offering to at least 30 cities by the end of this year, said Nicki Palmer, senior vice president of technology and product development, earlier Tuesday.

The biggest technical challenge to deploying millimeter-wave 5G has been vendor software, Ewaldsson said.

The company is poised to start rolling out 5G on its low-band 600MHz network, which reaches more than 3,500 communities with LTE. That whole network is software-upgradable to 5G, he said. It has also deployed 28GHz 5G gear that's currently in testing and holds licenses in the 39GHz band for future use.

T-Mobile's mid-band strategy depends largely on its proposed merger with Sprint, which regulators are still reviewing. The company hopes to use Sprint's 2.5GHz spectrum, though it already has some mid-band spectrum in the 1900MHz and AWS bands, currently being used for a combination of 2G, 3G and 4G services.

Why this matters
As the third-largest US mobile operator, T-Mobile is a key competitor to AT&T and Verizon. Its effort to combine spectrum in a broad range of bands highlights the importance of spectrum diversity to make 5G realize its potential. Mid-band spectrum, which offers a combination of coverage and high speed, is a critical need in the US, which hasn't made as much of it available as China and other governments. A successful T-Mobile-Sprint merger, which is increasingly in doubt, could give the combined company a powerful position from which to compete with the traditional industry leaders in the next generation of mobile.

— Stephen Lawson, special to Light Reading. Follow him on Twitter @sdlawsonmedia.