BARCELONA -- MWC19 -- T-Mobile is in the midst of a "material" deployment of millimeter-wave spectrum in downtown areas across the United States, where it's seeing speeds up to 500Mbit/s on the spectrum.

Although much of the operator's 5G commentary in recent months has focused on its substantial 600MHz spectrum holdings, T-Mobile also owns fairly significant holdings in the 28GHz and 39GHz millimeter-wave spectrum bands. And, according to CTO Neville Ray, T-Mobile is currently in the process of installing network equipment in major US downtown areas to offer services on that spectrum.

"We're doing some deployments, and some of them are pretty material, in dense, urban environments," Ray told Light Reading on the sidelines of the Mobile World Congress trade show here. The operator is conducting this effort by deploying mmwave equipment on both macro sites and small cells, he said.

According to a separate MWC presentation by T-Mobile Vice President of Technology Development and Strategy Karri Kuoppamaki, the operator garners speeds up to 500Mbit/s on its millimeter-wave network. However, those speeds are based on recordings made immediately adjacent to T-Mobile's 5G transmitter, and speeds on the spectrum decline as the receiver moves away from the transmitter Kuoppamaki clarified.

That's no surprise: Transmissions in millimeter-wave spectrum often travel only several hundred feet, and buildings or other structures can block them.

But Kuoppamaki and Ray both said speeds on T-Mobile's millimeter-wave spectrum would likely continue to improve.

"We're still learning," Ray said, adding that just a few months ago the performance on that spectrum was "miserable" mainly because the software from T-Mobile vendors Nokia and Ericsson running the technology was still "immature."

Yet the vendors' mmwave software likely will significantly improve toward the end of the second quarter, Ray noted.

T-Mobile's mmwave spectrum holdings largely stem from spectrum licenses the operator inherited through its acquisition of MetroPCS in 2012. MetroPCS purchased those licenses for backhaul uses, before 5G technology made such spectrum suitable for commercial mobility services. T-Mobile also bought mmwave spectrum covering Ohio in 2018.

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T-Mobile owns mmwave licenses averaging 200MHz across 100 million POPs in 10 major US cities, Ray said. Those holdings, though, aren't nearly as extensive as the mmwave holdings of competitors Verizon and AT&T (which is probably why both Verizon and AT&T have recorded faster speeds on their respective mmwave networks). But the FCC is auctioning more mmwave spectrum, and T-Mobile executives have expressed interest in participating in those auctions (these auctions are ongoing and company executives have declined to say whether they are bidding in the auctions, citing FCC rules).

T-Mobile views mmwave spectrum as just one element of a wider 5G service, Ray reiterated; eventually T-Mobile will deploy 5G across low-, mid- and high-band spectrum, said Ray, adding that the operator's initial 5G launch will occur in the first half of 2019 and that T-Mobile would sell the Samsung Galaxy S10 5G phone.

"I'm much more excited about having a millimeter-wave layer in a Manhattan or a downtown Chicago where it enhances the mobility experience [of low-band spectrum]," he said. "I think millimeter-wave has its place, don't get me wrong, but we're more focused on what we can do with the millimeter-wave story from a mobility perspective."

Ray also criticized AT&T and Verizon, which both launched 5G services using only millimeter-wave spectrum and no low-band spectrum.

"I think it's really, really hard to push out service in a few isolated environments, which is all I see from the competition," he said. "I think you're better waiting until you can couple that experience with mid-band and/or low-band assets."

Last year, Verizon launched its 5G Home fixed wireless service using 28GHz spectrum and AT&T used its 39GHz spectrum for a mobile 5G launch in a dozen cities. AT&T has pledged to expand its 5G service nationwide by 2020 using spectrum below 6GHz.

Sprint, meantime, said it is making progress toward its deployment of 5G in 2.5GHz spectrum in nine US cities; the operator recently showed off speeds on the network of around 430Mbit/s.

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— Mike Dano, Editorial Director, 5G & Mobile Strategies, Light Reading | @mikeddano