BARCELONA—New York, LA, Dallas, and Las Vegas will be among the first 30 cities T-Mobile outfits with 5G this year, the latest bit of 5G one-upmanship we've seen here at Mobile World Congress.

"By 2020 we will build a fully nationwide 5G coverage layer," T-Mobile CTO Neville Ray said at the carrier's press conference today. "I challenge my competition today: match what I'm saying, tell me that you're going to deliver 5G in a comprehensive national way in these timeframes."

T-Mobile's nationwide 5G coverage will rely on its 600MHz spectrum, which won't deliver the spectacular speeds that people associate with other carriers' 5G promises, but will act as a base layer that's somewhat faster than equivalent 4G. It will be supplemented by fast but short-range "millimeter wave" in large cities, which is the sort of 5G AT&T and Verizon are building out.

"Millimeter wave is going to work great in these dense urban environments, but across broad geographies, it doesn't compute. It's completely uneconomic across a geographic mass like the US," Ray said.

As for speeds, "Are we going to see average speeds start to move up by tens of megabits per second? For sure," he said. "We would love to see average speeds triple, or move to 100Mbps, but that's a journey that's going to take time in the industry."

There was a bit of reality distortion in T-Mobile's press release, but Ray was clear and straight up in person. While T-Mobile is "building" 5G in 30 cities this year, it won't actually launch it until 2019. That's because unlike Verizon, which is doing fixed wireless to homes, and AT&T, which is relying on a "puck" hotspot, T-Mobile will wait for 5G smartphones.

"We want to focus our energy and work on smartphones," Ray said. "I don't want to win the 2018 race; I think it's a meaningless race. What matters is when we're going to have consumer products that are broadly available and broadly usable, and that's next year."

Ray also called the fixed-wireless and wireless-hotspot markets that Verizon and AT&T are initially pursuing, "not very exciting."

Hotspots are "a very small volume, niche product today," he said. "I'd rather commit our effort to something way more meaningful and more expansive for the consumer."

Ray didn't name any devices or vendors, but the timing would be right for a Samsung Galaxy S10. "This time next year, we'll be talking about the first 5G smartphones coming into the wireless space on the bands that we use, both millimeter wave and 600MHz," Ray said.