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Late last year, T-Mobile released a teaser video touting speeds of nearly 1 Gbps on an unreleased smartphone hidden inside a box at one of the wireless carrier’s testing facilities — many times faster than the speeds typically experienced on smartphones on existing LTE networks.

It was another shot across the bow of AT&T, Verizon and Sprint in the battle over network performance.

This week, on a visit to the facility in Bellevue, Wash., GeekWire got to peek inside the box at the mystery device: Samsung’s new Galaxy S8.

A Samsung Galaxy S8 inside T-Mobile’s network testing facility. (GeekWire Photo / Todd Bishop)

As Samsung formally unveils the new Galaxy S8 this morning, T-Mobile is announcing that the new device will be the first phone on its network capable of “gigabit-class speeds.

RELATED: Samsung unveils Galaxy S8 and S8+ smartphones with redesigned screen, launch date April 21

The results in the real world won’t match the theoretical peaks achieved in the lab. However, T-Mobile’s testing suggests that the Samsung Galaxy S8, under the right conditions in areas with the key underlying technologies enabled, should be able to reach download speeds of “hundreds of megabits per second,” said Grant Castle, T-Mobile’s vice president of network engineering, in an interview this week.

T-Mobile says the faster speeds will mean, for example, that customers will be able to download a two-hour movie in 15 seconds. The company, which has been shifting to unlimited data plans, says the faster speeds won’t require any additional charge.

The new capabilities are enabled by the combination of three underlying technologies that boost LTE speeds: 4×4 MIMO, which uses four antennas to simultaneously transfer data; carrier aggregation, which combines multiple bands of spectrum in one transfer; and 256 QAM, a higher-order modulation scheme that allows more data to be transferred in one session.

A Samsung Galaxy S8 speed test inside T-Mobile’s network testing facility this week. (GeekWire Photo / Todd Bishop)

T-Mobile says it’s the only U.S. wireless carrier to roll out all three of these technologies in the U.S., available in up to 300 cities across the country, and the company believes it will have a speed advantage over rivals AT&T, Verizon and Sprint on the Galaxy S8 as a result.

“The great thing about these technologies is that they are all additive — so you can add them on top of each other to get a speed boost,” Castle explained, saying that the new phone “will allow us to fully unleash all the greatness that we’ve been working on.”

Samsung’s Galaxy S7 supported all three technologies, but not simultaneously, as the Galaxy S8 will.

In addition, T-Mobile says the new version of the device will be the first to tap unlicensed spectrum, known as LTE-U, in the 5 GHz band traditionally used by dual-band WiFi routers. The company says that will further boost the capacity and speed available to Samsung Galaxy S8 users, along with the ability to access TMobile’s new AWS-3 spectrum.

Watch the Samsung live stream here and stay tuned for more details on the Galaxy S8 launch this morning.

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