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T-Mobile says it's met an important milestone in 5G testing with the completion of its first 5G video call and data session using multiple wireless spectrum bands.

At CES 2019 in Las Vegas, the company and partners Ericsson and Intel finished a live test of its commercial network in which it completed a video call using 5G technology over its commercial wireless network. The video call was made to users using three different bands of spectrum: 600 MHz, 28 GHz and 39 GHz. Also as part of the test, T-Mobile generated 5G signals that covered more than 1,000 square miles using its 600 MHz, the company said.

T-Mobile says the test is a milestone in the evolution of 5G because it demonstrates how multiple types of wireless spectrum -- low-band, mid-band and millimeter wave -- can be used to deliver 5G services. Up to this point, T-Mobile's rivals, AT&T and Verizon, have only demonstrated testing of 5G services using very high frequency millimeter wavelength spectrum. T-Mobile says it's important to show the technology can work across a range of spectrum, which will ensure the service can be deployed nationwide and accessed indoors.

"While the other guys focus on 5G millimeter wave on a handful of blocks in a handful of cities, we're building 5G for everyone, everyone," T-Mobile CEO John Legere said in a statement. "And together with Sprint, we'll add much-needed spectrum depth, creating a truly transformative 5G network."

The term 5G refers to the fifth generation of cellular technology, which promises to greatly enhance the speed, coverage and responsiveness of wireless networks. It could be as much as 10 to 100 times speedier than your typical cellular connection, and even faster than anything you can get with a physical fiber-optic cable going into your house.

High-frequency millimeter wavelength spectrum is necessary for 5G to offer the speed and low-latency that is the hallmark of the technology. The laws of physics dictate that signals transmitted at higher frequencies deliver more data at faster speeds. But signals transmitted at higher frequencies can only cover short distances. Meanwhile, lower frequency spectrum allows signals to travel over longer distances and to penetrate obstacles like walls, but it generally doesn't offer the same capacity.

It's well understood that carriers will need a mix of spectrum types to deliver their 5G services nationwide.

When it comes to the 5G race, T-Mobile rivals AT&T and Verizon seem to be ahead. Verizon has already launched its 5G home broadband service to a limited customer base. And it plans on offering 5G mobile service in 2019. It tested the first phone to use mobile 5G in November. AT&T also plans to offer 5G service in 2019 and has tested a 5G browsing session using a commercial-grade hotspot device.

T-Mobile isn't expected to launch its mobile 5G network until 2020. But the company says it will deliver a nationwide network when it does launch its service, something its rivals won't do on day one. T-Mobile owns some low-band spectrum and is participating in auctions for millimeter spectrum. But it also hopes to get a lot of mid-band spectrum when it completes its acquisition of Sprint.

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