T-Mobile launches nationwide 5G

Be smart: High frequency bands, like millimeter wave, can carry data much faster, but only over short distances; lower frequencies can't carry data as fast, but travel farther and pass more easily through walls and other obstacles.

• T-Mobile also announced the first two devices that will run on the network: the OnePlus 7T Pro 5G McLaren and the Samsung Galaxy Note 10+ 5G.

The big picture: T-Mobile, like other carriers, is also slowly building out high-speed 5G in select metro areas, beginning with parts of six cities launched earlier this year.

Go deeper: 5G is off to a slow start