T-Mobile will announce its 4G LTE network rollout plans next week during a press conference in New York City, and the carrier has apparently already started activating the network in several launch markets. The discovery was recently made by OpenSignal, which has an application capable of detecting the networks.

4G LTE was detected in New York, New Orleans, Las Vegas, Denver, San Diego, Seattle, Kansas City and San Jose, OpenSignal told PCMag. Speeds were as fast as 25Mbps down and 8Mbps up. That's impressive, but we have to remember that the network isn't being slammed by T-Mobile users yet.

"The fact that our app has detected a T-Mobile LTE network in these cities suggests that they will be included in the initial LTE rollout," a company spokesperson told PCMag.

We know the Galaxy Note II, Galaxy S4 and BlackBerry Z10 support T-Mobile's 4G LTE network, but here's a surprise: OpenSignal said it noticed Galaxy S III devices on the network, too.