Following announcements earlier this month from both AT&T and Verizon, T-Mobile announced today it’s introducing Voice over LTE support starting with the Seattle market:

So I’m thrilled to congratulate my team on the launch of Voice over LTE (VoLTE) in the Seattle area for our existing LG G Flex and Samsung Galaxy Note 3 and Galaxy Light customers. Our friends at MetroPCS were the first to launch VoLTE in the U.S. back in 2012, and we’ve been working hard on a LTE Advanced version of VoLTE, which we plan to roll out to more T-Mobile customers throughout the coming year.

T-Mobile’s CTO Neville Ray noted that the new technology, which brings voice calls onto the same LTE radio layer previously reserved for data, will allow “faster call setup times (almost twice as fast as a non-VoLTE call setup) and the ability to enjoy lightening fast LTE data speeds while on a call.” It will also support the HD Voice or wide-band audio feature that Apple already supports. Ray explained how the technology works:

VoLTE calls will be carried over IP on our LTE network instead of a circuit-switched path on our 4G HSPA+ network. This is advantageous because your phone stays on our wicked fast LTE network to make a call. The tricky bit in all this is the smooth mobility between our various radio layers. Enhanced Single Radio Voice Call Continuity (eSRVCC) is a new LTE Advanced function and we’re excited to be the first to deploy it in the U.S. All of this basically helps ensure that your capable phone won’t drop a call if you leave an LTE area and it switches to 4G HSPA+ or 2G coverage.

While the iPhone’s current chipset does support voice over LTE, Apple is yet to make software side changes to support the technology. We previously reported that Apple might be planning to change that in time for iOS 8 and the iPhone 6 just as carriers are rolling out support:

Another significant addition being considered for iOS 8 and the next-generation iPhone is voice-over-LTE support (VoLTE), according to carrier sources. Currently, when an LTE-capable iPhone needs to make a phone call, the actual call is placed over last generation networks such as 3G. With VoLTE, calls will be transmitted over the same type of network that LTE data is processed through, and this can allow for benefits such as improved call quality.