updated 04:18 pm EDT, Thu May 22, 2014
Apple's iPhones already supported through hardware, software likely to come in iOS 8
Following recent announcements from AT&T and Verizon, the US' third-largest carrier has jumped on the Voice Over LTE (VoLTE) bandwagon, introducing VoLTE service in Seattle for select Android phone models. The technology allows for both very high-quality voice as well as LTE data speeds simultaneously during a call. Apple's iPhones already support the technology in hardware, but will need a software update likely coming in iOS 8, expected this fall.
Neville Ray, T-Mobile's chief technical officer, announced the VoLTE rollout in Seattle and noted that the recently-acquired MetroPCS had been the first to market with the technology. T-Mobile has been adapting the original VoLTE to work with LTE Advanced, and Ray said the carrier plans "to roll out to more T-Mobile customers throughout the coming year."
"VoLTE calls will be carried over IP on our LTE network instead of a circuit-switched path on our 4G HSPA+ network," Ray explained. "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 [compatible] phone won't drop a call if you leave an LTE area and it switches to 4G HSPA+ or 2G coverage." LTE-capable iPhone users on GSM networks have enjoyed a similar technology for some time now.
The audio quality is expected to be significantly higher with VoLTE/HD Voice than traditional cellular phone calls, using wide-band audio that Apple's iPhone already supports. Software integration for the change is expected to be incorporated into iOS 8, which will likely be previewed at the upcoming Worldwide Developers Conference and made available to users likely in the fall.
Currently supported in the Seattle tests are the LG G Flex, the Samsung Galaxy Light and the Galaxy Note 3.