Voice over LTE (VoLTE) has been a longtime promise of all the major carriers, and on May 22 T-Mobile became the first of the big four to offer it to subscribers.
VoLTE puts voice and data on a single radio layer. The result is faster call connections, the ability to experience LTE-speed data while on a call and clearer, more natural-sounding calls, since VoLTE enables high-definition (HD) Voice technology.
The sweetness of T-Mobile's victory is somewhat diminished by the fact that the technology debuted in a single market—Seattle—and it can be accessed by only three devices, the LG G Flex, the Galaxy Light (a budget-friendly Samsung model) and the Samsung Galaxy Note 3.
Also robbing it of some potential pomp is that AT&T will offer VoLTE May 23 in a handful of markets—though also in a limited way. For now, only Samsung Galaxy S 4 Mini users will be able to enjoy the technology, though more devices are coming soon, AT&T said in its May 15 announcement.
T-Mobile announced its news in a blog post by CTO Neville Ray. While people do more texting and emailing than calling, wrote Ray, there's "nothing like a human voice to make the connection real for me."
Ray also noted that the real bragging rights belong to MetroPCS (the prepaid carrier T-Mobile acquired last May), which first launched VoLTE in 2012.
In 2010, MetroPCS, then the nation's fifth-largest carrier, was also the first in the United States to roll out 4G LTE technology.
Ray, calling himself a fan of science, offered a quick explanation of how VoLTE works. Calls are carried over Internet protocol (IP) technology on T-Mobile's LTE network, instead of a circuit-switched path on the HSPA+ network, he said.
"The tricky bit in all this," he added, "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."
Ray added that T-Mobile's engineering team is working "tirelessly" to bring VoLTE to other cities.
AT&T's VoLTE network, complete with HD Voice, will be available in areas of Illinois, Indiana, Minnesota and Wisconsin May 23, and will continue to expand, the carrier said. That's good news, since the people on both ends of the call need to be in VoLTE areas and on HD Voice-capable phones to experience the technology.
In a video explaining HD Voice, AT&T added, "Maybe you're thinking, 'My phone calls sound fine to me.'"
It pointed out that people also used to think their televisions looked fine, and then they got HD. "It's the same idea," said AT&T. "You'll never want to go back."