Verizon, AT&T pledge Voice Over LTE interoperability coming in 2015

VoLTE interoperability between Verizon and AT&T is scheduled to arrive in 2015, though the companies didn't say exactly when. The all-IP connection, supported by Apple's new iPhone 6 and iPhone 6 Plus, provides superior call quality when compared to traditional cellular voice calls.

Engineers from both AT&T and Verizon are said to be working through a full set of requirements, set to begin with extensive testing in lab environments before moving on to field trials. The efforts will reportedly lay the foundation for other interoperability features including video calls and rich messaging.

"Interoperability among all VoLTE providers takes connectivity to the next level with HD quality voice and additional features that customers want," said Tony Melone, chief technology officer at Verizon. "We're pleased to be working with AT&T as our first interoperating carrier, and we look forward to working with other operators as VoLTE continues to grow."

AT&T has launched VoLTE services in initial markets, with more planned to come. Verizon introduced its Advanced Calling 1.0 services across the U.S. in September.

Verizon iPhone 6 users can take advantage of Advanced Calling 1.0 HD Voice and video calling by adding the free services to their account via the carrier's website. For AT&T customers, support is automatically available when connected in a supporting market.

Users to navigate to the the Settings application on their iPhone 6 or iPhone 6 Plus, and select "Cellular > Enable LTE > Voice & Data" to turn on the feature.

However, currently Verizon and AT&T customers who enable VoLTE will only be able to establish connections with other supporting customers on their same network. That will change at some point in 2015, when both Verizon and AT&T begin supporting VoLTE interoperability.

"Interoperability of VoLTE between wireless carriers is crucial to a positive customer experience," said Krish Prabhu, president, AT&T Labs and Chief Technology Officer, AT&T. "Customers expect to be able to connect anywhere, anytime- and as LTE technology continues to evolve, it's imperative that we provide a seamless experience between carriers. We are pleased to work with Verizon on this initiative."

In addition to VoLTE, the iPhone 6 and 6 Plus support Wi-Fi calling, a new iOS 8 feature that lets users place voice calls over Wi-Fi data networks. T-Mobile announced support for Wi-Fi calling in June, while AT&T promised its network will be compatible next year.