Verizon, AT&T to launch VoLTE-to-VoLTE calling interoperability in 2015

Verizon Wireless (NYSE: VZ) and AT&T Mobility (NYSE: T) are working to ensure that Voice over LTE calls made by customers on the different carriers can interconnect with one another. The two carriers said they are going to enable VoLTE-to-VoLTE connections in 2015.    

According to a Verizon blog post, engineers from both companies are working through a full set of requirements, starting with extensive lab testing and then moving on to field trials.  Verizon said this approach will ensure that customers will have a seamless experience making VoLTE HD Voice calls between the two networks and lays the foundation for interoperability of other Rich Communications Services (RCS) such as video calls, rich messaging and more.

Currently, to experience Verizon's VoLTE service both parties on a call need to be using a VoLTE-enabled Verizon smartphone. AT&T's VoLTE-enabled HD Voice service lets customers only make HD Voice calls with other AT&T customers using AT&T HD Voice-capable devices within AT&T HD Voice coverage areas.

Verizon and AT&T indicated that they will work with other carriers on VoLTE interoperability. AT&T and Verizon said they worked closely with the GSMA on the interoperability push. The GSMA's Network 2020 program is designed to encourage carrier to speed up the deployment of IP communication services such as voice and video calling over LTE as well as RCS.

"Customers use their smartphones to connect with friends, family and colleagues across service providers and around the world.  Interoperability among all VoLTE providers takes connectivity to the next level with HD quality voice and additional features that customers want," Verizon Communications CTO Tony Melone said in a statement. "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."

"Interoperability of VoLTE between wireless carriers is crucial to a positive customer experience," AT&T CTO Krish Prabhu, who is also the president of AT&T Labs.  "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.  We continue to work with others in the industry on similar collaborative arrangements and hope to see similar collaboration across the industry in the near future." 

Verizon now says six devices support its nationwide VoLTE service, including the Apple (NASDAQ: AAPL) iPhone 6 and 6 Plus, Samsung Galaxy S5, LG G2, and Motorola Droid Maxx and Droid Mini. However, the new iPhones do not support video calling (presumably because Apple's FaceTime video calling application takes precedence).

There is no extra cost to use Verizon's VoLTE service. HD Voice minutes will be deducted from a subscriber's normal voice-minute bucket. Video calling gets deducted from a subscriber's data bucket. Importantly, Verizon says that a video call using VoLTE will consume around 6-8 MB of data per minute of calling.

Most critically for Verizon's VoLTE service, if a customer is not on a call and the phone is in the idle state and drops out of LTE coverage, the phone will automatically switch over to CDMA 1X voice service. However, if a customer is on a VoLTE call and drops out of LTE coverage, the call will disconnect. Customers can also to turn VoLTE on and off in their phone's settings and return to CDMA 1X voice service.

AT&T offers VoLTE-based HD Voice in select areas in Georgia, Illinois, Indiana, Minnesota, Texas and Wisconsin and has said it will "continue to expand on a market-by-market basis to ensure the best possible customer experience." AT&T supports VoLTE-based HD Voice on the Samsung Galaxy S4 Mini as well as the iPhone 6 and 6 Plus, and will add more devices over time. An AT&T spokeswoman declined to comment on when and where AT&T will expand HD Voice service.

T-Mobile US (NYSE:TMUS) supports VoLTE service across its entire LTE footprint, which now covers 250 million POPs. Sprint (NYSE: S) has not given a timetable for when it will launch VoLTE, but its 1900 MHz LTE network covers around 254 million POPs.

For more:
- see this Verizon post

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