Japan's NTT DoCoMo, South Korea's KT and the US-based Verizon Wireless have completed feasibility tests of VoLTE roaming in a commercial environment.
DoCoMo and KT announced they have completed the world's first HD voice and video call via VoLTE roaming, while DoCoMo and Verizon Wireless achieved the first transoceanic HD VoTE roaming calls.
The trials used S8 Home Routed architecture, which is in use for existing LTE data roaming services, potentially providing an easy upgrade path for LTE operators.
The calls used an IP exchange and network equipment designed to replicate commercial networks.
On the strength of the results, NTT DoCoMo revealed it is now aiming to commercialize international VoLTE roaming services by the end of the year.
The operator said it will continue to work with KT, Verizon and other GSMA member companies to help shape the telecom industry's discussion of international VoLTE roaming architecture. The company also plans to continue to invest in VoLTE R&D.
DoCoMo has existing 3G and 4G roaming relationships with both KT and Verizon Wireless.