TOKYO, JAPAN, September 30, 2015---NTT DOCOMO, INC. announced today that it will launch a Voice-over-LTE (VoLTE) international roaming service in South Korea on October 7, becoming the Japan's first mobile operator to offer a VoLTE outbound roaming service.

Nine smartphones in DOCOMO's just-released winter/spring lineup are compatible with the new service. Customers with compatible DOCOMO handsets will be able to make the same high-quality voice and video calls as in Japan using VoLTE to and from Japan, as well as in countries and regions capable of using the service. First, the service will be offered between Japan and South Korea and within South Korea, through a cooperative initiative with Seoul-based KT Corporation, one of South Korea's largest mobile operators.

In addition to extra-high-quality voice and video calls, DOCOMO's VoLTE service offers high-speed LTE data communication during voice calls and minimized delays when connecting calls. DOCOMO users had placed VoLTE calls from more than 10 million smartphones in Japan, according to DOCOMO research as of August 31.

DOCOMO's VoLTE roaming service incorporates the S8 Home Routed (S8HR) architecture, which is used to enhance the existing LTE data roaming architecture to support VoLTE under roaming environment, enabling fast and efficient commercialization of VoLTE roaming services. The S8HR architecture is a method based on 3GPP standards to realize VoLTE roaming.

Going forward, DOCOMO expects to expand its VoLTE roaming service into other countries through partnerships with local companies, aiming to steadily broaden DOCOMO customers' global access to extra-high-quality voice and video calls.