September 30, 2015

DOCOMO to Offer VoLTE International Roaming in South Korea
—Japan's first mobile operator to provide VoLTE outbound roaming service—

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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.


NTT DOCOMO provides innovative, convenient and secure mobile services that enable smarter living for each customer. The company serves over 67 million mobile customers in Japan via advanced wireless networks, including a nationwide LTE network and one of the world's most progressive LTE-Advanced networks. DOCOMO is a leading developer of a 5G network that it plans to deploy by 2020, as well as network function virtualization (NFV), NFC infrastructure and services, emerging IoT solutions, and more. Outside Japan, the company is providing technical and operational expertise to seven mobile operators and other partner companies, and is contributing to the global standardization of all-new mobile technologies. DOCOMO is listed on stock exchanges in Tokyo (9437) and New York (DCM). Please visit

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