From early December 2014, KDDI and Okinawa Cellular will launch the next-generation voice calling service, au VoLTE, which utilizes the 4G LTE network.
With au VoLTE, users can use a next-generation voice call service featuring high quality and speedy incoming and outgoing calling that utilizes VoLTE . They can also perform data communication, such as browsing the Web and sending and receiving e-mail, during voice calls. Furthermore, this service utilizes VoLTE to provide Sync Call , a new communication service that allows callers to share their smartphone screens, location information, camera images, and more with a recipient during a call, and Voice Party , which allows simultaneous group calls with up to 30 people.
The au VoLTE rate plan will be available with the same charges as the Unlimited Voice & Data Freedom and LTE Plan for 4G LTE smartphones.
Supported models for this service are the isai VL LGV31 and URBANO V01 Winter 2014 models, and new models will gradually added.
KDDI and Okinawa Cellular are constructing a high speed and reliable data communication network using LTE areas, with their population coverage of 99% (Platinum Band 800MHz) , as a base and adding features such as being the first domestic telecommunications carrier to introduce Carrier Aggregation  technology with LTE-Advanced, the LTE next generation high speed communication standard. With the introduction of au VoLTE, we are the first domestic telecommunications carrier  to provide all voice calling and data communication utilizing only the 4G LTE network, thus achieving a higher quality and more reliable communication service. 
For more details, see the Attachment.
Attachment：Launch of the next-generation voice call service, au VoLTE