Japan’s mobile service provider NTT DOCOMO has announced that subscribers to Xi™, the company’s extra-high-speed LTE mobile service surpassed four million on July 22.

Xi reached four million subscribers just one and a half months after it surpassed the three million mark on June 8, 2012. The pace of new subscriptions nearly doubled after the introduction in summer 2012 of a Xi-compatible smartphone lineup that offered more variety to meet customer needs.

Going forward, DOCOMO expects to continue strengthening customer satisfaction with Xi-compatible smartphones, mobile Wi-Fi® routers and other devices, as well as beneficial services, such as Xi Talk 24™ for free, unlimited voice calls between DOCOMO users of Xi-compatible smartphones.