After significant deliberation, AT&T has been given the thumbs-up to launch its wifi calling service in the U.S.

The FCC gave the carrier a temporary waiver over an element of the discussion which was becoming a cause for concern. The U.S. regulator requires all telephony services to support text telephony (TTY) protocols which provide assistance to the hard-of-hearing. The temporary waiver means AT&T can launch its wifi calling service, which does not support TTY, while it finalises the development of an alternative protocol called real-time text (RTT) which is compatible with IP networking.

A statement from the FCC, announcing the ruling, said: “…the Federal Communications Commission (FCC or Commission) grant AT&T Services, Inc. (AT&T), a temporary, limited waiver of the Commission’s requirements to support text telephony (TTY) technology on wireless networks to the extent that they use Internet Protocol (IP) technologies. This waiver expires December 31, 2017, or upon the effective date of rules providing for alternative IP-based wireless accessibility solutions, whichever is earlier.”

AT&T immediately has gone ahead and made its wifi calling service available to all postpaid wireless customers with iPhone 6 handsets or newer with iOS 9 installed. There’s no mention of compatibility with Android phones, such as the Samsung 6 or Edge.

Interestingly, the carrier does stipulate that calls made on wifi will drop when the user gets out of range, unless they are an existing customer of its VoLTE HD voice service. While wifi signals can hand over to LTE based on both technologies being all-IP, the service is incapable of handing over from IP to traditional 2G or 3G voice networks. Regardless of VoLTE subscribtion, AT&T does say that any emergency calls made to 911 by wifi calling will drop if the user gets out of range.

Bill Smith, president of AT&T network operations, wrote about the launch of wifi calling on the company’s blog.

“With the FCC recently granting AT&T’s waiver request related to certain deaf and hard of hearing technology, AT&T customers will be able to use Wi-Fi in addition to the traditional cellular network to make and receive calls while in the U.S. beginning Oct. 8,” he said. “Wi-Fi Calling is a complement to AT&T’s already great network coverage.  Along with a network that covers more than 99 percent of all Americans, our customers now have an option for making calls in areas where a cellular signal is tough to get – such as a home or office with dense building construction.”