10 Jan

Making the Most of Wi-Fi Calling

By TheRuckusRoom

In the time since Apple’s revelation that iOS 8 would support a form of Wi-Fi calling, the industry has seen a barrage of announcements, even TV commercials, around Wi-Fi calling. Come to find out that many of them are actually existing products and technologies simply re-spun. A deeper dive into Wi-Fi calling’s history and characteristics reveals what is truly needed to properly support this exciting new Apple capability, as well as other Vo-Fi services.

So What is Wi-Fi Calling?

Sort of like the term “cloud,” Wi-Fi calling often means different things to different people.

Simply put, Wi-Fi calling is the ability to place a voice call using IP encapsulation over a Wi-Fi network, but this can be implemented in a variety of ways.

The iOS form of Wi-Fi calling is different from so-called over-the-top (OTT) services like Skype or Lync because it is integrated within the OS’s dialer (not a third- party app) and is architected to work in the same way a Voice over LTE (VoLTE) call works. It’s also being developed to support the transparent handoff of a call as the user moves between Wi-Fi and LTE coverage areas, something OTT approaches simply can’t do. It’s more of an evolution of about older UMA (unlicensed mobile access) based services, which were some of the first to support cellular voice services over Wi-Fi. Other implementations would include services from MVNOs such as republic wireless and Scratch Wireless.


While these are all examples of “Wi-Fi Calling,” they have very different characteristics, raising a number of important questions:

  • Where does the voice session terminate?
    In an IMS core, at a standalone SIP server/gateway, or on a MSC, does the voice session have to enter an operator’s core network? If so, how is the ‘untrusted/trusted’ border transited?

  • What codec is used?
    How …read more    

Comments are closed.

%d bloggers like this: