T-Mobile USA is a different sort of carrier. It's America's third largest national carrier, having overtaken Sprint last year. T-Mobile USA also behaves differently to other carriers with their "Uncarrier" marketing being a prime example of the difference. However, there is another way in which T-Mobile is different to the competition: it has offered Wi-Fi calling for a number of years now. Wi-Fi calling is as one might expect: allows customers to make and receive voice calls on a smartphone over a compatible Wi-Fi network rather than relying on a traditional cellular service. The technology can work because voice calls over a network can be transmitted over a data connection. This is known as VoIP, Voice Over IP, or a voice call over a network data connection. Over the years the technology has broadened and now includes VoLTE, Voice Over LTE, a means of keeping devices connected to today's modern, LTE networks that are supremely efficient at handling data connections but are unable to handle voice calls.
For T-Mobile USA, the carrier has traditionally had relatively poor coverage and one way to improve this was to offer customers the ability to make and receive calls over a Wi-Fi network. Over the years, Wi-Fi calling has been improved to help prevent calls dropping and a better handover between the cellular network and a Wi-Fi network and other carriers have adopted the technology. AT&T is one such carrier, launching their own Wi-Fi calling technology just last year. At their investor conference today, AT&T boasted that their systems are handling over 4 million calls a day over a Wi-Fi network. However, AT&T first launched the Wi-Fi calling system for the iPhone last year but only added support for selected Android devices last week. AT&T's Technology Operations President, Bill Smith, said: "We just recently started turning up Android-based operating systems, so I think that's going to go up tremendously, and we're doing that at extremely impressive performance levels." AT&T also extolled how they would start using unlicensed spectrum for as well.
T-Mobile contacted FierceWireless shortly after AT&T's announcement, explaining that over 6.5 million T-Mobile customers use Wi-Fi calling on a monthly basis. T-Mobile also tweeted to AT&T that it was "so cute" of America's second largest carrier to handle 4 million Wi-Fi calls a day, but their network handles 22 million and has been offering the service since 2007. And although T-Mobile USA are using the announcement to highlight their leadership at handling Wi-Fi calls, it also shows a huge difference in how these carriers work with customers. AT&T's tardiness at offering Wi-Fi calling appears to be about keeping control of customers and ensuring that their smartphone use is always routed through their infrastructure. T-Mobile USA, however, want customers to be able to use their device regardless and do not appear to have such a controlling lean. Either way, Wi-Fi calling is a useful feature to have because whatever network you use, it can suffer from black spots.