Wi-Fi may carry many voice calls within the next few years, but the technology required to make those calls is still young in some ways.
Mobile subscribers have been talking and doing video chats over Wi-Fi for a long time using Internet-based services such as Skype. Now carriers are offering ways to call up friends and family over wireless LANs using their regular phone numbers.
Wi-Fi calling made a splash last year when the iPhone 6 came out with the capability, though a number of Android and other devices also have it. T-Mobile USA and Sprint both allow Wi-Fi calling with selected smartphones. AT&T and Verizon, as well as EE in the UK, plan to follow.
Wi-Fi home networks and hotspots have become critical tools for carriers to keep up with growing mobile data use. The fat unlicensed spectrum bands available with Wi-Fi can carry bits that would otherwise have to ride on carriers' own frequencies. Adding voice calls to the mix can take more of the load off licensed spectrum, and even improve at-home coverage, but this traffic may need special treatment to meet our expectations of what a phone call should sound like.
Early deployments sometimes fell short, according to Ovum analyst Daryl Schoolar. Late last year, EE told subscribers it had pushed back its Wi-Fi calling launch to make sure the experience meets subscribers' expectations.
"The Nirvana that we want to reach is, when you make a call you don't really know what technology you're using," Farpoint Group analyst Craig Mathias said. That may be a ways off for Wi-Fi calling, because the technology has only begun to be used on a large scale, he said. It will probably become generally available in the next two to three years, Mathias said.
Some of the steps to making Wi-Fi voice work more like any other call will take place behind the hotspot. For example, turning cellular calls into data using VoLTE (voice over LTE) should let carriers put both types of calls under the same management software on the back-end network. That could make it more seamless for subscribers to talk on Wi-Fi networks, Ovum analyst Schoolar said.
Ruckus Wireless, which makes the APs (access points) that go into carrier hotspots as well as hotels and enterprises, is working to improve Wi-Fi calling at the other end. Software that Ruckus announced on Monday for its ZoneFlex APs can improve how they deal with voice traffic and with multiple smartphones trying to connect at the same time. Among other things, the software can identify and prioritize voice, keep an access point from getting overloaded and provide automatic roaming to a better AP.
In some cases, a Ruckus AP will make the caller's smartphone ask for as much bandwidth as it would need to carry out a call and won't let it connect if it can't get that much. The software can also turn away additional callers if the AP doesn't have enough capacity left to serve them all well. That doesn't necessarily mean those callers are stranded: Ruckus will also provide roaming capability, based on the IEEE 802.11v standard, to send a user to another nearby AP that has the free capacity to serve them.
The software features will only work on Ruckus APs. They will become available over the course of this year.
Ruckus will demonstrate the software features at Mobile World Congress next month in Barcelona, where there is likely to be other news on the spread of Wi-Fi calling. Verizon, AT&T and EE all have said they plan to launch Wi-Fi calling this year.