Wi-Fi calling promises to help people who have crappy mobile phone coverage. I had a good experience and a crappy experience. Here's what happened.
I go on a mini-rant on networking configurations.
I was visiting an office building with a colleague and I lost coverage deep in the building, and so did my colleague, who had a different phone and carrier than me. He had a conference call to make. One choice was to go outside but it wasn't ideal so he switched to Wi-Fi calling and it all worked fine within the building.
The coverage sucked for multiple carriers, so it must have been the building and location--it's unlikely that we both had bad carriers. Yes, I know it has a lot to do with frequencies that penetrate buildings, but most people don't know and don't care. We just want our voice and data to work. So chalk it up as a win for Wi-Fi calling as a way to save the day (at least for voice calls). Lots of modern LEED buildings do a great job keeping heat insulated but keep signals out, and maybe that's what happened. It's not like we were out in the sticks, since we got good coverage outside.
I was visiting another place, and texted a friend to tell him that I was waiting in the lobby. I got no reply, and looked at the message app and noticed that the message did not go through! I wondered why, and saw a funny Wi-Fi calling errror indicator on the phone, so I switched to normal mobile coverage and my text went through. Fortunately, this lobby had good mobile coverage, and I later wondered what was wrong.
The answer is that lots of things may be wrong. Perhaps some ports were closed, or IPSEC must be allowed on Wi-Fi, maybe some FQDNs were not accessible, no strange firewall rules were allowed, etc. So perhaps that building's open Wi-Fi APs were locked down just for web browsing. I may never know what was wrong, but I had a bad experience and so can many others. If I had tried to make a voice call, I would have known immediately that I failed. But instead, I tried to send a text message, and put the phone away, so I did not realize I had failed until a few minutes later.
That's a big lose for Wi-Fi calling. It's partially my fault for not realizing that the indicator was telling me that something had gone wrong, but since I kept Wi-Fi calling on as a default and it usually works, I really never trained myself to look at it.
So the moral of the story, and a lesson for us? The UI and user-experience needs to get a lot better on the phone (give me a little error beep!), and the office Wi-Fi administrator needs to be a bit more aware of what end-users are doing. Maybe a little captive portal that tells me that Wi-Fi calling won't work? Since this place had an open AP, I may not look at the browser to get notified, so it's a tricky issue to do the notification properly.
So for the time being, it'd be good to set the default to use the mobile network if you can, and then use Wi-Fi as a backup plan. I am going to investiage a bit more about what this means for the enterprise. Cisco has a handy guide, and that's a good start for Voice-over-Wi-Fi (VoWiFi)
There are options to Wi-Fi calling to make good mobile phone coverage in buildings -- ranging from special antenna systems to femtocells, and this experience shows that a wide range of offerings are still necessary. Wi-Fi calling cannot be the silver bullet, until there are better deployment guides and common dissemination of those best practices.
The promise of Wi-Fi calling is almost there, but not quite perfect.