Heads-up: Why Wi-Fi calling is a bigger deal than you’d think


You’d think that making phone calls over Wi-Fi is old news – and it is, at least from a tech point of view. But it’s also kind of a big deal. Here’s why.

In September last year Apple launched native Wi-Fi calling for iOS6. Right after that, TMo USA jumped on it with ‘Wi-Fi un-leashed’ that includes the CellSpot home router and native Wi-Fi calling in all smartphone devices.So what’s special about all of this?

First of all: Wi-Fi calling has been around for years with Android (I’m not talking about Skype or iChat but Wi-Fi calling for carriers that uses an actual mobile phone number, of course). But now there’s a difference: Apple’s launch is a pretty strong indication that it Wi-Fi calling (or VoWiFi) is ready to go mass market. They don’t seem to miss the boat on opportunities like that very often.

So how will Wi-Fi calling help carriers? There are a couple of pretty much no-brainer reasons for using it. They will have serious consequences for parts of the mobile infrastructure market.

A cheap fix to a tricky technical problem

The first is technical: One of the most expensive and difficult things to fix for a mobile network is indoor coverage for voice. To fix it, you need to do one of two (or three) things: Either uproot your network of towers and stick them closer to each other (a non-starter) or find some way of deploying small cells inside buildings (expensive) or find some low frequency bands to use for voice services (scarce). Either way, it’s going to cost you big bucks.

Wi-Fi calling fixes this because a lot of homes & buildings will have Wi-Fi already, and if they don’t – well, TMo has taken the additional step of nearly giving away the CellSpot home Wi-Fi router. That should fix the indoor (Wi-Fi) coverage problem for mobile telephony – and that’s a pretty big service fix.

Giving consumers what they want

The second big driver is customer retention. Of all annoying things in mobile, bad voice coverage is probably the most annoying. These days, mobile carriers don’t make much money (if any) on voice, but voice coverage & quality is still critical. With competition & price wars heating up, Wi-Fi calling is the little feature that can make a big difference for consumers. Even just using the word ‘Wi-Fi’ in marketing of new mobile services attracts consumers.

These two reasons make Wi-Fi calling nearly irresistible to mobile carriers right now. I believe that inside of the next two years pretty much all carriers with Apple devices on their networks will launch some form of Wi-Fi calling.

Are mobile indoor solutions doomed?

Here’s the bigger impact that Wi-Fi calling will have on the infrastructure part of the industry and this is where the big deal comes in: We will soon not need mobile indoor coverage solutions any more or at least not for voice. I expect that Wi-Fi calling will blow a serious hole in the market for DAS (distributed antenna systems) and small cells. Such networks are primarily designed to support voice and with Wi-Fi taking over that role… well, you can guess the rest.

Here’s another interesting perspective: You also don’t need to own or operate your own Wi-Fi network in order for Wi-Fi calling (Apple-style) to work. Apple has done it in such a way (using IPSec tunneling) that you can use any Wi-Fi network to call unless someone is purposely locking you out. And provided that you carrier supports 4G voice (VoLTE) you also get full mobility.

Some notes on technology

I just spoke to an expert at Aptilo Networks about the technical (architecture) requirements for Wi-Fi calling. There are four items that any carrier will need for Wi-Fi calling: Device support, ePDG network node, AAA, and an IMS platform. There are vendors offering ‘pre-IMS’ solutions (such as Taqua and SpectrumMAX) that don’t require carriers to install a full IMS platform. More comments on architecture:

  • Device support appears to be standard in high-end devices from Apple, Samsung, & others. It does need to be provisioned (activated) in the device by the carrier
  • ePDG is a part of LTE core network architecture (EPC) for terminating IPSec tunnels. It’s the IPSec tunnel that allows Wi-Fi calling to take place securely over any public Wi-Fi network whether it is owned & operated by the carrier or not (it’s called ‘untrusted 3GPP Wi-Fi access’ but don’t let the name fool you!)
  • AAA is the service management core for Wi-Fi that will need to include a SIM authentication server for EAP-SIM/AKA authentication of subscribers
  • IMS is the service platform also used for VoLTE (Voice over LTE) so some but not all carriers will have this already

A big Wi-Fi NOW welcome to SpectrumMAX 

We’re delighted to announce that SpectrumMAX is joining us at Wi-Fi NOW in Amsterdam – and if you’re interested in Wi-Fi Calling without the costs of a deploying an IMS platform, they are the folks to speak to. SpectrumMAX offers a full suite of telephony & messaging services with minimal impact on existing infrastructure. Meet them at Wi-Fi NOW – go to this link to register for the conference!

/Claus Hetting



  1. […] And core network support is the biggest financial hurdle for carriers looking into this. Not only does the Ericsson solution require IMS and EPC, it also will need (for SIM-devices) a carrier Wi-Fi AAA, or service management platform. For more on Wi-Fi calling also read this […]

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