• 10/22/2015
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WiFi Calling: Ready To Take Off?

With AT&T and Apple iPhone support for WiFi calling, the technology is poised to go mainstream. Heres how it works and its potential enterprise ramifications.

WiFi calling enables wireless handsets to connect to a mobile carrier’s network through WiFi access points. With expanded support from more carriers and Apple, I believe it’s poised to become popular. It can provide better indoor coverage, avoids roaming charges while traveling out of the country, and can be used for messaging aboard WiFi equipped planes. It also doesn’t require the installation of apps such as Skype, Viber or WhatsApp to make voice calls.

The original standard that enables WiFi calling is Unlicensed Mobile Access (UMA), which means that an unlicensed spectrum network (WiFi) is given access into the mobile network. Some call this VoWiFi, but let’s just call it WiFi calling here. Newer variants include the IR-92 profile for Voice over LTE, which is used by Apple.               

Ericsson’s Consumer July 2015 Insights Summary report shows that globally, four in 10 of users are satisfied with indoor cellular connectivity experience, and three in 10 satisfied with voice call quality, coverage and reliability. WiFi calling is said to increase satisfaction for four out of five US users. 

Given the benefits, why hasn’t it yet taken the US users by storm? It was initially only offered by T-Mobile in the US (small market share), and few handsets supported it.Quality of the calls were reported to be shaky, with spotty handoffs from WiFi and mobile networks, so even T-Mobile has not actively promoted it, which led to a lack of awareness.

But changes are afoot! Apple started to support the technology on the iPhone in September 2014 and AT&T received regulatory approval this month to offer WiFi calling; it’s expected to release it later in 2015. Sprint launched a service in April and Verizon has said it intends to support it. T-Mobile updated its existing service to include HD Voice, improved WiFi/mobile handoffs, and support on Android, Windows Mobile and Apple iPhone. It also offers free in-flight text and picture messaging using the GoGo in-flight WiFi.

So it looks like pieces are in place for WiFi calling to become widespread, especially given the market share of iPhone and AT&T. However, it could pose some issues in the enterprise.

Most office networks have WiFi coverage, and may even support Voice over WLAN (traditional VoIP phones on WiFi). If WiFi calling takes off in the enterprise, the responsibility may suddenly fall on IT to support WiFi callers. Mobile phones are probably already allowed access to WiFi, so end-users may hop on and start using WiFi calling without IT realizing it while the end-users may expect high levels of service.

As a result, IT teams will be faced with addressing two items: signal strength and managing traffic.

Signals: Design of voice over WLAN is a careful process involving RF audit and site surveys, and the same may apply for WiFi calling, which ensures a strong signal and requires increasing AP density to every 50 feet.  WiFi AP vendors can assist in getting good office signal coverage suitable for voice traffic.

Traffic: Even though WiFi calling traffic is encrypted, there are some ways to identify the traffic flows and categorize them. An enterprise’s WiFi vendor can assist with appropriate settings (examples: HP Aruba’s AppRF and Ruckus Wireless SmartCast features)

In enterprise BYOD environments, appropriate authentication, device and app managers can control which devices use WiFi calling to prevent uncontrolled access, but not every group does that. For example, it may be appropriate to block new users from connecting to WiFi if there isn’t enough bandwidth capacity to service them. With 802.11ac, however,bandwidth should not be a problem.

In my next post, I’ll take a closer look at how enterprises can prepare for WiFi calling adoption.



I think AT&T starting making WiFi calling available earlier this month, according to this report. The launch may be a bit rocky, just judging from the complaints about the service from one tech person earlier this week on Twitter.

Re: AT&T

This is going to be tricky to troubleshoot since you have multiple parts of the infra that belong to the user that one depends on.   Certainly ATT may need to improve things at launch, but there may be issues with your own WiFI. Whether end users complain to their IT department (or in case of home WiFi -- to their ISP like Comcast, or just blame yourself for not setting up the access point properly!) remains to be seen.  Reading the report you linked to, I think there's an awful of of misunerstanding.  Some people automatically think there's free international roaming, which is not necessarily true.

In any case, I hope the NWC articles try to clarify some issues.   I think it's important to remember that the calls are still processed through the carrier's mobile telephone network. WiFi is just one segment of it.

There's part 2 of the article coming up.

Re: AT&T

Good points, thanks Dan! 

Re: AT&T

You're welcome. The #wificalling hashtag seems popular on Twitter too.


."..Most office networks have WiFi coverage, and may even support Voice over WLAN (traditional VoIP phones on WiFi)."

This would be very interesting to see deployed. A major move from traditional VOIP implementations.

Re: WLANs and VOIP

Lots of VoIP handsets for office have WiFi options but many that I've used were all wired. But many new offices are forgoing wired ethernet, so even company provided handsets may go WiFi too.  I must admit that many people (especially people who work in the field) don't take calls on office supplied lines as much as they used to -- they just give their mobile #s out.  So the ofifice phone remains unused (and the voice mail box is full)

I believe Europeans and people in some other countries prefer to keep their personal numbers separate from work numbers though, so they resort to carrying two mobiles or (better) dual-SIMs. 

On the long-term, if the company supports BYOD - some new arrangement may take off that accomodates separation of work and personal calls, while mixing the devices, perhaps through clever call switching software. I think we're still in the early stages so expect more to come in the year to come.



Regulations and Wireless Deployment

@Dan  I am surprised wirless offerings have lagged so far behind the G-based network. Was this due to regulation primarily ?

Re: Regulations and Wireless Deployment

You're asking why WiFi calling lagged regular mobile stations? (i.e. ground based?)  There are FCC approvals required by regulation. There was a dust-up where AT&T went through the paperwork, although their claimed T-Mobile and Sprint rolled it without the equivalent amount of filings.  It was sort of moot until popular handsets did not support it, but since iPhone supoprts it now, it should be popular.

You'll be surprised at how much confusion there seems to be what WiFi calling is.  Some people wrongly claim that they are supplying the WiFi network therefore the calls plans ought to be free.

That's not true -- the calls get routed through the telco network -- which, by the way, is the one that assigned you the phone number.  It's quite unlike using Skype which runs over the top of the IP network.  And if you call a POTS number of Skype, you have to pay anyhow.

WiFi Calling: Ready To Take Off?

Very interesting topic here. WiFi Calling in itself is a great idea, necessarily relieving strain on ever-packed 3 & 4G networks (those six out of ten unhappy customers don't know how complicated the network they take for granted is to run... but, by that same token, they don't care and expect high quality). However, whether or not supporting it in an enterprise setting is IT's job at all is a seperate question entirely. Now, BYOD does assume that the reason you're allowing personal devices at work is because (part of) the time spent on will enhance productivity. So, one could say WiFi calling is certainly part of that... but you could also say it's a bonus users should not expect constant access to. QoS and traffic shaping seems like a lot to ask for IT shops that are stretched thin as it is - but, of course, your mileage may vary.

Re: WiFi Calling: Ready To Take Off?

Exactly.  One part of the BYOD equation is to lower IT hardware and support costs by "pushing" it to the end-user, but the real driver is that people are demanding to use their devices of choice (i.e. I want a Mac, iPhone or whatever). To the extent that enterprises are expected to support that, even if they save on some hardware costs, the support effort is going to be complex.  As you state, the productivity gains are what's going to be important, if it materializes.

I learn that a lot of WiFi calling related settings for networking is quite complex.  If a mobile operator cuts a deal with a WiFi operator in an aiport so that it carries WiFi calling signals properly, they both collaborate and understand exactly what to do. But for enterprises, I don't know!

I doubt ATT or T-Mobile will provide a lot of handholding on plain enterprise offices.  I learn that new offices that are very eco-friendly (LEED) are basically have to be very bad indoor mobile coverage, so the only way to get coverage is to do (this is in part two of my blog) DAS or small-cell or resort to WiFi.  Most enterprises are going to want the cheap route and push the responsibility over to IT supported WiFi.

If your WiFi AP prioritizes voice (if it's set-up like that) then lots of voice talk will get prioritized above plain enterprise data workloads. So in theory, real access to file servers or web sites may degrade.  Is that what you want? I'm not sure.

So in part 2 I talk about the real issue, which is "how to get indoor coverage" and look at the options.


Re: WiFi Calling: Ready To Take Off?

Well put. You made some good points about the APs and the Vendors' role here in the article, and I wanted to mention that as well. There is some concern here of people dropping a bunch of money on these sophisticated high-end APs with all these robust features and then taking a fire-and-forget approach to their WLAN setup, which would be a huge mistake. Definitely, if you're paying for a highly complex and customized approach, and you're an enterprise that needs it, you should maximize it. WiFi calling could be part of that. Likewise with 802.11ac - more bandwidth means more possible supported applications - WiFi calling could be one of them. I'll be looking forward to part 2.

Re: WiFi Calling: Ready To Take Off?

You have a good point about "fire and forget".  My research shows that enterprises are in the midst of upgrading to 802.11ac now.  It would be bad if the APs (and the settings, or placement or whatever) are optimized for the LAST generation of uses and miss the next. I guess this always happens so it's an endless treadmill and you'll never choose the perfect solution.

I learned that  most mobile phones have an antenna at the bottom of the handset means that it's oriented the WRONG way for talk to the antennas in many (but not all) APs for optimal signal.  That may differ from laptops which may have more than one antenna.  So people may say "hmm, my laptop gets a signal well, bu tmy WiFi calling is horrislble,  I wonder why".