Wi-Fi Calling – Success or solution?

what is wifi callingI’ve noticed more frequently these days issues with voice calls to some mobile phones. The other party quickly points out that they are using Wi-Fi Calling because of poor indoor coverage and that this is the best they can do. While it works for some, clearly it’s far from a perfect solution. Are there any other options?



What is Wi-Fi Calling?

A few years ago, operators provided their own dedicated Apps which could directly make and receive voice phone calls in areas outside good cellular coverage. Usually these had to be actively selected and calls placed directly using the App, instead of the regular voice dialler built into the phone. Results were variable.

More recently, Wi-Fi Calling has been standardised and embedded into many of the latest Apple and Android smartphones. Some operators have actively enabled it by default while others let each user decide if they want to opt in. In all cases, it’s optional and can be switched off.

When in Wi-Fi coverage, your phone will then receive and send calls, text messages and data using the Wi-Fi radio rather than the cellular network. Your call is encrypted and sent over the public internet to the mobile operator core network, where it is decrypted and processed as for any other phone call. Regular call charges typically apply, although calls are mostly included free in monthly bundles.

Apple phones have a feature called Wi-Fi Assist, which is supposed to spot when the Wi-Fi quality becomes inadequate and switches the call back to the cellular network. In areas of poor cellular service, that would often mean dropping the call completely. When roaming abroad, this feature is disabled.

Fewer residential femtocells on sale

ThinkSmallCell has tracked some 30 or so network operators worldwide who commercial and publicly rolled out femtocells, mainly for the residential mass market over the past 10 years. Many have now withdrawn the service from new sales, supported existing customers in the meantime. A few have terminated service completely, promoting Wi-Fi calling as the alternative.

Vodafone Group are perhaps the most visible, having withdrawn their SureSignal femtocell from sale in several countries. However they, and others, continue to actively promote Enterprise Femtocells and other small cell solutions for larger business users.

Notably Illiad (which owns Free France and has large stakes in Ireland and Italy) continues to ship every set top box with an integrated femtocells as part of their national footprint. They continue to go against the tide, winning their bigger market share, lower prices and the highest returns on investment.

Most of the residential femtocells are 3G, few operators took the upgrade to 4G and instead seemed to have favoured Wi-Fi Calling.

A critical problem with Wi-Fi

A key issue I have had with Wi-Fi for many years is that it can’t easily differentiate between the higher quality/low traffic service I get in a few places, such as home and in the office, with that of the poor quality/congested service found in public places. I have to remember to switch it off and on again manually, which I frequently forget to do, and this just becomes irritating – especially if I’m on a voice call.

What’s needed is a bit more control or significantly more intelligence built into the choice of connecting to Wi-Fi or not, and whether to use it for voice calls. Perhaps the Wi-Fi Assist feature of the iPhone (or similar features in other products) could be developed further based on crowd-sourced statistics.

Companies have tried to do this in the past – I recall some great technology on offer from DeviceScape and others – but this just didn’t seem to capture the interests of senior planners at the major operators.

Backhaul constraints

One common concern about femtocells (and also with Wi-Fi Calling) isn’t the radio interface, but the backhaul. Remote buildings connected through a constrained and shared DSL wireline broadband may just not have the predictable and adequate quality to sustain a continuous voice call.

Competing demands on a household broadband line, say from teenagers streaming video or gaming intensively, can also have serious impact.

This is one reason I’ve heard from network operators who would prefer to be in control of all elements of the communication link to your device.

LTE Relays being promoted as an alternative

Sprint’s Magic Box (from Airspan) and Vodafone’s own LTE relays (from Huawei) actively retransmit the cellular signal inside buildings that otherwise have poor coverage. They are backhauled using regular LTE cellular to a nearby cell tower. Unlike cellular repeaters, the indoor retranmissions are on a different frequency band so as not to interfere with existing outdoor signals. The larger size of the unit compared to a smartphone means that it can have larger and more antenna (so is able to receive a weaker signal) and have a more powerful transmitter (say 5W rather than 1W).

However these units are considerably more expensive than a standard femtocells and certainly more so than those that Free France embed in a set top box.

Larger and more densely used buildings should be able to justify their own in-building wireless system, whether some form of DAS or using small cells with a central controller. Even here, backhaul is critical and I’ve heard from several sources that this is usually the capacity bottleneck – you wouldn’t believe how much data users can consume given the opportunity.


  • The residential femtocell market that saw growth with 3G has been replaced by Wi-Fi Calling for 4G.
  • There are a few notable exceptions where residential femtocells are incorporated into set top boxes, providing high return on investment
  • The demand for better and more stable indoor wireless solutions remains. It is affected by both the final wireless link (Wi-Fi or LTE) and backhaul.
  • Larger buildings can easily justify their own inbuilding cellular installations. Smaller ones may benefit from LTE relay products. Residential may be left with Wi-Fi calling which continues to have its own quirks and operational issues.
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#1 Rob Smallwood said: 
WiFi Calling has had a remarkably positive impact on the reliability of mobile calls in this part of the world (Regional Western Australia)where the carrier coverage can be extremely patchy, even inside regional towns. Several of the carriers (in particular, Optus and Vodafone) are recently reaching out into agricultural communities to investigate the use of small cells, self-installed by property owners, to extend coverage into areas where a full-scale mobile tower can't be justified. Early days yet, but great to see this approach getting some visibility. As always, backhaul is the killer, though there have been some reasonably satisfactory outcomes using satellite--but a long way to go yet.

If you can land some capacity into agricultural properties via private fixed wireless links, connect this to a small cell that manages a couple of km of cell coverage, or even use wifi with WiFi calling,in many cases this solves a significant problem at an affordable cost on properties that to date had no hope of getting any form of cell phone coverage via traditional methods. Hoping the carriers will all continue to adopt this approach more universally in areas of poor coverage.
0 Quote 2018-04-26 06:42
#2 Wade said: 
I have noticed that Wi-Fi calling has come a long way. It works very well, I am pleasantly surprised by the quality. While not perfect, it works well.
It works best in an isolated network, I noticed that is crowded Wi-Fi environments it has issues, that's where LTE kicks in an does well. When in a public area, LTE works much better. That is my experience.
0 Quote 2018-05-03 16:10
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