What is Wi-Fi Calling?

What is Wi-Fi Calling?  Mobile operators can use any Wi-Fi network for voice calls, even the ones in people’s offices and homes. Wi-Fi Calling enable you to offer coverage indoors where people spend most of their time.

Wi-Fi Calling has been around for a long time. Voice calls have been transmitted over Wi-Fi either in the form of OTT applications such as Skype or as initiatives such as UMA and femtocells to enhance the reach of mobile voice services in subscribers’ homes.

The problem with OTT applications from an operator’s perspective is that the operator loses control. The UMA / femtocell initiatives have proven to be too expensive lacking widespread support among phone manufacturers. In an ideal world voice calling should be totally seamless for the user, built-in natively in the device and work over any network connection.

The technology has been available for some time but operators have been hesitant. They have wanted to protect their voice-related revenue including revenue from roaming charges. However, new business models allowing for flat-fee voice services, combined with the realization that users will use OTT applications for calls as much as they can, has removed the last obstacle for taking Wi-Fi Calling to the next level.

In September 2014, mobile operator T-Mobile pioneered this next-generation Wi-Fi Calling solution. This is a paradigm shift for Wi-Fi Calling as it is now implemented with native support embedded in the smartphones and working seamlessly through any Wi-Fi connection. Text messaging (SMS) also works in this way.

Learn more details about Aptilo’s Wi-Fi Calling solution.

Wi-Fi Calling – It’s all about indoor coverage…..

Wi-Fi is everywhere. People are already running the vast majority of their data through Wi-Fi. According to a study by Mobidia as much as 80% of all mobile data is going over Wi-Fi and a big portion of this is, of course, indoor traffic including traffic from within people’s homes. Making matters worse, cellular networks are having an increasingly harder time penetrating modern buildings and those LTE networks running on high frequency bands will not make things easier for them.

What if you could use all of the different Wi-Fi networks that users are connected to for transporting the voice calls that would normally go over the cellular network? All of a sudden mobile operators would be able to offer coverage for their voice services virtually everywhere people spend most of their time.

This is the value proposition of next-generation Wi-Fi Calling, and it is available today!

Don’t mix this up with the Voice over Wi-Fi solutions (VoWiFi) that have been available for many years. This is a next-generation Wi-Fi Calling with VoWiFi and Voice over LTE (VoLTE) support natively integrated in the smartphone dialer, which offers a totally seamless user experience. Newer smartphones such as the iPhone 6 and 6 Plus support a seamless call transfer. When a user moves between LTE and Wi-Fi networks, the call will continue without any interruption. The next-generation Wi-Fi calling will still work for operators that have not yet deployed VoLTE and are still using the circuit switched GSM for voice. However, in this case the call will be terminated when users move between the networks.

Wi-Fi calling is a cost saver and revenue generator

Wi-Fi calling reduces churn, which is a significant cost for operators. Mobile operators will also be able to reduce the cost for building out LTE base stations and femtocells, as Wi-Fi calling will take care of the indoor coverage for voice.

Wi-Fi calling works transparently over any Wi-Fi network, including when the user is abroad. This means zero roaming costs for the mobile operator. If the operator chooses to transfer this cost savings to subscribers by charging the same rate for Wi-Fi calling both domestically and internationally, Wi-Fi calling becomes highly attractive to frequent travelers, creating significant potential for the mobile operator to generate new revenue.

Mobile operators can also acquire new customers looking to replace their current landlines with mobile calls.

Wi-Fi Calling – What are the benefits?

The next-generation Wi-Fi Calling solution is just as seamless for the user as iMessage. Users will never have to consider whether or not they are connected to LTE or Wi-Fi. Voice calls and text will just work. From anywhere to anyone.

For mobile operators Wi-Fi Calling has become critical for customer retention, as subscribers in many countries are giving up their landlines. With the smartphone as the primary device for keeping in contact with friends and family, they will be forced to switch to a competing mobile operator if the mobile connection is poor or non-existing.


Benefits to the end user

  • Single, uniform voice dialer on their smartphone.
  • Allows for voice services over any Wi-Fi network (home, office, hotspots).
  • Wi-Fi Calling provides better indoor coverage.
  • Seamless call transfer support between Wi-Fi and LTE (using VoLTE) and specific support in the device.
  • Roaming charges will be minimized, if the operator is using the same business model as T-Mobile.  A call from anywhere in the world will be charged as a mobile call in your home mobile network whenever you have access to the Internet over Wi-Fi.

Benefits to the operator

  • Better indoor coverage compared to cellular macro base stations. This solves an increasing problem with the “radio tight” modern building structures.
  • Reduced churn.
  • With indoor coverage, subscribers can give up their landlines. By offering Wi-Fi Calling services now, mobile operators can expect higher customer acquisition rates.
  • Operators can get back in the driver’s seat making OTT players such as Skype and Viber less important to subscribers.
  • Wi-Fi is a low-cost solution to enhance voice service coverage.
  • Operators do not necessarily even have to invest in Wi-Fi footprint. They can instead rely on existing Wi-Fi networks.
  • Wi-Fi Calling is sharing similar infrastructure with IMS-based VoLTE.


Wi-Fi Calling – What are the potential drawbacks?

Wi-Fi Calling and QoS

It should be noted that by implementing a Wi-Fi Calling solution operators have to give up some control over QoS for voice, as the traffic will go over networks that they do not fully administer. However, through the ever-increasing capacity of Wi-Fi networks with 801.11ac providing Gigabit speeds and the improved capability to prioritize multimedia traffic with WMM, QoS will in most cases not be a major challenge. Also, Wi-Fi Calling is offering an alternative to cellular voice where the LTE network does not work at all or is of poor quality.

Wi-Fi Calling and emergency calls

As with any Internet-based voice service, emergency service operators can have a hard time tracking the user’s location. Upon registration of the Wi-Fi Calling service the user has to register a default location, usually the home address. The capabilities in Aptilo’s solution to map APs with location will improve location information in Wi-Fi networks over which the operator has control. Also, vendors such as Apple have collected data mapping location information using individual Wi-Fi access points. It remains to be seen how regulatory agencies will view this, but the location issue is not relegated to the Wi-Fi Calling solution only: the same kind of issue currently exists with OTT voice applications.

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