Demystifying the Wi-Fi calling phenomenon

Demystifying the Wi-Fi calling phenomenon

The Delta Perspective


Alessandra Pelliccia, Lluís Llavina and special guest contributor Ivan Mauricio Montenegro from ETB

Fancy making calls using your smartphone's native dialer when the only connection your device has is Wi-Fi? This may not be new for those who use their data connection to make voice calls with third-party VoIP applications. However, many subscribers have no choice but to rely on their cellular connection for domestic voice calls and other basic services due to poorer quality and limitations such as cost constraints and the necessity of installing and using a separate application when using one’s preferred services. This could change soon as leading device manufacturers and service providers take Wi-Fi calling to the next stage.

Is Wi-Fi calling really what most people think of and talk about?

Wi-Fi calling should be understood as something much more than just the possibility of making or receiving a call through a Wi-Fi network using a Skype-like application. The industry is really aiming at offering a seamless experience, no matter what radio access technology the customer is using. This means being able to use one’s personal mobile number to make and receive calls through a Wi-Fi connection following the same steps through the native dialer built in the device’s OS, and have access to products and services (be it voice, data, SMS or the voice mail) one might enjoy when registered to the cellular network. With Wi-Fi calling one might even “emulate” local services while being abroad enabling, for instance, local calls when out of the country.

Exhibit 1: A high-level timeline of Wi-Fi calling


Is it all somehow related to the SRVCC feature in VoLTE?

Single Radio Voice Call Continuity is used to seamlessly handle services in an LTE network. Both SRVCC and Wi-Fi calling rely on the same underlying concept of “assuring the appropriate interworking between different wireless access networks to deliver a seamless experience across them”.  In other words, Wi-Fi calling (based on 3GPP i-WLAN architecture) is another piece of the same puzzle.

Deploying the ecosystem to enable basic Wi-Fi calling is not a straightforward task

From a technical perspective, Wi-Fi calling can only be enabled if the user device, the operator’s wireless network infrastructure (access and data core) and the service core are ready to support it.  Firstly, the device must support advanced Wi-Fi capabilities (software and hardware capabilities). Secondly, on the network access and data core side, the key aspect is to ensure the appropriate interworking among heterogeneous access technologies like Wi-Fi, 3G and LTE to guarantee connectivity continuity across them (the 3GPP addresses this issue with a set of standards and specifications that define the Interworking Wireless Local Area Network (I-WLAN) Architecture). Finally, to achieve service transparency, an IMS core must control and manage the service-specific requirements.

Exhibit 2: Ecosystem required to enable a seamless experience in a multi-access mobility environment

Without this collective enablement, seamless handover between one radio access network and another, which is crucial to delivering a real Wi-Fi calling experience, is not possible, and a call initiated through a Wi-Fi connection would suddenly drop when the user loses Wi-Fi coverage. To be able to deliver the desired customer experience, IP address preservation during mobility between 3GPP and non-3GPP access, as defined by I-WLAN, is required.

ANSDF plays a crucial role in the enablement of Wi-Fi calling

In line with the previous point, there is the increasing need for devices to support Automatic Network Self-Discovery Feature (ANSDF), which allows customers to seamlessly register to the network that offers the best connectivity (based on a series of parameters such as quality, jitter, or latency) at any time, enabling policy-driven intelligent network selection and traffic steering by communicating with an ANDSF server located in the carrier’s core network.

Additionally, by distributing tailored policies to the ANDSF client, operators would be able to steer traffic between Wi-Fi and cellular networks for a better user experience and to allow better utilisation of technical resources, since many of the mobile devices sold today are already dual radio and are capable of using both radios simultaneously. Unfortunately, very few devices today support ANDSF.

But, is it possible to offer such a superior carrier-grade service through a network that uses unlicensed spectrum?

The answer is yes. Thanks to the introduction of new, more-robust Wi-Fi standards (such as the IEEE 802.11 ac, and Carrier-Grade Wi-Fi) and other industry initiatives (such as those led by the “Hotspot 2.0” working group by the Wi-Fi Alliance) that provide a whole new set of features to better control and manage a given Wi-Fi hotspot and its related equipment (e.g. Managed Wi-Fi, Secure Wi-Fi, QoS, Interference mitigation, etc.)1,2, offering an excellent service through a Wi-Fi network is today a reality.

In a nutshell…

Wi-Fi calling is rapidly maturing, and could become a disruptive technology in the mid-term. The industry is expecting it to enable a real seamless experience for all kinds of products and services, no matter what radio access technology the customer is using, be it one’s own mobile network or a third-party, properly-managed Wi-Fi hotspot. However, as we have seen, the technical challenges are multiplying. For this new phenomenon to become mainstream, close collaboration is thus required between operators, device manufacturers, and even Wi-Fi equipment providers.

1 T-Mobile has started offering a "Personal CellSpot" device — an 802.11ac Wi-Fi router especially enhanced to prioritise Wi-Fi calls — to customers looking to maximise their call quality.

2 In general, once service is activated, a user must select which access points (APs)/Wi-Fi networks will be authorised to use Wi-Fi calling.


Stay tuned for our next blog on the business implications for the different players in the value chain.


Authors’ bios

Ivan Mauricio Montenegro is the Mobile Networks Manager at ETB in Colombia who is responsible for the recent successful, technical launch of the company’s LTE network. He has an MBA and brings with him more than 15 years of knowledge in the telecommunications industry. He has extensive experience in technical aspects such as LTE, xDSL, IP, submarine cable systems, and network and connectivity solutions tailored to the business segment.

Lluís Llavina is a Senior Manager at Delta Partners’ Management Consulting division based in Barcelona. He is a telecommunications engineer with cross-functional expertise on strategy and business planning, technical, and commercial areas within the telecoms and digital segments. Lluís has more than five years of experience in business consulting in the telecoms space in the Middle East, Africa, Latin America and Europe. Previous roles include being a Founder, CEO, and Board Member in two Internet/TMT start-ups.

Alessandra Pelliccia is an Associate at Delta Partners’ Management Consulting division based in Dubai. Alessandra has more than three years of telecom experience in Europe, Latin America, Africa, Southeast Asia, and the Middle East. Her focus includes financial modelling, network, LTE start-ups, LTE commercial and network PMO, corporate strategy and organisation. Prior to Delta Partners, Alessandra was a consultant within the TMT practice at The Boston Consulting Group in Milan.



Delta Partners Management Consulting