WiFi Calling is a solution that allows you to make voice and video calls, as well as exchange text messages over the mobile operator’s core network through a connection to any Wi-Fi network. In fact, it solves the problem of poor-quality voice service or its complete absence in the premises without the need for the development of a mobile network in individual buildings. All that is needed is the support of this technology by the networks of the mobile operator and the subscriber device in which the corresponding function is implemented (“flashed” in the smartphone at the system level).
Technologically, WiFi Calling (or Voice-over-Wi-Fi) is a continuation of the Voice-over-LTE service (transmission of voice data over LTE networks), which is based on voice over IP protocol. The fundamental difference between WiFi Calling and existing IP-telephony services (Skype or many applications, such as WhatsApp, Viber, Facebook Messenger, etc.) is that the call is made through the core network of a mobile operator and is an ordinary telephone call from a subscriber’s mobile number.
Currently, Wi-Fi Calling is mainly used to improve the quality of voice coverage inside buildings, where for some reason the quality of cellular communication is insufficient and the use of VoLTE is impossible. And “white spots” in the coating can be present both in suburban homes, away from base stations, and in densely populated areas, for example, in buildings constructed using energy-saving materials, which significantly impede the penetration of a cellular signal. In the absence of sufficient bandwidth, video calls can only be made through a Wi-Fi network (even if voice connections are made in LTE). In these cases, Wi-Fi Calling technology can complement VoLTE, which gives operators the opportunity to launch voice and video services based on IMS even at an early stage of LTE network construction. This will provide a better user experience compared to CSFB.
Convenience for the subscriber
The main advantage of Wi-Fi Calling for subscribers is, first of all, the ability to use voice communication services from their smartphone in case of poor coverage of the mobile network or its absence. Being in a cafe located in the basement, you will no longer need to go outside in order to catch a signal, or download special applications – the connection can be established through a Wi-Fi router, which today is almost everywhere. The same applies to suburban homes with poor mobile coverage, and densely populated urban areas, where the indoor signal often leaves much to be desired, while the number of Wi-Fi routers rolls over.
A smartphone with Wi-Fi Calling installed automatically connects to an available Wi-Fi network at a time when the mobile signal becomes too weak to make a call or disappears completely.
Another advantage of Wi-Fi Calling for a subscriber is the ability to significantly reduce the cost of voice communications, including roaming for calls from abroad to the home operator’s network. Firstly, operators do not charge additional voice communications over IP protocol. Secondly, since voice over Wi-Fi is transmitted over the Internet, the call is not tied to the geographic location of the caller. Calls to numbers on your home network from abroad will remain free. At the same time, calls to the networks of international operators are charged as usual. Thus, while on a business trip or on vacation abroad, in a hotel with Wi-Fi, it is possible to make and receive calls as if you were in your home region.
Since Wi-Fi calling connections are made through the public Internet, subscribers can access their carrier’s network from anywhere in the world. In addition, users are relieved of the need to install additional applications when traveling outside the home network, and the process of using a subscriber device is no different from the usual one.
Benefits for operators
Wi-Fi Calling helps to reduce the churn of subscribers by improving the quality of voice and video coverage inside the building, where, as a rule, there are Wi-Fi access points. The technology of voice over Wi-Fi networks can be a decisive argument for the subscriber when choosing an operator when there is no mobile coverage in the apartment or house, or the signal is weak, the network is congested, etc.
it’s much more profitable for operators to reuse a huge amount of Wi-Fi networks already available in their Internet access points, including home routers of their subscribers, rather than, for example, invest in stimulating the development of femtocells. Given that the functionality to support Wi-Fi Calling services was originally integrated into smartphones by the manufacturer, operators will not need to spend additional funds on supporting and developing individual voice applications.
The introduction of Wi-Fi telephony also opens up new opportunities for operators in the field of convergence of mobile and fixed communications (FMC). For example, this service gives mobile operators the opportunity to take the place of fixed ones when it comes to customers from the category of small companies that own fiber and their own access point in their office. Thanks to WiFi telephony, office employees will be able to maintain their fixed numbers by replacing landlines with smartphones that support Wi-Fi Calling and continue to use them outside the office. In addition, the possible integration between different subscriber devices (mobile and landline phones, tablets and STB consoles) of all members of the same family can also help reduce customer churn.
Together with the opportunities that WiFi Calling offers both for subscribers and operators, the new technology poses a number of difficult tasks for communication companies and equipment manufacturers. The main one is the lack of the ability to switch between 2G / 3G networks and Wi-Fi. The possibility of a seamless transition is currently implemented only for the LTE network, as Both technologies are based on the IMS core. Therefore, outside the range of a Wi-Fi router, if there is LTE coverage, the conversation will not end. “Packet data transmission removes the question of which network is used – Wi-Fi or cellular, because, theoretically, packets are transmitted by that route and using the technology that is currently optimal for the user experience.
Another difficulty for operators whose task is to provide quality voice services is the ability to predict and control the quality of Wi-Fi networks. The operator is not related to the access point set by the user, and the quality of voice services that he provides will depend on the operation of the Wi-Fi network. Difficulties can be caused by interference from a neighboring access point, a high network load or a large range of the router. In addition, modern Wi-Fi technologies provide the transfer of large amounts of data, however, the quality of voice transmission depends not so much on the channel width as on the reliability and continuity of packet transmission from the subscriber device to the access point.
Another aspect that also requires a technological solution is calls to emergency services via Wi-Fi Calling, since voice transmission over the Internet does not allow receiving data about the location of the subscriber.
Wi-Fi Calling in the World
There are still few examples of Wi-Fi Calling implementation – the full-fledged provision of this service is carried out in the USA by Sprint and T-Mobile operators, as well as by the British operator EE. On the way are American AT&T and Verizon, British Vodafone, Singaporean Singtel and other companies that have already announced plans to implement Wi-Fi Calling.
Different operators use the technology and provide the service in different ways. Subscribers of American operators can use Wi-Fi Calling, located anywhere in the world, while EE allows its customers to make calls via Wi-Fi-networks, only located in the UK. Operators and the prospects for new technology are evaluated differently. For example, Wi-Fi Calling has been available to EE subscribers since April this year, while VoLTE launch on the operator’s networks will be possible only by the end of summer. The leadership of the American AT&T last fall, in turn, announced that the company was in no hurry with the introduction of Wi-Fi Calling, considering this technology, first of all, to expand the capabilities of LTE networks in addition to VoLTE.
As for subscriber devices that support Wi-Fi Calling, their number is growing rapidly. If more recently they were limited to several models of smartphones, today they are offered by most of the main manufacturers: Samsung, Apple, LG, Alcatel, Nokia, Sony, ZTE, Microsoft.