Bharti Airtel and Reliance Jio have started enabling WiFi calling -- routing the call via the user's WiFi network even if cellular network is available -- across the country on selected handset models.\n\n\n\nModels for which WiFi calling is being enabled include those from Apple, OnePlus and Samsung.\n\n\n\nOther models are likely to be supported going forward.\n\n\n\nThe feature is automatically turned on in some cases, while in some phone models, it has to be turned on manually.\n\n\n\nOnce enabled, the 'network name' will start showing 'Airtel Wifi' or 'Jio Wifi' instead of 'Airtel' or 'Jio', indicating that calls are being routed via the WiFi network.\n\n\n\n\n\n\n\nTECHNOLOGY\n\n\n\nThe technology behind the service is pretty simple, and has been available for a long time now.\n\n\n\nBasically, it converts the voice signal into Internet Protocol (IP) instead of the regular 2G or 3G format, and sends it to Airtel or Jio's servers via the Internet (using the WiFi connection). \n\n\n\nBesides the voice data, the stream also contains the phone number of the caller and the called person.\n\n\n\nAirtel and Jio collect the data coming to their servers and send it to the phone number indicated, using the regular cellphone network.\n\n\n\nThe WiFi service does not have to be from the same company that provided the SIM. It can be from any provider, such as You Broadband, Hathway or the local cable operator.\n\n\n\nThe person receiving the call will not see anything odd, and will continue to see your phone number on their caller ID, even though the call is being made over the Internet.\n\n\n\nThe call will be billed at the same rate as the regular voice call.\n\n\n\nEven though the technology is pretty old, Indian operators had not started offering this feature till now due to two reasons.\n\n\n\nFirst, these operators would have to set up servers connected to the internet to listen to such voice calls and admit them into their cellphone network. Because of their focus on rolling out 4G, this feature -- known as Voice over WiFi or VoWiFi -- was not considered to be a big priority.\n\n\n\nThe second reason is that in many cases, their own networks were simply not ready. To do this requires the telecom operator to have a fairly modern core network that supports ubiquitous conversion of traditional voice format to IP format and vice versa. It is only with the introduction of 4G -- which runs only on IP technology -- that many Indian operators upgraded their core network to support such technology.\n\n\n\nADVANTAGES\n\n\n\nThe biggest advantage of having WiFi calling or VoWiFi is that you no longer have to go to the balcony or near a window to ensure clear reception and good audio quality. VoWiFi works well wherever the WiFi signals are good. \n\n\n\nMoreover, the quality of voice is also far better than what you get on a normal 2G or 3G call. However, if the other person is getting his\/her call on a 2G network, then both persons involved in the call will get only a 2G-quality voice experience.\n\n\n\nOn the other hand, if both persons are on VoWiFi or VoLTE, the quality of the voice will be very high.\n\n\n\nSecondly, WiFi calling is also likely to reduce instances of call drops. Traditional GSM calls are prone to high levels of call drops due to interference and fluctuation in cellular signals.\n\n\n\nHowever, given that WiFi signals are stable -- as they are coming from your own house -- chances of call drops are very very low.\n\n\n\nAt present, only Reliance Jio and Bharti Airtel have enabled these services -- and that too, only for some brands and models.\n\n\n\nBoth have been testing these services for several months.\n\n\n\nIt is expected that the service -- which is currently available on nearly all telecom circles -- will be made ubiquitous in coming weeks by extending it to more and more Android phones.