Voice over Wi-Fi has been of interest to operators ever since the move toward IP networks began, but Apple created a new sense of urgency when it announced support for VoWi-Fi as part of iOS 8. Since that time, all four major U.S. carriers have launched or announced plans to launch VoWi-Fi support.
Meanwhile Wi-Fi-first operators are offering low-cost wireless plans that rely primarily on Wi-Fi for voice and data, and move users to cellular when Wi-Fi is weak or unavailable. Republic Wireless, Scratch Wireless and Google Fi all follow this model.
“Wi-Fi-first and voice over WiFi services … need more than just Wi-Fi authentication,” said Robert Gazda, senior director of technical solutions at InterDigital. “They, typically, require integration with the mobile packet core (i.e. Wi-Fi integration).”
Gazda said that VoWi-Fi typically requires EAP-SIM authentication for the IPsec tunnels that connect devices to the mobile core when the Wi-Fi access points are not carrier-operated. At this time only a handful of smartphones support this.
VoWi-Fi relies on an IP multimedia subsystem core, an investment that not all carriers are in a position to undertake. Cloud-based IMS gives carriers a way to offer VoWi-Fi without investing in an IMS core. Interop Technologies said it has seen strong interest in its hosted IMS solution from regional operators.
“An IMS core is a very expensive and complicated thing to implement, even for the largest of the carriers,” said Interop Technologies CTO Steve Zitnik. “By removing some of the complexities and obfuscating the complexity of the solution, Interop can allow our operators to move quickly down that path.” Interop’s solution is integrated with the operator network for billing and for 2G/3G fallback.
Not all VoWi-Fi services require integration with a cellular network. Cablevision has launched a service called Freewheel that does not include a fallback to cellular; the cable operator is promoting the service as a fit for those who live, work and play within range of Wi-Fi.
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