VoWiFi

VoWiFi, short for Voice over Wi‑Fi, is a technology that enables voice calls to be placed and received over a Wi‑Fi network using a carrier’s cellular core network. It typically relies on the IP Multimedia Subsystem (IMS) and SIP signaling to carry voice traffic, and is usually offered as part of a carrier’s Wi‑Fi Calling service. VoWiFi allows users to retain their mobile number and is designed to work when cellular coverage is weak but a connected Wi‑Fi network is available.

Operation and characteristics: When a device registers with the carrier over Wi‑Fi, voice calls can be routed through the Wi‑Fi path while still using the operator’s voice service. In many deployments, calls can be handed over to the cellular network as needed when moving out of Wi‑Fi coverage. Emergency services support (such as e911 in the United States) is provided where available, though location data and requirements may vary by region, and users may need to register a default emergency location with their operator.

Requirements and deployment: VoWiFi requires a compatible smartphone and operating system version, a carrier that supports the service, an active SIM with VoWiFi enabled, and access to a reliable Wi‑Fi network. Users may need to enable VoWiFi in device settings and choose preferred calling options (Wi‑Fi first or cellular first).

Benefits and limitations: VoWiFi can improve indoor coverage and call reliability in areas with weak cellular signals, enabling seamless calling and potentially faster call setup. Limitations include dependence on Wi‑Fi quality, varying regional support, device and carrier compatibility, and inconsistent emergency-service handling across networks and locations.