Voice over Wi-Fi (VoWiFi), also known as Wi-Fi Calling, allows you to make and receive phone calls over a Wi-Fi network instead of the cellular network.
Here's a breakdown of how it works:
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Registration and Data Bearer: First, your VoWiFi-enabled device needs to register with the mobile network operator (MNO) and establish a default data connection. This is crucial for security and authentication.
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Wi-Fi Connection and IP Address: Your phone connects to a Wi-Fi network and obtains an IP address. This effectively treats the Wi-Fi network like a mini-internet service provider for your phone calls.
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ePDG Selection: Your phone then selects an evolved Packet Data Gateway (ePDG). The ePDG acts as a secure tunnel between your phone on the Wi-Fi network and the mobile operator's core network. This selection is typically based on static IP configuration or DNS lookups. Think of it as a secure gatekeeper.
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IPsec Tunnel Creation: An Internet Protocol Security (IPsec) tunnel is established between your phone and the ePDG. This encrypts all voice and signaling traffic, ensuring privacy and security. IPsec helps protect your calls from eavesdropping.
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IMS Core Network: The ePDG connects to the MNO's IP Multimedia Subsystem (IMS) core network. The IMS handles call control, routing, and other telephony functions. Essentially, the IMS is the brains behind the call, handling the setup and management.
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Call Routing: The IMS routes your call just like any other call, whether it's to another mobile phone on the cellular network, a landline, or another VoWiFi user.
In simpler terms:
- Your phone finds a Wi-Fi network and gets an IP address.
- It securely connects to the mobile operator's network via the internet (through the ePDG).
- Your call is then routed like any other phone call, using the mobile operator's infrastructure.
Key Benefits of VoWiFi:
- Improved Indoor Coverage: VoWiFi helps you make calls in areas with poor cellular coverage, such as inside buildings with thick walls.
- Cost Savings: In some cases, VoWiFi calls may be cheaper than cellular calls, especially when roaming internationally (depending on your carrier's policy).
- Seamless Transition: Many phones can seamlessly switch between Wi-Fi and cellular networks during a call, ensuring call continuity.
