How to use Voice Over WI-FI on my Samsung phone?

VoWiFi is a complementary technology to VoLTE and utilizes IMS technology to provide a packet voice service delivered over IP via a Wi-Fi network. Where possible, VoLTE calls may be seamlessly handed over between LTE and Wi-Fi and vice versa.

If the device has weak 4G signal and there is available Wi-Fi network, then the device will camp on Wi-Fi and the VoWiFi icon will appear on the notification bar.

•  Calls sound better.
• Calls connect more quickly.
• VoWiFi alleviates indoor coverage problems (Calls without any mobile signals).

Operator have some requirements as below:

- No Wi-Fi preferred option in Wi-Fi calling option.
- If customer in location where coverage of 4G, Wi-Fi, 3G/2G exist:

 • The device shall prefer VoLTE.
 • And in case 4G signal is weak, device shall prefer VoWiFi (preferring IMS rather than 3G/2G CS).
 • And if both 4G and Wi-Fi signals are weak, device shall camp on 3G/2G.
- There is a timer (120S) to avoid Ping-Pong between VoLTE and VoWiFi,

o Ping-Pong:

•  It is a timer avoids ping-pong between LTE and Wi-Fi with signal quality.

Device establishes IMS connection to LTE if LTE is available.

If signal quality of LTE degrades or LTE is lost, device starts ping-pong timer and triggers handover of the IMS connection to Wi-Fi.

Then device does not trigger handover of the IMS connection to LTE until the timer expires.

After timer expires and if LTE is available, device triggers handover to LTE.