How does VoWIFI work in 5G and 4G?

  • My friend: Hi Ibrahim, I have a problem and I wish you can help me to solve it.

    • Me: Please, tell me.
  • My friend: I was trying to get the VoWIFI (Voice over WIFI) stats from the OSS at the radio site level, but I was not able to find any stats at all. Where can I find it?

    • Me: Actually, I don’t want to shock you, but you will never find it at the radio site level in the OSS stats.
  • My friend (staring at me): Really, why?

    • Me: To answer this question, you need to understand how the VoWIFI is working.
  • My friend: So, how does the VoWIFI work in 5G and 4G?

    • Me: Simply, you need to enable the VoWIFI option in your phone and also at the same time, the operator which you are using should support VoWIFI in its network. Then, if you made a voice call while your phone is connected to the WIFI network of any WIFI provider, the voice call would be using the WIFI signal then routed via the internet to the operator you are using or to be more specific to the ePDG (enhanced Packet Data Gateway) in case of 4G networks and N3IWF (Non-3GPP Interworking Function) in case of 5G networks and both act as a gateway between the WIFI provider network and the operator network, and this connection should be secure, so it is using IPSec tunnel between the UE and the ePDG/N3IWF. Then from ePDG/N3IWF towards the core network till it reaches the IMS at the end and so the VoWIFI traffic didn’t pass through the eNB or gNB and hence you won’t have stats for the VoWIFI from the OSS at the radio site, but you can get it from the core side. Please check the below figure.
  • My friend: But what is the advantage of VoWIFI?

    • Me: Usually, inside the buildings and in deep indoors, the 4G/5G signal is weak and this may affect the voice quality, while if the WIFI signal is strong, then you’ll have a better voice quality compared to the cellular one. Also, note that handover can be done between the VoWIFI and VoLTE for example, so you have a voice call continuity.
  • My friend: Thank you very much, you made it very clear.

    • Me: You are most welcome.

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