eli5 how international calls work?


Just made a mobile to another mobile from Australia to UK and was amazed by how clear and non laggy it was. How does the signal get sent back and forth from one side of the world to the other? Satellite or cable? Radio or fibre optic?

In: 43

Why are the two other comments so similar?!

Edit: They have been deleted now. They were eerily similar, like something ChatGTP would write 🙂

If it was a clear call it was a VoLTE end-to-end call. VoLTE is a flavor of VoIP (Voice over Internet Protocol). Your call most likely went through the same route as regular IP packets go between Australia and UK — submarine fiber optics cables. It is possible your carrier paid for a better than regular quality of IP transmission which resulted in fewer packets lost and delayed. How was the quality compared to a Whatsapp call?

The same way that you can load a webpage hosted in a server on the other side of the world without much latency. Your phone connects to a radio tower with a base station. That base station is connected to a core network by some combination of Fibre, copper cable, and radio waves.

Once your phone call reaches the core network, it will work out which international partner the call needs to be routed to (we call these interconnects) and sends the call to that partners network. This is most likely by undersea fibre but it could be other forms of connectivity too.

Once it’s in the partners core network, the process happens in reverse to get to the phone of the person you’re calling. It would be unusual for satellites to be involved these days, but it’s certainly possible. Phone calls do not use much data and so you get low latency reasonable quality even half way across the world