[mateuszbuda]

Do you have an idea what would be my external IP address? On my phone connected to a mobile network, I get assigned mobile IP address which is my external IP address. It's not attached to the SIM card because it changes when I reconnected. Is it handles by the BTS software? Do I get assigned an IP address and BTS communicates on my behalf using that address which comes from the mobile network operators pool?

[markus-k]

The LTE core assigns an IP address to your SIM card/UE. In the case of srsRAN, there's a simple CSV file mapping the IMSI to an IP address, but there are no limits on how complicated it can get.