[konstruktors]

It does use the built-in WiFi to connect to a WiFi network created by the mobile modem I placed at the neighbours house which has a permanent power supply.

I considered using a mobile USB modem attached directly to the Pi but that requires extra effort keeping it connected with something like a cron task that pings 8.8.8.8 and restarts the connection if there is no response.

[mtw]

ok, that makes sense. I thought it connects to a 3G/LTE network for internet connection. There are a few Raspberry HAT that offers this -- although that would be extremely costly for a live video feed