Can Android tethering provide net access through another fixed WIFI AP rather than mobile data network?

Question

When you enable the standard tethering on Android, can you specify/by default does it use an existing WIFI connection to transfer traffic if possible? For example, at home I might have a WIFI network named home_WIFI, which I don't want strangers connecting to for security reasons. On the other hand, I'd like to let set up a publicly accessible access point (my Android phone) by the name of say public_net which they can connect to. What I would then like is for my Android phone (public_net) to route any traffic through home_WIFI behind the scenes, rather than using the expensive/slow mobile data.

Does anyone know if Android already does this/can be made to do this? When I setup tethering, I get a tethering active notification, but am unsure whether it's defaulting to WIFI or mobile data behind the scenes...

Answer 1

Generally speaking, one wireless radio can communicate with only one wireless network.

Therefore:

If your phone is configured to connect to 'home_WIFI', that's the wireless network its radio is attached to, and it'll get its internet access there.

If your phone is configured to tether for 'public_net', that's the wireless network its radio is attached to, and it's getting its internet access from the cellular network.

I don't expect you'll find any phone with the multiple WiFi radios necessary to perform the function you're asking for.