Ok now you got my attention.
I am used to working with tcp/ip but not with 433 MHz wireless. How would such a setup look like? One arduino with both ethernet and 433 MHz module? Using the ethernet talking to a server and the wireless module to talk to the nodes?
Any tips on the communication between de basestation and the nodes?
That's what the links on reply #3 were about. Also, if you track down the datasheets
on the RFM12 and RFM22 transceivers, you'll see they are very sophisticated devices
with 100 configuration registers, and packet transmissions. There have also been
many threads on these in the Networking section of this forum.
Another popular transceiver is the nRF2401, but it operates at 2.4Ghz, and only has
an effective range of 10m or so, similar to low-power Bluetooth. IOW, forget it for
the discussion at hand.