I would like to setup a wifi network where the users connects to an AP and then goes, for instance, downstairs and connect to another AP in the same network, and the user have not to re-enter the user credentials. Is it possible with Nomadix?
reply to blancolandau davidhoffman has it right, "roaming" as it's called is accomplished automatically when all APs in the network have the same SSID (and encryption key) but different channels.
The client radio will automatically switch to the next strongest, or least congested AP, usually without any disconnect or the end-user noticing it happened.
You can visually inspect that it is working by walking around with your laptop while running a utility like inSSIDer
This is not a function of Nomadix or any other network management/captive portal product - it is a function of correctly configured APs. For it to work flawlessly all APs should be of the same manufacture and firmware.
P.S. Nomadix is really icky, I've had to pull it out of customer's networks for capacity/load reasons, there are better products out there if all you are interested in is captive portal.