How, besides the mac address, could the wifi router identify the device?

Question

Computer networks

There is, for example, a router. You can even without a password. How could he identify that this particular device is the same as "at four-twenty last morning"? And if the mac has changed (according to mac it is generally unacceptable, we completely exclude it from the identification process)?
There are two cases of interest:

• The device connected to the network and began to receive and transmit. Let's say we don't go into protocols higher than tcp / udp.
  
• What can be done at the connection stage, when there was no traffic yet?
  

The question is more theoretical and does not concern specific routers / firmware. Be there at least IBM Watson, trained devices to distinguish between the frequency response of the signal (we don’t consider this :)

Answer 1

I would advise you to read about 802.1X

Answer 2

It is better to put NAC in this case.
In the second case - nothing. How do you tell a person by their voice if they haven't said a word?