How do I detect that a signal is a WIFI signal and not noise

I am able to view the RF spectrum currently but how do I differentiate between a WIFI and noise signal?

WIFI looks like this:

../imgqa/eboard/Antenna/rf-ujsnuifofjx.jpg



and noise looks like...noise

../imgqa/eboard/Antenna/rf-aeqifiag5dm.gif

If I have WIFI signal and noise transmit in the air, what will their results be when I performed the demodulation?

Also, how do their constellation plot look like?