It is likely that without an IP address your cell phone couldn't work. Why?

 Because the microwave towers have to recognize the identity of your phone in order to send it information packets (sounds and texts) and they have to identify the other phone you are talking to all over the world. So, a combination of your IP address and GPS used to find that address no matter where it's actual location is on earth is necessary for any cell phone calls to take place anywhere on earth. Also, when you move in a vehicle usually between towers as you travel sometimes there are blips in communication as that communication tower passes off that transmission between towers as you move usually in some kind of vehicle at higher speeds or any speed.