Hello Vimal, as far as I know assignment of static or dynamic IP is part of subscription. Long time back, I worked in S6a interface i.e. the interface between MME and HSS. When an UE does attach to MME, it fetches APN subscription data from HSS by using the Update Location Answer message. The Update Location Answer message carries an AVP "Subscription-Data" which in turn carries "APN-Configuration-Profile".
If you go into depth of this AVP, you will find "Served-Party-IP-Address " . If user is subscribed for static IP address then this AVP will be present and network will assign the subscribed IP address.
Usually, when an device want to become server, it prefers to have static ip address. Please correct me if I am wrong.