How ENB will find out whether UE supports MIMO or not?

Question

Does LTE network send any specific message to UE so that UE come to know network supports IMS call ?
Or
Does the LTE network broadcast information such as "it does not support IMS call" ?

Answer 1

During the attach procedure, UE radio capability enquiry procedure is triggered by eNodeB if MME does not send "UE radio capability" IE in the Initial Context Setup Request message. This "UE radio capability" IE contains the information whether UE supports MIMO or not. And if it supports MIMO then in what combination it supports.
In short, this information eNodeB receives either through the initial context setup (ICS) request or UE capability information message.