What is the concept of network sharing in LTE, how it works and why it is introduced in LTE?

Question

How does it work actually and why it is introduced in lte network ?

Answer 1

As per my knowledge, network sharing in LTE signifies that an eNodeB can be shared among multiple operators. An eNodeB can broadcast up to 6 PLMNs within the system information block1.
While doing attach procedure UE checks it's home PLMN with the broadcasted ones, if plmn match succeed then UE proceed with further signalling and completes attach procedure if everything is successful.

This way, UE's belongs to different PLMN gets attached to different different MMEs through the same eNodeB.