MSC association in 4G Network

MSC association in the 4G Network refers to the association between the MME (Mobility Management Entity) in 4G network and the MSC (Mobile Switching Center).

The MSC exists in the 2G/3G Circuit-switched (CS) core network. And it is the node that is responsible for handling the voice calls and the CS services.

When the UE camps in the 4G Network, and the UE needs to initiate or receive a voice call, it may need to "fallback" to the 2G/3G network. So that the UE can use the CS services.

In this case, the MSC association is used. So that the UE temporarily fallback to 2G/3G network, and connects with the MSC that is associated with the MME. This occurs in order for the UE to initiate or receive the voice call.

And then after the UE finishes the voice call, it can "re-attaches" again to the 4G network.