What is MME In LTE? 

The MME is full form is the Mobile Management Entity. MME is the network node in the LTE-EPC network on the roaming network. MME connects to the UE via eNodeB. Towards the core network, MME connects on various protocols. All connectivity over the wire. In this tutorial, we will explain the interfaces with MME along with network management procedures.

S1AP Interface.

The signaling interface between MME and the eNodeB.  A UE attaches to the network using S1Ap protocol procedures.

S11 Interface:

The S11 interface is a GTP-CV2 based Interface with the SGW. SGW does signaling with the PGW in-home network over the s5/S8 interface.  SGW set up the tunnel with PGW. The eNodeB sends user data packets to the SGW using the GTP-U data plane protocol.

S6a Interface:

This is an interface with the HSS. HSS is the node that holds the subscription data for a subscriber.  The HSS may be co-located with the AUC for the 4G authentication.  S6a uses a diameter protocol over SCTP.

T6a interface:

The T6a interface is a diameter protocol interface with the SCEF for the Non-IP data delivery in the IoT network.

UE Attach procedure in MME :

Till now we have described key Interfaces of MME.  Here we will describe a basic attach procedure to understand the basic functionality of the MME in LTE.

When UE switches on, it sends an Initial UE message with Attach request for PDN connectivity to the MME.  MME does a send authentication info procedure with the HSS/AuC for authentication vectors.  Same time MME also does the Update Location procedures for subscriber information.

MME sends the authentication request to the UE. If UE verifies that vectors are good. UE sends an authentication response.  After authentication. MME sends a create session request to the SGW over the S11 interface.

To create a session success response, MME sends an Initial Context setup request with the GTP-U plane address of SGW along with other parameters. If UE sens the Initial Context Setup Response. And then Attach accept.