LTE Network: Understanding MME in EPC Network

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MME

Introduction to MME (LTE) in EPC Network:

The network architecture of LTE EPC Network consists of a many different network entities. Each network entity has a distinct role in the LTE network. In this article, we’ll cover the roles of Mobile Management Entity (MME) and its connectivity with in EPC Network.

Mobility Management Entity (MME):

MME is the main “control” node of LTE Access Network. It’s designed to function as the main control node and provides the following functionalities in the LTE EPC Network:

  • Serving GW (S-GW) for a UE during the Initial ATTACHMENT procedure,
  • Provides the ‘handover’ functionality between LTE networks,
  • Responsible for tracking and paging procedure of UE (in Idle mode) and to,
  • Provide the activation and deactivation of channel bearers on behalf of a UE.

Furthermore, MME also interacts with HSS (Home Subscriber Substation) through the S6a logical interface and provides the end-user authentication between them.  Subsequently, ensuring roaming control and restrictions of UEs over an entire (PLMN) network.

MME also provide the Control-plane functionality for mobility between LTE and 2G/3G access networks.

In a typical LTE EPC Network, the selection of MME is based on the network topology – according to the location that a UE is in the network cell.

If several MMEs serve a particular area, then the selection of MME is based on the following two concept:

  • The eNodeB is responsible for the selection of an appropriate MME at UE ATTACH procedure when no routing to an MME can be determined from the information provided by the UE. Thus, the MME selection function is located only in the eNodeB.
  • Load Balancing parameters (for example the weight factor in the eNodeB) by allowing the eNodeB to divert new UEs to other MMEs in the pool, thus ensuring that the MME in a pool are properly balanced during normal conditions.

Mobility Management Entity is also responsible for Non-Access Stratum (NAS) signaling and also acts as a termination point of NAS Signaling. Thus providing a ciphering and data encryption capabilities and handles the Lawful Intercept (LI) messages related to signaling.

 

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