Telecommunications Blog

EPS to EPC

   A key feature of the EPS is the separation of the network entity that performs control-plane functionality (MME) from the network entity that performs bearer-plane functionality (SGW) with a well defined open interface between them (S11).


LTE S11: -

    An IP interface between MME and SGW! GTPv2 is the protocols used at the application

   The picture shows main network elements, interfaces and the protocols used in LTE.
The main interfaces in LTE are Uu, S1-MME, X2, S1-U, S11 and S5.

LTE Uu : -
    This is the air interface between UE and eNB. LTE layer 1 is dealt with later. RRC is the protocol that is used for communication between UE and eNB. Above RRC there is a NAS layer in UE. This NAS layer terminates at MME and eNB shall silently pass the NAS messages to MME.

LTE S1-MME: -

    eNB and MME communicate using this IP interface. S1-AP is application layer interface. The transport protocols used here is SCTP. (Stream control transmission protocol).