Evolved Packet Core or EPC is the core network for LTE or 4G.  3GPP release 8 have specifications for EPC network. LTE is the packet switched only network. Packet only means , there is no voice circuit/truck reservation for a call. Earlier generation (3G or 2 G), core network have both packet and circuit network.  A voice call use ISUP based circuit switched signaling for voice transmission and data network uses packets based network for internet services. LTE is belongs to the fourth generation for mobile communication. Which brings more data speed to the mobile user. To achieve high speed,  Evolved packet core has reduces the hierarchy of network elements used in data core.

LTE EPC can connect to the non 3GPP access network e.g WiFi.  This is one of the major difference from last generations of mobile networks.

Evolved Packet core Network Components:


When a subscriber roams. It uses two types of core networks , one is home network and another is roaming network. MME is a node in LTE network located in roaming network. When a subscriber attaches to the network in LTE, MME does signaling to the home network. MME does signaling with HSS in home network over diameter protocol.  S6a is application interface for diameter protocol between HSS and MME.

MME does authentication and location management with the home over a wired interface. On another side it connects to the UE via eNodeB. Interface between UE and eNodeB is wireless.


This node manages data between eNodeB and PGW. S1-U interface between EURAN and SGW. S5 is interface between PGW and SGW.


This node is in home network. Interface SGW and external PDN. Authenticates a mobile user for data and create a pdp session. This is corresponding to  GGSN in 3G/2G.


A central data base for 4G subscriber. Authenticate a user based on authentication vectors. Vectors are generated by the AuC.  Store EPS subscription profile for data.

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