What is LTE-EPC and its network nodes?
The Evolved Packet Core, or EPC, is the LTE or 4G core network. The EPC network is specified in 3GPP release 8. LTE is a packet-switched network exclusively. There is no voice circuit/truck reservation for a packet call. Earlier generations (3G or 2G) had both packet and circuit networks in the core network.
How does LTE differ from earlier generations?
A voice call uses ISUP-based circuit-switched signaling for voice transmission, and a data network uses a packet-based network for internet services. LTE belongs to the fourth generation of mobile communication, which brings more data speed to the mobile user. The Evolved packet core has reduced the hierarchy of network elements used in a data core to achieve high speed.
LTE EPC can connect to the non-3GPP access network, e.g., WiFi. This is one of the significant differences from past generations of mobile networks.
MME in LTE:
Evolved Packet core Network Components:
When a subscriber roams, it uses two types of core networks: a home network and a roaming network. MME is a node in the LTE network located in the roaming network. When a subscriber attaches to the LTE network, MME signals to the home network. MME does signaling with HSS in-home network over diameter protocol. S6a is an application interface for the 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. The interface between UE and eNodeB is wireless.
S-GW
This node manages data between eNodeB and PGW. S1-U interface between EURAN and SGW. S5 is an interface between PGW and SGW.
P-GW
This node is in the home network. Interface SGW and external PDN. Authenticates a mobile user for data and creates a PDP session. This corresponds to GGSN in 3G/2G.
HSS:
A central database for 4G subscribers. Authenticate a user based on authentication vectors. The AUC generates vectors. Store the EPS subscription profile for data.