The EPC is the latest evolution of the 3GPP core network architecture. The Evolved Packet Core (EPC), the core network of the LTE system.
EPC was first introduced by 3GPP in Release 8 of the standard.
Good Reads on Evolved Packet Core (EPC)
It was decided to have a “flat architecture”. The idea is to handle the payload (the data traffic) efficiently from performance and costs perspective. Few network nodes are involved in the handling of the traffic and protocol conversion is avoided.
HSS : Home Subscriber Server is a database that contains user-related and subscriber-related information.It is based on the pre-3GPP Release 4 – Home Location Register (HLR) and Authentication Centre (AuC).
Serving GW:The Serving GW is the point of interconnect between the radio-side and the EPC. As its name indicates, this gateway serves the UE by routing the incoming and outgoing IP packets.
PDN GW: The PDN GW is the point of interconnect between the EPC and the external IP networks. These networks are called PDN (Packet Data Network), hence the name. The PDN GW routes packets to and from the PDNs.
MME:The MME (for Mobility Management Entity) deals with the control plane. It handles the signalling related to mobility and security for E-UTRAN access.