2G and 3G network architectures process and switch voice and data through two separate sub-domains: circuit-switched (CS) for voice and packet-switched (PS) for data. Evolved Packet Core unifies voice and data on an Internet Protocol (IP ) service architecture and voice is treated as just another IP application. This allows operators to deploy and operate one packet network for 2G, 3G, WLAN, WiMax, LTE and fixed access (Ethernet, DSL, cable and fiber).
The key components of EPC are:
- Mobility Management Entity (MME) - manages session states and authenticates and tracks a user across the network.
- Serving Gateway (S-gateway) - routes data packets through the access network.
- Packet Data Node Gateway (PGW) - acts as the interface between the LTE network and other packet data networks; manages quality of service (QoS) and provides deep packet inspection (DPI).
- Policy and Charging Rules Function (PCRF) - supports service data flow detection, policy enforcement and flow-based charging.
The standards for EPC operation were specified by an industry trade group called the Third Generation Partnership Project (3GPP) in early 2009. EPC is the core component of Service Architecture Evolution (SAE), 3GPP's flat LTE architecture.
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