Mobile Core

4G Mobile Core

The 4G Mobile Core, which 3GPP officially refers to as the Evolved Packet Core (EPC), consists of five main components.

• 1-3 runs in the Control Plane (CP)
• 4-5 runs in the User Plane (UP)

1. MME (Mobility Management Entity): Tracks and manages the movement of UEs throughout the RAN. This includes recording when the UE is not active.
2. HSS (Home Subscriber Server): A database that contains all subscriber-related information.
3. PCRF (Policy & Charging Rules Function): Tracks and manages policy rules and records billing data on subscriber traffic.
4. SGW (Serving Gateway): Forwards IP packets to and from the RAN. Anchors the Mobile Core end of the bearer service to a (potentially mobile) UE, and so is involved in handovers from one base station to another.
5. PGW (Packet Gateway): Essentially an IP router, connecting the Mobile Core to the external Internet. Supports additional access-related functions, including policy enforcement, traffic shaping, and charging.