What Is the Core Network?

The core network is the central part of a telecommunications system, such as 4G LTE, 5G, or fixed-line networks. It connects user devices (smartphones, PCs, etc.) to external networks (the Internet, other telephone networks) and is responsible for subscriber management, authentication, and service control.

For example, when a smartphone tries to access the Internet, it sends a connection request to start a packet data session (Attach/Session Request) to the nearest base station. The base station forwards this request to the core network, which interprets it as a request to establish a new data session and allow the device to communicate with the external Internet.

The core network then verifies whether the device is a legitimate subscriber. Specifically, it uses the IMSI and Ki stored in the USIM card to perform the authentication process, while also checking the subscriber’s plan, data limits, and available services.

Once authentication is successful, the core network approves the request, allowing the device to access the Internet. The connection is then established to the external Internet through a gateway (e.g., PGW in LTE, UPF in 5G).

In short, the core network is the central area of the system that handles authentication, control, routing, policy enforcement, and charging.