core network architecture

The architecture of a core network is complex and involves several elements that work together to ensure the smooth functioning of the network.

1. Mobile Switching Center (MSC):
   • The MSC is a central component of the core network in mobile telecommunications. It is responsible for call routing, call setup, and release functions.
   • MSC connects to Base Station Subsystem (BSS) in GSM networks or NodeB (or eNodeB) in the case of 3G and 4G networks.
2. Home Location Register (HLR):
   • The HLR is a database used for storage and management of subscriber information. It contains details such as user profiles, current locations, and service subscriptions.
   • When a mobile user roams into a new location, the HLR is queried to retrieve the necessary information for call routing.
3. Visitor Location Register (VLR):
   • The VLR is a temporary database that stores information about subscribers currently within the jurisdiction of the MSC that it serves.
   • When a mobile user enters a new location area, the VLR queries the HLR to obtain the subscriber information.
4. Authentication Center (AUC):
   • The AUC is responsible for subscriber authentication and encryption key generation to ensure secure communication between the mobile device and the network.
   • It prevents fraudulent access and eavesdropping on the network.
5. Equipment Identity Register (EIR):
   • The EIR is a database that stores information about mobile devices, including their International Mobile Equipment Identity (IMEI) numbers.
   • It helps in identifying stolen or unauthorized mobile devices.
6. Gateway MSC (GMSC):
   • The GMSC is responsible for interfacing with other networks (such as the Public Switched Telephone Network - PSTN) and routing calls to the appropriate MSC.
7. ** Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN) (for 2G/3G networks):**
   • In mobile networks with GPRS/EDGE or 3G technologies, SGSN and GGSN handle packet-switched data services.
   • SGSN manages the mobility of the user within the network, while GGSN acts as a gateway to external packet-switched networks (like the internet).
8. Packet Data Network Gateway (PDN-GW) and Serving Gateway (SGW) (for 4G LTE networks):
   • In 4G LTE networks, the SGW and PDN-GW handle the routing of data packets.
   • SGW manages the mobility of the user within the LTE network, while PDN-GW serves as the interface between the LTE network and external packet data networks.
9. Mobility Management Entity (MME) and Serving Gateway (for 5G networks):
   • In 5G networks, MME manages mobility and connection establishment, while the Serving Gateway routes data packets.
10. User Plane Function (UPF) (for 5G networks):

• UPF is responsible for the user data forwarding in the user plane. It handles the routing and forwarding of data packets.

11. Home Subscriber Server (HSS) (for IMS - IP Multimedia Subsystem):

• In networks that support IMS, the HSS stores subscriber information and provides services like voice over IP (VoIP) and multimedia services.

The interactions between these elements involve signaling and data transfer protocols, such as Signaling System 7 (SS7), Diameter, and the Internet Protocol (IP), depending on the generation of the network. Additionally, advancements in technologies like Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) are influencing the architecture to make it more flexible and scalable.