AMF

Technical Explanation

In the 3GPP 5G Service-Based Architecture (SBA), the AMF serves as the primary entry point for control plane signaling from the UE via the N1 interface and the gNodeB via the N2 interface. It acts as the 5G successor to the LTE MME (Mobility Management Entity), but with session management duties decoupled into the SMF. AMF handles connection management, registration management, reachability management, mobility management, NAS security (integrity protection and ciphering), authorization, and access authentication coordination with AUSF/UDM.

Key Functions

• Registration and Connection state management (RM-REGISTERED, CM-CONNECTED)
• Termination of User Equipment (UE) NAS signaling over N1
• Termination of Radio Access Network (RAN) control plane interface over N2 (NG-C)
• NAS ciphering, integrity protection, and security context distribution
• Mobility management (handover coordination, tracking area updates, paging)