5G NAS Mobility Management – 5GMM

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At 5GC, NAS Mobility Management (5GMM) procedures are responsible to keep track whereabouts of the UE, UE authentication and control integrity protection and ciphering. The 5GMM procedures also used by network to allocated temporary identities to the UE  such as 5G-GUTI and also request identity information such as SUCI and PEI from the UE. In addition, the 5GMM procedures provide the UE’s capability information to the network and the network may also inform the UE about information regarding specific services in the network.

5GMM Bullets

  • The 5GMM procedures can only be performed if a NAS signaling connection has been established between the UE and AMF
  • When no active connection, the 5GMM layer has to establishm NAS signaling by Registration or Service Request procedure
  • For downlink NAS signaling, when no active signaling connection, the AMF initiates a paging procedure to UE for Service Request
  • The 5GMM procedures works on underlying NGAP protocol between the gNB and AMF over N2 interface and RRC Protocol between UE and gNB to establish connectivity
  • 5GMM protocol works at UE level (per Access Type) where as 5GSM protocol works on a per PDU Session level
  • The 5GMM NAS signaling takes place between the UE and the AMF
  • Each of NAS Procedure is defined in 3GPP TS24.501

5GMM State Machine

5GMM state machine is managed seperated for UE and Network as per 3GPP specification TS 24.501. Below picture show the same.

  • 5GMM States at UE

  • 5GMM States at Network

Following is the types and list of NAS Message used 5GMM list of  basic 5GMM procedures:

  • 5GMM Specific Procedures
    • Registration
    • Deregistration
      • Deregistration request
      • Deregistration accept
  • 5GMM Connection Management Procedures
    • Service Request
      • Service request
      • Service Reject
      • Service Accept
    • Paging
    • Notification
      • Notification
      • Notification Update
  • 5GMM Common Procedures
    • UE configuration update
      • Configuration Update Command
      • Configuration Update Complete
    • Authentication
      • Authentication Request
      • Authentication Response
      • Authentication Reject
      • Authentication Failure
      • Authentication Result
    • Identity
      • Identity Request
      • Identity Response
    • NAS Security
      • Security Mode Command
      • Security Mode Complete
      • Security mode reject
    • NAS Transport
      • UL NAS transport
      • DL NAS transport

References:

  • 3GPP TS 24.501  5G;. System architecture for the 5G System (5GS)
  • 3GPP TS 29.518 5G System, Access and Mobility Management Services

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