NAS Elementary procedures for EPS Mobility Management

The main function of the mobility management sublayer is to support the mobility of a user equipment, such as informing the network of its present location and providing user identity confidentiality

A further function of the mobility management sublayer is to provide connection management services to the session management (SM) sublayer and the short message services (SMS) entity of the connection management (CM) sublayer.

All the EMM procedures can only be performed if a NAS signalling connection has been established between the UE and the network. Else, the EMM sublayer has to initiate the establishment of a NAS signalling connection.

Types of EMM procedures

• EMM common procedures
  
• GUTI reallocation
• Authentication
• Security mode control
• Identification
• EMM information
  
  
• EMM specific procedures
  
• Attach and combined attach.
• Attach.
• Detach and combined detach.
• Normal tracking area updating and combined tracking area updating (S1 mode only).
• Periodic tracking area updating (S1 mode only).
  
  
• EMM connection management procedures (S1 mode only)
  
• Service request.
• Paging procedure.
• Transport of NAS messages;
• Generic transport of NAS messages.