Why Registration onto any technology is required?
Be it 4G yesterday or 5G today or 6G tomorrow main reason to register is to access any 5G services like accessing internet and registering onto IMS for VoIP(voice over IP) calls. All the components in these technologies respectively will act as a pipe to provide a path to outside world. Any device wanting to enter outside world require an identity called IP address which helps to navigate which is provided by specific components in technologies.
There are different registration types when it comes to 5G namely
- Initial Registration
- Mobility registration updating
- Emergency Registration
- Periodic Registration update
other registration as per spec
Initial Registration: this is when a device trying to register first time onto this AMF or when device powered on, or when device enters into 5G coverage
Mobility Registration Update: when device changes its tracking area or if there is a change in AMF or during mobility from 4g to 5g with existing PDU sessions
Periodic Registration Update: this is based on the periodic timer configured by the network and tries to keep device in registered in idle state as well.
Emergency registration: this is when trying to utilise emergency services like dialling 112.
Device indication of 5G capable to Network:
message_type REGISTRATION_REQUEST
5gs_registration_type
5gs_registration_type_value mobility registration updating
pdu_session_status
- psi_7 pdu session not supported
- psi_6 pdu session not supported
- psi_5 pdu session not supported
- psi_4 pdu session not supported
- psi_3 pdu session not supported
- psi_2 pdu session not supported
- psi_1 pdu session not supported
- psi_15 pdu session not supported
- psi_14 pdu session not supported
- psi_13 pdu session not supported
- psi_12 pdu session not supported
There can be cases where N1 is sent 1 but still not registered for 5G.
One case will be the SIM card capability, SIM is also a network provider property where they need to allow this profile into their network. IF incase this is a new entry which is not known to AMF most common rejection would be N1 mode not allowed. This requires backend provisioning from the operator at their database UDM(unified data access) similar to HSS in 4G
3GPP Spec 24.501
