Registration Management is used to register or deregister UE to the network and create a user context in the network.
We know that UE needs to register to the network to get the services from the network.
There are 2 RM states used in UE and AMF.
1. RM-DEREGISTERED
2. RM-REGISTERED
Below image shows the state transition between the 2 states in UE and AMF.
1. RM-DEREGISTERED
1. In RM-Deregistered state UE is not registered to the network.
2. AMF will not have any context of UE.
In this state UE will below steps:
1. Try to register with selected PLMN during initial registration.
2. If the registration is rejected, then UE will remain in this state.
3. UE will move to RM-Registered state, upon receiving Registration Accept.
In this state AMF will perform below steps:
1. AMF will accept the initial registration and enter RM-Registered state for UE.
2. If the registration is rejected, then it will remain in RM_DeRegistered state.
2. RM-REGISTERED
1. In RM-Registered state UE is Registered to the network.
2. In this state UE will get the services from the network.
3. AMF will have context of UE.
In this state UE will perform below steps:
1. Perform Mobility Registration Update procedure of there is a change is current TAI.
2. Perform Periodic Registration Update procedure when periodic update timer is expired.
3. Perform a Mobility Registration Update procedure to update its capability information
4. If UE does not want services of the network, then perform Deregistration Procedure and enter RM-Deregistered state.
In this state AMF will perform below steps:
1. When applicable, perform accept or reject registration requests.
Source TS 23.501
