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UE needs to register to the network to get the services from the network.
Below are the different registration types:
1. Initial Registration
2. Mobility registration update in CM-CONNECTED and CM-IDLE state.
3. Periodic registration update
4. Emergency registration.
Registration Process:
1. gNB will select AMF based on 5G-GUTI or if 5G-GUTI is not available, it will select preferred AMF.
2. After that, gNB will forward registration request to AMF piggybacking on NGAP Initial UE message.
3. AMF will send identity request message to get SUCI from UE.
4. AMF will start Authentication procedure with AUSF and UDM.
5. AMF will get Mobility Subscription data, SMF selection data, UE context in SMF data by using Nudm_SDM_Get.
6. AMF will then apply the policy by communicating with PCF.
7. After that Registration Accept message will be sent to UE.