5G IV Flashcards
Describe in as much detail as possible the Registration procedure (UE becomes registered)
UE send RRC Setup Complete (“Registration Request”)
gNB select AMF
gNB send “Registration Request” to AMF
AMF request and receive UE identity via NAS message
Execute NAS Authentication and Security
AMF communication with UDM
AMF select PCF and contact PCF for policies
AMF SMF (Session update)
Registration accept/complete (UE registered)
Describe in as much detail as possible the AMF selection procedure (AMF is selected during registration) AMF is selected with assistance from the NSSF
Initial UE message (Registration Request)
UDM selection and get slice selection data from UDM
Querying the NSSF using UE identity
NRF gives network location to AMF
Direct: AMF forward message to target
Indirect: AMF forwards the message back to the gNB to “restart” the procedure with the target AMF
Describe in as much detail as possible the UE initiated de-registration (UE becomes unregistered)
UE triggers deregistration using NAS message
AMF triggers context release in SMF.
SMF notifies all the UPFs to release the sessions associated with the specific UE.
SMF-PCF policy association is terminated.
SMF unsubscribes to the UDM events
AMF-PCF policy association is terminated.
Deregistration is transmitted to the UE
Describe in as much detail as possible the Network initiated de-registration (UE becomes unregistered)
UDM sends trigger to AMF to start de-registration
de-registration request forwarded to UE
Same procedure as the UE triggered de-registration.
Describe in as much detail as possible the Service request procedure (UE gets connected)
UE requests activation
AMF receives activation request and forwards to SMF
UPF receives indication to update UE session with an active uplink
AMF updates mobility context of UE and initiates radio link connection establishment
SMF updates downlink for UE.
All buffered data packets are sent to UE
Describe in as much detail as possible the Network triggered service request (UE gets connected)
Pre-requisite: UE is registered and in idle state
Downlink data is received by UPF on data path
A notification is sent to the SMF that downlink data became available
A notification is sent by the SMF to the AMF that the UE needs to be activated
Paging messages are sent to all the gNBs in the given tracking area
UE initiates the UE triggered service activation procedure
Describe in as much detail as possible the UE Reachability request procedure
NF subscribes to events on the UE Reachability
NF is notified on UE reachability change
Describe in as much detail as possible the UE triggered session establishment
UE requests establishment of a data session to AMF
AMF wants to find out whether a session context is available for the given UE
Session is authenticated and authorized
PCF decides on the policies for the new session (optional)
UPF is selected.
An initial session creation is sent to the UPF in case no session was previously established.
RAN session is established
A downlink data session is also established
Describe in as much detail as possible the SMF selection procedure
AMF queries the NSSF which SMF to use
AMF queries the NRF with the information from the NSSF which is the network location of the given SMF
Describe in as much detail as possible the Session establishment with domain network authentication
A second authentication is requested from the special data network
The authentication request is forwarded to the UE
The UE responds to the authentication with the specific requested information
The rest of the PDU session is established as expected
Describe in as much detail as possible the Application Function Influence on User Plane configuration
Updating the information in the user data repository
Policies to update the data path are transmitted
User plane is reconfigured
Describe in as much detail as possible the Inter NG-RAN handover
Preparation phase:
i. The UE is associated with the Source gNB and the data path
ii. A decision of a potential handover
iii. A selection of a target AMF is executed.
iv. SMF is notified to start the data path preparation
v. A new data path is established if a new T-UPF is needed
vi. The target gNB is notified on the potential handover and that the data path will be established through TUPF and UPF (PSA)
vii. A redirect data path is established.
Execution phase
i. S-AMF transmits the handover command towards the UE. Preparation phase was completed
ii. Downlink data packets are already redirected to the target gNB
iii. Handover is executed at RAN level
iv. Uplink has the optimized path, downlink is still redirected
v. Downlink data path is re-established
vi. A new registration procedure may be executed in case the new network pertains to a private domain
Describe in as much detail as possible the Xn handover
A preparation phase is executed. It redirects the downlink data traffic from the source RAN to the target RAN in case the source RAN does not have an association for the UE
Target RAN receives a notification that the UE has handed over at RAN level
A path switch request is sent to the AMF, forwarded to the SMF, and updated in the UPFs
Downlink data is redirected
Session on the source gNB is terminated
