Page 466 - 5G Basics - Core Network Aspects

1 Core network aspects

1. When the AP receives a user registration request, the AP automatically initiates a call to the PSTN
network. The called number includes the service access code (SAC), request type (indicating the
registration request) and the terminal identifier of the terminal. In this example, the user identity is
sent afterwards during in-band FSK interaction to avoid the limitation of the length of the called
number supported in the fixed network.

2. The PSTN switch routes the call set-up request to the (MSC/VLR)/SSP according to the SAC.
3. The (MSC/VLR)/SSP triggers and sends a query to the PAM-SCP. The node (MSC/VLR)/SSP is currently
exercising IN SSP functionality only. MSC/VLR functions are not used in this scenario.
4. The PAM-SCP instructs the (MSC/VLR)/SSP to establish a connection with the IP to prepare the
special resource for FSK interaction.

5. The (MSC/VLR)/SSP sets up the connection with IP via ISUP signalling.
6. The IP acknowledges the (MSC/VLR)/SSP with a connection established response.
7. The call set-up response is forwarded to the PSTN switch, and the bearer connection is established
between the AP and the IP.
8. The IP informs the PAM-SCP of its availability and capability.
9. The PAM-SCP instructs the IP to send an "Info request (user identification)" (in FSK) to the AP.
10. The "Info request (user identity)" message is sent from the IP to the AP (in FSK).
11. The AP replies with the "user identity information" (in FSK).

12. The IP sends the received user identity to the PAM-SCP.
13. The PAM-SCP sends an authentication data request to the HLR/AuC (HSS) referenced by the IMSI
corresponding to the user identity.

14. The PAM-SCP receives and stores the authentication vector, including a random number, an
expected response, a cipher key, an integrity key and an authentication token.

15. The PAM-SCP instructs the IP to send the authentication data (random number, authentication
token) to the AP.
16. The authentication data is sent to the AP in FSK, the AP converts the message to wireless signalling
and sends it to the terminal.
17. The terminal verifies the authentication token and computes the result and sends the response with
RES.
18. The IP sends the received authentication result to the PAM-SCP.
19. The PAM-SCP compares the received RES with the stored expected result. If equal, the
authentication is successful and the PAM-SCP requests the user profile from the HLR/AuC (HSS).
20. The HLR/AuC (HSS) provides the user profile to the PAM-SCP.
21. The PAM-SCP stores the user's associated service data including MSISDN, the PSTN address of the
AP and the terminal identifier in the database and sends a request to the HLR/AuC (HSS) to activate
the PAM service status in T-CSI.
NOTE – Subscription to the PAM service needs to be performed in advance, and the initial status of the PAM
service is inactive.
22. The HLR/AuC (HSS) responds with a successful result for service activation.
23. The PAM-SCP instructs the IP to send the AP the successful treatment of the user registration in FSK.

24. The response is sent to the AP via FSK, the AP forwards the response to the terminal.
25. The IP sends the result to the PAM-SCP.
26a. The PAM-SCP indicates to the (MSC/VLR)/SSP to release the bearer connection with the IP.
27a. The MSC/VLR/SSP sends release to the IP.
28a. The IP responds with release complete confirmation.

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