Page 455 - 5G Basics - Core Network Aspects
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Core network aspects                                            1


            The PAM-SCF processes the originating call request accordingly and controls the modification of the CLI to
            the fixed PAM service number.

            7.3.1.4    Terminating call
            A terminating call to a fixed PAM service number is routed to the "home switch" supporting the assigned
            PAM service number which treats the call as an IN call and queries the PAM-SCF for instructions.
            •       If the user is currently registered at an AP, the PAM-SCF responds with routing instructions in the
                    form of a specific AP to which to route the call for completion together with the updated CLI carrying
                    the  terminal  identifier  in case  an  analogue  line  is  used, or  in the form of  a  subscriber  number
                    corresponding to the terminal to which to route the call for completion in case an ISDN line is used.
                    In case the call cannot be completed to the AP, the PAM-SCF provides the instructions to forward
                    the call to the MSISDN associated with the subscriber.

            •       Otherwise, if the mobile user is not connected to any AP, the PAM-SCF forwards the call directly to
                    the mobile network using the MSISDN associated with the subscriber.

            7.3.2   Overview of information flows when using MSISDN as the PAM service number

            7.3.2.1    Registration
            When an AP function receives a registration request from a MS PAM function containing the SAC and the
            user identity, the AP function assigns a dynamic terminal identifier (in case an analogue line is used) or a
            subscriber number (in case an ISDN line is used) to that terminal and initiates a call carrying the SAC, the
            request type (registration) and the terminal identifier or the subscriber number to the CCF/SSF.

            The CCF/SSF uses the CLI (subscriber number) received from the user (the AP function) if it is valid; otherwise,
            the CCF/SSF inserts the network provided CLI of the fixed access line to which the AP is connected, and the
            CCF/SSF triggers and queries the PAM-SCF for instructions.
            The PAM-SCF instructs the SRF to establish a bearer connection between itself and the AP function by the
            CCF/SSF.
            During the registration, the following information is exchanged between the AP function and the SRF in-band
            under the control of the PAM-SCF:
            •       The PAM-SCF instructs the SRF to collect the user identification information from the AP function.
            •       The AP function sends the user identity to the SRF which relays the information to the PAM-SCF.

            •       The PAM-SCF retrieves the authentication data of the terminal from HLR/AuC (HSS) and instructs
                    the SRF to interact with the AP function which uses the data provided by the MS PAM function to
                    perform the authentication.
            After authentication is successful, the PAM-SCF updates the mobile user's terminating subscription status in
            HLR/AuC (HSS) if the HLR/AuC (HSS) supports this function.

            After finishing the registration processing, the PAM-SCF instructs the SRF to send the registration result to
            the AP function in-band which relays the registration response to the MS PAM function.

            7.3.2.2    Deregistration
            When an AP function receives a deregistration request from a MS PAM function or when an AP function
            detects that a terminal is no longer accessible via the AP, then the AP function sends the deregistration
            request by initiating a call request to CCF/SSF containing the SAC of the PAM service, the request type
            (deregistration) and the terminal identifier (in case an analogue line is used) or the subscriber number (in
            case an ISDN line is used).
            The CCF/SSF uses the CLI (subscriber number) received from the user (the AP function) if it is valid; otherwise,
            the CCF/SSF inserts the network provided CLI of the fixed access line to which the AP is connected and triggers
            and queries the PAM-SCF for instructions.





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