Page 451 - 5G Basics - Core Network Aspects

Core network aspects 1

The PAM-SCF is an SCF which supports PAM service logic and data.

The functional model shown in Figure 2 can be applied in the case of the same operator for both the legacy
PSTN/ISDN and the mobile network as well as in the case of different operators cooperating by appropriate
interconnection and SLAs.

7.2 Functional entities

7.2.1 Mobile station PAM function
The mobile station PAM function provides dual mode radio access. It allows the user to access the public
mobile network via a 3G/2G air interface and to access the fixed network via an alternative air interface to
the AP.
The MS PAM function automatically initiates a registration request to the AP function when it detects an
appropriate AP to which it can connect. The MS PAM function initiates a deregistration request to the AP
function when the user manually deregisters through the menu in the terminal.

For a call origination, when both radio accesses (to the AP and to the mobile network) are available, the MS
PAM function selects the radio access to the AP, in case the call set-up through the AP radio access fails, the
MS PAM function sends the call request over the mobile network radio access.

The MS PAM function provides the user with indications of:
• whether the fixed network is available via the AP connection (reflecting the registration or
deregistration status);
• the selected radio access for the originating call in the ringing and conversation phase.
For authentication of a mobile user through fixed network access via an AP, the MS PAM function provides
the same network security mechanism as used in the mobile network, i.e., the same as used in another
(mobile radio access) mode of the terminal. The MS PAM function supports the GSM/UTRAN or ANSI-
41/cdma2000 network access security mechanism to perform terminal/network authentication by
interaction with the PAM-SCF via the AP function and the SRF.
The PAM service access code (SAC) and the user identity are to be pre-set in the terminal.

7.2.2 Access point function

The access point (AP) appears to the legacy PSTN/ISDN as a user equipment of that network. The AP appears
to the MS as if it were a mobile switching centre (MSC).

The AP function supports the basic functions of a POTS terminal or an ISDN terminal appropriate to the
interface to the legacy network, including support of calling line identification presentation. In addition, it
supports the sending and receiving of in-band DTMF/FSK signal.
The AP function provides conversion between the wireless protocol and the analog or digital line signalling
used on the PSTN/ISDN access.

The AP function provides media transcoding between the type of codec used in the terminal and the type of
codec used on the PSTN/ISDN access.

In addition, the AP function supports the following functions:
• Registration and deregistration
When an AP function receives a registration request from a MS PAM function, the AP function
supports the following ways of identifying the terminal requesting attachment:
– The AP function allocates a terminal identifier dynamically for that terminal in case a PSTN
analogue line is used.
– The AP function allocates a subscriber number for that terminal dynamically from a set of pre-
assigned multiple subscriber numbers when ISDN interface is used (the MSN service needs to
be active for the ISDN line and multiple subscriber numbers are assigned to the same ISDN line).

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