8.2 PLMN Selection

3GPP43.318Generic Access Network (GAN)Release 17Stage 2TS

There shall be no change from the PLMN selection procedures in the NAS layers (MM and above) in the MS, with the exception that in GAN mode the "in VPLMN background scan" shall be disabled.

A GANC can be only connected to one PLMN.

The PLMN selection in the NAS layers shall not lead to change of mode between GERAN/UTRAN/E-UTRAN mode and GAN mode. For a specific instance of PLMN selection only PLMNs available via GAN or only PLMNs available via GERAN/UTRAN/E-UTRAN are provided to the NAS layer (i.e. no combination of the PLMNs available via GERAN/UTRAN/E-UTRAN and GAN).

In the case of a GAN capable MS, a GANC selection process also may be required as part of the process of establishing the connectivity between the MS and the GANC. This takes place when, during GAN registration, a GAN capable MS has a choice among two or more GANC-PLMN pairs indicated by the Default GANC (i.e. in the GA-RC REGISTER REDIRECT message). The GANC selection process takes place while the MS is still in GERAN/UTRAN/E-UTRAN mode (i.e. before the MS roves into GAN mode) as follows:

– While a mobile station is attempting to become GAN registered, the GANC selection process shall attempt GAN registration with the currently registered PLMN if the currently registered PLMN is contained in the list of GAN PLMN pairs indicated by the Default GANC.

– If GAN registration with the currently registered PLMN is not possible and there are one or more remaining GANC-PLMN pairs that were received in the GAN PLMN list within a GA-RC REGISTER REDIRECT message, they shall all be treated as having sufficient received signal quality and PLMN selection should be performed according to the PLMN selection rules of 3GPP TS 22.011 [53] where the PLMN selected is in the GAN PLMN list.

If the MS does not have any stored information related to the Serving GANC for the cell ID or AP to which the MS is currently connected, the MS attempts to register with the Default GANC (always located in the HPLMN) stored in MS. The MS includes an indication, identifying the GANC as the Default GANC in the GA-RC REGISTER REQUEST message.

When an MS attempts to register on the Default GANC including an indication that it is in automatic PLMN selection mode:

– If the Default GANC wishes to serve the MS, the Default GANC responds with a GA-RC REGISTER ACCEPT message.

– If the Default GANC wishes to redirect the MS to another GANC within the HPLMN, the Default GANC responds with a GA-RC REGISTER REDIRECT message, not including a list of PLMN identities.

– If the Default GANC wishes to redirect the MS to a PLMN that is not the HPLMN, the Default GANC responds with a GA-RC REGISTER REDIRECT message and includes a list of PLMNs that may provide GAN service to the MS in its current location. The list contains one or more PLMN identities along with the identities of their associated GANC and SEGW nodes (either in IP address or FQDN format). Following the GANC selection process, the GA-RC shall attempt to register on the associated GANC.

If at any time the user wishes to perform manual PLMN selection or a "User reselection" irrespective of whether the MS is in manual or automatic PLMN selection mode, the MS sends a GA-RC REGISTER REQUEST message to the Default GANC, including an indication that it is in manual PLMN selection mode. The Default GANC is not allowed to accept the registration and responds with a GA-RC REGISTER REDIRECT message and includes a list of PLMNs that may provide GAN service to the MS in its current location.

If the MS includes the identity of the current serving network in the GA-RC REGISTER REQUEST message, the Default GANC uses this to identify the list of PLMNs to send to the MS in the response message.

The GA-RC REGISTER REDIRECT message may inform a mobile station that GAN A/Gb mode, GAN Iu mode or both GAN A/Gb mode and GAN Iu mode are supported for each PLMN indicated by this message.

After successful registration with a serving GANC, the MS shall not store the PLMN list. The MS shall not use the PLMN list, provided to the MS during the registration procedure, for background scanning.

NOTE: An MS cannot use Generic Access in a VPLMN unless the HPLMN supports and authorises Generic Access.

After entering GAN A/Gb mode, a mobile station may trigger handover back to GERAN/UTRAN mode by sending a GA-CSR HANDOVER INFORMATION message or GA-PSR HANDOVER INFORMATION message to the GANC and including an ordered list of preferred GERAN/UTRAN cells. After entering GAN Iu mode, a mobile station may trigger handover back to GERAN/UTRAN mode by sending a GA-RRC RELOCATION INFORMATION message to the GANC and including an ordered list of preferred GERAN/UTRAN cells. In each case, the list of preferred GERAN/UTRAN cells shall include cells having the same PLMN as the currently registered PLMN (if at least one such cell is known to the MS).