A supporting UE operating in Idle mode selects the core network operator and provides the PLMN-id of this operator to the network for routing purposes and to indicate which of the core network operators is selected. A supporting GERAN UE provides PLMN-index when establishing a connection with the MSC, and, when sending GPRS LLC frames with a non-local TLLI. A supporting GERAN UE, upon completion of a CS or PS handover, uses the PLMN index received during the CS handover and PS handover procedure to indicate the selected PLMN in the subsequent RAU in connected mode if the conditions for performing a normal RAU are met, see TS 24.008, when sending GPRS LLC frames with a non-local TLLI. Normal RAU following a CS handover is performed if the UE and the network support DTM and the conditions for RAU are met whereas a RAU following a PS handover is performed if the conditions for normal RAU are met.

Network sharing information, i.e. available core network operators in the shared network, shall be transmitted in broadcast system information. If system information relating to NAS is transmitted to a UE in dedicated signalling, the RNC sends information for both supporting and non-supporting UEs and the UE shall select the appropriate information to use. The RNC shall indicate the UE selected core network operator to the CN for supporting UEs when transferring initial layer 3 signalling. The selected CN operator is (i) indicated by the UE in RRC signalling or (ii) known implicitly from an already existing signalling connection. For non-supporting UEs, the RNC selected core network operator shall, if available, be indicated by the RNC to the CN. RNC selection of core network operator is described in clause 4.2.5.3. In case of relocation to a shared network:

• the source RNC determines a core network operator to be used in the target network, including the selection of PLMN(s) to support SRVCC functionality from CS domain to PS, based on available shared networks access control information, current PLMN in use, Anchor PLMN, or similar information present in the node, the source RNC shall at relocation indicate that selected core network operator to the source core network node as part of the TAI/RAI sent in Target ID in the Relocation Required message. The selected target core network operator should be the same as the one in use. If the source core network operator is not supported in the target cell the RNC selects the target PLMN based on either (i) pre-configured information in the RNC, or (ii) the SNA (Shared Network Area) Access Information IE (see TS 25.413) provided by the SGSN. When the RNC triggers the enhanced relocation and selects a new PLMN, the selected PLMN is indicated to the SGSN during the following RA update procedure.
• In order to support SRVCC from CS to PS, the source RNC informs the target RNC/BSC of the Anchor PLMN identity.
• The target RNC may need to know whether or not the UE supports UTRAN network sharing.
  The behaviour of the RNC in relation to CS/PS coordination for non-supporting UEs is described in clause 4.2.5.3.

Network sharing information, i.e. available core network operators in the shared network, shall be transmitted in broadcast system information. The eNodeB shall indicate the selected core network operator when transferring initial layer 3 signalling. The eNodeB uses the selected core network information (provided by the UE at RRC establishment, or, provided by the MME/source eNodeB at S1/X2 handover) to select target cells for future handovers (and radio resources in general) appropriately. In the case of handover to a shared network:

• the source eNodeB determines a core network operator to be used in the target network based on current PLMN in use, or other information present in the eNodeB, the source eNodeB shall at handover indicate that selected core network operator to the MME as part of the TAI/RAI sent in the HO required message. The selected target core network operator should be the same as the one in use. This is accomplished by not changing the serving PLMN if the PLMN in use is supported in the target cell. If the PLMN in use is not supported in the target cell the eNB selects the target PLMN based on either (i) pre-configured information in the eNB, or (ii) the Equivalent PLMNs list (see TS 36.413) provided by the MME.
• when multiple PLMNs are available for CS domain to support CS Fallback functionality, the source eNodeB determines a core network operator to be used in the target GERAN/UTRAN network based on the allocated LAI provided by the MME as specified in TS 23.272. The source eNodeB shall at handover indicate that selected core network operator to the MME as part of the Target ID sent in the HO required message. If the selected PLMN for CS domain is not supported in the target cell the eNodeB selects the target PLMN based on either (i) pre-configured information in the eNodeB, or (ii) the Equivalent PLMNs list (see TS 36.413) provided by the MME.
• when multiple PLMNs are available for CS domain to support SRVCC functionality, the source eNodeB determines a core network operator to be used in the target GERAN/UTRAN network. If the currently serving PLMN is not supported in the target cell, the eNodeB selects the target PLMN based local configured information in the eNodeB along with the information provided by the MME in HRL (see TS 36.413). The HRL provides the currently serving PLMN and equivalent PLMNs together with information about which PLMNs are preferred for SRVCC target cell selection. The source eNodeB shall at SRVCC handover indicate the selected core network operator to the MME as part of the Target ID sent in the HO required message.
• the target eNodeB uses the selected core network information to select target cells for future handovers appropriately.

In the case of dual connectivity (as described in TS 36.300):

• the Master eNodeB uses the selected core network information to select any Secondary Cell Group appropriately (e.g. to respect network sharing agreements).

Network sharing information, i.e. available core network operators in the shared network, shall be transmitted in broadcast system information. If system information is transmitted to a supporting UE in dedicated signalling e.g. to support handover to other RATs, the BSC shall indicate the PLMN-id of the core network operator towards which the UE already has a signalling connection (if a PLMN-id is included in the signalling). If the UE is non-supporting, the BSC shall indicate the common PLMN (if a PLMN-id identity is included in the signalling). The BSC shall indicate the selected core network operator to the CN for supporting UEs. The selected CN operator is:

1. indicated by the UE to the BSC as follows:
   • for the CS domain, in the Initial L3 message, a supporting UE shall send the PLMN Index that corresponds to the position of the chosen PLMN in the broadcast system information, as part of the Initial L3 message. The BSC shall then derive the PLMN-id chosen by the UE from the indicated PLMN Index, select the corresponding CN operator and inform the MSC of the chosen PLMN-id;
   • for the PS domain, when the UE has a non-local TLLI, a supporting UE shall send the PLMN Index that corresponds to the position of the chosen PLMN in the broadcast system information, as part of the AS signalling. The BSC shall then derive the PLMN-id chosen by the UE from the indicated PLMN Index, select the corresponding CN operator and inform the SGSN of the chosen PLMN-id;
   or:
2. known implicitly from an already existing signalling connection.

For non-supporting UEs, the BSC selected core network operator shall, if available, be indicated by the BSC to the CN. In the PS domain, when the UE has a local TLLI:

• for MOCN, the BSC uses the NRI bits from within the TLLI to derive the selected CN operator;
• for GWCN, the SGSN passes the selected CN operator identity with the downlink user data/signalling.

For handover to a shared network from GERAN:

• the source BSC determines a core network operator to be used in the target network, including the selection of PLMN(s) to support SRVCC functionality from CS domain to PS, based on current PLMN in use, Anchor PLMN, or other information present in the BSC. The selected target core network operator should be the same as the one in use. If the source core network operator is not supported in the target cell the BSC selects the target PLMN based on pre-configured information in the BSC.
• the source BSC shall indicate the target core network operator PLMN ID to the source core network node as part of the TAI/RAI sent in the Target Cell Identifier IE/Target RNC Identifier IE/Target eNodeB Identifier IE in the PS-Handover-Required message (TS 48.018) and in the LAI sent in the Cell Identifier List IE in the Handover Required message (TS 48.008).
• In order to support SRVCC for CS to PS, the source BSC informs the target RNC/BSC of the Anchor PLMN identity.

For handover to a GERAN shared network:

• The target BSS needs to know whether or not the UE supports GERAN network sharing.
• the source RAN determines a core network operator to be used in the target network and indicates the selected target core network operator PLMN ID to the source core network node. The target MSC/SGSN indicates the selected target core network operator to target BSC.
• At CS handover the target BSC (BSS-B) shall, for a GERAN supporting UE, provide PLMN index information corresponding to the selected target PLMN-id via the source RAN. When the UE arrives in the target cell the target BSC shall indicate the RAI corresponding to the selected PLMN.
• At PS handover the target BSC (BSS-B) shall, for a GERAN supporting UE, provide PLMN index information corresponding to the selected target PLMN-id via the source RAN. The target BSC shall also via the source RAN indicate the RAI corresponding to the selected PLMN.
• At normal RAU in connected mode after completing a handover, the target BSC is informed of the PLMN index corresponding to the selected target PLMN when the UE appears in the target access.

In all other non handover signalling from the GERAN to the MSC/SGSN, unless specified differently by stage 3 specifications, any PLMN ID sent is the Common PLMN ID. In signalling from the Core Network to the GERAN, the BSS shall accept signalling that uses any of the PLMN IDs that share the cell. The behaviour of the BSC in relation to CS/PS coordination for non-supporting UEs is described in clause 4.2.5.3.

When a UE accesses an MSC the first time, i.e. when there is no VLR entry for this UE, the MSC retrieves the IMSI from another MSC/VLR or from the UE. For GWCN, the MSC determines a serving CN operator based on the UE Selected operator (PLMN) indicated by the RAN, or, for a non-supporting UE, based on the RAN Selected CN operator (PLMN). The MSC/VLR shall also store the identity of the serving core network operator. In the case of a MOCN configuration, an MSC may not be able to provide service to the UE. The UE may then have to be redirected to a MSC of another core network operator. The MSC/VLR that finally serves the UE assigns a NRI to the UE. This will allow the RAN to route any subsequent UE accesses to the serving MSC/VLR. The behaviour of the MSC in relation to CS/PS coordination for non-supporting UEs is described in clause 4.2.5.3. For supporting UEs, i.e. when a UE selected core network operator has been indicated to the MSC by the RNC/BSC, the MSC indicates the selected core network operator PLMN-id in the LAI signalled to the UE in dedicated signalling. For sharing scenarios with both E-UTRAN and GERAN/UTRAN access, where the network also applies idle-mode signalling reduction (see TS 23.401), the contents of the SNA Access Information IE (see TS 25.413) provided by the MSC to the RNC for a specific UE guides the target PLMN selection if the UE's registered PLMN is not available in the target cell. The SNA Access Information IE should be configured such that for any target cell there is only one PLMN-ID that can be selected for the cell. Also, for the above scenario, in the routing areas and tracking areas between which ISR may be activated the "equivalent PLMNs" list provided by the SGSN, MSC and MME to a UE (see TS 24.008) should result in a single consistent "equivalent PLMNs" list stored by the UE. The single "equivalent PLMNs" list applies to all the UE's registered routing areas, location areas and tracking areas. In case of relocation to a GWCN or a MOCN:

• There is no functionality in the source MSC to select a target core network operator or to modify the target core network operator selected by the RNC/BSC.
• For handover to a shared UTRAN the source MSC shall forward the selected core network operator chosen by the source RNC/BSC to the target MSC, which relays this information unchanged to the target RNC so that the appropriate PLMN-id can be signalled to the UE in dedicated system information signalling, as described in clause 5.2.
• For handover to a shared GERAN the source MSC shall forward the PLMN-ID selected by the source RAN to the target MSC. Target MSC sends information of selected operator to the target BSC.
• For SRVCC from E-UTRAN PS to UTRAN/GERAN CS domain, in case of GWCN configuration, the MSC selects the target PLMN based on the indication of the selected target PLMN provided by the MME/SGSN in the PS-to-CS handover command. The MSC receives the Anchor PLMN from the MME/SGSN and forwards that information to the target BSC/RNC.

For SRVCC from UTRAN/GERAN CS domain to E-UTRAN/HSPA PS, the MSC selects the MME based on selected target PLMN provided by the RNC/BSC in handover required message and forwards the selected target PLMN to MME in the CS to PS handover request. In signalling to the HSS, the MSC shall ensure that any PLMN ID that is sent is the ID of the selected Core Network Operator for supporting UEs, or that of the allocated Core Network Operator for non-supporting UEs (unless the exception to send the Common PLMN ID for a non-supporting UE (see clause 4.4) is in use with that HPLMN).

When a UE accesses an SGSN the first time, i.e. when the UE is not yet known by the SGSN the SGSN retrieves the IMSI from another SGSN/MME or from the UE. For GWCN, the SGSN determines a serving CN operator based on the Selected PLMN indicated by the RAN, or, for a non-supporting UE, based on the RAN Selected CN operator (PLMN). The SGSN shall store the identity of the serving core network operator. In the case of a MOCN configuration, a SGSN may not able to provide service to the UE. The UE may then have to be redirected to a SGSN of another core network operator. The SGSN that finally serves the UE assigns a NRI to the UE. This will allow the RAN to route any subsequent UE accesses to the serving SGSN. The behaviour of the SGSN in relation to CS/PS coordination for non-supporting UEs is described in clause 4.2.5.3. For supporting UEs, i.e. when a UE selected core network operator has been indicated to the SGSN by the RNC/BSC, the SGSN indicates the selected core network operator PLMN-id in the LAI/RAI signalled to the UE in dedicated signalling. For sharing scenarios with both E-UTRAN and GERAN/UTRAN access, where the network also applies idle-mode signalling reduction (see TS 23.401), the contents of the SNA Access Information IE (see TS 25.413) provided by the SGSN to the RNC for a specific UE guides the target PLMN selection if the UE's registered PLMN is not available in the target cell. The SNA Access Information IE should be configured such that for any target cell there is only one PLMN-ID that can be selected for the cell. Also, for the above scenario, in the routing areas and tracking areas between which ISR may be activated the "equivalent PLMNs" list provided by the SGSN, MSC and MME to a UE (see TS 24.008) should result in a single consistent "equivalent PLMNs" list stored by the UE. The single "equivalent PLMNs" list applies to all the UE's registered routing areas, location areas and tracking areas. At relocation/handover to a GWCN or a MOCN:

• There is no functionality in the source SGSN to select a target core network operator or to modify the target core network operator selected by the RNC/BSC. Instead, the source SGSN uses the selected PLMN received from the RNC/BSC to determine the target core network operator. The source SGSN shall forward the selected core network operator chosen by the source RNC/BSC to the target SGSN/MME.
• For handover to a shared UTRAN the target SGSN indicates the selected core network operator chosen by the source RNC/BSC/eNodeB to the target RNC so that the appropriate PLMN-id can be signalled to the UE in dedicated system information signalling, as described in clause 5.2.
• For handover to a shared GERAN the source SGSN/MME shall forward the PLMN-ID selected by the source RAN to the target SGSN. Target SGSN sends information of selected operator to the target BSC.
• For SRVCC from UTRAN PS to UTRAN/GERAN CS domain, the SGSN selects the MSC based on the selected target PLMN indicated by the RNC. The SGSN includes the indication of the selected target PLMN in the target CGI/RNC ID and Anchor PLMN in the SRVCC PS-to-CS Request sent to the MSC (see TS 29.280).

In signalling to the GGSN/S-GW/P-GW and HSS, the SGSN shall ensure that any PLMN ID that is sent is the ID of the selected Core Network Operator for supporting UEs, or that of the allocated Core Network Operator for non-supporting UEs (unless the exception to send the Common PLMN ID for a non-supporting UE (see clause 4.4) is in use with that HPLMN).

When a UE accesses an MME for the first time, i.e. when the UE is not yet known by the MME, the MME verifies whether the UE is permitted to access the selected PLMN. For that purpose the MME retrieves the IMSI from another MME/SGSN or from the UE. The MME shall store the identity of the selected core network operator. The MME indicates the selected core network operator PLMN-id to the UE in the GUTI. For sharing scenarios with both E-UTRAN and GERAN/UTRAN access, where the network also applies idle-mode signalling reduction (see TS 23.401), the PLMN IDs included in the equivalent PLMN list (as defined in TS 24.008) provided by the MME to the eNB guides the target PLMN selection if the UE's registered PLMN is not available in the target cell. The equivalent PLMN list should be configured such that for any target cell there is only one PLMN-ID that can be selected for the cell. Also, for the above scenario, in the routing areas and tracking areas between which ISR may be activated the "equivalent PLMNs" list provided by the SGSN, MSC and MME to a UE (see TS 24.008) should result in a single consistent "equivalent PLMNs" list stored by the UE. The single "equivalent PLMNs" list applies to all the UE's registered routing areas, location areas and tracking areas. For sharing scenarios with both E-UTRAN and GERAN/UTRAN access, when multiple PLMNs are available for CS domain to support CS Fallback functionality, the MME provides the allocated LAI including the selected PLMN ID for CS domain along with "CS Fallback indicator" to the eNodeB as specified in TS 23.272, to guide the selection of the target GERAN/UTRAN network. If the operator-configured preferred target RAT for CS Fallback is a shared RAN not offering the broadcast of available Core Network operators for selection by the UE, the MME shall always select the common PLMN broadcasted in the shared RAN as the selected PLMN-id for the CS domain. If the operator-configured preferred target RAT for CS Fallback is a shared RAN offering the broadcast of available Core Network operators for selection by the UE, the MME shall take into account the UE's capability of supporting network sharing in the preferred target RAT when selecting the PLMN for the CS domain for CS Fallback. For GERAN network sharing, the UE signals its capability of GERAN network sharing support explicitly to the MME. If the UE is a network-sharing non-supporting UE with respect to the preferred target RAT, a common PLMN-id shall be selected, while if the UE is a network-sharing supporting UE with respect to the preferred target RAT, one of the PLMN-IDs in the broadcasted multiple PLMN-id list of the preferred target shared RAT shall be selected as the PLMN-id for the CS domain. The selected PLMN-id for the CS domain shall be included the allocated LAI sent to the MSC/VLR as defined in TS 23.272. If the shared network is in GWCN configuration, MME sends the 'selected CS domain operator' as indicated in clause 4.2.5a. The list of PLMN-ID(s) included in the handover restriction list (as defined in TS 36.413), if provided by the MME to the eNB for the target PLMN selection, shall be configured such that for any target GERAN/UTRAN cell, only PLMN-ID(s) associated with the same CN operator as the one that the UE has registered to in the CS domain can be selected by the eNB when one of the following conditions apply:

• the preferred RAT of the registered network is shared network not offering the broadcast of available Core Network operators for selection by the UE, or,
• the RAT preference for the UE is GERAN and the allocated LAI belongs to a shared GERAN and the UE is a GERAN network-sharing non-supporting UE.

The list of PLMN-ID(s) included in the equivalent PLMN list sent to the UE shall be configured to include the list of PLMN IDs in the handover restriction list. At handover/relocation to a GWCN or a MOCN:

• The source MME uses the TAI/RAI information supplied by the eNodeB to select the target MME/SGSN. There is no additional functionality in the source MME to select a target core network operator or to modify the target core network operator selected by the eNodeB. Instead, the source MME uses the selected PLMN received from the eNodeB to determine the target core network operator. The source MME shall forward the selected target core network operator chosen by the source eNodeB to the target MME/SGSN.
• The target MME indicates the selected target core network operator chosen by the source eNodeB/RNC/BSC to the target eNodeB so that the eNodeB can select target cells for future handovers appropriately. Subsequent Tracking Area Update signalling is used to update the UE about any change of core network operator.
• At SRVCC from E-UTRAN PS to UTRAN/GERAN CS domain, the MME selects the MSC based on the selected target PLMN indicated by the eNodeB. The MME includes the indication of the selected target PLMN in the target CGI/RNC ID and Anchor PLMN in the PS-to-CS Request sent to the MSC (see TS 29.280).

In signalling to the S-GW/P-GW and HSS, the MME shall ensure that any PLMN ID that is sent is the ID of the selected Core Network Operator. The behaviour of the MME in relation to CS/PS coordination in GERAN and UTRAN for non-supporting UEs is described in clause 4.2.5.3.