11 Function and information flows

3GPP43.073Release 17Stage 2Support of Localised Service Area (SoLSA)TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

11.1 LSA management

The LSA attributes, as given in subclause 8.2 shall be entered and modified by the network operator or the service provider.

11.2 Subscription management

When the subscriber record is created in the HLR, the list of allowed LSAs, priority of each LSA, the preferential access indicator of each LSA and information about access rights outside these LSAs shall be included.

The network operator can change the LSA information for a subscription at any time. A change of subscription shall not affect any on-going calls at the moment of change.

The update of SIM with user LSA information is done as depicted in subclause 11.3.

11.3 Update of LSA data in SIM

SIM Application Toolkit (SAT) SIM Data Download procedure, as specified in 3GPP TS 31.111, can be used to download LSA data to SIM over the air interface. SAT class 1 supports SMS as the bearer for LSA data.

When using over the air interface for updating LSA information on the SIM card the 3GPP TS 23.048 specifies Standardised SIM toolkit commands for Remote File Management:

– 3GPP TS 23.048 contains a standard format for remote file handling based on the instruction set from 3GPP TS 51.011. Operators have possibility to use and update SIMs from different vendors.

– The parameter(s) in the SIM Data Download Message is either a single command, or a list of commands, and each command is coded according to the generalised structure defined in 3GPP TS 23.048.

– Data field to be used in commands will be specified in 3GPP TS 51.011 for SoLSA.

GSM Rec. 03.48 also specifies various security mechanisms (e.g. various derivatives of DES) that can used to protect the remote file management commands.

New SIMs for SoLSA are needed to cater for SIM related security issues. Unauthorised modification of SoLSA data in SIM, either by users or by any other entity, is to be prohibited.

11.4 Functions related to MS in idle mode for support of LSA

11.4.1 Broadcast information

In cells belonging to a LSA, the LSA ID(s) and/or cell identity is broadcast.

Further, in cells belonging to a LSA, which shall give exclusive access to a subscriber group, an exclusive access indication is broadcast.

To be able to favour the LSA cells at cell reselection new LSA reselection parameters are broadcast.

11.4.2 Cell selection and reselection

The definition of a "suitable cell", as defined in GSM 03.22, is modified with the following criterion:

A SoLSA exclusive access cell is "suitable" only if the LSA of the cell is one of the allowed LSA according to the SIM. Emergency calls are always allowed if no cells are found suitable.

An MS with SIM indicating LSA subscription shall always try to reselect the cell with the highest LSA priority according to the information stored on the SIM. The LSA reselection parameters broadcast on the BCCH shall be used to calculate the reselection criteria. The broadcasting mechanism is as described in 3GPP TS 44.060. The MS shall follow the reselection procedures defined in 3GPP TS 45.008.

NOTE: The text above covers also the case when the MS is using GPRS together with SoLSA.

11.4.3 Location Updating

If the escape PLMN is broadcast the BSS shall, at location updating, inform the MSC/VLR about the LSA ID(s) of the cell where the location updating request message was received. This is done by adding the LSA ID(s) of current cell to the complete layer 3 information message for the exclusive access cell.

11.4.4 Routing Area Update

If the escape PLMN is broadcast the BSS shall, at routing area update, inform the SGSN about the LSA ID(s) of the cell where the routing area update request message was received. This is done by adding the LSA ID(s) of current cell to the UL UNITDATA message for the exclusive access cell.

11.5 Transfer of information from HLR to VLR

If the subscription contain LSA information then, when the subscriber registers on a VLR, the HLR shall send the LSA subscription data to that VLR, which is relevant in the VPLMN. This is done by adding the LSA information to the MAP_INSERT_SUBSCRIBER_DATA and for deletion in MAP_DELETE_SUBSCRIBER_DATA.

When there is a change in the LSA information the HLR shall include at least the new and/or modified LSA data. When there is a change in the access right outside the LSA(s) the HLR shall include the LSA only access indicator.

11.6 Transfer of information from HLR to SGSN

If the subscription contain LSA information then, when the subscriber registers on a SGSN, the HLR shall send the LSA subscription data to that SGSN, which is relevant in the VPLMN. This is done by adding the LSA information to the MAP_INSERT_SUBSCRIBER_DATA and for deletion in MAP_DELETE_SUBSCRIBER_DATA.

11.7 Functions related to active mode support of LSA

11.7.1 MS connection establishment

11.7.1.1 Indication of current LSA to the MSC

At initial connection establishment the BSS shall inform the MSC about the LSA ID(s) of the cell where the initial layer 3 message was received. This is done by adding the LSA ID(s) of current cell to the complete layer 3 message.

11.7.1.2 Indication of allowed LSA to the BSS

The MSC sends the LSA information message to the BSS including the A-interface LSA information of the connection as defined in 3GPP TS 48.008. The MSC maps the subscription LSA information on to the A-interface LSA information for LSAs requiring ‘active mode support’. The LSA information sent to the BSS indicates the allowed area for the MS connection. The BSS shall store the LSA information in order to use it on later actions, e.g. at handover.

The LSA information for the MS connection shall be used in the BSS at assignment of radio resources in order to e.g. prioritise cells in the allowed LSA(s) and to prevent allocating resources in cells outside the allowed area for the MS connection.

11.7.1.3 Indication of allowed LSA to the BSS

The SGSN may send the LSA information message to the BSS for a mobile station in ready mode as defined in 3GPP TS 48.018. The SGSN sends the subscription LSA information for LSAs requiring ‘active mode support’. The LSA information sent to the BSS indicates the allowed area for the MS connection. The BSS shall store the LSA information in order to use it on later actions, e.g. when determine specific cell selection parameters.

The LSA information for the MS connection shall be used in the BSS to e.g. prioritise cells in the allowed LSA(s) and to prevent allocating resources in cells outside the allowed area for the MS connection.

11.7.2 Handover

11.7.2.1 Indication of allowed LSA to the target BSS

In case of BSS external handover, the LSA information for the connection shall be included in the handover request message.

11.7.2.2 Indication of current LSA to the MSC

In case of BSS external handover, the BSS informs the MSC about the LSA ID of current cell. This is done by adding the LSA ID of the current/new cell to the handover request acknowledge message.

In case of BSS internal handover, the BSS informs the MSC when a change of LSA has occurred for a connection. This is done by adding the LSA ID of the current/new cell to the handover performed message or assignment complete message (if handover performed during assignment).

11.7.2.3 Indication of current LSA to the SGSN

In case of cell change, the BSS may inform the SGSN about the LSA ID(s) of current cell. This is done by adding the LSA ID(s) of the current/new cell to the UL UNITDATA message.

11.8 LSA indication procedures

Different indication procedures shall be applied in relation to the mode of the mobile station as presented in clause 4 and defined in the following sections.

11.8.1 Indication for mobile stations in idle mode

In addition to indicate the registered PLMN, an MS with subscription for a LSA in the registered PLMN shall indicate this LSA when it is available. The indication towards the user is optional and may be done by displaying the stored LSA name that corresponds to the ID of the current LSA.

An MS with LSA only access subscription may also give an indication towards the user, when the no subscribed LSAs are available to the user. The indication is optional and may be done by displaying the LSA only access text stored in the SIM.

11.8.2 Indications for mobile stations in active mode

The network decides when to send a notification to the MS about a change of current LSA. The information will be sent from the MSC to the MS and will contain the LSA ID. This is done by adding the LSA ID of the current cell to the MM Information message. If no LSA ID is included in the MM Information message the MS shall assume that the current cell does not belong to any of the allowed LSAs for the subscriber.

The indication towards the user is optional and can be heard as e.g. a beep in the receiver or by displaying the stored LSA name that corresponds to the received LSA ID.

11.9 Overview of signalling

In this overview, the messages required to implement the specified concept are identified and brief details are given of each message. These signalling flows are not normative, but provided as an illustration on possible signalling interworking (note that only those parts of the procedures that are relevant for the LSA service are included).

Figure 2: Signalling information required at location registration

LOCATION_UPDATING_REQUEST: Standard message.

COMPLETE_LAYER3_INFORMATION: If the escape PLMN is broadcast, the MSC is provided with location updating information together with the LSA ID(s) of current cell.

MAP_UPDATE_LOCATION_AREA: Standard message.

MAP_INSERT_SUBSCRIBER_DATA: The VLR is provided with the subscriber information including the allowed LSA ID(s), priority of each LSA, the preferential access indicator for each LSA and the LSA only access indicator of current PLMN.

Figure 3: Signalling information required at routing area update

ROUTING_AREA_UPDATE_REQUEST: Standard message.

UPLINK_UNITDATA: If the escape PLMN is broadcast, the SGSN is provided with routing area update information together with the LSA ID(s) of current cell.

MAP_UPDATE_LOCATION_AREA: Standard message.

MAP_INSERT_SUBSCRIBER_DATA: The SGSN is provided with the subscriber information including the allowed LSA ID(s), priority of each LSA and the LSA only access indicator of current PLMN.

Figure 4: Signalling information required at updating of the subscriber’s LSA information by using SMS

MT-SHORT-MESSAGE, MAP-MT-FORWARD-SHORT-MESSAGE request, SM TP SMS-DELIVER: Standard messages containing subscriber’s LSA information and are parts of SIM data download.

SM TP SMS-DELIVER acknowledgement, MAP-MT-FORWARD-SHORT-MESSAGE response: Standard messages containing result of the operation.

Figure 5: Signalling information required for mobile originating call establishment

SYSTEM_INFO: The network provides the cell identity and/or LSA ID(s) of the cell, LSA cell reselection parameters and the exclusive access indication.

Initial RACH CHANNEL_REQUEST: Standard message.

IMMEDIATE_ASSIGNMENT: Standard message.

SABM (SERV_REQ): Standard message.

UA (SERV_REQ): Standard message.

COMPLETE_LAYER3_INFORMATION: The MSC is provided with initial information about the requested service together with the LSA ID(s) of current cell.

CM_SERVICE_ACCEPT: Standard message. The service request is acknowledged. Acknowledgement of the service can also be performed by invocation of ciphering mode setting.

SETUP: Standard message.

CALL_PROCEEDING: Standard message.

LSA INFO: New message including the allowed LSA ID(s), priority of each LSA, the preferential access indicator for each LSA and an indication about the access rights outside these LSA(s) for the service subscriber. This message needs to be sent before Assignment request. Additional messages may be sent anytime during the lifetime of a call.

ASSIGNMENT_REQUEST: Standard message.

ASSIGNMENT_COMMAND: Standard message.

SABM: Standard message.

UA: Standard message.

ASSIGNMENT_COMPLETE: Standard message.

A_ASSIGNMENT_COMPLETE: Modified assignment complete including the LSA ID of current cell.

Figure 6: Signalling information required at BSS external handover initiation

HANDOVER REQUIRED: Standard message.

MAP_PREPARE_HANDOVER: Standard message. Including the modified handover request.

HANDOVER_REQUEST: Modified handover request including the allowed LSA ID(s), priority of each LSA, the preferential access indicator of each LSA and an indication about the access rights outside these LSA(s).

Figure 7: Signalling information required at BSS external handover acknowledgement

HANDOVER_REQUEST_ACKNOWLEDGE: Modified handover request acknowledge including the LSA ID of current cell.

MAP_PROCESS_ACCESS_SIGNALLING request: Standard message. Including the modified handover request acknowledge.

Figure 8: Signalling information required at BSS internal handover

HANDOVER_COMPLETE: Standard message.

HANDOVER _PERFORMED: Modified handover performed including the LSA ID of current cell.

MAP_PROCESS_ACCESS_SIGNALLING request: Standard message. Including the modified handover performed.

Figure 9: Signalling information required at notification of LSA change in active mode

MM_INFORMATION: Modified MM-INFORMATION message including the LSA ID of current cell.