5 Paging for non-GPRS services procedure

09.183GPPGeneral Packet Radio Service (GPRS)Gs interface layer 3 specificationServing GPRS Support Node (SGSN) - Visitors Location Register (VLR)TS

5.1 General description

This procedure is used by the VLR to send a BSSAP+-PAGING-REQUEST message to an MS via the GPRS service. This procedure applies to MSs that are simultaneously IMSI attached for GPRS services and non-GPRS services. The procedure can be performed simultaneously with any other procedure at the Gs interface.

5.2 Procedures in the VLR

The VLR shall handle the timers, queuing and retransmission for sending the BSSAP+-PAGING-REQUEST message on the Gs interface in the same way that it handles the sending of a PAGING message on the A interface.

5.2.1 Paging Initiation

When a VLR has to page a GPRS MS it shall check whether the MSC has an SCCP connection for that MS. If no SCCP connection exists the VLR checks the state of the association to an SGSN and the value of the restoration indicators for that MS. The VLR sends BSSAP+-PAGING-REQUEST messages to the SGSN if the state of the association for the MS is Gs-ASSOCIATED, LA-UPDATE-PRESENT or if the state of the association is Gs-NULL and the ‘Confirmed by Radio Contact’ restoration indicator is set to ‘false’. The sending of the BSSAP+-PAGING-REQUEST message does not change the state of the association with the SGSN.

If the ‘Confirmed by Radio Contact’ restoration indicator is set to ‘true’, the VLR shall include the Location area identifier IE into the BSSAP+-PAGING-REQUEST message, otherwise (i.e. after a VLR failure) the Location area identifier IE shall not be included. When sending the BSSAP+-PAGING-REQUEST message, the VLR shall start timer T5.

If the state of the association is Gs-NULL and the restoration indicator ‘Confirmed by Radio Contact’ is set to ‘false’, the VLR shall also perform a search procedure as specified in 3GPP TS 03.18.

5.2.2 Paging Response

The VLR stops the paging procedure on expiry of timer T5 or on receipt of an SCCP connection establishment containing the Initial L3 message from the MS via the A interface.

5.2.3 Paging Failure

On receipt of a BSSAP+-PAGING-REJECT message before the timer T5 expires, the VLR stops timer T5, the association is moved to the Gs-NULL state and within this state the association is marked with the contents of the Gs Cause IE.

5.2.4 MS unreachable

On receipt of a BSSAP+-MS-UNREACHABLE message before the timer T5 expires, the VLR stops timer T5 and the paging procedure for that paging request towards the SGSN is stopped. The state of the association at the VLR is not changed.

5.3 Procedures in the SGSN

The SGSN accepts BSSAP+-PAGING-REQUEST messages in any state of the association apart from Gs-NULL. Nevertheless the SGSN also accepts BSSAP+-PAGING-REQUEST messages in the Gs-NULL state if the ‘SGSN-Reset’ restoration indicator at the SGSN is set to ‘true’. When an SGSN receives a BSSAP+-PAGING-REQUEST message from a VLR, the SGSN shall first check if the MS is known by the SGSN. The handling of the paging request depends on the state of the association and the MM context variables at the SGSN:

a) The MS is known and the restoration indicator ‘SGSN-Reset’ at the SGSN is set to ‘false’:

– If the MS is considered to be IMSI attached for GPRS and non-GPRS services (i.e. the association is not in the state Gs-NULL), the SGSN shall page the MS based on the location information stored in the SGSN.

– If the MS is marked as IMSI detached for GPRS services or IMSI (implicitly or explicitly) detached for non-GPRS services (i.e. the state of the association is Gs-NULL), the SGSN shall return a BSSAP+-PAGING-REJECT message to that VLR indicating in the Gs Cause IE the detach circumstance (‘IMSI detached for GPRS services’, ‘IMSI detached for non-GPRS services’ or ‘IMSI implicitly detached for non-GPRS services’).

– If the MS is marked as unreachable (i.e. the PPF flag is set to ‘false’) the SGSN shall return a BSSAP+-MS-UNREACHABLE message to that VLR indicating in the Gs Cause IE ‘MS unreachable’. The state of the association does not change at the SGSN.

b) The MS is known and the restoration indicator ‘SGSN-Reset’ at the SGSN is set to ‘true’:

– If the BSSAP+-PAGING-REQUEST message includes the Location area identifier IE, the SGSN shall page the MS in all the routeing areas served by the SGSN that are included in the location area indicated in the Location area identifier IE.

– If the BSSAP+-PAGING-REQUEST message does not include the Location area identifier IE, the SGSN may page in all the routeing areas served by the SGSN that are also served by the sending VLR.

c) The MS is not known and the restoration indicator ‘SGSN-Reset’ at the SGSN is set to ‘false’:

– The SGSN shall return a BSSAP+-PAGING-REJECT message to that VLR indicating in the Gs Cause IE ‘IMSI unknown’.

d) The MS is not known and the restoration indicator ‘SGSN-Reset’ at the SGSN is set to ‘true’:

– If the VLR provides the Location area identifier IE, the SGSN shall page within the location area indicated by the VLR. Otherwise the SGSN may page in all the routeing areas served by the SGSN that are also served by the sending VLR.

If the SGSN accepts the paging request, the SGSN shall process the BSSAP+-PAGING-REQUEST message before sending the message on the Gb interface. The result of the processing on the BSSAP+-PAGING-REQUEST message is the PAGING CS message (see 3GPP TS 08.18) sent on the Gb interface.

The SGSN shall not retransmit the PAGING CS message.

If within a location area there are cells that do not support GPRS services, the SGSN shall group these cells under a ‘null RA’. The SGSN will perform the paging procedure described above within both the RA(s) derived from the location information and the ‘null RA(s)’ of the corresponding location area(s) (see 3GPP TS 04.08).

Note: the eMLPP priority information element relates to relative priorities within the paged MS and not to the priority in the sending of PAGING CS messages by the BSS.