16 Interactions with Other Services

23.0603GPPGeneral Packet Radio Service (GPRS)Release 17Service descriptionStage 2TS

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

16.0 General

This clause describes the interaction between packet-domain services and the following other services for a GPRS-attached MS which is in GERAN/UTRAN PS coverage:

– point-to-point Short Message Service (SMS);

– circuit-switched services;

– supplementary services; and

– CAMEL services.

16.1 Point-to-point Short Message Service

It shall be possible for a GPRS-attached MS to send and receive short messages over the PS domain when it is in GERAN/UTRAN PS coverage. An MS that is GPRS-attached and not IMSI-attached shall transfer SMs over the PS domain. MSs that are both GPRS-attached and IMSI-attached shall transfer SMs over the PS domain or over the CS domain (if the CS domain is used, then paging for Mobile-terminated SMS may go through the SGSN).

The following two clauses define the operation of mobile-terminated and mobile-originated SMS routeing and transfer over the PS domain. More detailed definitions are contained in TS 23.040 [8]. They apply to SGSNs supporting the Gd or the Gdd interface.

16.1.1 Mobile-terminated SMS Transfer

Figure 96 and the description below show an example of a successful delivery of an SM to an MS in GERAN/UTRAN PS coverage over the PS domain.

RAN

SGSN

GGSN/

PGW

MSC/VLR

HLR/

HSS

SMS-G

SM-SC

Message Transfer

(SM, MS Address)

Send Routeing Info For Short Message

Send Routeing Info For Short Message Result

(SGSN Number, SGSN Diameter Identity, MSC Number)

Forward Short Message

(SM)

Message Transfer

(SM)

Forward Short Message Result

Delivery Report

Figure 96: Mobile-terminated SMS Transfer, Successful

1) The short message service centre determines it shall send an SM to an MS. SM‑SC forwards the SM to an SMS gateway MSC (SMS‑GMSC).

2) SMS‑GMSC examines the destination MS Address, and sends a Send Routeing Info For Short Message message to the relevant HLR/HSS.

3) HLR/HSS checks the subscriber data (e.g. ODB data and Call Barring Info) for the MS and determines that the MS is allowed to receive the SMS. The HLR/HSS returns a Send Routeing Info For Short Message Result message to the SMS‑GMSC. The result may contain the MS’s current SGSN Number, the MSC Number, or both. The result also contains the SGSN Diameter identity if the SGSN number is present and if Gdd is supported. If the result does not contain an SGSN Number (i.e., the HLR/HSS knows that the MS is not reachable via an SGSN), and if the result does contain an MSC Number, non-GPRS SMS delivery procedures are followed. If the result contains an SGSN Number, the SMS transfer proceeds according to the following events.

NOTE: SMS delivery via the SGSN is normally more radio resource efficient than SMS delivery via the MSC/VLR. The preferred delivery path is selected by SMS‑GMSC operator-specific action.

4) SMS‑GMSC forwards the SM to the SGSN.

5) SGSN transfers the SM to the MS on the RP and CP layers, as defined in TS 24.011 [13b].

6) SGSN returns a Forward Short Message Result message to the SMS‑GMSC indicating successful delivery of the SM.

7) SMS‑GMSC returns a Delivery Report to the SM‑SC indicating successful delivery of the SM.

CAMEL is not supported by SGSNs using EPS interfaces; otherwise CAMEL procedure calls shall be performed according to TS 23.078 [8b]:

C1) CAMEL_T_SMS_INIT.

The procedure returns as result "Continue".

C2) CAMEL_T_SMS_DELIVERED.

This procedure does not return a result.

16.1.1.1 Unsuccessful Mobile-terminated SMS Transfer

The SGSN or the HLR/HSS may not be able to deliver the SM to the MS. This may for example happen when the MS is not attached to GPRS, when the radio channel conditions are bad, or when the Mobile-terminated SMS is barred.

When the SGSN cannot deliver the SM to the MS, the SGSN sets the Mobile station Not Reachable for GPRS flag (MNRG), and returns a failure report to the SMS‑GMSC. Based on the routeing information received from the HLR/HSS, the SMS‑GMSC shall do one of the following:

– If an MSC/VLR is available for the MS, the SM is forwarded to the MS via the MSC/VLR. A successful delivery report shall be returned to the SM‑SC.

– If an MSC/VLR is not available for the MS, the Message Waiting Indication information in the HLR/HSS shall be updated and an unsuccessful delivery report shall be returned to the SM‑SC.

Figure 97 illustrates one possible traffic scenario when neither the SGSN nor the MSC is able to deliver the SM.

RAN

SGSN

GGSN/

PGW

MSC/VLR

HLR/

HSS

SMS-G

SM-SC

Message Transfer

(SM, MS Address)

Send Routeing Info For Short Message

Send Routeing Info For Short Message Result

(SGSN Number, SGSN Diameter Identity, MSC Number)

Forward Short Message

(SM)

Message Transfer: Failure

(SM)

Forward Short Message Result

Forward Short Message

(SM)

Message Transfer: Failure

Alert Request

Forward Short Message Result

Report SM Delivery Status

Report SM Delivery Status Result

Failure Report

Figure 97: Mobile-terminated SMS Transfer, Unsuccessful

1) The short message service centre determines it shall send an SM to an MS. SM‑SC forwards the SM to a SMS‑GMSC.

2) SMS‑GMSC examines the destination MS Address, and sends a Send Routeing Info For Short Message message to the relevant HLR/HSS.

3) HLR/HSS checks the subscriber data (e.g. ODB data and Call Barring Info) for the MS to determine whether the MS is allowed to receive the SMS. If the Mobile-terminated SMS is barred, the HLR/HSS returns a Send Routing Info for Short Message Error message with an appropriate cause. If the Mobile-terminated SMS is not barred, the HLR returns a Send Routeing Info For Short Message Result message to the SMS‑GMSC. The Result contains an SGSN Number and an MSC Number. The result also contains the SGSN Diameter identity if Gdd is supported.

4) SMS‑GMSC forwards the SM to the SGSN.

5) SGSN attempts to transfer the SM to the MS, but fails.

6) SGSN sets MNRG and returns a Forward Short Message Result message to SMS‑GMSC indicating unsuccessful delivery of the SM.

7) SMS‑GMSC selects an alternative route for the SMS, and forwards the SM to the MSC/VLR.

8) MSC/VLR attempts to transfer the SM to the MS, but fails.

9) The MSC/VLR requests the setting of the NGAF at the SGSN.

10) VLR sets MNRF and returns a Forward Short Message Result message to the SMS‑GMSC indicating unsuccessful delivery of the SM.

11) SMS‑GMSC sends a Report SM Delivery message to the HLR/HSS.

12) HLR/HSS updates its Message Waiting Indication fields and returns a Report SM Delivery Result message to the SMS‑GMSC.

13) SMS‑GMSC returns a Failure Report to the SM‑SC indicating unsuccessful delivery of the SM.

CAMEL is not supported by SGSNs using EPS interfaces; otherwise CAMEL procedure calls shall be performed according to TS 23.078 [8b]:

C1) CAMEL_T_SMS_INIT.

The procedure returns as result "Continue".

C2) CAMEL_T_SMS_FAILURE.

This procedure does not return a result.

C3) CAMEL_T_SMS_INIT.

The procedure returns as result "Continue".

C4) CAMEL_T_SMS_FAILURE.

This procedure does not return a result.

Figure 69 shows that the SGSN sends a Ready for SM (MS Reachable) message to the HLR/HSS when the MS becomes reachable and MNRG is set in the SGSN. The SGSN indicates also to the MSC/VLR when the MS becomes reachable and NGAF is set in the SGSN. If the MNRF is set at the MSC/VLR, the MSC/VLR sends a Ready for SM (MS Reachable) message to the HLR/HSS. Reception of a Ready for SM message or Update Location message when MNRG is set in the HLR/HSS shall trigger the SMS alert procedure as defined in TS 23.040 [8].

MNRG remains set in the SGSN independently of whether the MSC/VLR was successful in delivering the SM or not.
This means that the SGSN in certain cases sends a Ready for SM message to the HLR/HSS when an MS becomes reachable via the SGSN, even if no SM is waiting. This causes a small amount of duplicate signalling between the SGSN and the HLR/HSS only.

16.1.2 Mobile-originated SMS Transfer

Figure 98 and the description below explain the steps involved in sending an SM from an MS in GERAN/UTRAN PS coverage over the PS domain.

RAN

SGSN

GGSN/

PGW

MSC/VLR

HLR/

HSS

SMS-IW

SM-SC

Message Transfer

(SM)

Forward Short Message

(SM)

Message Transfer

(SM)

Delivery Report

Forward Short Message Result

Delivery Report

Figure 98: Mobile-originated SMS Transfer, Successful

1) The MS has an SM to send, and transfers the SM to the SGSN via RP and CP.

2) SGSN checks the MS subscription data (e.g. ODB data and Call Barring Info), and determines that the MS is allowed to originate the SMS. SGSN forwards the SM to a SMS interworking MSC (SMS‑IWMSC). If the MS is not allowed to originate the SMS, the SGSN returns an RP Error message with an appropriate cause.

3) SMS‑IWMSC passes the SM to the addressed SM‑SC.

4) SM‑SC returns a Delivery Report to the SMS‑IWMSC indicating successful delivery of the SM.

5) SMS‑IWMSC returns a Forward Short Message Result message to the SGSN indicating successful delivery of the SM.

6) SGSN returns a Delivery Report to the MS indicating successful delivery of the SM.

CAMEL is not supported by SGSNs using EPS interfaces; otherwise; otherwise CAMEL procedure calls shall be performed according to TS 23.078 [8b].

C1) CAMEL_O_SMS_INIT.

The procedure returns as result "Continue".

C2) CAMEL_O_SMS_SUBMITTED

This procedure does not return a result.

16.2 Circuit-switched Services (A/Gb mode)

The ability for a GPRS user to access circuit-switched services depends on the subscription held, the network capabilities, and the MS capabilities. Interaction between GPRS and circuit-switched services is described in clause "Interactions Between SGSN and MSC/VLR".

16.2.1 Suspension of GPRS Services

The MS shall request the network for suspension of GPRS services when the MS or the network limitations make it unable to communicate on GPRS channels in one or more of the following scenarios:

1 When a GPRS-attached MS enters dedicated mode and the support of Class A mode of operation is not possible (e.g. the MS only supports DTM (see TS 43.064 [11]) and the network only supports independent CS and PS).

2 During CS connection, the MS performs handover from Iu mode to A/Gb mode, and the MS or the network limitations make it unable to support CS/PS mode of operation, e.g. an MS in CS/PS mode of operation in Iu mode during a CS connection reverts to class‑B mode of operation in A/Gb mode.

3 When an MS in class A mode of operation is handed over to a cell where the support of Class A mode of operation is not possible (e.g. a DTM mobile station entering a cell not supporting DTM).

16.2.1.1 Suspend and Resume procedure (A/Gb mode)

In the following procedures, when a suspended MS is resumed, the MS should either deactivate the PDP context of streaming or conversational traffic class, or the MS should modify the PDP context of streaming or conversational traffic class to reset the maximum bit rate to a proper value (see clause "RNC/BSS-Initiated PDP Context Modification Procedure").

16.2.1.1.1 Intra-SGSN Suspend and Resume procedure

The Suspend and Resume procedure for intra-SGSN is illustrated in Figure 99.

Figure 99: Suspend and Resume Procedure for intra SGSN

1) The MS enters dedicated mode and the MS or the network limitations make it unable to support Class A mode of operation, or during CS connection, a DTM MS performs handover from a cell supporting DTM to a cell not supporting DTM.

2) The MS sends an RR Suspend (TLLI, RAI) message to the BSS. The BSS may terminate any ongoing GPRS traffic for this TLLI.

3) The BSS sends a Suspend (TLLI, RAI) message to the SGSN, and the SGSN acknowledges by returning Suspend Ack. The BSS shall store TLLI and RAI in order to be able to request the SGSN to resume GPRS services when the MS leaves dedicated mode.

4) Eventually, the BSS may determine that the conditions for the GPRS suspension have disappeared. If the BSS is able to request the SGSN to resume GPRS services, the BSS shall send a Resume (TLLI, RAI) message to the SGSN. The SGSN acknowledges the successful outcome of the resume by returning Resume Ack.

5) If the circuit switched radio channel is to be released, the BSS sends an RR Channel Release (Resume) message to the MS. The Resume message indicates whether the BSS has successfully requested the SGSN to resume GPRS services for the MS, i.e., whether Resume Ack was received in the BSS before the RR Channel Release message was transmitted. The MS leaves dedicated mode.

6) The MS shall resume GPRS services by sending a Routeing Area Update Request message to the SGSN:

– if the BSS did not successfully request the SGSN to resume GPRS services,

– if the RR Channel Release message was not received before the MS left dedicated mode,

– if the MS locally determines that the conditions for the GPRS suspension have disappeared

The Update Type depends on the mode of operation of the network in use e.g. in mode I Combined RA/LA Update is made and in mode II Routeing Area Update is made.

The full handling of suspended MSs in the BSS and the SGSN is implementation dependent. Typically, the SGSN should not page suspended MSs.

If the MS performs an inter-BSC handover while suspended, the TLLI and RAI should be transferred as BSC-to-BSC information in the Handover Required and Handover Request messages, see TS 48.008 [18]. This allows the new BSC to initiate the Resume request procedure to the SGSN. If the BSC-to-BSC information was not transferred or not understood, the MS doesn’t receive an indication that resumption has been successful, and the MS shall resume GPRS services by initiating a Routeing Area Update or Combined RA/LA Updating procedure as described in step 6.

16.2.1.1.2 Inter-SGSN Suspend and Resume procedure

The Suspend and Resume procedure for inter-SGSN is illustrated in Figure 100.

This describes the scenario where the old cell and the new cell are handled by different SGSN’s, i.e. suspend message is received in an SGSN that is different from the SGSN currently handling the packet data transmission.

Figure 100: Suspend and Resume Procedure for inter-SGSN

1) During CS connection, a DTM MS performs handover from a cell supporting DTM to a cell not supporting DTM.

2) The MS sends an RR Suspend (TLLI, RAI) message to the BSS.

3) The BSS sends a Suspend (TLLI, RAI) message to the SGSN.

– Since the SGSN that receives the Suspend message is not the one currently handling the packet data transmission, an indication to perform suspend will be sent to the old SGSN by means of a SUSPEND REQUEST message on the Gn interface. The address of the old SGSN is derived by "old RAI" received in Suspend message. If the SGSN that receives the Suspend message provides functionality for Intra Domain Connection of RAN Nodes to Multiple CN Nodes, the SGSN that receives the Suspend message from the BSS may derive the old SGSN from the old RAI and the old TLLI and send the Suspend Request message to this old SGSN. Otherwise, the SGSN that receives the Suspend message from the BSS derives the old SGSN from the old RAI. In any case the SGSN that receives the Suspend message from the BSS will derive an SGSN that it believes is the old SGSN. This derived SGSN is itself the old SGSN, or it is associated with the same pool area as the actual old SGSN and it will determine the correct old SGSN from the TLLI and relay the Suspend Request message to that actual old SGSN.

– The Old SGSN returns a SUSPEND RESPONSE.

– The new SGSN then returns Suspend Ack to the BSS.

4) After CS connection is terminated, the BSS may send a Resume (TLLI, RAI) message to the new SGSN, but since resume is not needed against the old SGSN, the new SGSN acknowledges the resume by Resume Nack.
(Resume is not needed against the old SGSN since the MS in this case always will perform an RA Update for updating of GPRS services when the CS connection is terminated and the MM context will be moved from the old to the new SGSN.)

5) The BSS sends an RR Channel Release message to the MS, indicating that the BSS has not successfully requested the SGSN to resume GPRS services for the MS. The MS leaves dedicated mode.

6) The MS shall resume GPRS services by sending a Routeing Area Update Request message to the SGSN. The Update Type depends on the mode of operation of the network in use e.g. in mode I Combined RA/LA Update is made and in mode II Routeing Area Update is made.

16.2.1.2 Inter-System Suspend and Resume procedure

16.2.1.2.1 Intra-SGSN Suspend and Resume procedure

The Suspend and Resume procedure for intra SGSN is illustrated in Figure 101.

Figure 101: Suspend and Resume Procedure for intra-SGSN

1) During CS connection, the MS performs handover from Iu mode to A/Gb mode and the MS or the network limitations are unable to support CS/PS mode of operation.

2) The MS sends an RR Suspend (TLLI, RAI) message to the BSS.

3) The BSS sends a Suspend (TLLI, RAI) message to the SGSN and:

– The SGSN may request the SRNS to stop sending downlink PDU’s by the SRNS Context Request message. The SRNS then starts buffering the downlink PDUs.

– The SRNS responds with an SRNS Context Response message.

– The SGSN then returns Suspend Ack to the BSS.

4) After CS connection is terminated, the BSS may send a Resume (TLLI, RAI) message to the SGSN, but resume is not possible since the MS has changed the radio system, so the SGSN acknowledges the resume by Resume Nack.

5) The BSS sends an RR Channel Release message to the MS, indicating that the BSS has not successfully requested the SGSN to resume GPRS services for the MS.

16.2.1.2.2 Inter-SGSN Suspend and Resume procedure

The Suspend and Resume procedure for inter SGSN is illustrated in Figure 102.

This describes the scenario when the suspend message is received in an SGSN that is different from the SGSN currently handling the packet data transmission and would be valid for at least the following cases:

– MS performs inter-system handover from Iu mode to A/Gb mode during CS connection and the SGSN handling the A/Gb mode cell is different from the SGSN handling the Iu mode cell, i.e. the 2G and 3G SGSNs are separated.

Figure 102: Suspend and Resume Procedure for inter-SGSN

1) During CS connection, the MS performs handover from Iu mode to A/Gb mode, and the MS or the network limitations make it unable to support CS/PS mode of operation.

2) The MS sends an RR Suspend (TLLI, RAI) message to the BSS.

3) The BSS sends a Suspend (TLLI, RAI) message to the SGSN.

– Since the SGSN that receives the Suspend message is not the one currently handling the packet data transmission, an indication to perform suspend will be sent to the 3G SGSN by means of a SUSPEND REQUEST message on the Gn interface. The address of the old SGSN is derived by "old RAI" received in the Suspend message. If the SGSN that receives the Suspend message provides functionality for Intra Domain Connection of RAN Nodes to Multiple CN Nodes, the SGSN that receives the Suspend message from the BSS may derive the old SGSN from the old RAI and the old TLLI and send the Suspend Request message to this old SGSN. Otherwise, the SGSN that receives the Suspend message from the BSS derives the old SGSN from the old RAI. In any case the SGSN that receives the Suspend message from the BSS will derive an SGSN that it believes is the old SGSN. This derived SGSN is itself the old SGSN, or it is associated with the same pool area as the actual old SGSN and it will determine the correct old SGSN from the TLLI and relay the Suspend Request message to that actual old SGSN.

– The 3G SGSN may request the SRNS to stop sending downlink PDU’s by the SRNS Context Request message. Upon reception of the SRNS Context Request message, the SRNS starts buffering the downlink PDUs.

– The SRNS responds with an SRNS Context Response message.

– The 3G SGSN return a SUSPEND RESPONSE.

– The 2G SGSN then returns Suspend Ack to the BSS.

4) After CS connection is terminated, the BSS may send a Resume (TLLI, RAI) message to the 2G SGSN, but since resume is not needed against the 3G SGSN the 2G SGSN acknowledges the resume by Resume Nack.
(Resume is not needed in this case since the MS always will perform an RA Update for updating of GPRS services when the CS connection is terminated and the MM context will be moved from 3G to 2G SGSN.)

5) The BSS sends an RR Channel Release message to the MS, indicating that the BSS has not successfully requested the SGSN to resume GPRS services for the MS.

16.2.1.3 Inter System Resume procedure

The resume procedure is only applicable in case of A/Gb mode to Iu mode handover.

16.2.1.3.1 Intra-SGSN Resume procedure

The procedure for resume of GPRS traffic at intra SGSN case is illustrated in Figure 103.

Figure 103: Resume of GPRS traffic at intra SGSN

1) The MS in A/Gb mode class-B mode of operation during CS connection performs handover to CS/PS mode of operation in Iu mode;
or the MS in class-A mode of operation capable of DTM performs handover during CS connection from an A/Gb mode cell not supporting DTM to an Iu mode cell.

2) The MS shall resume GPRS services, directly after the CS handover is completed, by sending a Routeing Area Update Request message to the SGSN, as described in clause " Inter System Change Procedure".

16.2.1.3.2 Inter-SGSN Resume procedure

The procedure for resuming GPRS traffic at inter-SGSN case is illustrated in Figure 104.

Figure 104: Resume of GPRS traffic at inter SGSN

1) The MS in A/Gb mode class-B mode of operation during CS connection performs a handover to CS/PS mode of operation in Iu mode;
or the MS in class-A mode of operation capable of DTM performs a handover during CS connection from an A/Gb mode cell not supporting DTM to an Iu mode cell.

The MS shall resume GPRS services, directly after the CS handover is completed, by sending a Routeing Area Update Request message to the SGSN, as described in clause " Inter System Change Procedure".

16.2.2 GPRS and Dedicated Mode Priority Handling

An MS in class‑B mode of operation that communicates on GPRS radio channels when a dedicated channel is needed, shall immediately abort the GPRS communication and trigger the Suspend and Resume procedure.

Response to circuit-switched paging, non-emergency Mobile-originated circuit-switched calls, Mobile-originated SMS, and Mobile-originated supplementary services are exceptions to the above rule. In these cases, it is an implementation choice whether to immediately abort GPRS communication or to delay the dedicated mode establishment.

16.3 Supplementary Services

For SMS over GPRS, only the invocation of Call Barring Supplementary Service is supported. The user control by using the Supplementary Service protocol is not supported over GPRS.

Other supplementary services are not defined for GPRS. Supplementary services may be available in the interworked packet data networks, but this is outside the scope of this specification.

16.4 CAMEL Services

CAMEL may be used for session and cost control. It may also be used for other operator-specific services. Subscription data received over Gr, as described in TS 23.078 [8b], enables CAMEL interactions. In this Release of the specification CAMEL Services are not applicable to subscriptions without MSISDN as existing messages have unresolved MSISDN references.

NOTE: Cost control with ability to correlate, using the Charging Id, with charging information from a GGSN/P‑GW depends on GGSN (Gn/Gp) or S‑GW (S4) providing a Charging Id that is unique for the PDP context. For S4, such uniqueness requires the S5/S8 to be GTP.

Annex A (normative):
APN and P-GW/GGSN Selection