6.9 Service-level Interworking: Concatenated Short Messages delivered as a large Instant Message

23.2043GPPRelease 16Stage 2Support of Short Message Service (SMS) over generic 3GPP Internet Protocol (IP) accessTS

An IMS registered user with IM service or CPM service receives a concatenated short message delivered as two or more short messages. The information below describes the behaviour when the received concatenated Short Message exceeds the maximum payload size of an Instant Message.

Figure 6.9: Concatenated Short Messages delivered as an IM large message

1) The UE registers to the S-CSCF according to the IMS registration procedure.

2) The SMS-SC forwards a Short Message that is part of a concatenation of two or more Short Messages to the SMS-GMSC.

3a) The SMS GMSC interrogates the HSS to retrieve routeing information. Based on the pre-configured IP-SM-GW address for the user, the HSS forwards the request to the corresponding IP-SM-GW.

3b) The HLR/HSS returns the IMSI and the address(es) of the current MSC, SGSN, MME and/or SMSF to the IP-SM-GW for delivery of the SMS SM in CS/PS domain.

3c) The IP-SM-GW creates a MT Correlation ID as per TS 23.040 [2], which associates the Routeing Info retrieval with the subsequent Forward Short Message messages(s), and stores this along with the IMSI of the receiving subscriber. The IP-SM-GW returns to the SMS-GMSC the address of itself, along with the MT Correlation ID in the IMSI field, as routeing information. Alternatively, the IP-SM-GW may return the address(es) of the current MSC, SGSN, MME and/or SMSF, in which case, the subsequent procedure to forward the message is the same as defined in TS 23.040 [2].

4) The SMS-GMSC delivers the Short Message to the IP-SM-GW in the same manner that it delivers the Short Message to an MSC, SGSN, MME or SMSF, including the MT Correlation ID received from the IP-SM-GW, in place of the IMSI.

5) The IP-SM-GW checks whether the recipient is authorized for the interworking service. If the user is authorized, the IP-SM-GW recognizes that the received message is part of a concatenated Short Message and stores the received message.

NOTE 1: The IP-SM-GW needs to have access to a persistent storage in order to aggregate all the Short Message parts.

6) The IP-SM-GW acknowledges the Forward Short Message to the SMS-GMSC.

7) The SMS-GMSC may send a Report SM Delivery Status to the HSS. The HSS shall ignore the information provided in this report.

8) The SMS-GMSC sends a Delivery report (SMS-DELIVER-REPORT) to the SMS-SC.

9) The SMS-SC forwards the next Short Message that is part of a concatenation of two or more Short Messages to the SMS-GMSC.

NOTE 2: If this is not the last Short Message of the concatenation, then processing continues at step 4.

10) If this is the last Short Message of the concatenation, then the SMS GMSC delivers the Short Message to the IP-SM-GW in the same manner that it delivers the Short Message to an MSC, SGSN, MME or SMSF, including the MT Correlation ID received from the IP-SM-GW, in place of the IMSI.

11) The IP-SM-GW checks whether the recipient is authorized for the interworking service. If the user is authorized, the IP-SM-GW recognizes that the received message is part of a concatenated Short Message and stores it.

12-13) Once all the segments have been received, the IP-SM-GW establishes an MSRP session with the recipient’s UE to deliver the message. The session invitation is sent to the recipient UE.

NOTE 3: As a matter of implementation efficiency, the IP-SM-GW may initiate the connection towards the recipient after receiving the first Forward Short Message and passing a service authorization check. This may help prevent timeouts at the SMS GMSC (while it waits for the final Delivery report) but may also result in unnecessary session initiation signalling if there is a failure in a service check for subsequently received Short Messages.

14) The IP-SM-GW delivers the message in one or more MSRP SEND requests to the recipient UE.

15) -16) The IP-SM-GW closes the session after message delivery is complete.

17) The IP-SM-GW acknowledges the Forward Short Message to the SMS-GMSC.

18) The IP-SM-GW may send a Report SM Delivery Status to the HLR/HSS for either of the following cases:

– setting of the Message Waiting flags when the Forward Short Message was unsuccessful;

– clearing of the Message Waiting flags in HLR/HSS when the Forward Short Message was successful, but had previously failed.

NOTE 4: See TS 23.040 [2] for a full explanation of when the Message Waiting flags are set and unset.

19) The SMS-GMSC may send a Report SM Delivery Status to the HSS. The HSS shall ignore the information provided in this report.

20) The SMS-GMSC sends a Delivery report (SMS-DELIVER-REPORT) to the SMS-SC.