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.
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.
The IP-SM-GW creates a MT Correlation ID as per TS 23.040, 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.
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.
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.
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.
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.
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.