5.2 Procedure for SBI-based MO SMS

23.5403GPP5G System: Technical realization of Service Based Short Message ServiceRelease 17Stage 2TS

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

5.2.1 General

The procedure for SBI-based MO SMS is showed in Figure 5.2.2-1, which is based on MO SMS procedures in 3GPP TS 23.040 [2] clause 10.2. Compared to procedures in 3GPP TS 23.040 [2], new services are introduced in, including:

– Niwmsc_SMService service provided by SMS-IWMSC.

This new service is registered in NRF, and can be invoked by service consumers.

5.2.2 Procedure for Successful Mobile Originated short message transfer

Figure 5.2.2-1: Procedures for successful SBI-based SM MO message transfer

0 SMS-IWMSC registers Niwmsc_SMService service in the NRF, during the NF registration procedure.

1 MO SM message transfer from UE to SMSF through AMF follows the current procedure as defined in 3GPP TS 23.040 [2]

2a If SMSF knows from local configuration that the target SMS-IWMSC does not support SBI, it shall quit the SBI-based procedure and fallback to legacy (MAP/Diameter) protocol based procedures, as defined in TS 23.040 [2],

or SMSF invokes the Nnrf_NFDiscovery to discover and select serving SMS-IWMSC with the parameters of SUPI and/or GPSI and/or location (e.g. TAIs, CGIs, etc.) and/or E.164 address of the SC.

2b If no SMS-IWMSC could be discovered, the NRF shall feedback to SMSF, and SMSF shall quit the SBI-based procedure and fallback to legacy (MAP/Diameter) protocol based procedures, as defined in TS 23.040 [2].

If a SMS-IWMSC is discovered and selected, NRF returns the IP addresses or FQDNs of the serving SMS-IWMSC to provide Niwmsc_SMService service to SMSF.

3 SMSF sends a Niwmsc_SMService_MoForwardSm service request to the URI of serving SMS-IWMSC, which is obtained in step 2b. The payload body of the request shall contain the SM record to be sent, the Service Centre address, the callbackURI for MO SMS Delivery Report, the timer for waiting the MO SMS Delivery Report, and optionally contains the Access Type.

4 MO SMS delivery procedure between SMS-IWMSC and SC is the same as the definition in step 4 of Figure 4.13.3.3-1 of 3GPP TS 23.502 [4].

5 SMS-IWMSC sends Niwmsc_SMService_MoForwardSm response to deliver the MO SMS delivery report to the URI of serving SMSF, which is obtained in step 3

6 MO SMS delivery report procedure between SMSF, AMF and UE is the same as the 3GPP TS 23.502 [4].

When no more SMS is to be sent, the procedure for CP-ack and SMS ack is the same as the 3GPP TS 23.502 [4].

These procedures are defined in step 6a to 6d of Figure 4.13.3.3-1 of 3GPP TS 23.502 [4].

5.2.3 Unsuccessful Mobile Originated short message transfer

Figure 5.2.3-1 depicts procedure for unsuccessful SBI-based SM MO message transfer

Figure 5.2.3-1: Procedures for unsuccessful SBI-based SM MO message transfer

0-3 The same as the procedures in step 0-3 of Figure 5.2.2-1 in clause 5.2.2

4 SMS-IWMSC sends Niwmsc_SMService_MoForwardSm response with HTTP status code for application errors as defined in Table 5.3.2-1.

5 Failure report from SMSF to UE, with the error cause code as defined in Table 5.3.2-2.

SMS-IWMSC indicates the different errors for MO SM transfer in MoForwardSm response according to the different failure scenarios which happened during MO SM transfer. The Application Errors used in Niwmsc_SMService_MoForwardSm response are defined in Table 5.3.2-1 below

Table 5.3.2-1: Application errors

Application Error	HTTP status code	Description
UNKNOWN_SERVICE_CENTRE_ADDRESS	403 Forbidden	The delivery of the MO short message failed because SMS-SC was unknown.
SERVICE_CENTRE_CONGESTION	403 Forbidden	The delivery of the MO short message failed because SMS-SC was in congestion.
USER_NOT_SERVICE_CENTER	403 Forbidden	The delivery of the short message failed because the user didn’t belongs to the SMS-SC.
FACILITY_NOT_SUPPORTED	403 Forbidden	The delivery of the MO short message failed because of facility not supported.
INVALID_SME_ADDRESS	403 Forbidden	The delivery of the MO short message failed because the SME address is invalid.
UNREACHABLE_SMS_SC	504 Gateway Timeout	The delivery of the MO short message failed because the response is timeout.

If errors are indicated by the SMS-IWMSC, the SMSF shall send a failure report (i.e. a RP-ERROR message) to the UE, with the error cause coded as following map between errors indicated by SMS-IWMSC and error cause code in RP-ERROR message:

Table 5.3.2-2: MAP of Application errors

Return error from SMS-IWMSC	Cause value in the RP‑ERROR message
The Response from SMS-IWMSC is timeout Unspecified 4xx/5xx error code	38 Network out of order
403 Forbidden with FACILITY_NOT_SUPPORTED	69 Requested facility not implemented
403 Forbidden with UNKNOWN_SERVICE_CENTRE_ADDRESS	1 Unassigned number
403 Forbidden with SERVICE_CENTRE__CONGESTION	42 Congestion
403 Forbidden with USER_NOT_SERVICE_CENTER	28 Unidentified subscriber
403 Forbidden with INVALID_SME_ADDRESS	21 Short message transfer rejected

NOTE: The coding and the use of the RP‑ERROR message is specified in 3GPP TS 24.011 [8].

5.2.4 MSISDN-less MO SMS message transfer

The procedure for SBI-based MSISDN-less MO SMS message transfer is depicted in Figure 5.2.4-1,

Figure 5.2.4-1: Procedures for MSISDN-less MO SMS message transfer

0 NEF registers Nnef_SMService_MoForwardSm service and supporting long/short code ranges in NRF, during the NF registration procedure.

1 MO SMS transmit from UE to SMS-SC, as already defined in clause 5.2.2.

2a-2b SMS-SC provides destination SME address (long/short code of the AF) to NRF for NEF selection, and chooses Nnef_SMService_MoForwardSm service for MSISDN-less MO SMS submit.

3 SMS-SC forwards MO SM to NEF, by invoking Nnef_SMService_MoForwardSm service.

4-5 Nudm_SDM_Get and response between NEF and UDM, which refers to Step 3-Step 4 of Figure 4.13.7.2-1 in TS 23.502 [4].

6 The NEF provides a Nnef_MSISDN-less_MO_SMS Notify, which refers to Step 5 of Figure 4.13.7.2-1 in TS 23.502 [4].

7 NEF sends Nnef_SMService_MoForwardSm response to SMS-SC, carrying a success or failure delivery indication to SMS-SC.

8 SMS-SC indicates success/failure back to UE using existing SBI-based SMS delivery report defined in clause 6.2.2.