The Short Message Function in NMT includes handling of special call set-up procedure for mobile terminated short messages. The subscriber data shall content a subscriber category for terminals equipped with terminating SMS service.

The SMS-call is set up through the network as a normal telephone call and the «Short-Message» is delivered in the speech channel as «End to end» information between the SMSC and the MS.

When receiving a "Short Message" and there is no other pending message the SMSC shall immediately try to send the message to the subscriber by setting up a call.

In case the call set-up is unsuccessful or if clearing is initiated from the MS side, this is reported to the Gateway and "Short Message Waiting" indicator is set in the MTXV and in the HLR (See Message Waiting Indication).

When the indicator is sent to the MS the MTXV shall reset the flag and send a SUM message to reset the flag in the HLR.

If the subscriber has activated any call transfer service the HLR shall «raise a flag» in the MTXG and block for terminating SMS-calls from the SMSC until the Call forwarding is deactivated. In this case a "Message Waiting" indicator shall be set in the HLR/MTXH and in the MTXV.

If reception of the message is allowed, a roaming number is requested for a short message from the MTXV (If the MTXV does not support SMS, roaming number is fetched as for an ordinary call). The roaming number is returned to the MTXG in a GRM message

The MTXV will initiate the special call set-up procedure towards the MS. In case call set-up is unsuccessful or if clearing is initiated from the MS side, this is reported to the Gateway by telephony signals or in the MUP message SEM (as for an ordinary call).

In case the connection is terminated from the NMT side, the «Short Message Waiting» indicator is set both in the MTXV and in the HLR. The HLR is notified from the MTXG by existing call event reported in a GSE message.

In case the connection is terminated from the SMS centre, the delivery is considered as successful. The HLR is notified about successful delivery by existing call event reported in a GSE message and the indicator is reset.

The delivery procedure is terminated by a GET message sent from the HLR to the MTXG.

It is possible to receive messages even when the MS is roaming into a not upgraded VPLMN. Then no "Message Waiting "indicator is set and the message is received by a normal call set-up procedure.

From the MTX point of view, there is no difference between a mobile originated SMS call and an ordinary speech call. The subscriber calls the SMSC serving the terminating subscriber and the handshaking is starting when the speech path is established.

The short message is received as a normal call with telephony signalling (TUP or ISUP) in the MTXG.

A special «Calling Party Directory Number» sent to the MTXG from the Message Centre in an ordinary call reflects a «Message Waiting» indication. The message waiting call is identified and indicated in the «Call Origin» field in the GEI message.

The message waiting call is identified in the HLR by the «Call origin» and the «Calling Party Directory Number» in the GEI message. The Calling Party Directory Number indicates which message waiting indicator that is concerned. The concerned indicator is added to the current status of the message waiting indication in the HLR.

When the SMS-call from the SMS-Centre is received in the HLR, SMS waiting is set and a special SMS routing number is requested from the MTXV in the HRE message.

In case HRM is returned from the MTXV, the SMS call is delivered to the MTXV. The procedure is terminated in the HLR with a GET message indicating successful message call after reception of a GSE.

At successful(end to end) SMS call, the MTXV always initiates SUM with

"message waiting indication reset" to the HLR. SMS delivery is considered successful when the call clearing is initiated from the message centre.

In case HRR is returned from the MTXV, SMS waiting is indicated in the

MTXV. The procedure is terminated in the HLR with a GET indicating successful message call. Note that GET with reason "unsuccessful" is only returned if the SMS waiting indicator is not accepted and stored in the HLR.

When a Mobile station is updated in an MTXV the status of message waiting indicators are transferred in LUA message (see Message Waiting Indication).

When reading the "Short Message Indicator" in the MS the subscriber may call the SMSC and pick up the pending messages.

In case the short message is not allowed to be delivered due to unpermitted subscriber service active and the subscriber has the SMS active, SMS waiting may be marked and the procedure is terminated with a GET message towards the MTXG.

Figure 3.16.1.3a Short Message delivery, successful procedure

Figure 3.16.1.3b Short Message delivery, unsuccessful procedure

The Message Waiting Indication provides indication to the mobile station of the following types of message waiting indicators:

• short message
• voice mail
• FAX
• E-mail
• data

When a message enters the Message Centre, a normal call with telephony signalling is made towards the MTXG. The message waiting call is identified and indicated in the <<Call Origin>> field in the GEI message from the MTXG to the HLR/MTXH.

The <<Calling Party Directory Number>> received from the message centre together with the <<call origin>> is used to identify the concerned Message Waiting Indicator in the HLR.

When the GEI message is received in the HLR/MTXH, the message waiting indication may either be sent to the MTXV in the HRE message, for direct delivery to the mobile station, or in a CSU for delivery in the next MTX clearing towards the MS.

When HRM/HRR is returned from the MTXV, the procedure is terminated with a GET, indicating “successful message waiting call”. Note that GET with reason “unsuccessful” is only returned if the message waiting indicator is not accepted and stored in the HLR.

When a Mobile Station Registers in a new MTXV, the status of the message

waiting indicators are transferred in the Location Updating Accepted Message (LUA).

When reading the “Message Waiting Indicator” in the MS the subscriber may call the Message Centre and pick up the pending messages.

Figure 3.16.2.1 Message Waiting Indication delivery, successful procedure

The message centre may reset a message waiting indicator in the HLR/MTXH and the MTXV. The same procedure as when setting the indicator is utilized, but with a calling party directory number dedicated to reset the concerned type of message waiting indicator.

Figure 3.16.2.2 Procedure for Resetting of Message Waiting Indicators from the Message Centre

The MS will be alerted by the serving MTX if a message waiting indicator indicates pending messages. The message waiting indicator is cleared in the serving MTX when the information is sent to the MS in a MTX clearing sequence(Indicator in MS set). The MTXV is simultaneously sending a SUM message to clear the flag in the HLR.

Figure 3.16.2.3 Message Waiting Indication Reset procedure.