09.023GPPMobile Application Part (MAP) specificationTS
The procedure may be invoked either by the gsmSCF or by a USSD application local to the HLR. It may start by using either the MAP_UNSTRUCTURED_SS_REQUEST or MAP_UNSTRUCTURED_SS_NOTIFY service.
In both cases the HLR will first check whether the MS is reachable .
If the MS is reachable, the HLR will initiate a MAP dialogue with the VLR. Once the dialogue is successfully established the message received from the gsmSCF or USSD application will be sent to the VLR.
Following transfer of the message the HLR will wait for a confirmation from the VLR. This will be sent to the gsmSCF or USSD application as appropriate.
Following this, the HLR may receive further uses of the MAP_UNSTRUCTURED_SS_REQUEST or MAP_UNSTRUCTURED_SS_NOTIFY services, or may receive a MAP_CLOSE_ind.
In the event of an error, the MAP process with the VLR shall be released and if necessary the MAP process with the gsmSCF shall be aborted, as shown in the diagram.
Message Originated by gsmSCF
If the message is originated by the gsmSCF then the HLR shall transfer the message transparently to the VLR.
The HLR may subsequently receive one or more MAP_UNSTRUCTURED_SS_REQUEST_ind or MAP_UNSTRUCTURED_SS_NOTIFY_ind indications from the gsmSCF. These shall be sent transparently to the VLR. When a confirmation is received from the VLR this shall be returned to the gsmSCF.
When the HLR receives a MAP_CLOSE_ind from the gsmSCF then it shall pass this to the VLR and close the MAP dialogue.
The procedure in the HLR is shown in figure 22.10.4/1 and 22.10.4/2.
Figure 22.10.4/1 (sheet 1 of 5): Procedure NI_USSD_HLR
Figure 22.10.4/1 (sheet 2 of 5): Procedure NI_USSD_HLR
Figure 22.10.4/1 (sheet 3 of 5): Procedure NI_USSD_HLR
Figure 22.10.4/1 (sheet 4 of 5): Procedure NI_USSD_HLR
Figure 22.10.4/1 (sheet 5 of 5): Procedure NI_USSD_HLR
Figure 22.10.4/2: Macro Start_USSD_HLR