29.0023GPPMobile Application Part (MAP) specificationRelease 15TS
The MAP process invokes macros not defined in this clause; the definitions of these macros can be found as follows:
Receive_Open_Cnf see subclause 25.1.2;
Check_Confirmation see subclause 25.2.2;
Process_Access_Request_VLR see subclause 25.4.2.
The MAP_PROCESS_UNSTRUCTURED_SS_REQUEST from the MSC contains information input by the user; the message may be fed to an application contained locally in the VLR or to the HLR. The rules for determining this are specified in 3GPP TS 23.090 .
1) Message Destined for the HLR
If the message is destined for the HLR then the VLR shall transfer the message transparently to the HLR.
2) Message Destined for the Local Application
If the message is destined for the local USSD application then the VLR shall transfer the information contained in the message to the application.
The process in the VLR is shown in figure 22.9.3/1.