The following sections review the MAP operations that are used in each of these categories. Subscriber Tracing Subscriber tracing has two operations: activateTraceMode and deactivateTraceMode | Operation and Maintenance Operation and maintenance can be divided into the following categories Subscriber Tracing Miscellaneous The following sections review the MAP operations that are used in each of these categories. Subscriber Tracing Subscriber tracing has two operations activateTraceMode and deactivateTraceMode. activateTraceMode The HLR uses activateTraceMode to activate trace subscriber tracking mode for a particular subscriber IMSI the OSS requests activateTraceMode. The VLR waits for that particular MS to become active at which time it sends a request to its MSC to trace the MS. Figure 13-5. MAP Operation Sequence to Initiate and Terminate Subscriber Tracing deactivateTraceMode Upon receiving this message the HLR turns off the trace mode and sends the message to the VLR which also disables trace mode for that particular subscriber. See activateTraceMode. Miscellaneous The only operation in the Miscellaneous subcategory is sendIMSI. Following the OMC s request to the VLR to identify a subscriber based on his Mobile Subscriber ISDN Number MSISDN the VLR and HLR exchange sendIMSI messages. If the MSISDN cannot be identified an unknown subscriber indication is passed to the VLR. Otherwise the IMSI is obtained from the HLR and returned to the VLR. Figure 13-6. MAP Operation Sequence When an Operations and Management Center OMC Requests Subscriber Identity Call Handling The call handling procedures primarily retrieve routing information to allow mobile terminating calls to succeed. When a mobile originating or a mobile terminating call has reached the destination MSC no further MAP procedures are required. Other procedures performed by MAP s call handling routines include the restoration of call control to the Gateway Mobile Switching Center GMSC if the call is to be forwarded. In addition the call handling routing processes the notification that the remote user is free for the supplementary service message call completion to busy subscribers CCBS . Call .
