In Ericsson it is an optional feature working from BSS07
It is required to have OSS-RC
if you want to use the GUI.
You have to use only IMSI (no TMSI)
Here below a description how it is working:
To be able to perform an IMSI trace it is necessary to get IMSI in two of the messages from the MSC (Common ID and Handover Request). This means that the MSC must change these messages.
Since IMSI and IMEI numbers are not used internally in the BSC they must be matched towards an MS Identity and an MS Context Identity. This is handled internally in the BSC. The MS Identity Established and MS Context Established, as well as RealTimeTrace(RTT) Mapping events are sent to OSS so that they can perform the same correlation.
When an MS becomes active the BSC must check to see if it belongs to an IMSI or IMEI trace. If the mobile belongs to a trace the BSC must send subscribed events to the OSS. The OSS shall present the events in a log file and/or on screen.
The BSC shall stop the trace when OSS has sent Unsubscribe Requests for all events included in the trace.
The trace shall continue from one BSC to another independently of which MSC or SGSN it belongs to as long as it is in the same operator’s network. This is possible since the Common Id or Handover Request message is received from each new MSC.
To be able to continue the trace when the mobile returns from another operator’s network it is required that the mobile makes a new call or PS connection. The new call will generate Common Id and then we will have the IMSI again and the trace can continue.
It shall also be possible to continue a trace of a mobile when it comes back from WCDMA. For CS it is possible to continue the trace (an ongoing call) since an Incoming Inter-System Handover event is generated which includes the MS Individual. For PS the trace will continue when the events once again are generated in the GSM network.