25.6 IMEI Handling Macros

09.023GPPMobile Application Part (MAP) specificationTS

The following macros are used in the GSM network in order to enable handling and checking of the mobile equipment identity.

25.6.1 Macro Check_IMEI_MSC

This macro is used by the MSC to receive a request from the VLR, relay it to the EIR, and pass the result from the EIR back to the VLR. The macro proceeds as follows:

– a MAP_CHECK_IMEI service indication containing only the Invoke Id is received from the VLR;

– if the IMEI is not available in the MSC, it is requested from the MS using the IDENTITY REQUEST message;

– if the MS releases the radio resources, a MAP_U_ABORT request indicating "Application procedure Cancellation" is sent to the VLR, and the "Error" exit of the macro is used;

– when the IMEI is known, a connection is set up towards the EIR, and a MAP_CHECK_IMEI service request is sent including the IMEI;

– if the opening of the dialogue fails, a System Failure is reported to the VLR. Otherwise, the MSC waits for a response from the EIR;

– when the MAP_CHECK_IMEI service confirm is received, it is checked for errors. Any errors discovered in the MSC lead to the System Failure error to be reported to the VLR in the MAP_CHECK_IMEI response. Any errors reported from the EIR are sent directly to the VLR in the MAP_CHECK_IMEI service response. If no errors are detected by or reported to the MSC, the IMEI is added to the MAP_CHECK_IMEI service response returned to the VLR. The "OK" exit is used in all cases;

– if a MAP_P_ABORT, MAP_U_ABORT, MAP_CLOSE or MAP_NOTICE service indication is received from the EIR, the MSC closes the transaction with the EIR (if necessary), reports a System Failure error back to the VLR in the MAP_CHECK_IMEI response, and uses the macro’s "OK" exit;

– if a MAP_P_ABORT, MAP_U_ABORT, MAP_CLOSE or MAP_NOTICE indication is received from the VLR, the MSC closes the transaction with the VLR (if necessary) and aborts the connections towards the EIR and the MS; the macro takes the "Error" exit.

If the dialogue with the EIR drops back to version 1, the result or error returned by the EIR is checked. The use of the "Check_Confirmation" macro in the SDL diagram indicates that the checks carried out on the result returned by the EIR in a MAP v1 dialogue are functionally equivalent to those carried out on the parameters of the MAP_CHECK_IMEI confirm received from the EIR in a MAP v2 dialogue.

The macro is described in figure 25.6/1.

25.6.2 Macro Check_IMEI_VLR

This macro is used by the VLR to control the check of a mobile equipment’s IMEI. The macro proceeds as follows:

– a MAP_CHECK_IMEI service request is sent to the MSC, including only the Invoke Id;

– the VLR then waits for the response from the MSC;

– if a MAP_CHECK_IMEI service confirm including either:

– the IMEI and the Equipment Status; or

– an error;

is received, the VLR checks whether the response requires that an alarm be generated on the Operation and Maintenance interface. The criteria for such alarms are PLMN operator dependent;

– the VLR then checks whether the response from the MSC means that service is granted to the MS. The criteria for granting service depending on the equipment status or errors received in the MAP_CHECK_IMEI service response are also PLMN operator dependent;

– if a MAP_P_ABORT, MAP_U_ABORT, MAP_CLOSE or MAP_NOTICE indication is received from the MSC, then the MSC connection is closed (if necessary) and the macro takes the "Aborted" exit.

The macro is described in figure 25.6/2.

25.6.3 Process Check_IMEI_EIR

This process is used by the EIR to obtain the status of a piece of mobile equipment, upon request from the MSC or from the SGSN. The process acts as follows:

– a MAP_OPEN service indication is received (macro Receive_Open_Ind, subclause 25.1.1). If the dialogue opening fails, the process terminates;

– otherwise, a MAP_CHECK_IMEI indication is received by the EIR, containing the IMEI to be checked;

– the EIR checks the service indication for errors. If there are any, they are reported to the MSC or to the SGSN in the MAP-CHECK_IMEI response. If no errors are detected, the EIR data base function is interrogated for the status of the given equipment. Further details are found in GSM 02.16;

– the status of the equipment (white-listed, grey-listed, black-listed or unknown) is returned to the MSC or to the SGSN in the MAP_CHECK_IMEI service response;

– if a MAP_U_ABORT, MAP_P_ABORT, MAP_NOTICE or MAP_CLOSE indication is received from the MSC or from the SGSN at any time during this process, the process in the EIR terminates.

The process is described in figure 25.6/3.

25.6.4 Macro Obtain_IMEI_MSC

This macro is used by the MSC to respond to a request from the VLR to provide the IMEI. The macro proceeds as follows:

– a MAP_OBTAIN_IMEI service indication containing only the Invoke Id is received from the VLR;

– if the IMEI is not available in the MSC, it is requested from the MS using the IDENTITY REQUEST message;

– when the IMEI is known, it is returned to the VLR in the MAP_OBTAIN_IMEI service response. The macro terminates at the "OK" exit;

– if the IMEI cannot be obtained by the MSC, the System Failure error is reported back to the VLR in the MAP_OBTAIN_IMEI service response. The macro terminates at the "OK" exit;

– if a MAP_P_ABORT, MAP_U_ABORT or MAP_CLOSE indication is received from the VLR, the macro terminates at the "Error" exit.

The macro is described in figure 25.6/4.

25.6.5 Macro Obtain_IMEI_VLR

This macro is used by the VLR to obtain the IMEI from the MSC, e.g. to enable handling of emergency calls in case of authentication failure (in which case the IMEI may be used by some operators as an alternative to the IMSI). It proceeds as follows:

– the MAP_OBTAIN_IMEI service request is sent to the MSC, including only the Invoke Id;

– the VLR then waits for the response from the MSC;

– if the IMEI is received in the MAP_OBTAIN_IMEI service response, the macro terminates at the "OK" exit;

– if the System Failure error is reported in the MAP_OBTAIN_IMEI service response, the "Error" exit is used;

– if the MSC terminates the dialogue using a MAP_P_ABORT, MAP_U_ABORT, MAP_CLOSE or MAP_NOTICE service indication, the necessary connections are released, and the "Aborted" exit is used for termination of the macro.

The macro is shown in figure 25.6/5.

Figure 25.6/1 (sheet 1 of 2): Macro Check_IMEI_MSC

Figure 25.6/1 (sheet 2 of 2): Macro Check_IMEI_MSC

Figure 25.6/2: Macro Check_IMEI_VLR

Figure 25.6/3: Process Check_IMEI_EIR

Figure 25.6/4: Macro Obtain_IMEI_MSC

Figure 25.6/5: Macro Obtain_IMEI_VLR

25.6.6 Process Check_IMEI_SGSN

This process is used by the SGSN to control the check of a mobile equipment’s IMEI. The process proceeds as follows:

– if the MS does not complete successfully the procedure, the "Error" exit of the macro is used;

– when the IMEI is known, a connection is set up towards the EIR, and a MAP_CHECK_IMEI service request is sent including the IMEI;

– if the opening of the dialogue fails, a System Failure is set. Otherwise, the SGSN waits for a response from the EIR;

– if a MAP_CHECK_IMEI service confirm including either:

– the IMEI and the Equipment Status; or

– an error;

is received, the SGSN checks whether the response requires that an alarm be generated on the Operation and Maintenance interface. The criteria for such alarms are PLMN operator dependent;

– the SGSN then checks whether the response from the EIR means that service is granted to the MS. The criteria for granting service depending on the equipment status or errors received in the MAP_CHECK_IMEI service response are also PLMN operator dependent;

If the dialogue with the EIR drops back to version 1, the result or error returned by the EIR is checked. The use of the "Check_Confirmation" macro in the SDL diagram indicates that the checks carried out on the result returned by the EIR in a MAP v1 dialogue are functionally equivalent to those carried out on the parameters of the MAP_CHECK_IMEI confirm received from the EIR in a MAP v2 dialogue.

The process is described in figure 25.6/6.

Figure 25.6/6 (sheet 1 of 2): Process Check_IMEI_SGSN

Figure 25.6/6 (sheet 2 of 2): Process Check_IMEI_SGSN