4.3.2 Handling of FM control in FFNb

23.0943GPPFollow-Me (FM)Release 17Stage 2TS

If the FFN is an HLR, the FFN is responsible for handling the interactions between FM and CFU. Two kinds of request may be received in an FFN which deals with forwarding services:

– CFU requests sent by the VLR for CFU operations (only if the FFN is a HLR);

– FM-HLR-Requests which are USSD strings sent by HLRa for FM operations.

When the control process in the FFN receives a CFU request, it shall either pass the CFU operation request directly to a CFU process or reject it depending on the registration and/or activation states of both FM and CFU services (see Table A.1 for permission checks).

On receipt of an HLR-FM request, the control process in the FFN performs a series of FM specific checks and checks the states of both FM and CFU. If the checks are successful, a CFU operation request is sent to a CFU process. On receipt of an HLR-FM-Request from HLRa, the FFN performs a series of checks. e.g.:

– if the remote party is a GSM subscriber:

– provisioning of FM to the remote party;

– provisioning of CFU to the remote party;

– illegal interaction with CFU registered or active to remote party.

– if the remote number is registered in the FFN;

– if any operator specific restrictions to engage in FM activity with the initiating subscriber apply;

– specific checks for forced erasure.

Depending on the requested operation, one of the following procedures is performed:

– registration with implicit Activation (procedure Handle_Remote_Party_Registration, figure 4.6);

– erasure with implicit Deactivation (procedure Handle_Remote_Party_Erasure, figure 4.7);

– interrogation (procedure Handle_Remote_Party_Interrogation, figure 4.8).

For successful forced erasure by a service supervisor, the FFN shall generate an USSD-Notify message and send it to the HLRp, which will relay the USSD Notify towards the MS of the previously registered subscriber (MSp). On receipt of an error response that the USSD Notify message could not be transferred to the MS, the FFN shall check the error code of the response. Depending on the error types and the specific implementation the process shall decide to resend the USSD message after a predefined time.

For the resend procedure the process shall start a timer. On timer expiry it shall send the message again. The FFN shall repeat the messages up to 5 times.

The length of the timer is defined by operator and has the value in the range of 1 – 10 minutes.

Figure 4.3 shows the message flow between the process Forwarding_Service_Control and the processes handling CFU operation requests, defined in 3GPP TS 23.082 [9].

Figure 4.3: FFN_processes

4.4 Process Forwarding_Service_Control

Figure 4.5: Procedure: FM_Remote_Party_Handling_in_FFN

Figure 4.6: Procedure: Handle_Remote_Party_Registration

Figure 4.6a: Procedure Register_FM_for_Remote_Party

Figure 4.7: Procedure: Handle_Remote_Party_Erasure

Figure 4.7a: Procedure Erase_FM_for_Remote_party

Figure 4.8: Procedure Handle_Remote_Party_Interrogation

Figure 4.9: Process FFN_Forced_Erasure_Notify