12.053GPPSubscriber Related Call and Event DataTS
Figure B.7 illustrates a mobile originated call from subscriber "A" to a second mobile subscriber "B" who has registered and activated Call Forwarding on Busy (CFB) for the appropriate service. The call is subsequently forwarded to a third mobile subscriber "C". In this example, all three subscribers are currently located within the same (the home) network.
For simplicity the registration and activation of CFB have not been included in the diagram.
Having received a setup request from subscriber "A" (1), the originating MSC (MSC-A) interrogates the HLR of subscriber "B" in order to determine his current location (1a). The call is then routed to MSC-B (2).
MSC-A shall create an MOC record for subscriber "A" containing details of the call to "B". The HLR shall produce an HLR interrogation record.
On determining that subscriber "B" is busy and that CFB is active, the forwarding MSC/VLR (MSC-B) interrogates the HLR of subscriber "C" to determine his current location (2a) and forwards the call accordingly (3).
MSC-B shall produce an MTC record for the "B" subscriber for the call from "A" and an MOC record for the "B" subscriber for the call to "C". Both records shall include the supplementary service employed (CFB). The HLR shall produce an Interrogation record.
The terminating MSC (MSC-C) shall create a normal MTC record for subscriber "C".
The records generated are subsequently transferred to the OS of the PLMN.
Figure B.7: Call forwarding conditional (busy)