Mobile terminated call (MTC)
- If the subscriber receives the call, he is involved in a mobile terminated call (MTC). Then, the mobile subscriber is the called party.
- In this case, all entities cooperate to direct an incoming call to the mobile subscriber.
- First of all, only the home location register (HLR) knows the subscriber’s location. Therefore, during call setup, a certain switch in the network has to ask the HLR for this information, i.e. interrogation.
- If the call originates in the same PLMN, the interrogation procedure is started by the originating MSC/VLR, otherwise by the gateway MSC (GMSC).
- Secondly, when the call arrives at the servicing MSC/VLR, i.e. the MSC/VLR in whose area the subscriber is located, contact is made with the mobile subscriber and call setup is completed.