MT Mobile Terminating (call)

Mobile Terminating (MT) refers to a call scenario in mobile telecommunications where the recipient of the call is a mobile device. In this case, the call is initiated by a calling party and terminated on the mobile device of the called party. This term is commonly used in the context of GSM (Global System for Mobile Communications) and other cellular networks.

When a call is made from one mobile device to another, the call goes through various stages and processes to reach its destination. The Mobile Terminating call process involves several steps, including call setup, routing, and call termination.

The call setup process begins when the calling party initiates a call by dialing the phone number of the called party. The calling party's mobile device sends a signaling message to the nearest base station, indicating the intent to make a call. The base station then forwards this signaling message to the Mobile Switching Center (MSC), which acts as a central hub for call routing and management.

Once the MSC receives the signaling message, it determines the location of the called party's mobile device. This is done by querying the Home Location Register (HLR) or the Visitor Location Register (VLR) associated with the called party's mobile network. The HLR contains subscriber information such as the mobile device's location and services, while the VLR holds temporary information about mobile devices currently within the coverage area of a particular MSC.

After the MSC retrieves the called party's location information, it establishes a path for the call to reach the called party's mobile device. This involves selecting a suitable base station or cell that covers the called party's location. The MSC sends a request to the selected base station to allocate resources for the call, including radio channels for voice transmission.

Once the resources are allocated, the base station initiates paging to the called party's mobile device. Paging is the process by which the base station broadcasts a message to locate the called party's mobile device and alert it to an incoming call. The mobile device responds to the paging message, indicating its presence and readiness to receive the call.

Upon receiving the response from the called party's mobile device, the base station relays this information to the MSC. The MSC then establishes a connection between the calling party and the called party's mobile device. This connection is set up using circuit-switched or packet-switched technologies, depending on the network architecture and available services.

Once the connection is established, voice data is transmitted between the calling party and the called party's mobile device. The voice data is encoded, modulated, and transmitted over the air interface between the base station and the mobile device. In the case of a GSM network, the voice data is typically encoded using a codec such as the Adaptive Multi-Rate (AMR) codec.

During the call, the MSC continuously monitors the quality of the connection and manages handovers if necessary. Handover is the process of transferring an ongoing call from one base station to another as the mobile device moves between cells. Handovers ensure uninterrupted communication and optimal signal quality as the mobile device roams within the network coverage area.

Finally, when either party decides to end the call, they initiate call termination. The termination process involves signaling messages exchanged between the mobile devices, the base station, and the MSC to release the allocated resources and disconnect the call. The MSC updates the necessary network databases with the call duration and any applicable charging information.

In summary, Mobile Terminating (MT) refers to the scenario where a call is initiated by a calling party and terminated on the mobile device of the called party. The call setup process involves signaling messages exchanged between the calling party's mobile device, the base station, and the MSC. The MSC determines the location of the called party's mobile device, establishes a path for the call, and allocates resources for voice transmission.