MOC and MTC

CALL TO A MOBILE STATION

The difference between making a call to a mobile subscriber and a PSTN network subscriber is that the mobile subscriber’s location is unknown. Therefore, the mobile station must be paged before a connection can be made. The steps in the call setup procedure from a PSTN subscriber to a mobile station are listed below. The numbers refer to figure

1. The PSTN subscriber dials the mobile subscriber’s number. the Gateway MSC receives the call.

2. The Gateway MSC requires the HLR for the information needed to route the call to the serving MSC/VLR.

3. The GMSC routes the call to the MSC.

4. MSC checks VLR for the Location Area of the mobile station.

5. MSC contacts the mobile station via BSC and BTS by sending a page request.

6. The mobile station responds.

7. BSC selects a traffic channel and orders the mobile station to tune to this traffic channel. The mobile station generates a ringing signal and when the subscriber answers the speech-connection is established.

CALL FROM A MOBILE STATION

When a mobile station wishes to establish a speech call, the following steps are performed: the numbers refer to figure.

1. Mobile subscriber dials the number.
2. MSC /VLR receives a message requesting access.
3. MSC /VLR checks if the mobile station is authorized to initiates a call set up to the PSTN network.
4. the dialed number is analyzed by MSC /VLR , which in turn initiates a call set-up to the PSTN network.
5. MSC / VLR asks bsc to allocate a free traffic channel. This information is forwarded to BTS and the mobile station.
6. the person receiving the call answer and a connection is established.