MSC Functionalities

Mobile Switching Center (MSC) is a server which facilitates the communication between Gateway Mobile Swithching Center (GMSC) and the Mobile Station (MS)

Receiving Short Message (SM)

This is the context where MT messages are received by the MSC, to be delivered to the intended user. Messages will be sent to MSC through the Gateway MSC (GMSC) which is responsible of handling the MT messages from the Service Center (SC). When the MT message is received there are two actions to be completed by the MSC.

• Reception of the short message (SM) Transfer Protocol Data Unit (TPDU), that is the message
• Retrieving information from the VLR to perfome the delivery of the message.

If an error report is returned from the VLR, MSC should return appropriate error information to the GMSC, which will notify SC about that. And SC will execute necessary actions for that scenario.

If no error report is returned form the VLR, MSC will transfer the messge to the mobile station, that is to the subscriber.

Once the delivery confirmation is received by the MSC, that is a message indicating that it has been transfered to the subscriber, MSC will send it to the GMSC in a delivery report format, a success report.

If a negative report is received about the delivery process, the same process will be applied except that the MSC will send a failure report to the GMSC along with the associated reason.

If the delivery fails due to a temporary error, memory not available in the MS, once MS sends a notification indicating the memory availability, then VLR is queried. If an error is returned, MS will be notified about the situation or else if no errors are returned, will notify GMSC about the memory availability.

When the MS and MSC is busy perfomring anothe action, message will be stored in the MSC for a short amount of time, which is less than the supervision time (time taken to take necesary actions for stored messages). Just after MS becomes available, MSC sends the message to the MS.