MSC (Mobile Switching Center)

An MSC, also known as a mobile switching center, is a telephone exchange that connects mobile users to other mobile networks, the public switched telephone network and other mobile users within the same network.

In addition, MSC handles a wide range of other tasks, such as connecting with other networks and routing SMS messages, conference calls, faxes, and service billing.

How does MSC work?

An MSC serves as the network switching subsystem's (NSS) command center. The MSC establishes connections between subscriber calls by transferring digital voice packets between network channels.

The MSC is situated between the base station and Public Switched Telephone Network (PTSN). All mobile communications from the base station are routed to the MSC. Voice calls, SMS, and supplementary services like FAX are managed by the MSC. Real-time pre-paid billing, account management, and call setup between subscribers are also handled by the MSC.

What are the functions of the MSC (Mobile Switching Center)?

The MSC serves as the main node in a GSM network. It is the node that regulates calls to and from MSs. An MSC's key functions consist of the following:

• Switching & call routing
  To effectively establish a call, an MSC may interact with other nodes and control call setup, supervision, and release. This also applies to calls that are forwarded from MSs to other networks, such as the PSTN.

• Direct access to the Internet
  Traditionally, an MSC used established networks, such as the PSTN, to connect to an ISP's Internet nodes. However, this feature allows an MSC to communicate with Internet nodes directly, which speeds up call setup. Tigris is an access server that can be used to allow direct access.

• Charging
  An MSC includes features for billing mobile calls as well as details on the specific charge rates to apply to a call at any given time or for a certain destination. This information is captured during a call and is stored afterwards to be sent to a billing center.

• Communication with HLR
  The main time that an MSC and HLR interact is when an MS call is being set up, and the HLR is asking the MSC for certain routing data.

• Communication with other MSCs
  During call setup or handovers between cells belonging to various MSCs, two MSCs may need to communicate with one another.