!!! Overview
[{$pagename}] ([MSC]) is the primary service delivery node for [GSM]/[CDMA], responsible for routing [voice] calls and [SMS] as well as other services (such as conference calls, [FAX] and circuit switched [data]).

The [{$pagename}] sets up and releases the end-to-end connection, handles mobility and hand-over requirements during the call and takes care of charging and real time pre-paid account monitoring.

In the [GSM] mobile phone system, in contrast with earlier analogue services, fax and data information is sent directly digitally encoded to the [{$pagename}]. Only at the [{$pagename}] is this re-coded into an "analogue" signal (although actually this will almost certainly mean sound encoded digitally as PCM signal in a 64-kbit/s timeslot, known as a DS0 in America).

There are various different names for [{$pagename}]s in different contexts which reflects their complex role in the network, all of these terms though could refer to the same MSC, but doing different things at different times.

The [Gateway MSC] ([G-MSC]) is the [MSC] that determines which "[visited MSC] ([V-MSC])" the subscriber who is being called is currently located at. It also interfaces with the [PSTN]. All mobile to mobile calls and [PSTN] to mobile calls are routed through a [G-MSC]. The term is only valid in the context of one call since any [MSC] may provide both the gateway function and the [Visited MSC] function, however, some manufacturers design dedicated high capacity [MSCs] which do not have any [BSSs] connected to them. These [MSCs] will then be the [Gateway MSC] for many of the calls they handle.

The [visited MSC] ([V-MSC]) is the [MSC] where a customer is currently located. The [VLR] associated with this [MSC] will have the subscriber's [data] in it.

The anchor [MSC] is the [MSC] from which a handover has been initiated. The target [MSC] is the [MSC] toward which a Handover should take place. A mobile switching center server is a part of the redesigned [MSC] concept starting from 3GPP Release 4.


The [Mobile Switching Center] connects to the following elements:
* [Home Location Register] ([HLR]) for obtaining [data] about the [SIM] and mobile services [ISDN] number ([MSISDN]; i.e., the telephone number).
* [Base Station Subsystem] (BSS) which handles the radio communication with 2G and 2.5G mobile phones.
* [UMTS Terrestrial Radio Access Network ([UTRAN]) which handles the radio communication with 3G mobile phones.
* [Visitor Location Register] ([VLR]) provides subscriber information when the subscriber is outside its home network.
Other [MSCs] for procedures such as handover.


!! More Information
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