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loopt location updating-63

GSM procedures are sets of steps performed by the GSM network and devices on it in order for the network to function.

GSM (Global System for Mobile Communications) is a set of standards for cell phone networks established by the European Telecommunications Standards Institute and first used in 1991.

Its procedures refers to the steps a GSM network takes to communicate with cell phones and other mobile devices on the network.

IMSI attach refers to the procedure used when a mobile device or mobile station joins a GSM network when it turns on and IMSI detach refers to the procedure used to leave or disconnect from a network when the device is turned off.

In a GSM network, when a Mobile Station (MS) is switched ON, the International Mobile Subscriber Identity (IMSI) attach procedure is executed.

This procedure is required for the Mobile Switching Center (MSC) and Visitor Location Register (VLR) to register the MS in the network.

If enabled, then the MS must send location update requests at time intervals specified by the network.

If the MS is switched off, having not properly completed the IMSI detach procedure, the network will consider the MS as switched off or unreachable if no location update is made.

The HLR is not informed of this and the VLR does not acknowledge the MS about the IMSI detach.