Location Management

The network needs to keep track of where a GPRS user is physically to minimize
uplink signaling and downlink delivery delay. The network has to rely on the GPRS
handset telling it where it is—that is, which base station it is seeing.
The handset is either ready, in idle mode, or in standby, as follows:
 Ready means the handset has informed the SGSN of where it is.
 Idle means the network does not know the location of the handset.
 Standby means the network knows more or less where the handset (that is,
within a certain location area subdivided into several routing areas, which will
generally consist of several cell sites).
The status of the handset is determined by timeouts.
If an MS moves to a new RA, it produces a routing area update request to the SGSN.
The SGSN assigns a new P-TMSI to the user. It does not need to inform the GGSN or
HLR, since the routing context has not changed.