VLR:

Abbreviation for Visitor Location Register. Within the GSM Network Switching Subsystem, the VLR is connected to the MSC via the B-Interface.
  • Though initially, the VLR was designed as a separate network element to the MSC, today the VLR is integral part of what is called MSC/VLR. In other words, the B-interface between MSC and VLR is no more finely specified but proprietary.
  • Like the HLR, the VLR is basically a huge database that administrates the mobility of thousands of subscribers.
  • Compared to the HLR with its more static functions, the VLR dynamically administrates the subscribers that are currently present in the very area that the VLR covers.
  • The VLR is the peer of the mobile station during authentication, "Location Updating" and "IMSI Attach". Accordingly, the VLR "knows" a subscriber's precise location (location area).
  • The VLR is also in charge to allocate a TMSI to a mobile subscriber.
  • As the figure illustrates, each PLMN is defined by the area that all the MSC’s / VLR’s cover.

 

[2GTS 03.02 / 2GTS 12.02 / 2GTS 12.03 ]