The Visitor Location Register (VLR) is a key component of the telecommunications network architecture used in mobile networks. It is a database that is connected to the Mobile Switching Center (MSC) and contains the most important information about the mobile subscribers that are currently active within the area covered by the MSC. This information is used by the MSC to route incoming calls to the correct mobile device, allowing the mobile user to receive calls even when they are roaming in a different location.
The VLR contains the following information about each active mobile subscriber:
International Mobile Subscriber Identity (IMSI) - a unique identifier for each mobile subscriber.
Mobile Station ISDN Number (MSISDN) - the telephone number of the mobile device.
Mobile Station Roaming Number (MSRN) - a temporary number used to route incoming calls to the correct mobile device while the device is roaming in a different location.
Location Area (LA) - the geographical area in which the mobile device is currently located.
Mobile Equipment Identity (MEID) - a unique identifier for the physical mobile device.
Mobile Equipment Status (MES) - information about the status of the mobile device, such as whether it is active or inactive.
The VLR is constantly updated as mobile devices move between different location areas. When a mobile device enters a new location area, the VLR is updated to reflect the new location information. The VLR also provides important information for billing and customer service purposes, such as the type of services the mobile subscriber is using and their current location.
Overall, the VLR plays a critical role in ensuring that mobile users are able to receive incoming calls and access other services while roaming in different locations. It helps to provide seamless connectivity for mobile users, allowing them to stay connected even when they are on the move.
