What is the Difference Between HLR and VLR?
🆚 Go to Comparative Table 🆚The Home Location Register (HLR) and Visitor Location Register (VLR) are databases used in mobile networks to manage and store information about subscribers. They serve different purposes within the network:
HLR:
- Contains information regarding users who are registered as subscribers in the area.
- Holds permanent subscriber details, such as a subscriber's profile and the MSC address where they are currently located.
- Acts as a fixed reference point for a given mobile station (subscriber).
- Can be standalone and serve multiple Switching Centers (MSCs).
- Handles subscriber administration activities within the network.
VLR:
- Contains information regarding users who are registered as subscribers somewhere else but happen to be roaming in the area.
- Supports the mobility function and other dynamic information, such as location updates, handovers, paging, charging, and call setup.
- Knows the exact location of the mobile station.
- Generally integrated with every MSC.
- Contains authentication information passed from the HLR.
The interface between the HLR and VLR is called the D-Interface as per the GSM standard, which helps share information about location, such as Location Area Information (LAI), attached status, and Temporary Mobile Subscriber Identity (TMSI). The capacity of both the HLR and VLR can directly affect the subscriber capacity of the mobile network operator.
Comparative Table: HLR vs VLR
HLR (Home Location Register) and VLR (Visitor Location Register) are databases used in mobile communication networks to store and manage subscriber information. Here is a table summarizing the differences between HLR and VLR:
| Feature | HLR (Home Location Register) | VLR (Visitor Location Register) |
|---|---|---|
| Purpose | Contains permanent information about subscribers, such as cell phone numbers, services, and whether the numbers have been ported to another network. | Contains temporary information about subscribers, such as location and status, which can change due to mobility and network design. |
| Data | Static and permanent data. | Dynamic data, updated as subscribers move between locations. |
| Location | Central database, typically one per mobile network operator. | Local database, typically one per each Mobile Services Switching Centre (MSC). |
| Information Storage | Stores authentication information, MSISDN numbers, and other static data. | Stores location area information, attached status, Temporary Mobile Subscriber Identity (TMSI), and some authentication information. |
| Inter-network Communication | No communication with other networks. | Communicates with HLRs through the D-interface to share information about location, attached status, and temporary mobile subscriber identity. |
In summary, HLR stores permanent information about subscribers, while VLR stores temporary, dynamic information. HLR acts as a central database for the network, while VLRs are local databases located in each MSC.