What Does HLR Stand For?
Today, let’s talk about HLR, a crucial element in mobile telecommunications. If you’ve been following along with our previous discussions, you might remember how we explored core network functions and components. In this article, I’ll explain what HLR is and how it fits into the bigger picture of mobile networks.
HLR – Home Location Register
HLR stands for Home Location Register. It’s a central database used by mobile networks to store essential information about mobile subscribers. This database plays a vital role in managing subscribers’ services, tracking their current locations, and enabling features like call routing and text messaging.
To make it clearer for you, think of HLR as a central hub for managing subscriber profiles in a mobile network. It stores data such as the phone number, the services associated with that number, and information about the user’s home network. In the previous article, we learned about how networks communicate with each other to provide seamless connectivity, and HLR is central to this process, especially in the handling of roaming and service provision.
Functions of HLR
HLR serves several essential functions in mobile networks:
- Subscriber Information Storage: HLR keeps all the necessary details about a subscriber’s profile, such as their IMSI (International Mobile Subscriber Identity), phone number, and services like voicemail or call forwarding.
- Authentication: It authenticates users when they attempt to connect to the network. It ensures that the subscriber is legitimate and allowed to access the services.
- Roaming Support: When users travel to a different area or country, HLR helps the network determine whether the subscriber can access roaming services. It ensures the correct routing of calls and texts even if the user is outside their home network.
- Call Routing: HLR also helps in routing incoming calls and messages to the correct destination, ensuring the communication reaches the right subscriber.
HLR vs. VLR
Before diving deeper, you might wonder how HLR compares to other databases, like the VLR (Visitor Location Register). Here’s a quick comparison:
| Feature | HLR | VLR |
|---|---|---|
| Function | Stores subscriber details, services, and home network information | Stores temporary data about subscribers who are currently within the area served by a particular MSC (Mobile Switching Center) |
| Location | Located at the subscriber’s home network | Located at the mobile network’s MSC |
| Data | Permanent information like IMSI, services, and subscription status | Temporary data like the user’s current location and active session information |
HLR in Modern Networks
In modern LTE and 5G networks, the HLR has evolved into what is now known as the HSS (Home Subscriber Server). While HLR was used predominantly in 2G and 3G networks, the HSS performs a similar function in newer systems but with additional features required for modern services like VoLTE (Voice over LTE). The HSS still manages subscriber information and enables key features, but it also interacts with newer components like the PCRF (Policy and Charging Rules Function) for better handling of QoS (Quality of Service) and network resource management.
As we have discussed in previous articles, the evolution of mobile networks from 2G to 3G, and now to LTE and 5G, shows how the network architecture has improved. While the HLR was central in 2G and 3G, its functionalities have become more sophisticated with newer technologies.