Signal & Syntax · Networks, HLR and porting

What Is an HSS?

The HSS (Home Subscriber Server) is the 4G LTE and IMS successor to the HLR. The HSS answers subscriber queries over the Diameter protocol.

Also calledHome Subscriber Server

HSS in Practice

The HSS holds the same records as the HLR: identifiers, services and the serving node. The HSS speaks Diameter, where the HLR speaks MAP over SS7. Operators running 3G and 4G side by side run both, or one combined node. In 5G core networks, the UDM takes over the role.

Related Terms

HLR The HLR (Home Location Register) is the subscriber database in a mobile operator's core network. SS7 SS7 (Signaling System No. 7) carries call setup, SMS routing and subscriber queries between networks. IMSI The IMSI (International Mobile Subscriber Identity) is the up-to-15-digit code on a SIM. MNO An MNO (mobile network operator) runs its own radio network under a spectrum license.

Read the Guide

Guide

HLR Lookup vs eHLR

Two ways to check whether a number is in use. Read the guide →

Run the Checks on Your Own List

Upload a file in a free workspace, or walk through your use case with our team.