Plain-language definition
The 4G/IMS equivalent of the HLR.
Technical definition
The HSS holds LTE and IMS subscriber profiles and authentication vectors, serving MME/SGSN over Diameter S6a/S6d and CSCFs and application servers over Cx and Sh.
Why it matters
Unified HLR/HSS/UDM platforms let one subscriber record serve 2G through 5G.
Last reviewed 2026-09-12 by the Guardivia QoS Engineering Team. Product facts on this page describe current capabilities; items marked “where supported”, “optional”, “integration” or “consultancy” are confirmed per deployment.