Home Subscriber Server (HSS) (May be called User Profile Server Function, UPSF) - In IP Multimedia Subsystems (IMS), often applicable customer information and preferences are put in one database, or set of databases, called the Home Subscriber Server (HSS).
http://en.wikipedia.org/wiki/Home_Subscriber_Server

Conventional 2G or 3G networks store customer data in more traditional Home Location Registers (HLRs), while Wi-Fi networks often use Authentication, Authorization and Accounting (AAA) databases.