Patent ID: 8582563

Claim:
A Home Subscriber Server (HSS) holding subscriber data of users of an Internet protocol Multimedia Subsystem (IMS), the HSS having a data structure stored on a non-transitory computer readable medium per subscriber that includes a plurality of IMS Public User Identities, each IMS Public User Identity (IMPU) associated with at least one IMS Private User Identity (IMPI), wherein a number n of IMPUs is distributed in a number m of Implicit Registration Sets, and wherein all the IMPUs in each Implicit Registration Set (IRS) share a same registration status, wherein each IRS is associated with an access condition, a given IMPU is shared by more than one IRS, and an explicit registration of the given IMPU under a given access condition triggers an implicit registration of the IMPUs in the IRS associated with the given access condition, wherein a registration status of IMPUs in any other IRS remain unchanged.