Patent ID: 8554882

Claim:
A method of registering during a single registration process in an IP Multimedia Subsystem (IMS) an implicit registration set of ‘j’ IMS private identities, the method comprising the steps of: configuring at a Home Subscriber Server (HSS) which holds subscriptions for subscribers of the IMS, an IMS subscription for a subscriber with a number ‘n’ of IMS private identities (IMPI) and a number ‘m’ of IMS public identities (IMPU), wherein each IMPI is associated with at least one IMPU and each IMPU is associated with at least one IMPI, and wherein one or more IMPU is shared by more than one IMPI; and receiving at the HSS from a Serving Call Session Control Function (S-CSCF), which is currently assigned for serving the subscriber, an indication of a registration of the subscriber with a given IMPU and a given IMPI, and an identifier of the S-CSCF; and wherein the method also comprises: for at least one shared IMPU, configuring at the HSS the IMS subscription for the subscriber with an implicit registration set of ‘j’ IMPI's associated with the shared IMPU; configuring at the HSS at least one IMPI as ‘primary’ IMPI and any other IMPI as ‘secondary’ IMPI of the IMS subscription for the subscriber; determining at the HSS whether the given IMPI is configured as a ‘primary’ IMPI or as a ‘secondary’ IMPI; and where the given IMPI is a ‘primary’ IMPI and the given IMPU is the shared IMPU associated with the implicit registration set of ‘j’ IMPI's which comprises the given IMPI, registering the implicit registration set of ‘j’ IMPI's and downloading from the HSS towards the S-CSCF the implicit registration set of ‘j’ IMPI's; or where the given IMPI is a ‘secondary’ IMPI not previously registered by a ‘primary’ IMPI within an implicit registration set, rejecting the registration of the subscriber with the given IMPU and given IMPI.