Abstract: An application server for managing communications towards a set of user entities, the set of user entities having a first user entity. The application server includes a receiver for receiving a first session initiation request, the first session initiation request having a public identification identifying the set of user entities, a processor for assigning a first user identification to the public identification, the user identification identifying the first user entity, and a transmitter for transmitting a second session initiation request to establish a communication link towards the first user entity, the second session initiation request including the first user identification.

Abstract: An application server for managing communications towards a set of user entities, the set of user entities having a first user entity. The application server includes a receiver for receiving a first session initiation request, the first session initiation request having a public identification identifying the set of user entities, a processor for assigning a first user identification to the public identification, the user identification identifying the first user entity, and a transmitter for transmitting a second session initiation request to establish a communication link towards the first user entity, the second session initiation request including the first user identification.

Abstract: The invention relates to a method for improving the security of authentication procedures in digital mobile radio telephone systems. In order to make it more difficult if not impossible to work out a secret code KI, several different secret SIM-specific codes KI are contained in the mobile radio telephone network and on a subscriber identity module SIM and a code KI for the implementation of said authentication is selected from the various secret codes thus contained during the authentication process between the subscriber identity module and the mobile radio telephone system pertaining to said SIM.

Abstract: A method of real-time billing of telecommunications links when a subscriber is located outside his or her own network. The method is characterized in that the establishment of the telecommunications links and the control of the real-time billing are carried out through the home network so that the home network remains in control of the cost-generating links.