Abstract: It is provided a method, comprising monitoring whether an apparatus will perform a first mobility procedure from a first network of a first radio access technology to a first other network of a second radio access technology; storing an old identifier, wherein the old identifier identifies a first network element of the first network to which the apparatus is registered before the first mobility procedure starts; monitoring whether the apparatus performs a second mobility procedure from a second other network of a third radio access technology to a second network of the first technology; retrieving the stored old identifier; providing a mapped identifier and the retrieved old identifier to a base station of the second network when the apparatus performs the second mobility procedure, wherein the mapped identifier is based on an identification of a part of the second other network to which the apparatus is registered.

Abstract: In certain communication systems, such as wireless communication systems, there may be benefit to knowing a user equipment's registration status. For example, there may be benefit to observing a user equipment's registration status via a home subscriber server, including whether the user equipment is attached/detached. The communication system may be for example, a long term evolution (LTE) of the third generation partnership project (3GPP). A method can include determining, in a mobility node, that a user equipment is currently deregistered. The method can also include notifying a subscriber server that the user equipment is currently deregistered, responsive to the determination that the user equipment is currently deregistered.