A TAI (Tracking Area Identifier) assigned to a small, ‘presence’ cell (106), which is different from that assigned to a neighbouring cell (101), forces a User Equipment (105) entering the presence cell's coverage area to attempt to register with the presence cell. The presence cell forwards the registration request (which includes the UE's temporary subscriber identity and the identity of the most recently serving Mobility Management Entity) to an additional network node (107) that appears as a Mobility Management Entity to other MMEs in the network. The network node then generates a request for the permanent subscriber identity of the UE and sends it to the most recently serving MME (103). The received permanent identity can be forwarded to a presence analytics server (108) for presence purposes. In some examples, use is made of the relevant ‘Context Request’ or ‘Identification Request’ message and ‘Tracking Area Update’ message or ‘Attach Request’ message to obtain details of the UE despite the fact that it has not completed authentication with the presence cell.