Patent EP-1993310-A1 (EP)
Inventor: BALTUS GUIDO
IPC: H04W8/02
Filed: 2007-05-16
Abstract: A mobile communication network (GSM, UMTS), provided with at least one mobile services switching center (MSC) and a radio network system which is communicatively connected with the at least one mobile services switching center, wherein the network is further provided with a plurality of mobile communication units (MSE) such as mobile telephones, which are each provided with a memory module (SIM) in which a user identification code (IMSI) is stored and which are each arranged for wirelessly communicating with the radio network system, wherein the network is further provided with at least one HLR register in which information about users of the network is stored such as the user identification codes (IMSI), associated telephone numbers (MS-ISDN) and locations of activated associated mobile communication units within the network and at least one VLR register which is associated with the at least one mobile services switching center (MSC) and in which information, such as the user identification codes (IMSI) and/or temporary identification codes (TMSI), is stored of mobile communication units (MSE) which are or have been activated in an area covered with the at least one mobile services switching center (MSC) and wherein a plurality of the memory modules of mobile communication units are provided with a same user identification code (IMSI) so that a plurality of mobile communication units (MSE) are present which are provided with a same user identification code (IMSI), characterized in that the network is further provided with at least one auxiliary register in which information is stored representing the fact that a user identification code (IMSI) is stored in a plurality of memory modules (SIM) of mobile communication units (MSE), how many communication units of a collection of communication units with a same user identification code (IMSI) the collection comprises and/or are activated, with which VLR registers the activated communication units of the respective collection of communication units are registered, the user identification codes (IMSI) and/or temporary user identification codes (TMSI) associated with the activated communication units, in which location area (LAI) associated with a VLR register the activated communication units of the respective collection are registered and which of the activated communication units is reachable within the system, and wherein the network is arranged such that, in use, when a mobile communication unit (MSE) is switched off, the network carries out the following steps: 
a. on the basis of the at least one auxiliary register, the network checks whether a communication unit is switched off which is part of one of the said collections and which is reachable within the system and whether the respective collection comprises another communication unit which is activated; 
b. if it is found in step a. that a communication unit has been switched off which is part of one of the said collections and which was reachable within the network prior to said switching off and whereof, prior to said switching off, the respective collection comprises another communication unit which is activated, a recovery procedure is carried out which ensures that one of the communication units of the collection which has not been switched off becomes reachable within the network.