Method of improving the management of mobility in a cellular mobile communications system

1 . A method of improving the management of mobility in a cellular mobile communications system in which cells are grouped together in location structures comprising cells that support different radio access technologies, said method comprising steps in which:

a mobile terminal (MT) in a given cell sends ( 1 ) to a network entity (CN) a request to register in a location structure including said cell; and

on receiving said request, said network entity (CN) transmits ( 2 ) to the mobile terminal (MT) a reply including at least one radio access technology (RAT) indication relating to at least one radio access technology that is authorized and/or to at least one radio access technology that is not authorized for said mobile terminal, at least in said location structure.

2 . A method according to claim 1 , in which said radio access technology indication is explicit, said response including at least one specific parameter.

3 . A method according to claim 1 , in which said radio access technology indication is implicit, the various radio access technologies being assumed to be authorized for said terminal providing said reply does not contain any specific parameter.

4 . A method according to claim 1 , in which said reply further includes a geographical area indication relating to a geographical area applicable to said authorization and/or non-authorization.

5 . A method according to claim 4 , in which said geographical area indication indicates whether said authorization and/or said non-authorization apply solely for said location structure, or for the entire network.

6 . A method according to claim 1 , in which said request corresponds to a location updating request, and said reply corresponds to the location updating request being accepted or rejected.

7 . A method according to claim 1 , comprising steps ( 3 ) in which:

on receiving said reply, said mobile terminal determines whether the radio access technology supported by said cell corresponds to a radio access technology that is not authorized, as indicated by said reply; and

if the radio access technology is not authorized, the mobile terminal selects another cell that supports a radio access technology that is authorized.

8 . A method according to claim 1 , including steps ( 3 ) in which:

on receiving said reply, the mobile terminal causes information corresponding to at least one non-authorized radio access technology as indicated by said reply to be stored; and

prior to selecting a cell, the mobile terminal verifies that the radio access technology supported by the cell does not correspond to a radio access technology that is not authorized according to the information as stored in this way.

9 . A method according to claim 8 , in which:

the mobile terminal causes said storage to be performed in a subscriber identity module associated with said mobile terminal.

10 . A method according to claim 8 , in which said stored information is deleted in the event of changing PLMN.

11 . A method according to claim 7 , in which said stored information is deleted in the event of said subscriber identity module being withdrawn, or under the control of the user.

12 . A mobile terminal (MT) comprising:

means ( 10 ) for transmitting to a network entity (CN) in a given cell, a request to register in a location structure including said cell; and

means ( 11 ) for receiving from said network entity (CN), in response to said request, a reply including at least one radio access technology indication relating to at least one radio access technology that is authorized and/or to at least one radio access technology that is not authorized for said mobile terminal, at least in said location structure.

13 . A mobile terminal according to claim 12 , including:

means ( 12 ) for acting on receiving said reply to determine whether the radio access technology supported by said cell corresponds to a radio access technology that is not authorized, as indicated by said reply; and

means ( 13 ) for acting if the radio access technology is not authorized to select another cell that supports a radio access technology that is authorized.

14 . A mobile terminal according to claim 12 , including:

means ( 14 ) for acting, on receiving said reply, to cause information corresponding to at least one radio access technology that is not authorized as indicated by said response to be stored; and

means ( 16 ) for acting, prior to selecting a cell, to verify that the radio access technology supported by said cell does not correspond to a radio access technology that is not authorized according to the information as stored in this way.

15 . A subscriber identity module (SIM/USIM) including:

means ( 15 ) for storing information corresponding to at least one radio access technology that is not authorized for a mobile terminal associated with said module, as received from a network entity in response to a registration request sent by said terminal.

16 . A mobile communications network entity (CN) including:

means ( 20 ) for receiving from a mobile terminal (MT) in a given cell, a request to register in a location structure including said cell; and

means ( 21 ) for transmitting a reply to the mobile terminal (MT) in response to said request, the reply including at least one radio access technology indication relating to at least one radio access technology that is authorized and/or to at least one radio access technology that is not authorized for said mobile terminal, at least in said location structure.