Nortel Networks Corporation

Claire Mousset

Denis Fauconnier

The infrastructure has a core network, radio network controllers linked to the core network and base stations provided with radio interfaces and each linked to one of the controllers. Ciphered information is transmitted over a first communication path in circuit mode between the core network and the terminal, passing through a first master controller, then over a second communication path in circuit mode between the core network and the terminal, passing through a second master controller. The second path is established in a transfer procedure comprising the transmission of adjustment data from the first to the second master controller and the suppression of the first path. These data are representative of a current value of a sequence number used to encipher the information and incremented at regular intervals, and of an offset between this sequence number and a time reference available to the second controller.

Method of controlling a channel between a radio terminal and a cellular radiocommunication infrastructure, and access network implementing such a method

Ciphered information is transmitted over a first communication path in circuit mode between a core network and a terminal, passing through a first master controller, then over a second path between the core network and the terminal, passing through a second master controller. The second path is established in a procedure comprising the transmission of data from the first to the second master controller, a phase of simultaneous transmission of radio signals by the infrastructure on the first and second paths, then the suppression of the first path. The radio signals transmitted on the two paths during the phase of simultaneous transmission transport the same information, ciphered with offset sequence numbers, and the radio terminal switches over from the first to the second path while advancing the ciphering sequence number in such a way as to align it with the offset number used by the second controller.

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Grande-Bretagne, France

Claire Mousset