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.
