Patent ID: 6483919
Filing Date: 2002-11-19
Classification: H04W

Abstract:
In a mobile telephone system comprising a mobile services switching center, a method of establishing an encrypted connection between a mobile station and a base transceiver station, comprising the steps of the mobile station requesting the base transceiver station to establish a signalling link, the base transceiver station confirming to the mobile station that a link is available and informing the mobile services switching center that a link is available for signalling purposes, the mobile services switching center, upon receiving such information, sending a cipher mode command to be forwarded to the mobile station by the base transceiver station, which sets the base transceiver station and sets the mobile station to encryption mode or changes the encryption mode of the mobile station, respectively, wherein only if the base transceiver station receives information indicating that the mobile station is in multiple-frame-mode, the base transceiver station is set to or changes its decryption mode in the uplink direction and forwards the cipher mode command to the mobile station.