Patent ID: 6957061
Filing Date: 2005-10-18
Classification: H04L,H04W

Abstract:
1. A method of allowing a home mobile telecommunications network to authenticate mobile user equipment located in an area covered by a serving mobile telecommunications network, wherein the mobile user equipment has a subscription with the home mobile telecommunications network, the mobile user equipment is adapted to make and receive telephone calls when within an area covered by the home mobile telecommunications network by wireless communication between the mobile user equipment and the home mobile telecommunications network, and the home mobile telecommunications network is operable to generate authentication vectors for enabling the mobile user equipment to obtain an identifier having a value from the serving network, which identifier is transmitted from the mobile user equipment to the serving network to allow the mobile user equipment to make calls by wireless communication between the mobile user equipment and the serving mobile telecommunications network when within the area covered by the serving mobile telecommunications network, the method comprising the steps of: passing an authentication element forming at least part of an authentication vector, from the serving mobile telecommunications network to the mobile user equipment, deciding in the user equipment, based at least in part on the value of a predetermined field contained in the authentication element, when to generate a termination message, and passing the termination message from the mobile user equipment to the serving mobile telecommunications network, which message comprises said identifier but with a second value different from ad value, and which second value indicates that the serving mobile telecommunications network must obtain a further authentication vector from the home mobile telecommunications network before allowing the user equipment to make further calls.