System (FIG. 2) and method for use of internet authentication technology to provide UMTS authentication. An SGSN (260) in an Integrated Network Contoroller (240) in a UMTS network and a RADIUS server (270) are adapted to support signalling therebetween whereby authentication of a USIM is performed in the RADIUS Server. This allows a conventional Authorisation Centre (AuC) to replaced by the RADIUS Server, and it is substantially cheaper, because it is based largely on existing off-the-shelf Internet access authentication technology, modified to this purpose.