Abstract: A general global gateway (GGG) permits authenticating between a CDMA network and a GSM network such that a mobile station having a subscription in a GSM network can roam into a CDMA network and be authenticated to use the CDMA network. The GGG obtains authentication parameters from the mobile station and determines whether the authentication parameters satisfy GGG authentication criteria. During the authentication process, the mobile station is placed in “SMS only” status until authorized by the GGG. Checks are made during the authentication process to assure the GGG and mobile station agree on the number of GSM network accesses and to assure the mobile station is authorized for GSM access for a time period.

Abstract: A method of effecting handoff of a mobile station from a first base station in a first cellular communications system controlled by a first mobile switching control station to a second base station in a second, different cellular system controlled by a second mobile switching control station is described. The method comprises generating at the second cellular communication system an authentication code as the result of applying an algorithm to a private key assigned to the mobile station for the second cellular communications system and a random number generated by the second cellular communications system. An authentication code is also generated at the first cellular communication system as the result of applying an algorithm to the private key and the random number. The authentication code generated at the first cellular communication system is then transmitted to a mobile station in a data packet, and, from there, the authentication code is transmitted to the second cellular communication system.