Patent ID: 7668121

Claim:
A base station comprising: a storage medium to store an authentication key context, including an uplink packet number and a downlink packet number that respectively correspond to a media access control (MAC) message received by the base station from a mobile subscriber station and a downlink MAC message transmitted to the mobile subscriber station from the base station, for an authentication key associated with authenticating the mobile subscriber station to be serviced in a coverage area of an access network serviced by the base station, the mobile subscriber station to be serviced while the authentication key remains unexpired; and an authentication module coupled to the storage medium and configured to purge the authentication key and the authentication key context of the mobile subscriber station from the storage medium when the base station hands off the mobile subscriber station to be serviced in another coverage area of the access network by another base station and prior to expiration of the authentication key of the mobile subscriber station; to receive, subsequent to the authentication key and the authentication key context being purged, a range request MAC message from the mobile subscriber station, the range request MAC message including the authentication key context and being signed with an uplink MAC key derived from the authentication key; to retrieve, from an authenticator of the access network, the authentication key based at least in part on the received range request MAC message; and to retrieve the authentication key context from the range request MAC message by using the retrieved authentication key to derive the uplink MAC key, wherein the base station is to receive the range request MAC message, retrieve the authentication key, and retrieve the authentication key context when the mobile subscriber station is being handed back to be serviced by the base station.