A dual modem device is disclosed. The present invention includes a first processor configured to communicate with a first communication network, a second processor configured to communicate with a second communication network, and a subscriber identity module configured to store a user equipment identifier corresponding to the first communication network, at least one authentication parameter corresponding to the first communication network and an authentication algorithm corresponding to the first communication network, the subscriber identity module performing the authentication algorithm corresponding to the first communication network, wherein the subscriber identity module is connected to the second processor. The first communication network is an LTE (long term evolution) communication network. And, the second communication network is an eHRPD (enhanced high-rate packet data) communication network.