A wireless transmit/receive unit (WTRU) may include two or more modems, each configured to link to a different network, and a media independent handover (MIH) client. An application programming interfaces (API) may provide the MIH client with mechanisms to receive information about links, control the modems for handover, discover a MIH server and IP multimedia system nodes, trigger mobile IP handover, etc. If a link has been successfully established, the MIH client may start a MIH session. When the modem indicates that a connection is going to be terminated, the MIH client may activate the second modem for handover. If the first modem indicates that a link parameter has crossed a threshold, the MIH client may send signal measurements to a MIH server. After receiving a media independent handover switch request, the MIH client may initiate handover to the second network.