A WTRU may send a registration message to a core network (CN) that is associated with a first cell of a first radio access technology (RAT) and a second cell of a second RAT. The WTRU may receive, on the first cell of the first RAT with a first radio resource control (RRC) protocol, a RRC reconfiguration message that includes information for communications with the second cell of the second RAT. The first cell of the first RAT may be utilized for mobility management and a second RRC protocol may be utilized with the second cell of the second RAT.