A dual-radio access technology (dual-RAT) wireless transmit/receive unit (WTRU) may transmit, over a cellular RAT, a registration message that includes a wireless local area network (WLAN) device identifier (ID) for a WLAN associated with the dual-RAT WTRU. A transceiver of the dual-RAT WTRU may receive, from the cellular network over the cellular RAT, assistance information that includes a security key for the WLAN. A processor of the dual-RAT WTRU may perform, over a WLAN RAT, device-to-device D2D direct discovery using the WLAN device ID and the security key for the WLAN.