A method and apparatus are described for supporting a two-stage device-to-device (D2D) discovery using a D2D interworking function (IWF). A D2D IWF component may be configured to perform mapping between an application running on an application server and a third generation partnership project (3GPP) network, and provide a set of application programming interfaces (APIs) to allow discovery to be provided as a service to D2D applications. An application identifier may be mapped to a 3GPP identifier. Further, a method and apparatus are described for performing client-server discovery. A first wireless transmit/receive unit (WTRU) may be configured for a listen-only operation, and a second WTRU may be configured to transmit beacons. The first and second WTRUs may perform a radio access network (RAN) discovery procedure at an access stratum (AS) layer. A method and apparatus for performing charging for D2D service using a D2D IWF are also described.