Mechanisms to extend UMA (Unlicensed Mobile Access) or GAN (General Access Network) to inter-work with a UMTS (Universal Mobile Telecommunications System) core network. A UMA network controller (UNC) is provided to interface between a UMA network and a UMTS core network using the standard Iu-CS and Iu-PS interfaces. From the viewpoint of the UMTS core network, the UNC appears as another Radio Network Controller (RNC). Protocol layer schemes are disclosed for mobile stations, UNCs, SGSNs and MSCs to support signaling and data messaging in both the packet-switched and connection-switched domains. The mobile stations provide dual-mode operation, such that they are able to access the UMTS core network via unlicensed service when in a UMA access area, and to access the UMTS core network via licensed service when outside of a UMA access area and in a UTRAN service area.