UMA allows mobile users to access cellular voice and data services over unlicensed wireless networks like WiFi. The UMA architecture includes an unlicensed wireless network, IP access network, and UMA Network Controller (UNC) that authenticates and authorizes mobile devices to access the core cellular network. The UNC facilitates seamless handovers between licensed cellular networks and unlicensed wireless networks, allowing subscribers to roam between the networks transparently while on calls or data sessions.