Methods and messages for performing handovers between an unlicensed mobile access network (UMAN) comprising a first radio access network and a second radio access network. URR (UMA radio resource) handover messages are exchanged between a mobile station (MS) and a UMA network controller (UNC) operating in the UMAN. The MS may access the UMAN via a wireless access point (AP) that is communicatively coupled to the UNC via an IP network. The URR handover messages are sent between the MS and the UNC using an Up interface comprising a set of layered protocols over an underlying IP transport. The handover methods include both handover from a UMAN to the second radio access network, and handover from the second radio access network to the UMAN.