UMA - Generic Access Network - Wikipedia, the free encyclopedia
Generic Access Network (GAN), also known as Unlicensed Mobile Access (UMA), is a telecommunication system allowing seamless roaming and handover between local area networks and wide area networks using a dual-mode mobile phone. It lets mobile operators deliver voice, data and IP Multimedia Subsystem/Session Initiation Protocol (IMS/SIP) type applications to mobile phones. Its ultimate goal is the convergence of mobile, fixed and Internet telephony (Fixed Mobile Convergence).
I will leave it to the others to edit and fill in, but I thought I would start this.