Unlicensed Mobile Access 101
Unlicensed Mobile Access (UMA) is gearing up to be the "next big thing" in wireless communications. It’s the ‘Reese’s Peanut Butter cup’ of the mobile phone industry. You know: "You got your WiFi in my cell phone; you got your cell phone is my WiFi". Actually, maybe you don’t know what UMA is: UMA phones are WiFi-enabled cellular phones that are essentially smart enough to use a cellular network when they have to, but they seamlessly switch your call to a WiFi network when they can. The transparent network switch allows for lower costs and potentially more coverage, depending on the WiFi mesh during your travels.
Mobile Crunch has a detailed primer, with plenty of techie terms and diagrams; probably worth a read now that you have the bare-bones basics.