Uma Technology

UMA, stands for "Unlicensed Mobile Access". The technology provides access to GSM and GPRS mobile services over unlicensed spectrum technologies, including Bluetooth and 802.11. By deploying UMA technology, service providers can enable subscribers to roam and handover between cellular networks and public and private unlicensed wireless networks using dual-mode mobile handsets. With UMA, subscribers receive a consistent user experience for their mobile voice and data services as they transition between networks.
There are some ethical reflections that should be considered when using this kind of technology. The use of an unsecured network may be considered the use of another persons property, however, should not the owner of an Internet connection secure it if he does not want others to use it, "keeping it behind locked doors"? As far as I know, there has never been any legal disputes on this matter. The UMA phones have already been used for a while, but just only for operators of different business networks.
In order to promote the widespread adoption of UMA technology, a number of leading companies within the wireless industry have jointly developed a set of open specifications. These specifications can be used by vendors and carriers of wireless communications systems and applications to develop and deploy interoperable solutions. In addition to developing and maintaining the initial specifications, the participating companies are actively working with the 3rd Generation Partnership Project (3GPP) standards organization to use the specifications as the basis for the development of a formal standard.
How UMA Technology Works :-
A mobile subscriber with a UMA-enabled, dual-mode handset moves within range of an unlicensed wireless network to which the handset is allowed to connect.

Upon connecting, the handset contacts the UMA Network Controller (UNC) over the broadband IP access network to be authenticated and authorized to access GSM voice and GPRS data services via the unlicensed wireless network.

If approved, the subscriber’s current location information stored in the core network is updated, and from that point on all mobile voice and data traffic is routed to the handset via the Unlicensed Mobile Access Network (UMAN) rather than the cellular radio access network (RAN).
ROAMING:

When a UMA-enabled subscriber moves outside the range of an unlicensed wireless network to which they are connected, the UNC and handset facilitate roaming back to the licensed outdoor network. This roaming process is completely transparent to the subscriber.

HANDOVER:

If a subscriber is on an active GSM voice call or GPRS data session when they come within range (or out of range) of an unlicensed wireless network, that voice call or data session can automatically handover between access networks with no discernable service interruption. Handovers are completely transparent to the subscriber.