Wi-Fi calling
[2] Using this feature, compatible handsets are able to route regular cellular calls through a wireless LAN (Wi-Fi) network with broadband Internet, while seamlessly changing connections between the two where necessary.
Essentially, GAN/UMA allows cell phone packets to be forwarded to a network access point over the internet, rather than over-the-air using GSM/GPRS, UMTS or similar.
A separate device known as a "GAN Controller" (GANC)[5] receives this data from the Internet and feeds it into the phone network as if it were coming from an antenna on a tower.
To improve quality of service (QoS) in the home or office, some providers also supply a specially programmed wireless access point that prioritizes UMA packets.
The latest generation system is named or VoWiFi by a number of handset manufacturers, including Apple and Samsung, a move that is being mirrored by carriers like T-Mobile US and Vodafone.
This allows the carrier to route the call to the nearest GANC, set the correct rate plan, and comply with existing roaming agreements.
At the end of 2007, the GAN specification was enhanced to support 3G (Iu) interfaces from the GANC to the mobile core network (MSC/GSN).
The gateways provide call handling among wireless IP phones and connections to traditional telephone systems.
The companies then contributed the specifications to the 3rd Generation Partnership Project (3GPP) as part of 3GPP work item "Generic Access to A/Gb interfaces".
[22] The announcement, the largest to date, covers more than 60m of Orange's mobile subscribers in the UK, France, Poland, Spain and the Netherlands.
The GIP/IWP standard for DECT provides similar functionality, but requires a more direct connection to the GSM network from the base station.
[33] GAN/UMA's ability to use the Internet to provide the "last mile" connection to the GSM network solves the major issue that DECT/GIP has faced.
Had GIP emerged as a practical standard, the low power usage of DECT technology when idle would have been an advantage compared to GAN.
[citation needed] There is nothing preventing an operator from deploying micro- and pico-cells that use towers that connect with the home network over the Internet.
Several companies have developed femtocell systems that do precisely that, broadcasting a "real" GSM or UMTS signal, bypassing the need for special handsets that require 802.11 technology.
