The use of WiFi access networks to provide GSM/GPRS/UMTS services to the subscriber is a growing area of interest and development in the telecommunications industry. There are several ongoing efforts to standardize and define WiFi access and roaming.
Early efforts included Generic Access Networks (GAN) defined by 3GPP TS143.318. Unlicensed Mobile Access (UMA) is an implementation of GAN that has been realized in North America. UMA allows subscribers with dual WiFi mode devices to establish 802.11 IP data connections to any available HotSpot or private WLAN. Once WLAN is established, the UMA procedures authenticate and connect the subscriber to their home network, enabling voice, SMS, and data services.
Recent efforts have focused on leveraging WiFi as an extension to MNO IP Multimedia (IMS) Networks through home and visited access networks. This implementation of WiFi roaming is under development between the GSMA and Wireless Broadband Alliance and is based on the 3GPP 124.234 WLAN internetworking standard as well as the 802.11u-2011 IEEE standard.
WiFi Roaming allows the subscriber to authenticate on a permitted HotSpot using their USIM and/or ISIM credentials. This differentitates WiFi Roaming from current UMA deployments.