IEEE 802.21 Standard

The IEEE 802.21 standard supports algorithms enabling seamless handover between networks of the same type as well as handover between different network types also called Media independent handover (MIH) or vertical handover. The standard provides information to allow handing over to and from cellular, GSM, GPRS, WiFi, Bluetooth, 802.11 and 802.16 networks through different handover mechanisms.

The IEEE 802.21 working group started work in March 2004. More than 30 companies have joined the working group. In January, 2009, the standard was ratified as a IEEE standard. Here, you have the official site.