A Mobile Station (MS) is able to vertically roam in either direction between two different networks, i.e., WWAN and WLAN. The MS is equipped with a dual mode Radio for WWAN and WLAN transmissions. The WLAN Radio is linked to a WLAN Enterprise Gateway Controller (EGC) via a first air link and the WWAN...http://www.google.com/patents/US7561547?utm_source=gb-gplus-sharePatent US7561547 - Automatic and seamless vertical roaming between wireless local area network (WLAN) and wireless wide area network (WWAN) while maintaining an active voice or streaming data connection: systems, methods and program products
