Date Added: Jul 2010
Dual-Mode handsets containing both WLAN and cellular interfaces are becoming increasingly common. When moving between WLAN and cellular radio coverage, the switching of an active session from one interface to another is referred to as Vertical HandOver (VHO). To provide successful VHO the WLAN link has to be maintained until the cellular connection is established. The authors' previous measurements of the WLAN coverage inside a building shows that this is very difficult given the time constraints in a loosely coupled cellular/WLAN architecture. In this paper, they extend their previous work and propose an explicit trigger node to assist early detection of a VHO when transitioning out of a building, which will give the handset enough time to connect to the cellular network before losing its WLAN link.