TOHOKU ELECTRIC POWER
In a heterogeneous wireless network, different wireless access technologies with different operating parameters coexists in an overlay fashion. These wireless networks are deployed in order to provide different type of services to Mobile Stations (MSs) equipped with multiple interfaces, based on the principle of Always Best Connected (ABC) network. In such a dynamic environment, an MS can seamlessly switch from one wireless Access Network (AN) to another to guarantee continuity and quality of the current session. This is where the need for intelligent and efficient Vertical HandOffs (VHOs) between technologies in a heterogeneous wireless environment becomes apparent.