Media Independent Handover (IEEE 802.21): Framework for Next Generation Vertical Handover Protocols

Although various wireless access network technologies with different characteristics and performance level have been developed, no single network that can satisfy the anytime, anywhere, and any service wireless access needs of mobile users. A truly seamless mobile environment can only be realized by considering vertical and horizontal handoffs together. One of the major design issues in heterogeneous wireless networks is the support of vertical handoff. Vertical handoff occurs when a user with a multi-interface terminal changes association from one type of wireless access technology to another while maintaining an active session. It is believed that vertical handoff decision will be based on multiple criteria. In this paper review of Vertical Handoff Mechanisms (VHM), decision models and IEEE standard 802.21 (also called Media Independent Handover) have been discussed for seamless vertical handover.