Institute of Electrical & Electronic Engineers
Even though different wireless Network Access Technologies (NAT) with different specifications and applications have been developed, no single wireless technology can satisfy the anytime, anywhere, and any service wireless access needs of mobile users. A real seamless mobile environment is only realized by considering vertical and horizontal handoffs together. One of the major design issues in heterogeneous wireless networks is the support of Vertical HandOff (VHO). VHO occurs when a user with a multi-interface terminal changes connection from one type of wireless access technology to another while maintaining an active session.