Future generation wireless networks are envisioned to be a combination of diverse but complementary access technologies. Internetworking these types of networks will provide mobile users with ubiquitous connectivity across a wide range of networking environments. The integration of existing and emerging heterogeneous wireless networks requires the design of intelligent handoff and location management schemes to enable mobile users to switch network access and experience uninterrupted service

more »

... tinuity anywhere, anytime. Real deployment of such mobility strategies remains a significant challenge. In this article, we focus on handoff management. We discuss in detail handoff decision and implementation procedures and present recent handoff techniques that aim at providing mobility over a wide range of access technologies. We also discuss some of the capabilities of mobile terminals that are necessary to implement seamless mobility over hybrid wireless networks. Furthermore, we also present and discuss limitations of recent handoff design architectures and protocols as well as outstanding challenges that still need to be addressed to achieve portable and scalable handoff solutions for continuous connectivity across wireless access networks. q