In the recent time there is a strong need to provide seamless connectivity anywhere at anytime to the mobile users with best possible quality. This necessitates the deployment of a required set of mechanisms that integrate different communication technologies. Researchers around the globe are working on the integration of different communication technologies. This book provides an overview of different components of UMTS and IEEE 802.11 network and different internetworking architecture between them. It also discusses different vertical handover management methods between these technologies.