Date Added: Jun 2010
Mobile users move across different types of network, such as WiFi, WiMAX and UMTS. The mobile equipment is already capable of connecting to different network types simultaneously, but in such a heterogeneous environment, session continuity is still a challenge when changing connection from one network to another. The differences in properties on the physical layer and link layer promote higher-layer solutions for handover. Several architectures have already been proposed in either the network layer, in the application layer or as hybrid solutions. The application-layer-based Session Initiation Protocol (SIP) supports terminal mobility, but this procedure suffers from long handover delays.