Using SIP for seamless handover in heterogeneous networks

Today´s mobile telephone users are often equipped with advanced handsets with multimode capability. Such handsets are capable of connecting to different network types such as WLAN, WiMAX and UMTS, which enables the user to utilize the preferred network type regarding cost and quality of service. A major challenge is to maintain session continuity when changing connection across heterogeneous networks. With the increased demand for mobility support in VoIP we therefore propose a proactive scheme to enable seamless handover across heterogeneous networks using SIP, the SIP Handover Extension. In contrast to other schemes, our extension omits the need for additional network entities and maintains backward compatibility with standard SIP. The SIP Handover Extension is analyzed in a network simulator and implemented in a demonstrator. The analysis and simulation results presented show that our proposal can effectively eliminate the handover period in certain scenarios.