Mobility of real-time multimedia flows using SIP services

Mobile communication is becoming more and more ubiquitous. Users require mobile devices that can be used to access applications running at corporate data-centers, either from the local intranet network, or more generally, from the Internet. Moreover, some communication paths should seamlessly migrate to new addresses, when the device is changing the access point to the network. E.g. such a change occurs every time when the device drops from the WiFi network into cellular 3G network, and vice versa. While for applications like a web browser it is only necessary to reload the page in the new connected network, for real-time applications, such as VoIP, it may cause much bigger issues for the quality of user´s experience. And while VoIP is used more widely than ever, moving the mobile device between different networks with an active VoIP call causes termination of the active call. The method to overcome these issues presented in this paper is using the functionalities already found in the SIP signalization protocol. Using SIP re-INVITE messages, mobile VoIP devices can reinitialize connections without having to use additional legacy mobility applications. The resulting handover is therefore faster and is not affected by the additional delay caused by encapsulating original data into mobility tunnels.