A Practical Mechanism for Vertical Handoff in WLAN/3G Integrated Networks

Owing to the applications provided more convenient and less expensive, 3G network service are getting popular than ever. In addition to the WLAN infrastructures are built ubiquitously. The integration between these two systems is unavoidable. 3GPP defines a node, PDG (Packet Data Gateway) to be the entry point for user in WLAN to access 3G PS services. The PDG is suggested to be composed of TTG and GGSN. To build a connection from WLAN UE to the node within 3G PS domains, IPSec tunnel is established between the WLAN UE and TTG via IKEv2 protocol. TTG has to transfer the IPSec tunnel to GTP tunnel toward GGSN. The first issue we addressed in this paper is how to do the translation between IPSec tunnel and GTP tunnel. We observe the mapping relation between the TS payload and TFT packet filter. Vertical handoff is another issue in this heterogeneous network. In order to minimize packet loss and handoff latency when UE moves to 3G networks, we propose a practical mechanism to reuse the PDP Context which was created when UE was in WLAN.