Modularized two-step vertical handoff scheme in integrated WWAN and WLAN

The integration of the 3G wireless wide-area networks (WWAN) and the IEEE 802.11 wireless local-area networks (WLAN) has drawn much attention from both industrial institutes and academia in the past years. However, to achieve an effective and efficient integration for the two networks with very different characteristics is still an open question. One of the challenges is to provide an integrated strategy for a seamless vertical handoff between the two network domains for the end users where the delay, delay jitter, and packet loss probability can be minimized. This paper is committed to solving the problem of vertical handoff, where a modeling approach for handoff delay is introduced. Based on the modeling approach, a novel modularized two-step vertical handoff scheme based on mobile IP addressing is proposed, which intends to minimize vertical handoff delay and decrease packet loss rate during vertical handoffs by running different steps of handoffs in parallel As such, the vertical handoff procedure is separated into two steps: pre-handoff and handoff. Also, we divide the vertical handoff system into two functional modules: decision module and action module. An intelligent algorithm based on predicting handoff time for triggering pre handoff actions and handoff action is introduced in the decision module; while in the action module, a multi tunnel technique is introduced. We verify the proposed system and algorithms by simulation.