Recent growth of the wireless Internet provides various multimedia services including video, audio, and voice. Especially, the VoIP has been become an important technology supporting transmission of voice data over wireless environment. In this paper, we propose a fast handoff scheme based on state information for guarantee QoS of VoIP services in wireless environment. The proposed handoff reduces delay of the session timer by checking session states and avoids the termination due to the handoff delay in the SIP. The function of the session timer, tracks the states of the current session, is not supported initial version, recognizes the failure of the session and release resource reserved for the failed session, which results in this resource is reused by the other sessions. The proposed scheme performing handoff, mobile node informs the proxy server of its handoff state. The proxy sever doesn't change the period of UPDATE requests adding the handoff state to the exiting states which utilized by set UPDATE request interval. Simulation results show that the proposed scheme reduces the number of state transition and preserves time interval.

VoIP, Handoff, Delay, SIP, QoS