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WLANs will become a major portion of the fourth generation (4G) cellular system. The seamless handoff problem in WLANs is a very important design issue to support the new astounding amazing applications in wireless networks. The entire delay time of a handoff is divided into probe, authentication, and reassociation delay times. Because the probe delay occupies most of the handoff delay time, efforts have focused mainly on reducing the probe delay to develop faster handoff schemes. This paper presents a new fast handoff scheme, called the DeuceScan scheme, to further reduce the probe delay for 802.11- based WLANs. A spatiotemporal approach is developed in this work to utilize a spatiotemporal graph to provide spatiotemporal information for making accurate handoff decisions by correctly searching for the next AP (access point). The DeuceScan scheme is a pre-scan approach which efficiently reduces the MAC layer handoff latency. Two factors of stable signal strength and variable of signal strength are both used in our developed DeuceScan scheme. Finally, the simulation results illustrate the performance achievements of the DeuceScan scheme in reducing the handoff delay time and packet loss rate.
Date of Conference: 25-28 Sept. 2006