User mobility in wireless data networks is increasing because oftechnological advances, and the desire for voice and multimediaapplications. These applications, however, require handoffs between basestations to be fast to maintain the quality of the connections. Previouswork on context transfer for fast handoffs has focused on reactivemethods, i.e. the context transfer occurs after the mobile station hasassociated with the next base station or access router. In this paper, wedescribe the use of a novel and efficient data structure, neighbor graphs,which captures dynamically the mobility topology of a wireless network asa means for pre-positioning the station's context at the potential nextbase stations-- ensuring that the station's context remains one hop ahead.From experimental and simulation results, we find that the use of neighborgraphs reduces the layer 2 handoff latency due to reassociation by an order of magnitude from 15.37 ms to 1.69 ms, and that the effectiveness ofthe approach improves dramatically as user mobility increases.(UMIACS-TR-2003-46)
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