Mishra, AruneshShin, Min-hoArbaugh, William A.User mobility in wireless data networks is increasing because of technological advances, and the desire for voice and multimedia applications. These applications, however, require handoffs between base stations to be fast to maintain the quality of the connections. Previous work on context transfer for fast handoffs has focused on reactive methods, i.e. the context transfer occurs after the mobile station has associated with the next base station or access router. In this paper, we describe the use of a novel and efficient data structure, neighbor graphs, which captures dynamically the mobility topology of a wireless network as a means for pre-positioning the station's context at the potential next base stations-- ensuring that the station's context remains one hop ahead. From experimental and simulation results, we find that the use of neighbor graphs 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 of the approach improves dramatically as user mobility increases. (UMIACS-TR-2003-46)en-USTechnical Report