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IEEE 802.15. 4 is designed mainly for static low duty cycle wireless personal area network and its capability to support mobility has not been extensively explored yet. We observed that the amount of time required for the association process is the key reason for making IEEE 802.15. 4 unable to handle mobility. In a beacon-enabled network, mobile node can only learn about the existence of any neighbor by listening to incoming beacons. Nevertheless, as neither the channel on which the neighbor operates nor its frequency of beaconing are known, nodes have to scan every available channel, which can take from few to several seconds depending upon the beacon interval. In this paper, we propose a new fast association technique, which prevents nodes from scanning multiple channels. In our proposed scheme, by scanning just a single channel, node can learn about all the coordinators working in different channels. Our single channel scan scheme is able to decrease the association time of IEEE 802.15. 4 operation in 2.4 GHz by 32 times. Experiment results have verified that our scheme works well in the mobile environment.