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The recent proliferation of smart mobile devices with IEEE 802.11 interfaces for real-time multimedia services such as VoIP, IPTV and video conference, strongly requires guaranteed QoS provisioning with seamless secure mobility during handover among IEEE 802.11 access points. The most important element of handover delay is channel scanning. Most of the existing channel scanning schemes, however, take more than 100 ms and do not guarantee the jitter requirement of less than 50 ms, which is required to guarantee the QoS of real-time services. This paper proposes a smart channel scanning where the channel scanning is carefully scheduled based on predicting the channel scanning time and interleaved frame delivery with limited jitter. This paper also describes an analytical model for predicting smart channel scanning time. The correctness of the prediction of channel scanning delay is analyzed through a series of experiments in a real testbed environment with more than 20 mobile nodes with MadWiFi interface cards. Also, the performance of the proposed smart scanning is compared with that of other schemes via network simulations. It is verified that the proposed smart channel scanning can provide QoS-guaranteed handovers with limited jitter of less than 50 ms and no packet losses in various conditions. The proposed smart channel scanning outperforms the existing scanning scheme under various topology configurations in terms of packet loss, jitter, service disruption time and total scanning time.