Enabling faster and smoother handoffs in AP-dense 802.11 wireless networks

0140-3664/$ see front matter 2010 Published by doi:10.1016/j.comcom.2010.04.044 * Corresponding author at: Department of Comput Hong Kong, Hong Kong SAR, China. Tel.: +852 219420 E-mail addresses: [email protected] (C. Xu), tengj@ [email protected] (W. Jia). Nowadays, 802.11-based wireless networks have gained greater popularity as they cover more schools, restaurants, offices, and cities. Unlike static wireless connections, people expect user-friendly features from 802.11 wireless networking infrastructures such as support for seamless roaming. In this paper, we study the handoff process in large AP-dense 802.11 networks, which are among the most commonly used forms of 802.11 networks. To enable faster and smoother handoffs in these AP-dense networks, we focus on improving the AP scan process, which is a bottleneck to such handoffs. We carry out a series of field experiments and evaluate critical handoff parameters through extensive analysis of the acquired data. From these experiments, we discover two key features, differentiated probe response time and rich AP information hidden in wireless traffic, which can improve the AP scan process. We present our solution, Scan in AP-dense 802.11 Networks (D-Scan for short), that leverages these features to do so. We conduct real-world experiments that show D-Scan’s strong performance compared with current AP scan solutions. 2010 Published by Elsevier B.V.