ZiFi: wireless LAN discovery via ZigBee interference signatures

  • Authors:

  • Ruogu Zhou;Yongping Xiong;Guoliang Xing;Limin Sun;Jian Ma

  • Affiliations:

  • Michigan State University, East Lansing, USA;Chinese Academy of Sciences, Beijing, China;Michigan State University, East Lansing, USA;Chinese Academy of Sciences, Beijing, China;Nokia Research Center, Beijing, China

  • Venue:
  • Proceedings of the sixteenth annual international conference on Mobile computing and networking
  • Year:
  • 2010

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Abstract

WiFi networks have enjoyed an unprecedent penetration rate in recent years. However, due to the limited coverage, existing WiFi infrastructure only provides intermittent connectivity for mobile users. Once leaving the current network coverage, WiFi clients must actively discover new WiFi access points (APs), which wastes the precious energy of mobile devices. Although several solutions have been proposed to address this issue, they either require significant modifications to existing network infrastructures or rely on context information that is not available in unknown environments. In this work, we develop a system called ZiFi that utilizes ZigBee radios to identify the existence of WiFi networks through unique interference signatures generated by WiFi beacons. We develop a new digital signal processing algorithm called Common Multiple Folding (CMF) that accurately amplifies periodic beacons in WiFi interference signals. ZiFi also adopts a constant false alarm rate (CFAR) detector that can minimize the false negative (FN) rate of WiFi beacon detection while satisfying the user-specified upper bound on false positive (FP) rate. We have implemented ZiFi on two platforms, a Linux netbook integrating a TelosB mote through the USB interface, and a Nokia N73 smartphone integrating a ZigBee card through the miniSD interface. Our experiments show that, under typical settings, ZiFi can detect WiFi APs with high accuracy (ms), and little computation overhead