Design of WiFi-AP operating channel estimation scheme for sensor node

Sensor localization is one of the big problems when building large scale indoor sensor networks because GPS (Global Positioning System) is unavailable in indoor environments. We are developing a sensor localization system using WiFi APs as anchors, which requires no anchor deployment. Because sensor nodes cannot demodulate WiFi signals, we have developed a cross-technology RSS (received signal strength) measurement scheme with an AP recognition scheme [1, 2]. In this paper, we present WiChest, a WiFi-AP operating channel estimation scheme to accurately measure AP-RSS on sensor nodes. AWiFi channel overlaps with four ZigBee channels. AP-RSS depends on a ZigBee channel in which a sensor node measures the RSS. Using WiChest, a sensor node automatically switches its channel based on an estimated AP channel prior to RSS measurement. We implemented WiChest using a MICAz sensor node. The experimental evaluations reveal that WiChest accurately estimates AP operating channels with an F-measure of 0.80.