We present a zoned presence detection system using multiple ultrasonic array sensors. In active mode, sensors transmit consecutive bursts of sinusoidal pulses over a transmission slot in a time-division multiplexed manner. We present a transmission slot synchronization method to maintain assigned transmission slots of each sensor. The proposed method is distributed and does not rely on a central coordinator or unique identifiers for the sensors. In a transmission slot, the corresponding receiver array uses moving target processing on received echoes to derive range and direction-of-arrival, defining a zone. A tracking algorithm is used to make the zoned presence detection more robust. The presented methods are evaluated using ceiling-installed ultrasonic linear array sensors in an experimental office setup.
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