Network demonstration of low-cost and ultra-low-power environmental sensing with analog backscatter

Recent advances in antennas used as sensors have clearly demonstrated sensing capabilities. However, such approaches typically require manufacturing precision or high-sensitivity, expensive receivers. Furthermore, sensors that utilize communication by means of reflection have been proposed. However, such sensors typically suffer from small communication range. In sharp contrast to prior art, this work adopts analog bistatic backscatter radio principles and demonstrates a network of simultaneously operating sensors. Communication range on the order of 60m was achieved with commodity, low-cost receiver. Environmental humidity was measured with accuracy 1.9%RH RMS error, 0.5milliWatt power consumption and cost approximately 5€ per tag. Interesting tradeoff between measurement accuracy and number of sensors is briefly described.