LTE-Based Low-Cost and Low-Power Soil Moisture Sensing

Soil moisture sensing is a basic function required by applications like precision irrigation. Recently, RF based soil moisture sensing solutions [10, 43] have been proposed, which, however, can hardly support large scale deployment in challenging outdoor environments, since they must have dedicated signal emitters and also require power supply for either the signal emitters (WiFi or RFID reader) or both the transceivers (WiFi AP and client). LTE signal provides a unique opportunity for soil moisture sensing as the ubiquitously deployed base stations are naturally always-on signal emitters, eliminating the need for deploying extra hardware. In this paper, we implement a low-cost LTE based soil moisture sensor using commercial off-the-shelf hardware. We also realize duty-cycled soil sensing by automatically self-calibrating the phase offset after powering on the devices, significantly reducing the overall power consumption of the sensor. Extensive experiments show that our low-cost sensor ($55) achieves a high accuracy (3.15%) which is comparable to high-end soil moisture sensors ($850), wide coverage (2.4 km from the base station) and low power consumption (lasting 16 months using batteries).