Batteryless Backscatter Sensor Networks—Part II: Lessons From Scalable Deployment

Inspired by the challenges presented in Part I, Part II examines analog ambient backscatter for scalable, batteryless, wireless and ultra-low cost sensing of soil moisture. Ultra-low power ambient backscatter sensors are built, with accuracy below 4%, cost of a few euros per sensor and ability to report soil moisture to any conventional FM radio-equipped smartphone. Calibration, characterization, extensive usage and evaluation was conducted in research greenhouses and small-scale farms. Probabilistic graphical model-based algorithms were also devised that complete missing measurements. Hopefully, this work will spark further interest in batteryless backscatter sensor networks with holistic approaches and tremendous socioeconomic impact.