Soil Moisture Scatter Radio Networking With Low Power

Abstract

A low-cost (6 Euro per sensor), low-power (in the order of 200 µW per sensor), with high communication range (on the order of 250 m), scatter radio sensor network is presented, for soil moisture monitoring at multiple locations. The proposed network utilizes analog frequency modulation in a bistatic network architecture (i.e., the emitter and reader are not colocated), while the sensors operate simultaneously, using frequency-division multiple access. In contrast to prior art, this paper utilizes an ultralow-cost software-defined radio reader and offers custom microstrip capacitive sensing with simple calibration, as well as modulation pulses for each scatter radio sensor with 50% duty cycle; the latter is necessary for scalable network designs. The overall root mean squared error below 1% is observed, even for the range of 250 m. This is another small (but concrete) step for the adoption of scatter radio technology as a key enabling technology for scalable, large-scale, low-power, and cost environmental sensor networking.Index Terms-Scatter radio, sensor networks, soil moisture (SM).

Ambient Backscatter Communications: A Contemporary Survey

“…In [118], the authors indicate that the backscattered power at the backscatter transmitter will be increased when the dutycycle approaches 50% [119], [120]. The authors also note that square waves having the duty cycle different from 50% occupy additional bandwidth.…”

“…As the sub-carrier frequency reserved for each backscatter transmitter is unique, the collisions among the backscatter transmitters are eliminated [13]. As a result, a majority of models in the literature, e.g., [4], [13], [65], [85], [115], [118], use FDM as a multiple access scheme.…”

“…The experimental results show that the backscatter sensor transmitters are able to communicate with the backscatter receiver in a collision-free manner. Similar to [115], the authors in [118] also define an expression to estimate the sub-carrier frequency for the backscatter sensor transmitters. However, the authors indicate that the outdoor temperature variations affect the circuit operation of the backscatter sensor transmitters, and thus the reserved subcarrier frequency for each backscatter sensor transmitter may be drifted.…”

Efficient and Sensitive Electrically Small Rectenna for Ultra-Low Power RF Energy Harvesting

“…The number of RF emitters has been rapidly increasing due to the development of new wireless technologies and it remains an engineering challenge how to capture unused ambient RF energy and use this to supply small electrical devices, such as backscatter radio sensor networks 28–30 .…”

“Jam Me If You Can:” Defeating Jammer With Deep Dueling Neural Network Architecture and Ambient Backscattering Augmented Communications

“…Note that ABC, by contrast to bistatic backscattering communications, does not require a dedicated RF signal source. Specifically, in bistatic backscattering communications, e.g., [19], [41], [42], [43], backscatter devices transmit information by backscattering the RF signals generated by a dedicated RF source which is controllable. With the recent development of RF energy harvesting, the transmitter can harvest energy from RF signals with a high efficiency.…”