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Wireless Underground Sensor Networks (WUSNs) play a crucial role in precision agriculture by providing information about moisture levels, temperature, nutrient availability, and other relevant factors. However, the use of radio-frequency identification (RFID) devices for WUSNs has been relatively unexplored despite their benefits such as low power consumption. In this work, we develop a hardware platform, called OATSMobile, that enables radio-frequency identification (RFID) communications in WUSNs. OATSMobile is a mobile platform that carries a sensor reader for scanning underground RFID tags and is equipped with communication modules to transport collected data. In addition to collecting RFID data, our edge computer collects machine location and speed from a Real Time Kinematics (RTK) GPS device, soil moisture from externally installed LoRaWAN sensors, and ground-to-antenna height from a Wi-Fi enabled LiDAR sensor. Data is automatically transferred over the cell network to an Avena-based data pipeline for analysis and processing. With OATSMobile, we investigated the feasibility of RFID communications in the Ultra High Frequency (UHF) band for WUSNs. We evaluated the impact of soil moisture and temperature on RFID scanning performance by randomly placing corn seed sized RFID tags in soil blocks of different drainage classes at 2.5 cm depths and measuring the Received Signal Strength Index (RSSI) and scanning success rates at different stages of the corn growing season. The nominal antenna height was 32 cm above ground, and the machine traveled at 0.44 m/s. As a result, we confirmed that 152 out of 282 tags were detected, for an overall success rate of 53.9%. Other results, such as the impact of soil moisture, antenna height, and machine speed impact will be discussed in this paper. Finally, we outline pathways for developing communications frameworks for WUSNs applied to precision agriculture.
Castiblanco et al. (Fri,) studied this question.