Objective  To simplify network deployment in orchards, extend the signal coverage, provide precise and real-time irrigation monitoring, and improve its compatibility with traditional equipment.

Method  Remote data transmission and extended coverage of base station signals were realized by combining narrow band internet of things (NB-IoT) and LoRa network. The circuit was examined using terminal electrical parameter and the power was calibrated, which was combined with the anomaly detection algorithm to accurately monitor the operation status of the equipment. The abnormal status was uploaded immediately, and the data upload frequency was reduced. Meanwhile, the main frequency of the processor was reduced to extend the standby time under the premise of ensuring the processing capacity.

Result  Abnormal status was uploaded within 150 ms and the frequency was limited to 20 000 times per year for the orchard real-time monitoring system. After calibrating the detection power, the determination coeffecient was 0.999 8 for the linear regression prediction of power. The process time of JSON data generated by macro was 10% of that of cJSON method, which further reduced the calculation requirement of MCU. On the premise of meeting the requirements of calculation and control, the main frequency of 2 MHz microprocessor and 200 mA·H lithium battery could meet the minimum requirements of calculation and continuous operation of orchard irrigation monitoring system. The use of low-power microprocessor could further extend the working time.

Conclusion  This monitoring system extends the coverage of NB-IoT network and realizes accurate, low-cost and real-time remote monitoring.