Optimal design of wireless monitoring system in mountain citrus orchard and improvement monitoring

Abstract: In order to monitor in real time the growth environment of a mountain citrus orchard and its variation with spatio-temporal and weather status, the optimal design and evaluation of a wireless monitoring system in a mountain citrus orchard was introduced in this paper. The wireless monitoring system is comprised of end nodes used for obtaining citrus growth environment information including air temperature, air humidity, soil moisture and light; router nodes used to relay citrus growth environment information; and a network coordinator, which performs functions such as managing the nodes, collecting and analyzing the data received from the end nodes, and connecting as a gateway for remote data access. CC2530 is adopted as the core processor of the monitoring system; it has the capability of wireless communication and central processing. The optimal design was introduced in this system including information frame structure suitable for a mountain orchard environment, bidirectional instruction control function, topology discovery, routing monitoring mechanism and node information diversification collection mechanism, so as to effectively enhance the robustness and controllability of monitoring the citrus orchard environment. In this paper, the citrus orchard in the subtropical garden of SCAU (South China Agriculture University) was selected for the test. The orchard hill has sloping terrain; citrus trees are planted by terraced distribution. The average slope is 20 degrees, the citrus trees have a height of 2.8m, their shrub diameters are 3m, and the average spacing of citrus plants is 2.8m. The citrus orchard wireless channel was measured in citrus orchard, and the wireless channel model was established through blocking factor and rain attenuation factor, it was used to guide the evaluation of the wireless monitoring network. Experimental results of RSSI (Receiver Signal Strength Index) and communication quality under different distances and climates show that reliable collection and transmission were available in the mountain citrus orchard when the wireless system was deployed with an antenna height of 1.5m and a maximum single-hop communications distance of 30m. Continuous 744h online test results show that the optimized wireless monitoring system improved the transmission success rate; it has a success rate of at least 99.12% for data transmission within the 30m distance. The system ran well, worked stably, and was suitable for the remote, real-time monitoring of the citrus growth environment in a mountainous orchard.