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为解决苹果园中无线传感器网络的规划和部署问题,研究2.4GHz无线信道在苹果园中的传播特性。在山东省肥城市普通的苹果园进行实地试验。选取对信号传播影响最大的一列果树,发射天线固定在两棵树之间发射信号,分别测量6个高度18个位置点的接收信号强度和丢包率。回归分析结果表明:无论发射天线多高,不同水平高度上的接收信号强度衰减均符合对数路径损耗模型,拟合的决定系数为0.927~0.987。发射天线高度不变时,衰减系数n值能用接收天线高度的二次函数曲线拟合,拟合的决定系数为0.71~0.89;模型参数A和接收天线高度符合线性关系,拟合的RMSE为0.2~1.2。建立以发射天线高度、接收天线高度和传播距离为参数的衰减模型并进行验证试验,结果表明:RMSE为2~5,94%的R2值大于0.9,预测模型能较好的估算收发天线高度不同时的信号强度损耗。
In order to solve the planning and deployment of wireless sensor networks in apple orchards, the propagation characteristics of 2.4GHz wireless channels in apple orchards are studied. Field test in ordinary apple orchard in Feicheng, Shandong Province. Select a fruit tree that has the most influence on the signal propagation. The transmitting antenna fixedly transmits the signal between the two trees, and measures the received signal strength and the packet loss rate at 6 locations with 18 locations respectively. Regression analysis results show that, no matter how high the transmitting antenna is, the received signal strength attenuation at different horizontal heights accords with the logarithmic path loss model, the fitting coefficient of which is 0.927-0.987. When the height of the transmitting antenna is constant, the attenuation coefficient n can be fitted by the quadratic function curve of the receiving antenna height, the fitting coefficient is 0.71-0.89; the model parameter A and the receiving antenna height are in a linear relationship, and the fitting RMSE is 0.2 ~ 1.2. The attenuation model with the parameters of transmitting antenna height, receiving antenna height and propagation distance is established and verified. The results show that the RMSE is 2 ~ 5 and the R2 value of 44% is greater than 0.9. The prediction model can better estimate the height of the transmitting / receiving antenna Simultaneous loss of signal strength.