麦田环境2.4GHz无线信道路径损耗建模方法分析

Path Loss Modeling for 2.4 GHz Wireless Channel in Wheat Fields

针对麦田环境无线传感器网络(WSN)应用需求,开展了4种无线信道路径损耗建模方法研究及适用性分析。首先利用WSN节点进行2.4 GHz无线信号的麦田实地测试,得到不同传播距离上的路径损耗变化趋势;然后分析了自由空间模型、双射线模型理论计算路径损耗与实测路径损耗差异,同时提出改进的双折线对数距离模型,并采用单折线和改进后的双折线对数距离模型对实测路径损耗运用最小二乘法进行回归分析建模。结果表明:自由空间模型和双射线模型所计算路径损耗与实测路径损耗存在较大差异,无法直接用于麦田环境路径损耗建模;单折线和改进后的双折线对数距离模型的回归分析拟合度分别为0.879和0.943,回归剩余标准差分别为3.242和2.229,均适用于麦田无线信道路径损耗建模,且改进后的双折线对数距离模型较单折线对数距离模型建模精度更高。

As path loss modeling for wireless channel is an essential issue for applications of wireless sensor network in wheat fields, 4 kinds of path loss modeling methods were studied and their adaptability was analyzed. Firstly, path loss of 2.4 GHz wireless signals was measured by wireless sensor modules in wheat fields, and the trend of path loss was analyzed. Then the measured data were compared with the path loss predicted by the free space model and the two-ray model respectively. A modified two-slope log- distance model was proposed and then the one-slope log-distance model and the modified two-slope log- distance model were applied to perform regressions for the measured data of path loss based on the least square method respectively. The results show that there were big differences between the path loss predicted by the first two models and the measured data, and thus the first two models couldnot be used to predict path loss directly in the environment. The R2 values of the latter two models were 0. 879 and 0. 943 and the standard error of the estimate were 3. 242 and 2. 229 respectively, which indicated both of the two models were applicable for path loss modeling in wheat fields and the modified two-slope logdistance model had a better accuracy.