针对无线传感器网络研究对地表无线信道路径损耗预测的需求,以草原地表环境为研究对象,测量了2.4 GHz无线信号的传播特性,并用最小二乘法对测量数据进行了线性回归.结果表明,基于对数距离的路径损耗模型仍适用于地表无线信道的路径损耗建模,且双斜率模型的拟合精度优于单斜率模型.突变点的位置取决于天线高度,突变点前的路径损耗指数小于2,突变点后的路径损耗指数在3～4之间.通过对比远场的路径损耗预测值与实测值,进一步验证了双斜率模型的预测精度优于单斜率模型.最后,对传统模型与所得双斜率模型进行了性能对比,证实了传统模型无法用于地表环境,进而说明所得模型对无线传感器网络研究更具实际意义.%As path loss prediction for a near-ground wireless channel is an essential issue in most research activities of wireless sensor networks, this paper measures and analyzes the transmission characteristics of a 2. 4 GHz wireless signal in a grassland environment and performs a linear regression for collected data based on the least square method. The results indicate that the log-distance based model is still suitable for the path loss modeling in the near-ground wireless channel, and the fitting accuracy of the two-slope model is better than that of the one-slope model. Furthermore, the breakpoint position is determined by the antenna height, and the path loss indexes are less than 2 or between 3 and 4 before or after the breakpoint. With comparison of the predicted path loss and the measured path loss in a far-field, it proves that the prediction accuracy of the two-slope model is superior to that of the one-slope model. Finally, the performance of the generic models and the proposed two-slope model is compared, which suggests that the generic models are not suitable for research activities in the near-ground environment and the proposed model has a more practical value for research on wireless sensor networks.
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