多路径下桃园射频信号传输特性

为解决无线传感器网络在桃园中的快速部署问题,该文研究了2.4 GHz无线射频信号在桃园中的传播特性。依据角度选取4条传输路径,在3种(0.5、1.5、2.5 m)典型的天线高度,同时测量丢包率和路径损耗情况,分析表明两者具有明显的相关性,天线高度和通信距离是路径损耗的主要影响因素。在天线高度为0.5和1.5 m时,可靠传输距离为6个行距(27 m);在天线高度为2.5 m时,可靠传输距离大于14个行距(63 m),因此冠层顶部为布设天线的最佳位置。对路径损耗数据进行回归分析,发现其在每种天线高度,每条传输路径下对数模型最适合作为路径损耗模型,模型的R2最大为0.945,最小为0.732。为研究节点部署于桃园任意位置时的路径损耗情况,便于节点快速灵活地部署,在3种天线高度下对路径损耗数据进行对数回归分析,R2最大为0.976,最小为0.939。最后对2组模型进行了验证,表明模型可以预测射频信号在桃园中的路径损耗情况,该文研究结果为无线传感器网络在桃园中的部署提供了参考。

Radio frequency signal transmission characteristics under multipath in peach orchard

Abstract: For solving the rapid deployment of wireless sensor network in peach orchard, this paper focused on the radio frequency signal transmission characteristics of 2.4 GHz radio frequency in peach orchard. Four transmission paths were selected according to different angles and packet loss rate and pass-loss of radio frequency signal were calculated under three antenna heights (0.5, 1.5, 2.5 m) at the same time. A correlation analysis was conducted to verify if they were related with each other. Communication distance and antenna height were considered to be the main influencing factors of path-loss. Under any antenna height and transmission path, packet loss rate was very low when communication distance was within six-row spacing and the maximum of packet loss rate was 8.3%. From seven-row spacing, packet loss rate began to increase significantly and with the increase of row spacing, the packet loss rate became increasingly high. Due to the shielding effects from branches and leaves, radio frequency signal could cause the phenomenon such as reflection, diffraction and refraction which might lower the path-loss of radio frequency signal. When the antenna height was 0.5 and 1.5 m separately, the shielding effects were relatively large. The reliable transmission distance was only six-line spacing (27 m). When the antenna height was 2.5 m, the reliable transmission distance was fourteen-line spacing (63 m), and the canopy top was the best position for setting up antenna. Using regression analysis to analyze data of path-loss, it can be concluded that logarithm model was the most suitable model of path-loss under three antenna heights and four transmission paths. The maximum of R2 was 0.945 and the minimum of R2 was 0.732. The influence of path-loss to radio frequency signal in peach orchard was not very significant. In order to research the path-loss and deploy the nodes quickly and flexibly when nodes were deployed in any site of the peach orchard, Logarithmic regression analysis was used to analyze the data of path-loss under three antenna heights. The maximum of R2 was 0.976 and the minimum of R2 was 0.939. The two groups of models were validated during peach's young stage and mature stage lastly and it showed that the two models could predict the path-loss of radio frequency signal under three antenna heights and any transmission path in peach orchard. The two models and the analysis of reliable transmission distance can be selected flexibly and conveniently when establishing wireless sensor network. The conclusion in this paper can provide reference for radio frequency signal transmission and wireless sensor network deployment in peach orchard.