2.4GHz无线信道特性在火龙果园的试验与研究

为解决火龙果园无线传感器网络监控系统的规划和布置,研究无线网络射频信号在坡地火龙果园特定环境下的信道传播特性和衰减模型。选用2.4GHz为载波频率,基于ZigBee协议改变通信距离、发射功率、数据包长度、天线高度等多项参数,试验和分析无线信道在约35°坡地果园中的接收信号强度和平均丢包率;建立接收信号强度和环境因子、通信距离间的数学模型;改变试验环境,对比开阔环境和果园环境对无线网络通信质量的影响。试验结果表明:接收信号强度随着通信距离的增加而减小;其平均丢包率随距离增大、作物密度增强、数据包长度增大、天线高度降低而增大;相对于开阔环境,火龙果园会加速信号的衰减、增大平均丢包率。对试验数据进行拟合,并建立其与通信距离间对数数学模型,其r2在0.8889~0.958之间,得出火龙果园信号衰减系数平均为-18.29。

Propagation characteristics of 2.4 GHz wireless channel in pitaya orchard

For configuring wireless sensor network （WSN） monitoring system in pitaya orchard, the propagation characteristics and attenuation model of RF signals in sloping pitaya orchard were analyzed based on WSN. The received signal strength index （RSSI） and the average packet loss rate （PLR） of about 35° in slope orchard were tested and studied with the carrier frequency of 2.4 GHz and ZigBee protocol in different communication distance, transmit power, packet length, antenna height and other parameters. The mathematical model of RSSI, communication distance and environmental factors was set up. The communication quality of WSN was compared in an open environment and orchard environment. The test results demonstrated that with the increasing of the communication distance the RSSI was reduced, and the PLR would get bigger with increasing distance, packet length and antenna height, the density of the crop enhancement. By fitting the experimental data the logarithm mathematical model with R2 from 0.8889 to 0.958 was established between RSSI and communication distance. The signal attenuation coefficient in the pitaya orchard was about -18.05 from the fitting model.