农业环境信息无线传感器网络监测技术研究进展

无线传感器网络是实现农业环境变量信息多方位、网络化远程监测的主要技术手段。无线地上传感器网络应用研究集中在作物不同生长期内节点布设距离和高度以及作物高度等对无线电信号传输损失的影响，从而合理选择节点布设参数。无线地下传感器网络应用研究集中在气象环境、土壤类型、土壤含水率、土壤结构与成分、节点埋藏深度、节点距离、频率与功率范围、网络拓扑结构、路由算法、组网方式等对电磁波多路径传输的路径损失、误码率、最大传输距离、含水量测试误差等方面的影响。研究指出，300～500 MHz的频率更适合土壤无线地下传感器网络，其最大传输距离为5 m，传输距离将是系统大面积推广应用的主要限制因素。今后重点应研究433 MHz电磁波在不同土壤和空气多层介质中的传输特性、信道模型及路径损失，优化节点和网络技术参数，确定不同农业应用环境条件下传感器网络节点合理位置和最优的网络拓扑结构方案。

Research progress in wireless sensor network for agricultural environment monitoring

Wireless sensor network (WSN) technology is a major solution for networking remote monitoring for multi-faceted variable of agricultural environment. The researches of WSN applications are focused on radio path-loss caused by distance between transmitter and receiver, as well as influences of the height of transmitters or receivers, plant canopy height and shape, so as to choose the reasonable parameters for system based on the research. The researches of wireless underground sensor network (WUSN) are focused on path-loss, error rate, the maximum transmission distance, the water content test error of multi-path transmission of electromagnetic waves, which are affected by meteorological environment, soil type, soil moisture content, soil structure and composition, burial depth of the node, node distance, frequency and power range, the network topology, routing algorithms, networking. According to the research, frequency of 300 MHz to 500 MHz, the maximum transmission distance of which can reach 5 m, is more appropriate for WUSN. Transmission distance is the main limiting factor for system in large scale. Transmission characteristics, channel models and path-loss of 433MHz electromagnetic waves in different soils and air multi-media will be the focus of future researches. Based on that, we can choose the reasonable position of network nodes and optimal network topology under different agriculture environment.