考虑无线传输损耗的农业物联网节点分布规划算法研究

针对传统的农业物联网路由以及网关选址时，考虑实际地形对传输损耗的影响不够，导致节点电能的浪费以及维护费用增加的问题，本文首先对农场地形以及已布置终端的位置进行建模，使用K-means算法确定路由初始位置以及该路由负责对接的终端。在考虑电磁波自由空间损耗以及绕射损耗的前提下设计合理的适应度函数，基于一种可变惯性系数的粒子群优化算法对路由和网关的位置进行优化。最终模型给出最大的电磁波损耗数据，用于在确定节点的最大发射功率时提供参考。算例仿真发现，路由位置通过PSO算法寻优，最大传输损耗最多可降低27.82%。实地检验发现，本算法所选取的最优点通信质量显著高于其附近的点，RSSI提升达12%～20%。模型最终给出的路由和网关最大传输损耗与最优布局位置对于实际节点铺设具有指导性意义。

Algorithm for Distribution Planning of Agricultural IoT Nodes Considering Wireless Transmission Loss

The node location of the agricultural IoT node is of great significance for reducing power consumption. However, the existing literature rarely considers the loss in the signal transmission process in the node location problem, especially the diffraction loss caused by the terrain factor. A method of node location based on K-means and PSO algorithm was proposed. Firstly, the K-means algorithm was used to determine the approximate location of each route and the terminal which were responsible for docking according to the distance of the straight line. Then, considering the electromagnetic wave free space loss and diffraction loss, combined with the modeling of the nodal topography, using the Fresnel integral and free space loss formula, a fitness function was constructed. A variable inertia coefficient PSO algorithm was used to solve this function. This method increased the inertia weight factor to improve the particle search ability when the global optimal point was updated. Anyway, the inertia to accelerate the convergence of the algorithm was reduced. The improved PSO algorithm was used to optimize the location of routers and gateways. The simulation found that the routing position was optimized through the PSO algorithm, which can reduce the maximum transmission loss by up to 27.82%. Field inspection showed that the optimal communication quality selected by this algorithm was significantly higher than that of the nearby points, and the RSSI was improved by as much as 12% to 20%. In addition, the model gave the maximum electromagnetic wave loss data, which can be used to determine the maximum transmission power of the node and estimate the energy loss of the node, so as to make a more rational estimate of the overall energy consumption of the node, and effectively reduced the subjectivity and arbitrariness of nodes planning.