| When the transceiver node of the wireless communication system is located in the forest environment,the channel quality is affected by forest density,tree species,distribution and other factors.It is difficult to accurately predict the propagation loss between transceiver nodes especially in the area with dense trees or radio wave propagation path fading changes dramatically.In this paper,FDTD(Finite-Difference Time-Domain)algorithm is used to model and calculate radio wave propagation in forest environment and study the characteristics of radio wave propagation in forest environment.The main contents are as follows.(1)The stability of FDTD algorithm is analyzed to ensure the reliability of forest wave propagation by FDTD;The effect of FDTD convolutional perfect matching layer on computational performance is studied.A CUDA(Compute Unified Device Architecture)-based 3D CPML＿FDTD parallel algorithm is designed,which utilizes the parallel processing capability of GPU to improve the efficiency of FDTD algorithm in modeling and calculating radio wave propagation in forest environment.(2)A simplified hierarchical tree model was established and used to generate a forest model,and the electromagnetic scattering of trees was calculated using FDTD method.Experimental results show that FDTD algorithm can calculate tree scattering accurately.Gaussian pulse signal is used as excitation signal and dipole antenna is used as excitation source.(3)CUDA-based 3D CPML＿FDTD parallel algorithm calculated and analyzed the radio wave propagation in the sidewalk forest model,the forest model with random tree distribution,the forest model with random tree size,the forest model with random tree distribution and the forest model with random tree size.The radio wave propagation in a forest composed of trees of different sizes and distributions is calculated and analyzed.The experimental results show that the propagation loss of high frequency wave is larger in the forest,while low frequency wave is smaller.Large or dense trees absorb electromagnetic waves strongly,hindering the propagation of radio waves and leading to fast signal attenuation. |
