| The technology of electromagnetic wave,especially the millimeter wave electromagnetic field,has developed very rapidly in the new century,which makes the electromagnetic environment becomes complex.In the daily life and national defense technology,especially radio applications such as over-the-horizon early warning,electronic countermeasures,wartime automated command systems,and battlefield dynamic perception,it is necessary to obtain accurate electromagnetic environment data.In addition,an important reference for the rational layout and optimal design of modern communication networks represented by the fifth-generation mobile communication system(5G)is the radio wave propagation characteristics in urban micro-cells and indoor office.In addition,the frequency increases and the cellular networks become denser in 5G millimeter-wave communication,which is more likely to cause problems such as co-channel interference.Therefore,it is more important to study the propagation characteristics in millimeter-wave high-frequency bands.Firstly,a three-dimensional fully polarized ray method is proposed to study the effects of different scattering angles and different numbers of scattering rays on the electric field and path loss in the microcell.Secondly,based on the wireless channel data of the real scene in the millimeter-wave frequency band,the three-dimensional bouncing ray method is used to study the diffraction effect and the scattering effect and analyze the necessity of modeling in the millimeter-wave.Finally,this paper studies the wireless channel parameters of the millimeter-wave frequency band in typical open indoor scenarios,and analyzes the differences between different frequency bands in different indoor scenarios.The paper is summarized as follows:1.Aiming at the problem that the three-dimensional ray tracing method cannot accurately calculate the field strength of any receiving point and the path loss in the transmission of incident waves of different polarizations,the three-dimensional wide-angle vector parabolic equation method is used to calculate the electromagnetic wave signal without obstacles and and the direction of the incident ray in this paper.The electric field and magnetic field components and the direction of the incident ray generated in propagating on the flat ground are used as the initial field and the initial ray direction of the three-dimensional ray tracing method.Considering that the initial ray incident on the wall and the ground,the different polarization effects is produced,and a three-dimensional fully polarized ray model is established.Taking the non-line-of-sight scene in the microcell of the China Institute of Radio Propagation in Qingdao as an example,the simulation was carried out to analyze the influence of the number of scattered rays,the scattering angle and the number of divisions on the running speed and prediction accuracy of the 3D fully polarized ray method.The results show that the number of scattered rays and the number of divisions are positively correlated with the running time.When the scattering angle is 5°and the number of scattered rays is 9,both the mean square root error(RMSE)and mean square error(MSE)reach the minimum value in the multiple verifications,which is in good agreement with the experimental data,and the running time is relatively optimal.2.The scattering generated by rough grounds and walls in the millimeter wave has a great influence on the prediction accuracy in the mobile three-dimensional communication.Therefore,the reflection of the signal cannot be simply equivalent to specular reflection using the three-dimensional ray tracing algorithm.A single typical wall is taken as the research object firstly in this paper.The three-dimensional reverse ray tracing method is used to analyze the influence of the scattering coefficient and scattering lobe width of the two-station scattering model of the typical wall on the distribution of scattered signals.Then,the scene is modeled in the micro-cell,and the scattering effect is taken into account in the 3D bouncing ray method.The 3D polar sweep algorithm is used to determine the effective scattering surface,and the 3D reverse ray tracing method is used to optimize the rough wall scattering coefficient and scattering lobe width.The simulation results of the electric field and transmission path loss distribution are more consistent with the experimental data,and a millimeter-wave channel propagation model is established on this basis.This provides theoretical support for the base station layout of the fifth generation mobile communication system.3.Based on the standard format in the typical open indoor,the three-dimensional(3D)reverse ray tracing method is adopted to analyze the path loss and electric field with frequency,and the polarization mode of the transceiver antenna,and the distance of the transceiver antenna in the typical open indoor.Visualize the transmission effects from the3 D ray path diagram of the receiving point,and compare the simulation results of the 3D reverse ray tracing method with the SAGE algorithm to verify that the 3D reverse ray tracing method is suitable for typical open indoor.A reliable theoretical basis for network optimization and radio wave propagation prediction can be provided in typical open indoor scenarios.4.In the non-line-of-sight,the calculation results of the outdoor 3D bouncing ray method without considering the diffraction effect are quite different from the experimental data,and no ray is arrived from the transmitting point to the receiving point.Therefore,the diffraction effect needs to be considered in the outdoor 3D bouncing ray method,but the acquisition of the diffraction point is a big problem.Based on the theory of three-dimensional bouncing ray method,a method for judging diffracted rays is proposed in this paper.The receiver sphere technology is adopted to determine the diffraction point according to the shortest distance method of two straight lines,and then the loss of the diffraction ray can be calculated.It is found that the 3D bouncing ray method considering only specular reflection has a large error with the experimental results,while the calculation results of the 3D bouncing ray method considering both specular reflection and diffracted rays are in better agreement with the experimental results.Therefore,the three-dimensional bouncing ray method considering the diffraction effect can improve the prediction accuracy in the millimeter wave.The above results provide technical support for base station location layout,network optimization and electromagnetic situational awareness in millimeter-wave mobile communications. |
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