Theoretical And Experimental Study On Millimeter Wave Blockage Diffraction And Coverage

Millimeter wave technology is one of the key technologies for the development of 5G.Its bandwidth is very wide,ranging from 30-300GHz.Therefore there are abundant frequency resources that can be developed and utilized.The technology can meet the requirements of high speed data,high bandwidth image service and other large capacity information transmission and processing.Combining the millimeter wave technology with other technologies,the communication capacity can be much larger than that of LTE technology.This enables high performance services such as large capacity,high transmission rate,low delay,and flexible extension for 5G communication.In this dissertation,the theoretical and experimental research on the channel characteristics of millimeter wave in visual and blocked environment are carried out,and the following work has been accomplished.(1)The LOS measurements of the indoor and outdoor wireless channels have been carried out at 28 GHz and 45 GHz,respectively,on the basis of study of the path loss model.A discrete least square fitting method is proposed to process the measured data,getting the path loss index and the variance of shadow fading of the experimental environment.A more accurate channel loss prediction model suitable for the experimental environment is obtained.(2)A model for the blockage of EM wave and base stations in millimeter wave cellular networks is built by applying the model of Poisson's point process.The line segment method is used to simplify the rectangular building in the modeling according to the characteristics of the poor penetration of millimeter wave.The quantitative calculation of the number of building blocks on the propagation path is carried out.The influence of the density and the size of the buildings,and the density of the base station on the coverage of the cellular network is derived,and systematical simulations are carried out.(3)Edge diffraction theory of EM propagation is studied.The 3-ray and 4-ray methods are proposed,respectively,aiming at rectangular obstruction of several common materials.The rectangular block diffraction measurement experiments are carried out on wood board,mirror,and white iron board with thickness of 12mm,6mm,and 0.35 mm,respectively,in the laboratory.The experimental results show that the average transmission attenuation of 45 GHz millimeter wave blocked by 12mm rectangular wood board is about 4.28 dB,and average transmission attenuation of 45 GHz millimeter wave blocked by 0.35 mm rectangular white iron board is about 18.2 dB.The attenuation of the mirror lies between those of the wood board and the iron board.By adjusting the height of the transmitting antenna,the signal attenuation characteristic of the transmitting antenna at different heights is measured by a rectangular blockage.The experiment results show that the higher the transmitting antenna position is,the smaller the diffraction attenuation is.(4)Four kinds of cylindrical barrier models are proposed on the basis of the thorough study of UTD theory,and measured by 45 GHz millimeter wave for the four models.The results are in compliance with those of the theoretical analysis.The measurement results show that the characteristics of diffraction attenuations are very close for the cylinder plastic bucket full of water with diameter of 30 cm and the cylinder metal bucket with diameter of 26 cm.The results of diffraction attenuation are much larger than that of a human body.The measurement results of the two models,combining a man and a cylinder,reveal sharp difference.When the cylinder is fixed on the side of the transmitting antenna,the diffraction attenuation is less than that of fixed on the side of the receiving antenna.(5)A simple and easy to implement communication transfer method is proposed to realize indoor and outdoor communication by millimeter wave and other communication problem with no LOS between transmitting and receiving antennas,aiming at the problem susceptible blockage of millimeter wave.The indoor and outdoor communication measurement in the microwave anechoic chamber at 26 GHz frequency,and the experimental measurement in a large laboratory with workshops at 45 GHz frequency are carried out,respectively.All the measurements proved that the method is effective.