Study On The Path Attenuation Estimation Of Microwave Signals And The Attenuation Fields Reconstruction Under Complex Meteorological Conditions

Microwave attenuation is an inevitable power loss phenomenon in the progress of microwave signals transmission in the air,and it is also one of the most important reasons for the deterioration of wireless communication quality.Whether it is the scattering and absorption caused by water vapor and oxygen in the atmosphere and the free space path loss(FSPL)under clear weather condition or additional effects caused by complex meteorological conditions such as rainfall,fog,haze,and dust,all will cause significant power attenuation to the microwave signal transmission.It is great significance for the design of microwave communication systems,the compensation of wireless communication quality loss,and the inversion of attenuation source to analyze the causes of microwave attenuation and to accurately observe and estimate the microwave attenuation.In this thesis,the estimation problem of power attenuation of point-to-point microwave links,and the reconstruction problem of two-dimensional and three-dimensional attenuation fields under complex meteorological conditions based on link attenuation estimation are studied.Methods of path attenuation estimation due to complex meteorological conditions are proposed,reconstruction models of the 2-D and 3-D attenuation fields are established,and the performance of various attenuation estimators is theoretically studied and simulated in this thesis.Firstly,the existing received signal level(RSL)based attenuation estimator due to complex meteorological is studied in this thesis.In view of the current lack of theoretical analysis of its performance,an ideal RSL model is proposed for the first time without considering the quantization error.Using this model,the theoretical performance limit of the RSL based attenuation estimator is given,which makes up for the lack of theoretical analysis.Theoretical and simulation results show that the RSL based attenuation estimator has better performance when the receiving signal-to-noise ratio(SNR)is high,but it performs poorly for low SNR.Meanwhile,the estimation resolution is low when the microwave link has suffered a large attenuation under complex meteorological conditions.Based on the study of the existing attenuation estimation methods and attenuation field reconstruction technology due to complex meteorological conditions,the SNR estimation is used for estimating the path attenuation caused by complex meteorological conditions in this thesis,and a new path attenuation estimator based on the estimation of clean signal power(CSP)is proposed for the first time.The theoretical performance limits of the path attenuation estimator based on SNR estimation and CSP estimation are obtained,respectively.Comparing the above three kinds of path attenuation estimators due to complex meteorological conditions,the theoretical and simulation results both show that when the SNR at the receiver is low,the SNR-based estimator and the CSP-based estimator have more significant performance advantages;under the condition of high receiving SNR,the estimated resolution of the SNR-based path attenuation estimator cannot be continuously improved,while the CSP-based estimator has the best performance in most cases;when the attenuation caused by complex meteorological conditions is large,the performance of the SNR-based and the CSP-based path attenuation estimator also decreases,but the declining trend is slower than that of the RSL-based path attenuation estimator.Regarding the problem of using microwave links to observe and reconstruct the microwave attenuation field caused by complex meteorological conditions,this thesis,for the first time,takes rainfall events as an example,and uses the SNR-based and the CSP-based attenuation estimators due to complex meteorological to reconstruct the near-ground 2-D attenuation field caused by rainfall,and uses the CSP-based attenuation estimator based on satellite communication links to reconstruct the 3-D attenuation field caused by rainfall.The comparison of the 2-D and 3-D attenuation field reconstruction results based on RSL measurement,SNR estimation and CSP estimation shows that in the reconstruction problem of near-ground 2-D attenuation field,the reconstruction accuracy of the SNR-based and the CSP-based methods are better than that of the RSL-based method,and the performance difference between the former two methods is small;for the reconstruction problem of the 3-D attenuation field,it is difficult to reconstruct the attenuation field by using the RSL-based method,while the CSP-based method shows obvious performance advantages.Although the SNRbased method can reconstruct the attenuation field accurately there is a significant gap between its reconstruction precision and that of the CSP-based method.This thesis not only proposes a new method of path attenuation estimation due to complex meteorological based microwave links,which improves the accuracy of attenuation estimation,but also makes up and improves the performance analysis of a variety of path attenuation estimators using the combination of theoretical derivation and simulation.At the same time,the 2-D and the 3-D attenuation field is reconstructed by using different path attenuation estimators,respectively,which expand the application range of path attenuation estimators,thus completing the research from point-to-point microwave link attenuation estimation to multidimensional attenuation field reconstruction.The thesis has 56 figures,21 tables,and 174 references,totally.