Study On Object Imaging Method Based On Wi-Fi Signal

In the context of the massive deployment of Wi-Fi wireless networks,there are more and more researches on application technologies based on Wi-Fi wireless networks.There are mature tools to obtain Channel State Information(CSI)sent by Wi-Fi devices.Therefore,the research on Wi-Fi related technologies is no longer limited to the traditional communication and data transmission fields.The sensitivity of fine-grained CSI signals to environmental changes is used for research in the field of wireless sensing.Image,as the most intuitive information carrier,has always been a popular research field.Traditional electromagnetic wave-based imaging requires the deployment of special imaging equipment,and the use scene is limited by equipment.This article discusses the possibility of using the widespread Wi-Fi to image target objects.The research content and results are as follows:(1)Due to the limitations of Wi-Fi signal bandwidth and transmission system,Wi-Fi signal-based imaging cannot use existing radar imaging methods.Therefore,this article is based on the principle of optical MRI imaging,using the angle of arrival technology combined with signal strength The method of imaging research,combined with the easy-to-obtain CSI signal with fine-grained characteristics in Wi-Fi devices,an imaging model based on the amplitude of the CSI signal is proposed.(2)According to the imaging model,the acquired raw CSI data is preprocessed,including amplitude and phase.Aiming at the error caused by environmental noise and multipath interference to the original CSI data,first,the Hampel filter is used to filter out the signal outliers,and then the principal component analysis method is used to reduce the dimensionality of the data,and also to reduce the noise.Finally,for multipath signal interference,set the cutoff threshold to keep only the path energy within the cutoff threshold,thereby suppressing the amplitude measurement error caused by multipath;for the phase error caused by the hardware device in the signal acquisition process,use The linear transformation phase error elimination algorithm eliminates the influence of offset and offset on the entire frequency band,and obtains phase data with a smaller fluctuation range after correction.(3)Perform angular separation on the preprocessed CSI signal.The Wi-Fi signal-based imaging algorithm proposed in this paper needs to estimate the azimuth and elevation angles of the signal arriving at the receiving array through the target object,so as to separate the signal.Aiming at the problem that the MUSIC algorithm fails to estimate the angle of the coherent signal source,the spatial smoothing is improved.After simulation verification,the improved MUSIC algorithm reduces the degree of freedom of the source array,reduces the number of coherent signals that need to be solved,and can adjust the signal azimuth.And the elevation angle is accurately estimated and the accuracy is higher.(4)Based on the super-resolution angle estimation algorithm,design the imaging system design in this paper.The imaging system includes three modules: interference suppression,target detection and imaging.Select a metal object that is easy to realize imaging for simulation imaging research.The experimental scene built in the ANSYS system combined with the imaging algorithm can obtain the approximate outline of the object.Image the metal material target in the experimental scene,set up different observation distances to analyze the imaging accuracy of the control experiment,and introduce the contour difference and boundary key point accuracy to evaluate and analyze the cumulative error of the imaging accuracy.The experimental results can observe the target The approximate outline of the object.The paper has 43 figures,5 tables,and 84 references.