| In recent years,in order to realize the commercialization of the fifth-genera-tion mobile communication system as soon as possible,the application research on various basic theories has emerged one after another.The establishment of the channel model is one of the important ways to understand and apply the commu-nication system.At the same time,because the millimeter wave has the ad-vantages of wide spectrum resources and high transmission rate,the channel model of the millimeter wave band has gradually become one of the key research points of 5G.Faced with the new requirements of 5G systems,the traditional channel mod-eling method,which means the statistical modeling method,is based on the meas-urement data of specific environments.The establishment of such a channel model has high requirements on data acquisition equipment and measurement methods.The clock accuracy and storage rate of channel detection equipment are facing high challenges,especially in the millimeter wave band.Therefore,this paper uses the ray tracing technology in the deterministic modeling method to build a simulated platform suitable for high and low fre-quency band communication.The channel measurement data in indoor hotspot scenes at 28 GHz and 3.5 GHz is analyzed,and compared channel characteristics with which extracts with ray tracing simulation.At the same time,the applica-tion value of ray tracing technology in the channel modeling method under 5G demand is analyzed.The specific research content of this paper includes:(1)Building a ray tracing platform based on 3D scene modeling:Using the 3D modeling software Google SketchUp to model the interior 3D scenes,and then input the coordinate,material,thickness and other parameters of the indoor ob-jects,and finally output them into Matlab readable data format.Ray tracing tech-nology is used to configure different simulation parameters such as the maximum number of reflections,the maximum number of diffractions,and the maximum number of penetrations.All possible effective multipath are determined by geo-metric optics theory,and the parameters of the dielectric constants are calculated by using the dielectric constant and other electrical parameters.Finishing all eli-gible multipath channel parameter extraction,the deterministic channel model is established.(2)High frequency and low frequency channel measurement and parameter extraction in a typical conference room environment:Using the existing millime-ter-wave channel detection platform of the laboratory,the 28 GHz channel meas-urement of the typical indoor conference room scene is performed for the indoor hotspot scene requirement in 5G.In order to analyze the channel parameters of the large scales and small scales separately,different antenna configurations are adopted.One is that two omnidirectional antennas are placed at transmitting and receiving points,another is that horn antennas are rotating in the horizontal and vertical directions to collect the channel angle domain parameters.At the same time,for the 3.5GHz indoor channel data that the team has collected,the param-eters are extracted again according to the research needs.(3)Comparison of channel parameters between ray tracing and measured data:Channel parameters such as path loss,K-factor,delay spread and angular spread of ray tracing and measured data in the same conference room scene at 28 GHz and 3.5 GHz.According to the comparison results,the ray tracing simulation configuration parameters closest to the actual measurement at 28 GHz are 1-2 reflections,1 diffraction and 5 penetrations.At the same time,the difference be-tween the measured data and ray tracing at 3.5 GHz is large so that similar ray tracing configuration parameters cannot be determined.Finally,based on the com-parison of high and low frequency channel characteristics,the deterministic chan-nel model based on ray tracing can be a powerful complement to the statistical channel model based on traditional channel measurement data,while considering the challenges and difficulties encountered in current millimeter wave channel measurement,In summary,this paper,which is for 5G demand,focuses on the wireless channel characteristics of ray tracing simulation and measured data in indoor con-ference room scene at 28GHz and 3.5GHz.The results make it clear that the chan-nel modeling method based on ray tracing can be used as an alternative to tradi-tional channel measurement to some extent,which provides reference for subse-quent research. |
