Research On Propagation Characte-Ristics And Modeling Of Multi-Band Channel In Typical Urban Scene

The emergence of new services such as the intelligent connection of all things,holographic communication,and integration of communication and sensing has put forward higher requirements for 6G network capacity and transmission rate.Therefore,it is necessary to use a wider range of spectrum resources for multi-band collaborative wireless networking.The higher the frequency,the shorter the wavelength,which causes differences in the propagation processes of electromagnetic waves of different wavelengths such as scattering and diffraction,which ultimately leads to different wireless channel propagation characteristics in the same environment.The propagation characteristics of wireless channels determine the upper limit of performance of wireless communication systems and are the basis for base station deployment,network design,and performance evaluation.Therefore,it is very valuable to study the propagation characteristics of wireless channels in multiple frequency bands.As a mobile communication hotspot scene,the urban scene is also one of the typical scenes defined by the 3 GPP channel model standard.Compared with indoor scenes,it has a larger spatial scale and a more complex scattering and diffraction environment.Therefore,it is necessary to research the propagation characteristics and modeling of multi-band wireless channels in typical urban scenarios to support the development of key technologies for multi-band collaborative wireless networking in typical urban scenarios.This thesis focusing on the propagation characteristics and modeling of multi-frequency channels in typical urban scenarios.The frequency points studied in this article are in the[3.3,7.5]GHz range,with a total of eight frequency points.This thesis first constructs a multi-band broadband wireless channel measurement platform based on the principle of timedomain spread spectrum sliding correlation and then uses statistical methods to study the distance dependence and frequency dependence of channel characteristic parameters at different scales.Finally,research is conducted on the cross-correlation of the size scale parameters of multiband channels and the frequency autocorrelation of channel parameters.The main content and innovative points of this thesis are as follows:(1)Multi-band broadband wireless channel measurement platform construction.The measurement platform built in this thesis supports signal transmission and collection in the frequency range of 100kHz-40GHz with a maximum bandwidth of 2.4GHz.This platform achieves high-speed switching of carrier frequency bands and real-time channel sampling,saving time costs while ensuring the consistency of multi-band channels.To solve the problem of gain attenuation of the omnidirectional antenna in the case of high elevation receiving and transmitting,this thesis conducts multi-band full elevation angle gain calibration for the used omnidirectional antenna,obtains the multi-band three-dimensional pattern of the omnidirectional antenna,and then compensates the power value of its channel response according to the channel data when the elevation angle of the receiver and transmitter is too large.In this way,a richer arrangement of receiving endpoint can be carried out to obtain more complete wireless channel results in urban scenarios.(2)Analysis of characteristic parameters of multi-band wireless channels in typical urban scenes.This thesis investigates three parameters:path loss,root mean square delay spread,and Rician K factor for multi-frequency wireless channels in urban scenarios.In addition,according to the difference between the scene and channel parameter results under the NLOS condition,this thesis divides the NLOS scene into two categories:roadside sidewalk and dense building area.Compared with the unified model in the standard,it has more reference value for the targeted channel models established respectively for these two types of scenes.For path loss,this thesis uses single-band and multi-band path loss models to fit the path loss results and compares the fitting results with the 3GPP standard values.In addition,this thesis found that the frequencydependent factor of path loss in LOS scenarios has distance dependence and conducted a fitting analysis on it.Regarding the root means square delay spread,this thesis found the distance dependence and frequency dependence of this parameter in LOS and NLOS scenarios and fitted it using the proposed distance frequency dependence model.Then,the fitting results were compared and analyzed with the standard values.For the Rician K factor,this thesis found the distance dependence and frequency dependence of this parameter in the LOS scenario and fitted it using the proposed distance frequency dependence model.Finally,the results were compared with other literature.(3)Multi-band channel correlation analysis of typical urban scenes.This thesis focuses on the correlation of multi-band wireless channels in urban scenes and conducts research on three parameters:shadow fading,root mean square delay spread,and the Rician K factor.For the inter-frequency correlation of the three parameters,this thesis finds that the inter-frequency correlation coefficients of shadow fading and the Rician K factor are random in the studied frequency band.Through the KS test,the results are fitted with normal distribution.For the root mean square delay spread,this thesis found that the frequency correlation and frequency difference of this parameter has a good linear relationship.This thesis conducts a theoretical analysis based on the differences in channel correlation between three parameters in frequency.Then,this thesis studied the correlation of the three parameters with frequency changes and found that the negative correlation between root mean square delay spread and shadow fading would increase with frequency,while the correlation between shadow fading and Rician K factor,as well as the correlation between Rician K factor and root mean square delay spread,did not show frequency dependence.Then,this thesis compared the cross-correlation results of the three parameters with the reference values provided in the 3GPP standard.Finally,this thesis explains from the perspective of parameter definition regarding the frequency dependence of the different correlations among the three parameters.