Research On The User Access Method Of MMW-UW Frequency Hybrid Network

With the continuous increase of wireless mobile communication users and the continuous increase in user demand and business volume,the data volume of mobile communications has seen an explosive growth.Currently,mobile communications are limited by the bandwidth of the microwave frequency band and can no longer meet the needs of technological development.For this reason,the development of broadband mobile communications using the millimeter wave band has become a research hotspot.The small millimeter wave wavelength makes the physical size of the antenna small,so that the massive MIMO technology can be applied to a millimeter-wave communication system and can provide a beamforming gain.Compared with traditional microwave communications,millimeter wave penetration is poor and attenuation is large.Application of MIMO technology and beam forming technology make the access technology of current wireless communication not applicable to millimeter wave systems.Therefore,the access of millimeter wave system become the focus of research.In the future,wireless communication will be a converged,collaborative multi-system coexistence heterogeneous network.Researching user access methods in high-and lowfrequency hybrid networking.MmWave communication relies heavily on highly-directional transmissions to overcome the large isotropic pathloss and the use of directional transmissions significantly complicates access.It is this very procedure that will be triggered in case of an intermittent link or recovery from idle mode.Hence,addressing this problem will have significant impact on the latency.Especially in high mobile application scenarios,such as car networking,frequent reconstruction and restoration of wireless links are required.Reducing the access delay can greatly improve the safety and automation of automatic driving.Utilizing the spatial information of the low-frequency channel-out-of-band information,can effectively reduce the training overhead for establishing a millimeterwave link.Using out-of-band information can have a positive effect on all programs that apply millimeter-wave communication.Thesis focuses on the issue of beam selection in the user access procedure of high-and low-frequency hybrid networks.The current methods for access in millimeter-wave systems include exhaustive search,iterative search,compressive sensing search,access method based on geographical location information,multi-cell user access method based on uplink control.Thesis uses spatial information extracted at sub-6 GHz to help establish the mmWave link.The frequency of the low-frequency channel is less than 6 GHz(sub-6 GHz)and all-digital beamforming architecture is used.The millimeter-wave system uses the 28 GHz band and uses an analog beamforming architecture.A multi-band correlation channel model was established based on multi-band correlation channel characteristics.Sub-6GHz channel and millimeter-wave channel have spatial consistency,extracting spatial information of sub-6GHz channel(Out-of-Band Spatial Information),and then use it for compressed-sensing beam selection in millimeter-wave systems.Based on the extracted out-of-band spatial information,the sparse signal is reconstructed using a logweighted orthogonal matching pursuit algorithm(LW-OMP).In addition,according to the iterative search,the iterative beam selection of the low frequency auxiliary millimeter wave system is proposed.Finally,compared the performances of exhaustive search,compressive sensing method of low frequency auxiliary millimeter wave system,LWSOMP compressive sensing method of low frequency auxiliary millimeter wave system,and iterative method of low frequency auxiliary millimeter wave system.Simulation results show that the use of iterative method to assist millimeter wave system access is better than LW-SOMP method in hybrid network with high and low frequencies.