Research On Key Technologies Of Wireless Coverage Based On Reconfigurable Intelligent Surface

A new generation of cellular mobile communication system appears almost every decade.The basic development idea is to improve the quality of service by introducing new key enabling technologies.However,the development of various individual technologies in the field of mobile communication network has tended to the performance limit.The traditional communication technology is encountering a major obstacle that the gradual improvement of mobile communication has great difficulty in developing continuously.As a new enabling technology of 6G,reconfigurable intelligent surface(RIS)is a new paradigm being actively explored.The various applications on RISs make the control ability of electromagnetic wave no longer limited to transmitter and receiver,but to realize the active improvement of wireless propagation environment by flexibly controlling electromagnetic wave transmission.Motivated by the above background,this paper focuses on the key technologies of new wireless coverage based on RISs.The specific research contents are as follows:Firstly,for the emerging hardware paradigm of RIS in the field of wireless communication,this paper focuses on its digital coding principle,which lays a theoretical foundation for RISassisted wireless communication system.After introducing the basic principle of coding,the RIS working at 35 GHz,1-bit phase configurable and unit independent controllable is introduced in detail.The hardware parameters such as electromagnetic unit structure,electromagnetic unit size,regulation degree of freedom,electromagnetic unit power consumption and interface type of RIS are given,the hardware characteristics such as the curve between electromagnetic unit reflection coefficient amplitude and phase between frequency are clarified,and the mapping relationship between control code and electromagnetic unit,and the software application method of communication between computer and RIS are introduced.It provides theoretical support for the numerical simulation and measurement verification of RISassisted wireless communication system.Secondly,for the multipath transmission of RIS-assisted wireless communication system,a two-path propagation model for RIS-assisted wireless communications is proposed and the measurement verification is completed.By modeling the RIS-assisted two-path propagation model,the fast fading phenomenon caused by signals traveling from different paths is revealed.In particular,four types of RISs with different configuration capabilities are introduced and their performances on improving received signal power in virtue of the assisted path to resist fast fading are compared through extensive simulation results.Moreover,the upper bound of the received signal power is derived.The experimental results verify that an RIS has the ability to combat fast fading and thus improves the receiving performance.Subsequently,for the multi-user broadcasting of RIS-assisted wireless communication system in free space,the path loss model of multi-user broadcasting in RIS-assisted wireless communication system is proposed and the measurement verification is completed.The path loss formula of free space in multi-beam case is derived,and the relationship between multibeam path loss and single beam path loss is revealed.The simulation results reveal that multiple beams can be generated in the far field of the RIS with appropriate phase gradient configuration.The beam pattern is scanned in the microwave anechoic chamber using an RIS operating at 35 GHz to verify the simulation results that two beams with the same power can be generated in the far field of the RIS with appropriate phase gradient configuration.In addition,the path loss of the two-beam is measured at the peak position.The derivation result of the path loss formula is verified by the experimental measurement.Finally,for the impact of the location deployment of RIS on the receiving performance of base station-RIS-user link,the viewpoint that the influence of deployment location of RIS on the receiving performance depends on the spatial location relationship of user,base station and RIS is proposed and the measurement verification is completed.Considering the actual indoor and outdoor location deployment scenarios,the impact of the deployment location of the RIS on the received power is simulated respectively.At the same time,the impact of the electromagnetic unit radiation pattern of the RIS on the location deployment results is analyzed.The actual measurement environment is built in the indoor and outdoor scenes to verify the derivation and simulation results.