Research On Multi-user Wireless Transmission Method Of Reconfigurable Intelligent Surface Aided Communication

The reconfigurable intelligent surface(RIS)has received extensive attention from academia due to its low cost,low energy consumption,and reconfigurability characteristics in recent years.RIS is composed of a large number of passive reflection units,which can be deployed in the wireless communication environment to enhance useful signals and eliminate interference by changing its phase.A lot of current research work shows that the application of RIS can help wireless communication systems increase the transmission rate,reduce energy consumption and improve system security.The phase of the passive reflection unit of the RIS needs to be changed to adapt to different scenarios and obtain the best performance.Therefore,how to design the phase of the RIS become an urgent problem.For the above problems,this article does the following research on the transmission method of RIS-assisted wireless communication system:First,an overview of several common application scenarios of RIS in wireless communication systems is given.Then,the signal model,hardware architecture and phase shift model of RIS are further introduced.It then introduced the frequency band resources in the fifth-generation mobile communication.The transmission technologies commonly used in wireless communication systems,like: analog beamforming,digital beamforming and hybrid beamforming are introduced and a comparison of the three beamforming technologies is given.Secondly,for the transmission problem of RIS-assisted multi-user downlink wireless communication system,a RIS phase optimization method based on particle swarm algorithm for maximizing ergodic sum-rate is proposed.Consider a RIS-assisted wireless communication system with multiple users,it assumes that the channel between the RIS and the user obeys the rice distribution,the base station uses regularized zero-forcing precoding.It proposed the deterministic equivalent formula of the ergodic sum-rate by using the theory of large-scale system analysis.The simulation results show that the deduced deterministic equivalent formula has a good approximation effect,and the proposed algorithm can effectively improve the performance of the system.Finally,for the energy consumption problem in the RIS-assisted secure downlink wireless communication system,a robust beamforming and RIS phase optimization method for minimizing the transmission power under the system's secrecy rate constraint is proposed.Consider the RISassisted wireless communication system with eavesdroppers,the base station doesn't know the imperfect channel state information(CSI).It proposed the robust beamforming and RIS phase alternation optimization algorithm by minimizing the transmission power and analyzed the convergence and complexity of the proposed alternative optimization algorithm.The simulation results show that the proposed alternative optimization algorithm can effectively reduce the energy consumption of the system and ensure the safety of user communication.